Mass analyzer system for the direct determination of organic
Contents
1. IE IE HE DIE IEEE 8807 1 NRME 8808 8810 ASTART CVS SS 8812 AEND CVS SES 8812 AEND CVS SES 1LIST 2RUN SLOAD 4SAVE SFILES CONT 7 LFT1 SLOCATE 9COLOR 10PALET 8810 ASTART CVS SS 8812 AEND CVS SES 8819 OPEN 2 14 8820 FIELD 42 14 AS AMUNS 4 757 198 27 28 8823 CLOSE 1 8840 FOR CL ASTART TO AEND 8880 GET 2 CL 8880 AVALUE CL 2 2CVS AMUN 8900 NEXT CL 8920 CLOSE 42 8921 OPEN R W2 BKGRND 14 SUBROUTINE TO READ THE BACKGROUND DATA 8922 FIELD 42 14 AS AMUNS STORED IN BKGKND FILE AND FLACE IT IN 8924 FOR CL 1 TO 300 THE ARRAY AVALUE CX 2 8925 GET 2 CL 8925 AVALUE CL 0 2CVSCAMUNS AVALUECCL 3 CL 8927 NEXT CL 8928 CLOSE 2 8940 RETURN 9000 CLS LO ATE 10 40 O PRINT ACKNOWLEDGE WITH Yes 9001 AS INKEY 9002 IF LEN AS 0 THEN 9001 9003 IF ASC AS 78 THEN RETURN 9004 IF ASC AS s89 THEN 9019 9004 IF 5 5 89 THEN 9019 1LIST 2RUN SLOAD 4SAVE SFILES CONT 7 LPT1 SLOCATE COLOR 9003 IF ASC AS 78 THEN RETURN 9004 IF 89 THEN 9019 9005 BEEP GOTO 9001 9019 OPEN R 1 LOOKUP 40 9020 FIELD 01 8 AS KS 4 AS TPS 4 AS 55 4 AS SES 10 AS 069 8 AS TES 9040 INITz2 9060 LSET OKS MKIS INIT 9080 PUT 1 1 9100 CLOSE 9120 RETURN 10000 CLS SUBROUTINE TO INPUT THE NAME OF A FILE TO BE SAVED 10005 INPUT NAME AES2. 12550 REM 13000 REM HHHHHHHEROUTINE FOR TABULAR PRINTOUT OF SPECTRUM rfe tenen 13005 CLS1RIZG0 LEF 550 90 8012292 BLAx106 13007 LOCATE 1 77 COLOR 0 2 0 80 PRINT WAIT 13008 COLOR 6 0 0 0 13010 LINE RI 80 LEF 80 1 TOP LINE 13020 LINE RI 100 LEF BLA 1 BF 20 THICK LINE 13090 LINE RI 124 LEF 124 1 13040 LINE RI 148 LEF 148 1 4TH 13050 LINE RI 172 LEF 172 1 STH 1300 LINE RI 196 LEF 196 1 6TH 13070 LINE RI 220 LEF 220 1 13000 LINE RI 244 LEF 244 1 4 757 198 31 32 13090 LINE RI 268 LEF 258 9TH 13100 LINE RI 292 LEF 292 1 10TH 13110 LINE 140 BLA 140 B0T 1 13120 LINE LEF TOP LEF B0T 1 LEFTMOST 13130 LINE RI TOP RI BOT 1 RIGHTMOST 13140 LINE 254 BLA 254 BOT 1 1319 LINE 37 LIST 300 4SAVE SILES 7 LPT1 GLOCATE COLOR 10PALET 13150 13160 13170 13180 13190 13200 LINE 370 BLA 370 BOT i LOCATE 8 11 PRINT MASS LOCATE 8 17 PRINT INTENSITY LOCATE 8 30 PRINT CALCULATED LOCATE 8 44 PRINT BACKGROUND IF THEN LOCATE 24 60 PRINT NO DATA AVAILABLE FOR DEL 1 TO 2000 NEXT DEL GOTO 13570 13210 13220 13230 13240 13250 13260 13270 13360 13370 13380 13390 13395 Pd N1 ASTART SQ SORT de 9F 48 E AE de 3F HE IERI DE IE IER 4F E FOR I N1 TO AEND is 13280 IF AVALU
3. HW WILEAS p 22 2702 U S Patent Jul 12 1988 Sheet 2 of 6 4 757 198 FIG 2 SEPARATOR SYSTEM gt a0 N 5 eX 24 BENZENE R N 3 24 0 2 22 30 2 IO 60 MASS CORRECTION KENS ALERITURE US Patent Jul 12 1988 Sheet 3 of 6 4 757 198 22 MASS O SPECTROMETER LLECTROW MULTIPLIER TRAJECTORY OF SELECTED 2 MASS FILTER SAMPLE IZ YLT LOW AFF A 224 FIG 3 007127 72 VACUUM F IG 4 Sheet 4of6 4 757 198 Jul 12 1988 US Patent Z 914 ke LO eS ee ee E SIZZI VNE SSW Z7Z7ZZ2 ge NE e 47 4 5 SOV SEE Z How PA 2 9 3 YAS Wit GA JE k d lt x D LA TY an Z THALYS TSE T 20 N 26 IAS SSUW amp 22700000000 77 gt H E L FAW YS ov N LIAW 25 gt 77772 e DE E 9 a 4727 WO2032 W WLSASP rg B 2294402 gt US Patent Jul 12 1988 Sheet 5 of 6 4 757 198 87 ZZ PORTABLE COMPUTER TS RE VARIJABLE OLNLRATOR LEAK VALVE 72 77 i COMPUTER AMLE ZAZ7224 22 PUMP CONTROL UNIT um 9 n LO
4. 3409999 4F 8 3F 8 3F FF RE 815 COLOR 7 0 LOCATE 24 57 PRINT Fi 820 GOSUB 1500 825 GOTO 45 830 REM 3E E E 8 Ie IE E 3F E E 4F E E 835 REM SAVE SPECTRUM 840 1LIST 2RUN SLOAD 4SAVE SFILES 6CONT 7 LPT1 SLOCATE COLOR 10PALET 840 COLOR 7 O LOCATE 24 57 PRINT F2 845 GOSUB 10000 850 GOTO 45 855 mde d 4 9 9F e ae 4E 9F E FF E E 4 DF E E 860 REM HHHH READ TOTAL PRESSURE FHKE R E 865 COLOR 7 08 LOCATE 24 971PRINT F3 866 GOSUB 7500 867 OUT FUNC CONSOLE FIL MULT 870 GOTO 730 875 REM 9 FF 4F 4F 3F 2F 3F E 4E E E 3F EXE E AE 880 REM DISPLAY BACKGROUND 3x33 3 885 COLOR 7 0 LOCATE 24 57 PRINT F4 887 GOSUB 26000 890 GOTO 45 895 REM FF HF 9 4 E IE IE IEEE IEEE IE IEEE SERE E 900 REM TIME SCAN 905 COLOR 7 01LOCATE 24 57 PRINT FS 910 GOSUB 14000 915 GOTO 45 s 920 REM PRINT SPECTRUM 3 4 9 3 399 925 COLOR 7 0 LOCATE 24 57 PRINT F6 930 GOSUB 13000 935 GOTO 45 940 1LIST 2RUN SLOAD 45 SFILES 6CCINT 7 LPT1 SLOCATE CCLOR 10FALET 940 REM HIE HE FF E c d M Y I IX EXHI OCURRE I FF E I E E 3E FE AE AE 945 REM der CALIBRATE 950 COLOR 7 0 LOCATE 24 57 PRINT F7 955 GOSUB 24000 960 GOTO 45 965 REM 970 975 977 980 985 990 995 996 4
5. The optimum aperture area for trichloroethylene how 10 20 25 30 35 40 45 50 55 60 65 10 ever is about 42 of the area of a full opening i e internal diameter of about 29 mm In each case the pressure during mass analysis was 2 2 X 10 6 torr In view of FIG 5 it is advantageous to provide means for automatically selecting the aperture area during mass analysis to optimum areas for each com pound to be detected For this purpose a photographic iris diaphram was installed in lieu of the 2 mm thick copper disc mass correction lens 15 in FIG 1 There fore the curves as shown in FIG 2 can be obtained by continuously varying the area of the aperture and not ing the change in the ion current for a characteristic ion of a standard sample of the compound to be detected Preferably these tests are run for a number of different compounds and the optimum values are prestored in the memory of the microcomputer 4 Then during analysis of a sample they are recalled from memory for readjusting the aperture area before the scanning of each of the respective fragment ion masses of interest Preferably the system is provided with automatic means for adjusting the aperture area of the mass cor rection lens A proposed device is shown in FIG 6 The iris diaphram 51 is mounted inside a two part vacuum housing 52 which is provided with studs 53 or holes for attachment of the housing to the standard flanged
6. 10010 00509 8000 10020 GOSUB 8409 10030 RETURN 10200 REM MESA LOOKUP TAB SUBROUTINE TO CALL SHOW DIRECTORY AND THEN 10210 GOSUB 8400 et INPUT THE NAME OF FILE TO BE USED BY VIEW 10215 LOCATE 22 5 SPECTRUM 10220 INPUT SPECTRUM DESIRED NRME 10230 GOSUB 9800 GET THE STARTING VALUES ASTART ETC 10240 00508 20000 10245 EFLAGs 10250 RETURN 11000 CLSILOCATE 1 77 ILIST 3L0AD 4SAVE SFILES 7 LPT1 9COLOR 10PALET 10250 RETURN 11000 CLSILOCATE 1 77 COLOR 0 2 0 80 PRINT WALT 11020 COLOR 4 0 0 0 11040 LOCATE 1 111PRINT STARI ANUS 11042 LOCATE 2 113PRINT WIDTH AMU 11044 LOCATE 3 118PRINT RANGE 1X10 11040 LOCATE 1 32 PRINT TIME 11080 LOCATE 2 32 PRINT PRESSURE X10 11100 LOCATE 3 32 PRINT OAIN 11120 LOCATE 1 SSIPRINT DATE 11140 LOCATE 2 SS PRINT OPERATOR 11160 LOCATE 3 5S PRINT IDENTITY 11165 IF FLAGL 1 THEN 11525 11180 LOCATE 1 22 1 0 12 GET START SCAN 11200 00508 12500 11220 ASTART VAL RESPONSES 11225 IF ASTARTC OR ASTART2299 THEN 11190 11240 LOCATE 2 22 1100508 12500 4 GET WIDTH START WIDTH END SCAN 11260 WIDE VAL RESPONSES 1AENDSASTART WIDE 11255 IF AENDKO OR AENDDS00 THEN 11240 11270 ASTARTOAEND THEN 11190 11280 LOCATE 3 22 11G0SUB 12500 GET RANGE 11440 RIVAL RESPONSES 1OPALET 4 757 198 29 30 11440 RASVAL
7. nitrogen and other gases in industry and for the moni toring of thermal decompositions of chemicals during combustion and pyrolysis BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which 20 30 35 40 45 50 55 60 65 4 FIG 1 is a schematic drawing of an apparatus ac cording to a preferred embodiment of the invention including a vacuum controllable sampling manifold and also showing an optimized mass analyzer a special separator system and a control and data system FIG 2 is a detailed drawing of the special separator system FIG 3 is a schematic drawing of the internal con struction of the quadrupole mass spectrometer unit including the electron multiplier FIG 4 is a schematic diagram of the mass filter in the quadrupole unit of FIG 3 FIG 5 shows respective graphs of the relative ion current intensities for benzene and trichloroethylene as a function of the area of the aperture in the mass correc tion lens FIG 6 is a schematic drawing of a control mecha nism for automatic adjustment of the aperture of the mass correction lens FIG 7 is a schematic drawing of the optimized mass analyzer of FIG 1 after the installation of the automatic control mechanism of FIG 6 and an automatic control for variably selecting the operating voltage of the elec tron
8. wherein said high sensitivity electron multiplier is a Channeltron 8 elec tron multiplier 5 The system as claimed in claim 1 wherein said quadrupole mass spectrometer also includes an ionizer for generating ions from said substances and a mass filter disposed about an axis between said ionizer and said electron multiplier for selecting a particular ion mass for transmission from said ionizer to said electron multiplier and wherein said metering device admits said substances to said mass filter in a direction substan tially perpendicular to said axis and said vacuum pump is connected to said ionizer generally along said axis and draws said substances along said axis from said mass filter toward said ionizer 6 The system as claimed in claim 1 wherein the mass correction lens has an aperture area which is selected to optimize the detection of a particular molecular mass in said substances to be detected 7 The system as claimed in claim 6 wherein the mass correction lens has an aperture having an area of about 50 of the area of the passage between the mass spec trometer and the vacuum pump 4 757 198 43 8 The system as claimed claim 7 wherein the passage between the mass spectrometer and the vacuum pump is provided by a pipe having an internal diameter of about 48 mm 9 A system for the analytical determination of or 5 ganic substances in low concentrations by transferring the substances from a source at r
9. 15140 15160 15180 15200 15220 15240 15250 15261 15262 15263 15264 15265 15266 15267 15268 15269 15270 15271 15272 15280 15300 15320 15340 LIST 15360 15380 15400 15420 15440 15460 15480 15500 15620 19000 19001 19002 19003 19004 19005 19006 19007 19008 19010 19020 19040 19060 19080 19100 1LIST 19080 19100 20000 20010 20015 20020 20021 20022 20023 20024 20040 20060 20080 4 757 198 37 38 FEIN 600 FULL MEDIUM FEIN 5 GROB MEDIUM 4 COLOR 7 0 0 0 PALETTE PALETTE 2RUN SLOAD 4SAVE SFILES 6CONT 7 LPT1 8LOCATE 9 COLOR 10FALET PALETTE 412Y1 42 X2 641 Y22282 COLOR 2 0 0 0 REM LINE X1 Y1 X2 Y1 TOP LINE FOR D Y1 TO Y2 STEP 24 LINE X1 D X2 D MITTLE LINES NEXT D COLOR 6 0 LOCATE 4 21PRINT 10 LOCATE 6 31PRINT 9 LOCATE 8 3 PRINT LOCATE 10 3 PRINT 7 E LOCATE 12 3 PRINT 6 LOCATE 14 31PRINT S5 LOCATE 16 3 PRINT 4 LOCATE 18 3 PRINT 3 LOCATE 20 3 PRINT 2 LOCATE 22 3 PRINT 1 LOCATE 24 3 PRINT O COLOR 7 0 0 0 FOR W X1 TO X2 STEP GROB 7 LINE W 2 2 4 Y2 15 NEXT 2RUN SLOAD 45 SFILES 6CONT 7 LPTi 8LOCATE 9COLOR 10PALET FOR WzX1 TO X2 STEP MEDIUM LINE W Y2 2 W 2 8 XT W IF FEIN lt 3 THEN GOTO 15500 FOR W X1 TO 2 STEP FEIN LINE W Y242 ll Y2 4 NEXT W REM RETURN IF AEND ASTART 0 THEN LOCATE 12 40 DATA AVAILABLE GOTO 22020 IF gt 12 THEN RA 12 IF RACS T
10. 400 liters 0 3 110 gl and may include accessory devices for specific purposes such as a lamp 6 for irradiation The reactor 5 is equipped with a heating mantle 7 allowing temperatures of up to 200 C 400 The entire system 1 is evacu ated by means of a turbomolecular pump 8 e g Galileo model PT 60 to a pressure of 10 8 torr The exhaust of the turbomolecular pump 8 is removed by a fore pump 9 e g Edwards model E2 8 The reactor 5 can be separated from the pump system 8 9 by a sliding valve 9 with viton seals In a typical mode of operation solid or liquid samples are introduced into an inlet system 10 After achieving 4 757 198 5 the desired pressure in the inlet system 10 the samples or portions thereof become vaporized The concentra tions in the gas phase can be determined by measuring the pressure The inlet system 10 consists of a stainless steel casing with vacuum tight sealable openings A spring loaded metal rod 11 serves to liberate mechani cally volatile samples kept in standardizable glass capil laries Porcelain boats are available for the introduction of solid samples Placed underneath the inlet system 10 a commercially available combination of variable gas valves 12 e g CJT Vacuum Technik Ramelsbach controls the flow of material into the reactor 5 The sampling manifold 1 may be used at pressures within the range of of 1 10 8 torr and also works with variable volumes of gas mixtures at variab
11. 757 198 17 REM VIEW SPECTRUM COLOR 7 0 LOCATE 24 571PRINT FO GOSUB 10200 GOTO 45 REM 4F 46 4 4F 46 E 4F 3 E 3F E 8 d 3F E 3F 3F E 4F AE IE 3 18 REM INITILIZE DISKETTE EE d E COLOR 7 0 LOCATE 24 57 PRINT F9 GOSUB 9000 1000 GOTO 45 1005 REM 3 4 9 3 I I IE III 1010 REM 2444 RESERVED 4 48 9 9F 46 9F 4F 4F 9F 3F 4F 4F 4F 3 1015 COLOR 7 01LOCATE 24 57 PRINT F10 1020 REM 4 4F 4F 4F dttd IE IE IE IE DIE 1025 1030 1032 1033 1035 14 18 1035 REM s RESERVED 33 3 3 3 4 4 4 3 9 EE 9E 3F 3 t COLOR 7 01 LOCATE 24 57 PRINT F11 GOSUB 40000 GOTO 45 REM 33 4 dd EIER IE 4 IE IEEE IE AR T ZRUN SLOAD 4SAVE SFILES CONT 7 LPT1 SLOCATE 9COLOR 1 REM it JI IHE AE AERE AE 4F 4F 3F 1040 REM xx EXIT TO SYSTEM 3 33 1045 COLOR 7 0 LOCATE 24 57 12 1050 CLS 1055 EN 2CHR 13 1060 KEY 1 LIST 1065 KEY 2 RUN ENS 1070 KEY 3 LOAD CHRS 32 CHRS 34 1075 KEY 4 SAVE CHRS 32 CHRS 34 1080 KEY S5 FILES EN 1085 KEY 6 CONT ENS 1090 KEY 7 34 LPT1 1095 KEY 8
12. IF ASC A 2 77 THEN 5320 280 IF ASC A 275 THEN 5420 5300 IF ASC A 213 THEN PUT N Y1 LIX XOR 5520 310 GOTO 5220 5220 PUT 5 1 11 0 5340 MARK xMARK 1 5360 IF gt 2 THEN N X2 5370 5380 5400 5420 5440 5460 5470 4 757 198 23 24 IF MARK gt AEND THEN MARK AEND PUT N 5 Y1 LIX XOR GOTO 5200 PUT N 5 Y1 LI XOR MARK MARK 1 IF N X1 THEN N X1 1115 2RUN SLOAD 45 SFILES 6CONT 7 LPTi SLOCATE 9COLOR 10PALET 6320 6340 6360 6380 6400 5 1 XOR GOTO 5200 RETURN REM 3t eee SUBROUTINE TO CALCULATE DAC VALUE AMU 3 4 3 3 A 10 B 65535 03333333 D A B AMU 0333333 RESULT E AMU D B sHEX CRESULT 16 LSBS RIGHTS BS 2 L LEN LSBS 3 0 0 FOR I 1 TOL A ASC MIDS LSBS 1 1 IF gt 64 THEN A A 55 GOTO 6300 A A 48 0 0 1 1 NEXT I RES ABS RESULT REA CINT RES D 256 OUT amp H202 D 11157 2RUN SLOAD 4SAVE SFILES 6CONT 7 LPT1 SLOCATE 9COLOR 10PALET 6380 6400 6420 7500 7505 7510 7515 7516 7517 7518 7520 7321 7522 7530 7540 7550 7560 7571 7572 7573 7580 7585 7590 7590 OUT amp H202 D OUT amp H203 REA RETURN REM 3OHieeieei ie SUBROUTINE TO READ PRESSURE R 8 OUT RANGE RANGED R OUT FUNC CONSOLE FIL TP R 11 OUT RANGE RANGED R FOR 20 Q COLOR 4 0 LOCATE 1 32
13. LOCATE 1 1100 KEY 9 COLOR 7 0 0 0 1105 KEY 10 PALETTE 1110 COLOR 7 0 0 0 1115 KEY OFF 1120 SYSTEM 1500 GOSUB 11000 PRINT HEADER AND COLLECT VALUES 1735 GOSUB 8921 LOAD AVALUE X O WITH BACKGROUND 1740 FOR E ASTART TO AEND 1750 GOSUB 6000 BUMP THE AMU 1752 COLOR 4 0 LOCATE 1 42 0 PRINT TIMES 1752 COLOR 4 0 LOCATE 1 42 0 PRINT TIMES 1LIS 0 1752 1753 1760 1770 1780 1790 1800 1810 1820 1850 2000 2001 2002 2010 2020 2025 2030 2035 2040 2080 2100 2120 2140 2160 T 2RUN SLOAD 45 SFILES CONT 7 LPT1 SLOCATE 9COLOR 10PALET COLOR 4 0 1 42 0 PRINT TIMES LOCATE 3 221PRINT R GOSUB 2000 READ IT GOSUB 4000 PLOT IT NEXT E GOSUB 7700 ZERO THE DAC ASSINKEYS IF AS THEN LOCATE 1 42 PRINT TIME GOTO 1800 IF ASC A lt gt 13 THEN GOTO 1800 EFLAGw1 RETURN eee SUBROUTINE TO READ AMP TORR METER 3430 4 9699 IF gt 12 THEN R 12 Je IF RCS THEN 5 OUT RANGE RANGED R IF AIT O THEN GOTO 2040 FOR 1 TO 1000 NEXT AIT O FOR DEL 1 TO 300 NEXT DEL WAIT amp H208 254 255 STATUS INP amp H208 1 OVERRANGE SGN STATUS AND 2 2 IF OVERRANGEs1 THEN GOTO 2530 7 Cu WAIT amp H208 254 255 DIGITO12INP amp H205 0 2180 2200 2220 2240 2260 2280 2300 2320 2340 2360 2380 2400 2420 2440 2460 2470 4 757 198 19 20 IF THEN GOTO 2140 MAIT amp H208 254 255 DIGITO2 INP amp H205 10KsSGN DIGITO2 AN
14. LOCATE 1 42 PRINT TIMES ES GOSUB 2000 TPRESS VALUE RPRESS R COLOR 4 0 LOCATE 2 32 PRINT PRESSURE 10 LOCATE 2 42 PRINT USING VALUE LOCATE 2 50 PRINT R 4 REM REM R27 OUT RANGE RANGED R Pd RETURN RETURN 1LIST 2RUN SLOAD 45 SFILES 6CONT 7 LPT1 SLOCATE COLOR 10PALET 7700 7720 7740 8000 8020 8040 8060 8080 8100 8120 OUT DAC16MSB O OUT DACi6LSB O RETURN REM eeneeeeenee SUBROUTINE CREATE FILE IN THE CROSS REFERENCE REM TABLE FILE JJ 3 E 3 3 JE IE IE IE IE OE E OPEN 1 LOOKUP TAB 40 FIELD 1 8 AS OK 4 AS TP 4 AS 55 4 AS 5 10 AS DEs 8 AS TES GET 1 1 ALLOCATE FIELDS BUFFER 4 4 3 3 3 COUN CVI IF COUN lt O THEN PRINT NO FILE AVAILIABLE GOTO 8360 4 757 198 25 26 8140 K1 COUN 1 8160 LSET OKS MKIS K1 8180 PUT 1 1 8200 LSET 0 8220 DATA INTO THE RECORD BUFFER 8240 LSET DES DATES i 8260 LSET TES TIMES 8280 LSET TPS MKS TPRESS 8300 LSET SS xMKS ASTART 8320 LSET SES MKSS AEND 8340 PUT 1 1 8350 CLOSE 1 8360 RETURN 840 1LIST ZRUN SLOAD 45 SFILES CONT 7 LPT1 S8LOCATE COLOR 10PALET 8400 OPEN R K1 LOOKUP TAB 40 SUBROUTINE TO SHOW THE DIRECTORY 8420 FIELD 41 8 AS OK 4 AS TPS 4 AS 55 4 AS SES 10 A
15. PUT 2RUN SLOAD 4SAVE SFILES 6CONT 7 LPT1 SLOCATE COLOR 10PALET LSET SES MKS AEND PUT 41 2 CLOSE 1 GOSUB 8600 RETURN OPEN R 42 BKGRND 14 SUBROUTINE TO READ BG FROM DISKIH FIELD 82 14 AS AMUNS hes 4 757 198 41 CLOSE 41 FOR CL ASTART TO AEND GET 2 CL AVALUE CL 2 CVS AMUNS NEXT CL CLOSE 2 RETURN REM ASTART 25 FLAGBG 1 AEND 90 GOSUB 24380 GOSUB 20000 FLAGBG O RETURN CLS LOCATE 24 40 PRINT INPUT 707 24400 24410 24420 24430 24440 24450 24460 26000 26010 26020 26030 26040 25045 25050 40000 40001 42 TO DISPLAY STORED BACKGROUND ZERO TO EXIT 7 LPT1 SLOCATE 9COLOR 10PALET STORED BACKGROUND 3333 3 40002 LOCATE 12 40 INPUT AMU VALU 1LIST 2RUN SLOAD 4SAVE SFILES CONT 24440 NEXT CL 24450 CLOSE 2 24460 RETURN 26000 REM six eSUBROUTINE TO DISPLAY 26010 ASTART 25 FLAGBG 1 26020 AEND O 26030 GOSUB 24360 26040 GOSUB 20000 26045 FLAGBG 0 26050 RETURN 40000 CLS 40001 LOCATE 24 40 PRINT INPUT O ZERO TO EXIT 40002 40005 40010 40020 40030 40040 40100 M0110 40120 40130 Ok oooooooo 141871 2RUN IF THEN 40030 GOSUB 6000 GOTO 40001 GOSUB 6000 RETURN CLS SLOAD 4SAVE SFILES ___ What is claimed is 1 A system for the analytical determination of or ganic substances in low concentrations by transferring the substances from a source at a relatively high pres sure int
16. RESPONSES R RA LIST 3040 ASAVE SILES amp CONT 7 amp LOCATE 9COLOR 10PALET 11440 LOCATE 2 65 1 005U8 12500 GET OPERATOR 11465 IF LEN RESPONSES1214 THEN 11440 11490 OPERS RESPONSES 11500 LOCATE 3 65 10058 12500 GET IDENTITY 11505 IF LEN RESPONSES128 THEN 11500 11520 IDENS RESPONSES 11525 LOCATE 1 42 0 PRINT TIMES 11525 LOCATE 1 22 01PRINT ASTART 11527 LOCATE 2 22 0iPRINT AENO ASTART 11528 LOCATE 2 42 01PRINT USING 8 TPRESS LOCATE 2 50 1 PRINT RPRESS 11530 LOCATE 1 65 0sPRINT DATES 11535 LOCATE 3 42 0 PRINT GAIN 11540 GOSUB 15000 60 WRITE THE SCREEN 11560 REM GOSUB 7500 READ THE TOTAL PRESSURE 11580 QUT FUNC CONSOLE F IL MAT 11620 RETURN 11640 11660 11580 11700 11720 174 11760 11780 ILIST RN ASAVE SFILES amp CONT 7 1 LOCATE COLOR 10PALET 11780 11900 7 11820 11840 11860 1860 1 1920 11940 11960 12000 REM 12020 REM 12040 REN 12060 REM 12100 REM 12120 RE 12140 REN 12160 REM 12220 REN 12240 REM 12500 RESPONSESa Mee ee ee SUPROUTIME TO INPUT VALUES HHHH 12510 INKEY IF LEN AS 0 THEN 12540 12530 PRINT 12535 IF AS 300 4SAVE FILES 7 LPT1 SLOCATE COLOR 10PALET 12530 PRINT 12535 IF ASCLAS 213 THEN RETURN 12540 RESPONSE S RESPONSES AS 12550 GOTO 12510
17. THEN 13570 GOTO 13540 RETURN 14000 14010 14020 14030 14040 14050 14060 14070 14080 14090 14100 14110 14120 14130 14140 14140 1LIST 14140 14150 14160 14170 14172 14173 14175 14180 14190 14200 14210 14220 14230 14240 14250 14250 14270 14280 14290 14300 14310 14320 14330 1LIST 14330 14340 14350 14360 14370 14380 14390 14400 14410 14420 14430 14440 14460 14470 14480 14489 14490 14500 14510 14520 14525 14527 14530 1 4 757 198 33 34 REM 34 3E 33e 4 Je E JE 3e 3 3 TIME SCAN SUBROUTINE CLS COLOR 6 0 0 0 INDz1 AFLAG 0 LOCATE 1 67 PRINT TIME SCAN FOR Is4 TO 10 STEP 2 LOCATE 1 67 1 2 1 COLOR 7 0 0 16 I 74 PRINT s LINE 702 1 1 12 719 1 1 12 10 1 3 BF KEY OFF LOCATE 1 74 GOSUB 12500 PKSEL IND lt RESPONSES IF PKSEL IND 0 gt 285 THEN 14080 IF PKSEL IND O 1 THEN PKSEL IND O O IND IND 1 D COLOR 6 0 0 0 COLOR 0 0 0 2RUN 3LOAD 4SAVE SFILES amp CONT 7 LPT1 SLOCATE COLOR 10PALET COLOR 6 0 0 0 NEXT I LOCATE 16 67 PRINT PERIOD LOCATE 17 67 PRINT SECONDS LOCATE 17 67 GO08UB 12500 IF VAL RESPONSE 0 THEN PER 40 GOTO 14175 PER VAL RESPONSES LOCATE 17 67 PRINT PER SECONDS IF PER lt 10 OR PER2900 THEN 14160 MIN 12 SECS LOCATE 12 67 PRINT TOTAL TIME LOCATE 13 47
18. applications illustrate the various fields of application for our mass analyzer sys tem but they are in no way intended to limit the uses or fields to which this invention is capable of being ap plied 1 Determination of work place concentrations of organic chemicals in production units By means of our mass analyzer system the concentra tions of chemicals in factories and production units can be determined and controlled continuously The opti mized analyzer system 2 with the separator system 3 is able to measure directly air samples taken at ambient pressure By using the separator 3 with the optional selector valve 21 FIG 1 samples from different loca tions can be taken Since one spectrum only takes 10 seconds the time dependent work place concentration at different locations can easily be determined and mon itored Also acute maximum concentrations which are extremely important for the evaluation of work place safety can be measured Chemical concentrations of benzene and 1 2 transdichloroethylene for example can be detected to 100 500 ppt 2 Determination of indoor concentrations of chemicals Since the sensitivity of the described gas phase mass analyzer reaches the low ppb to high ppt level the concentrations of pollutants in indoor areas e g homes offices can easily be measured Concentration time diagrams allow the elucidation of the actual indoor exposure to pollutants Pentachlorophenol for exam pl
19. can therefore control the mass spectrometer to scan any desired range or discrete points of the mass spectrum The microcomputer has also been programmed to present the spectrometer data according to several standard formats Scans are per formed prior to analysis to characterize background noise as a function of total pressure and this pre deter mined background noise level is subtracted from the molecule or fragment ion concentration taking into account continuous total pressure monitoring during 4 757 198 7 analysis The total pressure is continuously displayed on the monitor The molecule concentrations are also nor malized taking into account the total pressure in order to display normalized line spectra on the monitor or to output the mass spectra to a printer as listings or graphic matrix reproduction The intensity of freely selectable peaks can be monitored as a function of time The peak intensity can be transmitted in serial RS 232 format to a remote location The microcomputer can perform specific peak mode monitoring of a maximum of eight selected AMU peaks as a function of time The spectra be automatically calibrated for m c and their intensities Quantitation is performed using both second order approximation and suitable calibration substances e g Freons carbon tetrachloride benzene toluene Moreover specified standard spectra can be Stored using five selected fragment ions following suggested
20. i HOLD DATA LET KV3 4 4 D2 1 ACTIVE LET FIL 8 x 03 FILAMENT OFF NEED PULL UP LET TP 16 7 04 1 SELECTED MULT 32 7 DS 1 SELECTED LET FAR 44 06 1 SELECTED LET CONSOLE 128 07 O CONSOLE OFF NEED PULL UP LET K 41 4 10000 LET AIT O TOP 5 100000 TOP 6 1000000 8 1 08 9 1E 09 10 1 10 TOP 11 1E 11 TOP 11 1E 11 12 1 12 8 INIT VALUE LET RANGE amp H207 OUTPUT CHANNEL 0207 RANGE SWITCH LET 10 5 8 LET RANGED S s LET X10 6 9 LET RANGED 4 9 LET 10 7 4 LET RANGED 7 4 LET 10 8 5 LET RANGED 8 5 LET 10 9 2 LET RANGED 9 2 LET 10 10 3 LET RANGED 10 3 88 4 757 198 21 22 3600 LET 10 11 0 3620 LET RANGED 11 0 3620 LET RANGED 11 0 3620 LET RANGED 11 0 3640 LET X10 12 1 3660 LET RANGED 12 1 3680 LET 5 3700 REM INIT VALUE HEX 3720 LET DACI2LSB amp H200 12 BIT DAC LSB o 3740 LET DACiI2MSB amp H201 12 BIT DAC MSB o 3760 LET DACiG6LSB amp H202 16 BIT DAC LSB 3780 LET DACiI6MSB kH203 16 DAC MSB 3800 OUT RANGE RANGED R 3820 CHECK O 3822 AFLAG O 3840 OUT DACiI2LSB O 3860 OUT 12 5 0 3880 OUT DACi6LSB O 3900 OUT DAC16MSB O 3920 LET IREAD amp H205 READ CHANNEL PICOAMMETER 3950 LET MISC amp H208 READ CHANNEL MISC FUNCTIONS 3980 RETURN 4000 REM 3444 SUBROUTINE PLOT GRAPH 3db dinieeneeeeen 40
21. it has been found that the detection limit can be greatly increased by introducing the sample from a central side port 75 FIG 3 in the UTI100C mass spectrometer unit 13 and evacuating the unit from its ionizer end with a turbomolecular pump during mass analysis Also the ion pump 16 in FIG 1 should be used to reduce the partial pressure of the light mole cules in the mass spectrometer unit 13 prior to the intro duction of the sample although it cannot be used during the subsequent mass analysis of the sample since its power supply generates electrical interference with the electrical signal from the Channeltron 6 14 Moreover it is very advantageous to use the mass correction lens 15 in FIG 1 at the inlet to the turbomolecular pump 17 and to select the area of the aperture in the lens in accordance with the mass of the molecules to be de tected Turning now to FIG 5 the criticality of the area of the aperture of the mass correction lens is illustrated along with the dependance of the optimum aperture area as a function of mass of the molecules to be de tected The relative intensity of the detected ions as a percentage of the maximum intensity is plotted as a function of the relative aperture area in terms of the percentage of the maximum aperture area for a full opening having a 45 mm internal diameter The opti mum aperture area for benzene is about 54 of the area of a full opening i e an internal diameter of 33 mm
22. mass spectrometer unit 13 In order to initially put the optimized mass analyzer in a high vacuum state the fore pump 17 is turned on to pump the system down to a low vacuum Then the turbomolecular pump is turned on until a higher vac uum is obtained The system is then baked out by turning on a heat wrap resistance heater 85 which is energized by a triac power control 86 to bring the mass spectrometer unit 13 up to between 200 C to 320 C heat wrap 85 and triac control 86 are supplied by CJT Vacuum 8061 Ramelbach Asbacherstr 6 West Germany After the system is sufficiently baked out to obtain a high vacuum e g better than 10 8 torr the ion pump 16 is turned on to obtain an ultra high vacuum e g better than 10 9 torr Prior to analysis power to the heat wrap 85 is turned off and the spectrometer unit is allowed to cool for about one to two and a half hours depending on the bake out temperature to a final temperature of 150 C or lower For analysis the ion pump 16 is turned off and 20 25 30 35 4 50 pole mass spectrometer of increased sensitivity A high sensitivity electron multiplier is used along with a mass correction lens arranged with respect to a sample inlet and a vacuum source so that the detection limit is 55 60 65 12 then the mass spectrometer 13 is switched on from the UTI control console 76 thereby energizing the RF generator 77 the ionizer filamen
23. negative rods caus ing the selected ions to travel about the axis in a circular orbit and thereby permitting them to travel to the Channeltron where they are detected as an ion cur rent A simplified model of the operation of the mass filter assumes that the resonance condition of the selected ions results from a centripetal acceleration which is known from Newton s law to be related to the electro static force according to mra q where m is the mass of the selected ion is the radius of the centripetal motion about the central axis of the mass filter o is the angular frequency of the alternating potential Vicoswt V jsinot q is the charge of the ion and E is the maximum radial component of the alternat ing electric field at the radius r The maximum radial component Er however is approximately a linear func tion of r according to E r where a is a constant distance the order of the radius of the rods 138 from the central axis and which is re lated to the diameter and spacing of the rods By elimi 4 757 198 9 nating E from the two equations above it is seen that the resonance condition becomes independent of r and the selected mass to charge ratio can be varied by ad justing V or m E 4 oa In practice it is most convenient to adjust V while hold ing constant to obtain a mass spectrum This simplified theory of operation does not take into account the effects of co
24. there is shown a schematic drawing of the internal components of the UTI100C mass spectrometer unit 13 At the bottom is an ionizer 131 in which a thoriated irridium thermionic filament 132 emits electrons which are attracted to a cylindrical grid 133 pass through it and form a negative space charge region 134 within the grid 133 Some of the electrons strike molecules in the gas sample causing them to ionize and the ions are attracted to the negative space charge region 134 The grid 134 is itself positive causing ions to be emitted through a central aperture in a focus plate 136 and travel upward to the Channel tron 6 electron multiplier 14 In order that ions of only a selected mass reach the Channeltron 14 mass filter generally designated 137 is interposed between the ionizer 131 and the Chan 14 The mass filter 137 includes four pre cisely machined rods 138 two of which are charged positive Vo and the other of which are charged negative Vo setting up a quadrupole electric field 139 as shown in FIG 4 This quadrupole electric field 139 has a value of zero on axis and increases from zero as a function of the distance from the axis tending to cause the ions to move away from the positive rods and toward the negative rods But ions of a selected mass or more precisely a selected mass to charge ratio are di verted by an additional alternating potential V 1cosot Visinot between the positive and
25. vac uum connections e g see FIG 8 A ring gear 54 mounted to the iris diaphram 51 is adjusted by a worm gear 55 attached to a control shaft 56 protruding from the housing 52 through a vacuum seal 57 A second ring gear 58 is attached to the control shaft 56 and is selec tively rotated by a servomotor 59 via a worm gear 60 for adjustment of the iris opening The shaft of a multi turn potentiometer 61 is coupled to the control shaft 56 in order to sense the degree of opening of the iris dia phram 51 Ring gear 58 servomotor 59 worm gear 60 multi turn potentiometer 61 and servo error amplifier 62 are generally designated as regulator 32 In order to provide automatic as well as manual ad justment of the iris aperture the servomotor is driven by a servo error amplifier 62 responsive to a command signal on a line 63 The command signal is provided either by a manually set potentiometer 64 or by a digi tal to analog converter 35 driven by an output interface 36 coupled to the microcomputer 4 as selected by a switch 43 The optimized analyzer 2 with the automatic aper ture adjusting mechanism installed is shown in FIG 7 When the aperture 31 of the adjustable mass correction lens 15 is preset to a new area for a new substance as commanded by the computer 4 it is also desirable to automatically adjust the multiplier voltage of the Chan neltron electron multiplier 14 to preselected values which optimize the signal to noise rat
26. 14590 14700 14720 14730 14740 14760 14770 14780 4790 4800 14805 14810 14820 14830 14840 14850 14860 14870 1LIST 14860 14870 14880 14890 14900 14910 14920 14930 14940 14950 14960 14970 14980 14990 14995 15000 15020 15040 PKSEL C IND 1 2VALUE 10 R NEXT IND COL 24 FOR IND 1 TO 4 IF PKSEL IND O 0 THEN 14610 RUSPKSEL IND 4 1 1 PINT2PKSEL IND 1 TOP RU 240 PSET PLOTT BOT PINT COL 3 COL 2COL 42 NEXT IND AFLAG 1 GH GH 1 GOSUB 14960 ASAVE TIMER GOSUB 14960 IF TIMERCASAVE PER THEN 14640 AS INKEYS IF LEN A O THEN 14660 IF ASC A 213 THEN 14665 2RUN SLOAD 4SAVE SFILES 6CONT IF ASC A 13 THEN 14665 NEXT PLOTT IND S J FOR I 5 TO 11 STEP 2 LOCATE I 67 PRINT 9 99410 1 IND IND 1 NEXT I FOR DEL 1 TO BEEP NEXT DEL AS INKEYS IF LEN A 0 THEN 14760 IF ASC A 213 THEN 14760 RETURN NS S 44 S 58 2RUN SLOAD 45 SFILES CONT A AA NNN A A 2 36 7 LPT1 SLOCATE 9COLOR 10PALET 7 LPT1 SLOCATE COLOR 10PALET 7 LPT1 SLOCATE 9COLOR 10PALET REM 3eehneeees SUBROUTINE TO RETURN THE PRESENT TIME IN SECONDS TIMER VAL RIGHTS TIMES 2 3 LOCATE 25 1 1 VAL MIDS TIMES 4 2 60 TIMER T IMER VAL LEFTS TIMES 2 3600 RETURN REM SUBROUTINE TO CREATE A SCALED GRAPH 33d REM CLS FULLZzAEND ASTART 15060 15080 15100 15120 15140 15140 1LIST
27. 15 PRINT F9 Initilize Diskette 620 LOCATE 12 40 625 PRINT F10 Standby 625 PRINT F10 Standby 1LIST 2RUN SLOAD 45 SFILES amp CONT 7 LFT1 SLUCATE COLOR 10FALET 615 PRINT F9 Initilize Diskette 520 LOCATE 12 40 I uo 625 PRINT F10 Standby 630 LOCATE 14 40 635 PRINT F11 Identify Spectrum 540 LOCATE 16 40 545 PRINT F12 Exit to System 550 LOCATE 24 40 555 COLOR 6 0 560 PRINT Selection gt SPRINT 219 565 REM LOCATE 1 1 0 PRINT 670 KEY 1 A 4 757 198 15 16 675 KEY 2 B x 680 KEY 3 C 685 KEY 4 690 KEY 5 E 695 KEY amp 700 KEY 7 G 705 KEY 8 H 710 KEY 9 715 KEY 10 J 720 KEY 11 725 KEY 12 L 730 LIST 2RUN 3LOAD 45 SFILES 6CONT 7 LPT1 SLOCATE 9COLOR 10FALET 730 IF RIGHTS TIME 2 RIGHTS TEMES 2 THEN 745 ELSE 735 735 LOCATE 1 32 0 COLOR 4 0 0 0 SLOCATE 1 42 PRINT TIMES TEMES TIMES 745 CMD sINKEYS 1IF CMD THEN GOTO 730 750 IF CMDS A THEN GOTO 810 755 IF CMDS B THEN GOTO 835 760 IF CMDS C THEN GOTO 855 765 IF CMD D THEN GOTO 875 770 IF CMD E THEN GOTO 895 775 IF CMD F THEN GOTO 920 780 IF CMDS G THEN GOTO 940 785 IF CMD H THEN GOTO 965 790 IF CMDS I THEN GOTO 985 79 IF CMDS J THEN GOTO 1005 800 IF CMDS K THEN GOTO 1020 808 IF CMD L THEN GOTO 1035 806 GOTO 500 810 REM 3s READ SPECTRUM
28. 20 REM 4040 REM 4060 ARANGEZAVALUE E 2 AVALUE E 0O 4065 4070 IF ARANGE lt O THEN ARANGE 0 4075 AVALUE E 1 ARANGE 4080 STARTzARANGE TOP RA 1 240 LPRINT E START 4100 TEPx 600 AEND ASTART 4110 IF START 2240 THEN START 240 LINE K TEP 1 Y1 K TEP 1 Y1 6 2 4120 LINE K TEP 1 2 START CK TEP 1 2 2 6 4140 4160 RETURN 5000 REM DIM LI 303 7 MARKER SUBROUTINE 9F 9F 4F 4F 4 3F E 9E E IEEE de E 4F 4F 3F 4F 4 3F 5020 1 411 2 541 5040 1 286 5060 2 299 5080 1 30 MARKxASTART 5100 LINE 1 8 2 7 5101 LINE 1 5 1 8 7 5102 LINE N Y1 N 5 Y1 9 7 5103 LINE N 5 Y148 N 5 Y148 7 PAINT 1 2 2 7 5120 GET N 5 Y1 ON 5 Y2 L IX 5140 PUT N 5 Y1 LI4 XOR 5150 LOCATE 1 77 COLOR 0 4 0 146 PRINT 5160 1 5180 PUT 5 1 XOR 5200 COLOR 6 0 0 16 KEY OFF LOCATE 14 73 0 12 MARK 5210 LOCATE 15 73 200 COLOR 6 0 0 16 KEY OFF LOCATE 14 73 0 12 PRINT MARK 5210 LOCATE 15 73 PRINT USING 44 amp AVALUE MARK 1 AVALUE MARK 5211 COLOR 7 0 0 0 D 5220 ASmINKEYSIIF lt gt 5220 5225 LOCATE 1 421PRINT TIMES A INKEY IF AS THEN 225 ELSE IF LEN A 21 THEN AS RIGHTS AS 1 5238 REM 3239 REM 5240 IF ASC A 72 THEN RA RA 1 GOSUB 12000 GOTO 5020 5250 IF ASC AS 60 THEN RA RA 1 GOSUB 19000 50 0 5020 5220
29. D 276 IF 0 THEN GOTO 2200 WAIT amp H208 254 255 STATUS INP amp H208 DIGITOSmINP amp H205 OK SGN DIGITO3 AND 2 7 IF OK 0 THEN GOTO 2260 OVERRANGE SGN STATUS AND 2 2 IF OVERRANGE 1 THEN GOTO 2470 DIGITIA 15 AND DIGITO DIGITZA 15 AND DIGITO2 DIGIT3A 15 AND DIGITO3 VALUESDIGIT1A DIGIT2A 1 DIGIT3A 01 REM IF CHECK 0 THEN GOTO 2500 IF VALUEX 8 AND VALUE 0 THEN R R 1 IF R 13 AND VALUECX 8 THEN 2500 IF R 13 HEN 2500 AIT 11GOTO 2000 2480 2490 2500 2515 2520 2530 2530 2540 2550 2560 2570 3000 3020 3040 3060 3080 3100 3120 3140 3160 3180 3200 3220 3240 3260 3280 3290 3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310 3320 3340 3340 3380 3400 3420 3450 3460 3480 3500 3520 3540 3560 3580 IF VALUE29 5 THEN R R 1 2AIT 1 GOTO 2000 IF VALUE O THEN R R 2 AIT 13GOTO 2000 AVALUE E 1 VALUE AVALUE CE 2 amp VALUE 10 R GOTO 2570 VALUE 9 99 VALUE 9 99 REM BEEP 1 1 GOTO 2460 RETURN REM REM REM 5 REM333 4 4 4 4 4 3 4 3 3 DEF INE I O 339 39 t 9 4 9 J JEJE HE E EE IEEE REMH 46 26 6 I Ib ORE HE LET FUNC amp H206 OUTPUT CHANNEL 0206 FUNCTION REM 4 4F 9F 40 46 46 96 46 E E E E E LET 2 7 Di
30. E I 2 lt AVALUE I 1 2 OR 1 285 THEN 13330 13290 Z AVALUE I 2 3 13300 AVALUE I 2 AVALUE I 1 2 AVALUE I 3 AVALUE 1 1 3 13310 AVALUE I 1 2 Z 1 1 3 13320 1 13330 NEXT I 13340 IF S21 THEN 13250 END SORT tiet ite 13341 13342 13342 ur 1L IST 2RUN 4SAVE SFILES 6 7 LPT1 SLOCATE 9COLOR 10PALET 13343 13344 13350 1 AC AEND 6 2 0 FOR IsASTART AEND TEMP2 TEMP2 AVALUE 1 1 NEXT I MAXPK AVALUE AB 2 13400 FOR I AB TO STEP 1 13405 IF AVALUE I 1 20 THEN X I 1E 13 G0TO 13420 13410 X I AVALUECI 2 MAXPK 100 1 20 NEXT 13430 13440 7 13450 13460 AB ASTART AC ASTART 7 13470 I AEND 1 TO AEND 6 1 13430 13490 13500 13510 13520 13530 1353 LIST 13530 13535 13536 13540 13542 13550 13550 13570 LOCATE 10 INC 11 PRINT AVALUE I 3 MASS LOCATE 10 INC 17 PRINT USING amp 44 AVALUECI 2 INTENSITY LOCATE 10 INC 3O PRINT USING 44 AES X 1 CALCULATED LOCATE 10 44 USING 7777 s AVALUE I O BACKGROUND INC INC 2 NEXT I 2RUN 3LOAD 45 SFILES 7 LPT1 SLOCATE COLOR 10PALET NEXT I LOCATE 1 77 COLOR 0 4 0 16 PRINT COLOR 6 0 0 0 AS INKEY IF AS lt gt THEN 13540 AS INKEYS IF A THEN 13542 ELSE IF LEN A 21 THEN AS RIGHTS AS 1 IF ASC A 213
31. HEN RA 5 CLS1FLAG1 1 GOSUB FLAG1 O LOCATE 3 22 PRINT RA 11000 LOCATE 3 65 PRINT AMES LOCATE 2 22 PRINT AEND LOCATE 2 65 PRINT OPERS GOSUB 15000 K 41 FOR E ASTART TO AEND GOSUB 4000 NEXT E 2RUN SLOAD 4SAVE SFILES CONT 7 LFT1 SLOCATE COLOR 10FALET NEXT E RETURN IF AEND ASTART 0 THEN LOCATE 12 40 0 PRINT NO DATA AVAILABLE GOTI 22020 REM FLAG1 1 GOSUB 11000 K 413FLAG1 0 FPLAGBG 1 THEN 20022 ELSE 20040 FOR E1L ASTART TO AEND AVALUE E1 0 0 NEXT Ei FOR E ASTART AEND GOSUB 4000 NEXT 20090 20100 22000 22001 22002 22003 22010 22020 24000 24001 24001 1LIST 24000 24001 24002 24010 24040 24045 24050 24055 24060 24061 4 757 198 39 49 LOCATE 3 22 PRINT RA COLOR 4 LOCATE 1 42 PRINT TIMES REM GOSUB 7500 DISPLAY TOTAL PRESSURE REM REM 0 THEN 20100 REM IF ASC A lt gt 13 THEN 20100 GOSUB 50600 RETURN REM SUBROUTINE CALIBRATE 9 EHH CLS COLOR 5 0 0 16 LOCATE 10 38 CLS COLOR 6 0 0 16 LOCATE 10 38 ARUN SLOAD 4SAVE SFILES CONT 7 LPT1 SLOCATE 9COLOR LOPALET REM 442 SUBROUTINE TO CALIBRATE CLS COLOR 6 0 0 16 LOCATE 10 38 PRINT Calibrating One Moment Please 10 E 28 GOSUB 5000 OUT RANGE RANGED R OUT FUNC CONSOLE FIL FAR FOR 1 3000 NEXT A GOSUB 2000 IF VALUE
32. N PUMP aQ UNIT 27970 ase UIT COWTAUK COWSOLE OPTIMIZED MASS ANALVZER IGG 1 5 Patent Jul 12 1988 Sheet 6 of 6 4 757 198 UTI MASS SPECTROMETEPE 7 73 VARIABLE LLAK VALVE NLL BE GATE VALVE GI ila ir TETY MOUNT 8 OFTIMIZLO MASS 2 17029 4 757 198 1 MASS ANALYZER SYSTEM FOR THE DIRECT DETERMINATION OF ORGANIC COMPOUNDS IN PPB AND HIGH PPT CONCENTRATIONS IN THE GAS PHASE RELATED APPLICATIONS The present application is a continuation in part of U S application Ser No 840 496 filed Mar 17 1986 BACKGROUND OF THE INVENTION 1 Field of the Invention The invention relates generally to the field of mass analysis The invention more specifically relates to a method and apparatus for gas phase analysis of organic compounds at low concentrations in test samples 2 Description of the Prior Art 5 generally well known problems associated with mass analyzers limit the range of concentrations over which organic compounds can be detected and ana lyzed in the gas phase Test samples usually must be concentrated in an enrichment step prior to analysis Because complicated procedures for taking the sample and concentrating it cannot be standardized consider able deviation and error in measurement occur Consid erable amounts of the test sample are lost
33. PRINT PER 540 40 MINUTES LOCATE 14 67 PRINT USING 44 44 PER 540 60 60 LOCATE 14 73 PRINT HOURS TOP LEFT 41 BOT 246 RIGHT 581 LINE LEFT TOP LEFT BOT 2 LINE LERT BOT RIGHT BOT 2 FOR AQ TOP BOT STEP 24 LINE LEFT 5 AQ RIGHT 40 2 NEXT AQ Di INC 9 ZAHL 0 KEY FOR AsLEFT TO RIGHT STEP INC LINE 5 2 NXTeA SILOCATE 23 67 PRINT M I N U T E S LOCATE 22 NXT PRINT MID TR ZAHL 2 1 REM IF ZAHL lt 9 THEN 14390 ZRUN SLOAD 45 SFILES CONT 7 LPT1 8LOCATE 9 COLOR 10PALET REM IF ZAHL lt 9 THEN 14390 LOCATE 23 NXT PRINT MIDS STRS ZAHL 3 1 REM IF ZAHL lt 99 THEN 14390 LOCATE 24 NXT PRINT MIDS STRS ZAHL 4 1 REM IF ZAHL lt 999 THEN 14390 LOCATE 25 NXT PRINT MIDS STRS ZAHL 5 1 ZAHL ZAHL PER 9 60 NEXT A REM FOR EW 1 TO 21 STEP 2 READ ZAHL LOCATE EW 2 PRINT USING 44 ZAHL NEXT DATA 10 9 8 7 6 5 4 3 2 1 0 RESTORE GH OtRA 11 FOR PLOTT LEFT TO RIGHT FOR IND 1 TO 4 E PKSEL IND O IF E O THEN 14560 GOSUB 6000 IF AFLAG 1 THEN R PKSEL IND 4 1 GOSUB 2000 1LIST 14527 14530 14540 4 757 198 35 ZRUN SLOAD 4SAVE SFILES amp 6CONT IF AFLAG 1 THEN R PKSEL IND 4 1 GOSUB 2000 IF AFLAG O THEN PKSEL IND 4 1 2R 14545 14550 14580 14555 14570 14572 14575 14580 14590 14600 14610 14612 14615 14620 14630 14640 14650 14651 14652 14653 ILIST 14653 14660 14665 14670 14680
34. S DES 8 AS TES 8421 GET 1 1 f 8422 COUN CVI OK CLS 8423 ASTART CVI SSS 8424 AEND CVI SES 8430 PRINT 6 20 RNG TAB 25 START TAB 32 END TAB 40 DAT TAB S1 TIME PRINT 8440 FOR Ki 2 TO COUN 8460 GET 1 K1 8461 PRINT USING K1 8462 PRINT TAB 5 8463 PRINT 8464 PRINT TAB 7 8465 PRINT OK 8466 PRINT 20 8467 PRINT USING 44 CUSCTP 8468 PRINT 25 8469 PRINT USING CVS SS 8470 PRINT TAB 31 8471 PRINT USING CVS SE 8472 PRINT TAB 37 8473 PRINT DE 8474 PRINT T 1LIST 0 2RUN SLOAD 4SAVE SFILES 6CONT 7 LPT1 8LOCATE 9COLOR 10PALET 8475 PRINT TES 8500 NEXT 8520 REM CLOSE 1 8540 RETURN 8600 OPEN 2 14 SUBROUTINE TO STORE THE CONTENTS OF AVALUE X 2 8635 FIELD 42 14 AS AMUNS ss ON DISK ENTER WITH ASTART AND AEND INITIALIZED 8640 FOR CLsASTART TO AEND FILE NAME IN AMES 8660 LSET AMUNSxMKSS AVALUE CL 2 9680 PUT 2 CL 8700 NEXT CL 8720 CLOSE 2 8740 RETURN 8800 REM HF 4F 0 3F SUBROUTINE READ THE OF DATA FILE 8801 REM OUT OF THE CROSS REFERENCE FILE CALLED 8802 REM LOOKUP TAB IDENTIFIED BY NRME REMOVE 8803 REM ASTART AEND DATA AND XFER THE DATA TO THE 8804 REM ARRAY AVALUE X 2 8805 REM
35. United States Patent Korte et al 54 MASS ANALYZER SYSTEM FOR THE DIRECT DETERMINATION OF ORGANIC COMPOUNDS IN PPB AND HIGH PPT CONCENTRATIONS IN THE GAS PHASE 75 Inventors Friedhelm Korte Ahmet H Parlar both of Attenkirchen Fed Rep of Germany Frederick Coulston Alamogordo N Mex Coulston International Corporation Albany N Y 21 Appl 910 371 22 Filed Sep 22 1986 73 Assignee Related U S Application Data 63 gt Continuation in part of Ser No 840 496 Mar 17 1986 30 Foreign Application Priority Data Mar 22 1985 DE Fed Rep of Germany 3510378 1 59 44 52 US Cl 250 288 250 282 250 289 58 Field of Search 250 281 282 288 289 56 References Cited U S PATENT DOCUMENTS 2 610 300 9 1952 Walton et al 250 288 2 714 164 7 1955 Riggle et al 250 289 SIAN i VACUUM CONTROLLABLE SAMPLING a 4 757 198 Jul 12 1988 11 Patent Number 4 Date of Patent 3 187 179 6 1965 Craig et al 250 289 3 700 893 10 1972 Seidenberg et al 250 289 4 442 353 4 1984 Baubron 250 288 4 672 203 6 1987 Holkeboer 250 289 Primary Examiner Bruce C Anderson Attorney Agent or Firm Leydig Voit amp Mayer 57 ABSTRACT A single stage quadr
36. area of said aperture to a different optimum area for the detection of each of said substances 12 The system as claimed in claim 11 wherein the optimum area for each substance is prestored in mem ory in said data processor 13 The system as claimed in claim 11 further com prising an automatic device for adjusting an operating 45 value of said electron multiplier in response to data transmitted by said data processing unit and wherein Said data processing unit is programmed to adjust said operating value of said electron multiplier to respective 50 15 20 25 30 40 55 65 44 different values for different ions from said substances 14 The system as claimed in claim 13 wherein said operating value is the gain of said multiplier and said automatic device adjusts the value of high voltage ap plied to said electron multiplier to cause electron multi plication 15 The system as claimed in claim 14 wherein said operating value is predetermined for the mass of each of said ions to optimize the signal to noise ratio of detec tion of the ions and the predetermined operating values are stored a memory of said data processing unit and later recalled for automatic adjustment during mass analysis 16 A method of using a quadrupole mass spectrome ter for the analytic determination of organic substances in low concentration by the steps of 1 admitting a flow of said substances through a metering device t
37. be used economically for onsite sampling and monitor ing or controlling industrial processes 4 757 198 13 14 APPENDIX MASS SPECTROMETER CONTROL PROGRAM FOR THE TEXAS INSTRUMENTS PROFESSIONAL COMPUTER BASIC VERSION 1 10 i tiomal and Gesellschaft Fur 1986 StrahleR Und Umweltforschung mbH 1LIST ZRUN S3LOAD 4SAVE SFILES 6CONT 7 LPT1 SLOCATE COLOR 10FALET BKGRND Ok LOAD GSF Ok LIST 5 KEY OFF 6 CLEAR 10 DIM LIX 303 15 DIM PKSEL 16 16 20 DIM RANGED 13 30 DIM AVALUE 301 3 31 DIM X 300 35 DIM TOP 13 45 GOSUB 3000 INITILIZE 50 COLOR 2 60 LOCATE 1 10 70 41 90 GOTO 500 lt MASTER MENU 500 REM wT SUBROUTINE MASTER MENU 505 CLStKEY OFF 510 LOCATE 3 23 515 COLOR 0 2 0 64 520 PRINT 1LIST 2RUN SLOAD 4SAVE SFILES 6CONT 7 LPT1 SLOCATE COLOR 1 515 COLOR 0 2 0 64 520 PRINT SYSTEM MENU 525 COLOR 6 0 0 0 S30 LOCATE 6 5 35 PRINT F1 Read Spectrum 40 LOCATE 8 5 545 PRINT F2 Save Spectrum 550 LOCATE 10 5 E 555 PRINT Read Total Pressure 560 LOCATE 12 5 555 PRINT F4 Display Background 70 LOCATE 14 5 575 PRINT FS Time Scan 580 LOCATE 15 5 585 PRINT F Print Routines 590 LOCATE 6 40 595 PRINT FZ Calibrate 600 LOCATE 8 40 605 PRINT FS View Spectrum 610 LOCATE 10 40 6
38. by the use of gas sampling devices such as gas syringes for transfer of the concentrated sample to the analyzer Additionally gas phase reactions continue during transfer of the sam ple to the analyzer further impairing the analysis Very rarely is the detector satisfactorily combined with the sampling or reaction volume and in such cases the systems are based on special spectroscopic methods Conventional mass analyzers cannot be used for the direct detection and measurement of organic com pounds in ppb concentrations The low signal to noise ratio at regular pressures of 10 4 to 10 6 torr prevents analysis in the ppb range A straight increase in the vacuum reduces the concentration of the chemicals below the detection limit These conventional mass analyzers include single stage magnet sector units and more recently introduced single stage quadrupole units No practical device for directly analyzing chemicals in the gas phase in ppb concentrations was previously available which operated without a preliminary enrich ment concentration step For a mass analyzer using a single stage magnet sector to obtain the required resolu tion and sensitivity a very large magnet is required resulting in a very massive machine An alternative approach is to use two or more stages of magnet sectors or quadrupole units in which the first stage in effect provides a preliminary enrichment or concentration for the second step Such multiple stage mac
39. e be detected down to 40 55 ug m 3 Analysis of aqueous and solid samples studies of water and soil samples After placing aqueous or solid samples into the inlet system 10 the volatile compounds are transferred into the gas phase by the high vacuum and analyzed in the way described above CO from sand for example has been detected by means of our invention at 10 ppb and the detection limit is about 100 ppt 4 Determination of the photostability of organic compounds The material to be examined is placed on a suitable carrier e g on a cold finger by dissolving the material applying on the cold finger and evaporating the solvent or placing the material directly on the cold finger e g plastic foils and irradiated by external light sources 6 with variable wave lengths The volatile photoproducts 5 10 25 30 40 45 50 65 8 determined by the mass analyzer system the con centrations are determined by measuring the pressure 5 Monitoring of inhalation experiments Our analyzer can be used particularly well for the monitoring of toxicological inhalation studies since both the administered chemicals and the substances exhaled by the animal can be measured over any desired period of time Acetylacetone benzene tetrachlorome thane freons 11 and 12 benzaldehyde chlorobenzene and 1 2 transdichloroethylene for example can be de tected down to 100 to 500 ppt Turning now to FIG 3
40. e molecules to be detected remain in the quadrupole sens ing unit and thereby increases their concentration in the sensing unit relative to the population of the back ground molecules This hypothesis is supported by the discovery that there are respective optimum areas of the aperture of the mass correction lens for various sub stances to be detected In any event the improved performance is surprising in view of the fact that at low pressures the mean free path of the molecules is much greater than the physical dimensions of the quadrupole sensing unit and normal non linearties were previously observed at pressures above 1x 10 5 Torr These normal non linearities were attributed to the molecular collisional effects and were previously minimized by operating the ionizer of the quadrupole unit at reduced electron emission current settings The effect of the aperture area of the mass correction lens and the variation of the optimum area for various substances are so striking that in accordance with an important aspect of the present invention the mass correction lens is provided with means for variably selecting the area of the aperture for the specific sub stance to be detected If the concentrations of a number 4 757 198 3 of substances of varying molecular weights are to be determined the aperture area is preferably reset a num ber of times during the mass scanning process to use respective optimum values when scanning the f
41. ed by an RF generator 77 by the Uthe Co but it does not have any operator adjusted con trols The control console 76 also provides the power supplied to the Channeltron 6 which was supplied by the Uthe Co The ion pump 16 is powered by an ion pump control unit 78 The ion pump is a Varion No BL S No 911 505 with a magnet No 911 0030 from Varion Co 700 Stuttgart 8 Handwerk str 5 7 West Germany The ion pump control unit is part No 929 0062 supplied by Varion The turbomolecular pump 17 is an Electronana model ETP63180 controlled by a control unit 90 model No CST 100 distributed by Vacuum Technik GMBH 8061 Ramelbach Asbacherstr 6 West Germany The turbomolecular pump 17 is run continuously at 6 000 RPM and is cooled by a heat sink 79 and a fan 80 To prevent backflow of lubricating oil mist an in line filter 84 Model No TX075 by MDC Vacuum Products Corp 23842 Cabot Blvd Haward Calif 94545 con nects the turbomolecular pump 17 to its associated fore pump 17 The fore pump 17 is part No ZM2004 sup plied by Alcatel 7 Ponds St Hanover Mass 102339 reduce vibration to the mass spectrometer unit 13 the turbomolecular pump 17 is mounted to the cart 70 via rubber mounts 81 type SLM 1 supplied by Barry Controls GmbH D6096 Raunheim West Germany The mass spectrometer unit is also more directly mounted to the top of the cart via rubber mounts 82 and a beam 83 which is clamped to the outer shell of the
42. elatively high pressure into the mass analyzer at a low pressure said system comprising a a metering device by which the source is selec tively connectable to the mass analyzer for trans ferring the substances b a quadrupole mass spectrometer having a high sensitivity electron multiplier in said mass analyzer c a vacuum pump for creating a source of vacuum to said quadrupole mass spectrometer and d a mass correction lens disposed between said quadrupole mass spectrometer and said vacuum pump for regulating the flow if said substances from said quadrupole mass spectrometer toward said vacuum pump and e means for adjsting an aperture in said mass correc tion lens such that substances are detactable with increased sensitivity by said quadrupole mass spec trometer 10 The system as claimed in claim 9 further compris ing a data processing unit and an automatic adjusting device for adjusting the area of said aperture in response to data transmitted by said data processing unit to said automatic adjusting device 11 The system as claimed in claim 10 wherein said data processing device includes means for commanding said quadrupole mass spectrometer to analyze the con centrations of a number of different substances in said sample and wherein said data processing device is pro 35 grammed to command said quadrupole mass spectrome ter to analyze the concentrations of said substances and is also programmed to adjust the
43. f detection for different ion masses
44. hines are more complicated and still tend to be physically large Their relatively large size and high cost generally preclude their use for on site sampling or the continuous moni toring of industrial processes BRIEF SUMMARY OF THE INVENTION The primary object of the invention is to provide a method and apparatus for analyzing chemicals in the gas phase at ppb and high ppt concentrations without a preliminary concentration step A specific object of the invention is to provide a single stage quadrupole mass analyzer with increased sensitivity capable of detection even at pressures of 10 9 torr 5 10 20 25 30 35 40 45 50 55 65 2 Another object of the invention is to provide a quad rupole mass analyzer of increased sensitivity with a more efficient device for transferring samples to the detector of the analyzer Yet another object of the invention is to provide an economical and portable mass analyzer of increased sensitivity for on site sampling and continuous monitor ing of industrial processes Briefly in accordance with a primary aspect of the invention the method comprises transferring organic substances from a storage vessel or reservoir at high pressure through a metering device into a quadrupole mass analyzer at low pressure decreasing the concen tration of the substances by evacuating the mass analy zer to pressures below usual operating conditions and detecting the substances with a
45. ingly this invention is useful for a variety of applications requiring the measurement of ppb and high ppt concentrations of chemicals The invention was used for the determination of work place concentrations of chemicals in production units e g benzene and 1 2 transdichloroethylene detection limit 100 500 ppt indoor concentration of chemicals of homes offices etc pentachloro phenol detection limit 40 55 ug m analysis of water and soil samples benzene from water detection limit 10 ppb from sand detection limit 100 ppt determination of the photostability of organic compounds determination of toxic compounds in inha lation chambers acetylacetone benzene tetra chloromethane freons 11 and 12 benzaldehyde chloro benzene 1 2 transdichloreothylene detection limit 100 500 ppt Also the invention can be used for the determination of blood alcohol of volatile compounds in urine of chlorinated hydrocarbons in fat tissues of volatile products in sewage sludge in slag of waste incineration and in fly ash for the monitoring of atmo spheric concentrations of chemicals pollutants such as NOx SO and organic environmental chemicals of exhaust fumes of internal combustion machines for the indentification and quantification of industrial gas phase reactions e g NH3 synthesis of thermal degradability of raw materials used in the semiconductor industry for the determination of gases such as hydrogen helium
46. io of the detection process for the ions corresponding to the substance For this purpose regulator 39 of the Channeltron B power supply is controlled in response to a central signal A switch 40 is provided to obtain the control signal from either another digital to analog converter 38 driven by the output interface 36 or from a manually adjustable potentiometer 42 Turning now to FIGS 8 and 9 there is shown a scale drawing of a mobile version of the optimized mass ana lyzer 2 of FIG 1 mounted on a cart 70 having a frame of which is 32 high 24 wide and 32 deep Instead of the sampling valves of FIG 2 there is provided a flanged sample inlet 71 and a variable leak valve 72 4 757 198 1i Series 203 by Granville Phillips Co of Boulder Colo rado having a digital readout 73 indicating a multitude of possible settings To quickly shut off the inlet flow an inlet valve 74 is placed in series between the variable leak valve 72 and an inlet pipe 75 attached to the mass spectrometer unit 13 See the back side in FIG 9 The controls for the system 2 are shown in FIG 8 on the front of the cart The mass spectrometer unit 13 is controlled by a UTI control console 76 which indicates the ion mass being scanned in AMU and the vacuum in the spectrometer unit in torr The vacuum is sensed from the electrical conditions in the ionizer 131 in FIG 3 The alternating voltage for the mass filter 137 in FIG 3 is provid
47. le pressures The optimized mass analyzer system 2 consists of a quadrupole mass spectrometer unit 13 UTI model 100 02 including a Channeltron electron multiplier 14 The quadrupole mass spectrometer unit 13 is further described in the UTI100C Precision Mass Analyzer Operating and Service Manual Uthe Technology International 325 North Mathilda Avenue Sunnyvale California 94086 1979 which is incorporated by refer ence herein The UTI100C unit 13 is sold along with a control unit 76 in FIG 8 which enables manual opera tion and provides an interface for direct connection to a standard microcomputer 4 which provides the control and data system Without the modifications described below the UTI100C was found to have a detection limit for nitrogen of 10 14 torr 0 1 ppm In accordance with an important aspect of the inven tion the quadrupole unit 13 was further optimized by installing an ion pump 16 e g Varian Vaciono 8 1 5 at a right angle a mass analyzer turbomolecular pump 17 and a mass correction lens 15 installed at the inlet of the 10 15 20 25 30 35 turbomolecular pump The mass correction lens is copper disc having an outer diameter of 48 mm a thick ness of 2 mm and an aperture of from about 20 mm to 45 mm which should be selected for the particular sub stance to be detected as further described below The exhaust of the turbomolecular pump 17 is eliminated by an associated fore pum
48. llisions between ions or ions and molecules which might occur in the mass spectrom eter unit 13 and tend to disturb the highly selective resonance condition Although the low pressures in the unit during mass analysis insures that intermolecular collisions are infrequent they are manifested by the so called normal non linearities which appear at pres sures greater than about 1 10 5 torr These effects have previously been minimized by operating the ther mionic filament 132 FIG 3 at reduced emission cur rents Apparently this reduces the normal non linearties by reducing the ionization rate in the ionizer so that nonlinear effects caused by ion ion interactions such as inter ion collisions or the build up of an ion space charge in the mass filter 137 are reduced Experimentation with the UTI100C however re vealed that the placement and orientation of the inlet and pumps had a critical effect on the mass spectrome ter s detection limit Apparently these factors affect the detection limit by preferentially affecting the flow of the background constituents e g 2 in an air sample relative to the ions to be detected and also tend to shield the highly sensitive Channeltron 6 from interfer ence which would otherwise be caused by the flow of the sample toward rather than away from the Channel tron if the vacuum pumping system is on during sensing to preferentially deplete the background con centration In any event
49. lt C 8 THEN R R 1 IF R 12 AND VALUE lt amp THEN 20470 IF 13 THEN R 12 G OTO 24050 24062 24063 24070 24080 24085 24090 24100 24120 24121 24122 24123 24130 24140 1LIST 24130 4140 4160 24180 24200 24220 24230 24240 242550 24260 24265 24270 24280 24290 24300 24303 24304 24305 24306 24307 24308 24309 24310 24311 iLIST 24310 24311 24312 24320 24370 24380 24390 IF VALUE 9 5 THEN R R 1 IF 5 THEN R amp GOTO 24050 IF VALUE 0 THEN R R 1 GOTU 24050 VALY R FARVAL VALUE LOCATE 11 40 0 PRINT FARVALZ FARVAL X10 R R 7 OUT RANGE RANGED R OUT FUNC CONSOLE FIL MULT FOR A 1 TO 2000 NEXT GOSUB 2000 IF VALUEC 8 THEN IF R 12 THEN 24130 ELSE R R 1 GUTO 24090 IF VALUE 9 5 THEN R R 1 GOTO 24090 IF VALUE O THEN R R 1 GOTO 24090 VAL XxR MU 2RUN 3LOAD 4SAVE SFILES 6CONT 7 LPT1 OCATE 9 COLOR 10PALET VALX R MULTVALSVALUE LOCATE 12 40 0 PRINT MULTVAL MULTVAL X10 R LOCATE 13 40 0 GAIN MULTVAL amp 10 C VALX CFARVAL 107 C VALY TPRINT GAINZ GAIN REM FOR 1 TO LOCATE 14 38 PRINT Reading Background One Moment Please CHECK 1 5 25 AEND 90 FOR EsASTART TO AEND GOSUB 6000 GOSUB 2000 NEXT E AME BKGRND R 1 LOOKUP TAB 40 FIELD 1 8 AS OK 4 AS 4 AS SS 4 AS 5 10 AS DE 9 AS TES LSET OKS AMES LSET DES DATES LSET TES TIMES LSET TP MKS R LSET SS MKS ASTART LSET SES MKS AEND
50. mass analyzer 2 in such a way that the neces sary levels for both pressure and concentration of the materials in the mass spectrometer are achieved In case these operating parameters exist already in the manifold 1 the manifold 1 and mass analyzer system 2 can be connected directly via valve 18 A control and data system 4 FIG 1 uses a Texas Instruments Portable Professional microcomputer for interpretation and storage of information about the state of the system The microcomputer includes a TMS 9995 microprocessor board 16 bit microprocessor with 8 bit data bus 73 commands 3 0 MHz system frequency floppy disc control RS 232c 64 K byte storage double Euroboard format an RS 232 input board single Euro board format an input board 16 bit single Euroboard format an output board 16 bit single Euroboard for mat a color video board high resolution 512X512 single Euroboard format a first D A converter board 12 bit resolution single Euroboard format a second D A converter board 16 bit resolution single Euro board format an E Bus back wall board single Euro board format a power supply 5 15 V with overwattage protection and current limiter a high resolution color monitor a system chassis a VT 100 compatible keyboard a dual Floppy Disk DSDD an interface cable for the UTI 100c 02 quadrupole spec trometer 13 and a housing for the processor and moni tor The microcomputer was programmed to perfo
51. multiplier FIG 8 is a front elevation view of the optimized mass analyzer and microcomputer of FIG 1 mounted on a cart to provide on site sampling and FIG 9 is a rear elevation view of the system of FIG 1 drawn to scale to illustrate the arrangement of the quadrupole sensor unit with respect to the sample inlet ion pump mass correction lens and turbomolecular pump While the invention is susceptible to various modifi cations and alternative forms specific embodiments thereof have been shown by way of example in the drawings and will herein be described in detail It should be understood however that it is not intended to limit the invention to the particular forms disclosed but on the contrary the intention is to cover all modifi cations equivalents and alternatives falling within the spirit and scope of the invention as defined by the ap pended claims DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to FIGS 1 and 2 there is shown a gas phase mass analyzer system including a vacuum controllable sampling manifold 1 for obtaining a test sample in gaseous form an optimized mass analyzer 2 for detecting minute concentrations of molecules a special separator system 3 for controlled transfer of gas from the sampling manifold 1 to the mass analyzer 2 and a control and data system 4 all of which are further described below The sampling manifold 1 consists of a spherical reac tor 5 with varying volumes of 1
52. o a mass analyzer at a low pressure said system comprising a a metering device by which the source is selec tively connectable to the mass analyzer for trans ferring the substances b a quadrupole mass spectrometer said mass lyzer said quadrupole mass spectrometer having a high sensitivity electron multiplier c a vacuum pump for creating a source of vacuum to said quadrupole mass spectrometer and d a mass correction lens disposed between said quadrupole mass spectrometer and said vacuum pump for regulating by the area of its aperture the flow of said substances from said quadrupole mass spectrometer toward said vacuum pump whereby said substances are detectable with increased sensi tivity by said quadrupole mass spectrometer 2 The system as claimed in claim 1 further compris ing an ion pump for obtaining said low pressure at said mass analyzer and wherein said ion pump is connected at a right angle to the connection between said quadru LOCATE 12 40 INPUT AMU VALUE E CONT 45 50 55 60 65 REM sas ROUTINE TO PLACE INSTROMENT IN REQUIRED MODE LOCATE 2 14 PRINT STANDBY FILAMENT ON MULTIPLIER 752 LOCATE 3 141PRINT OFF FILAMENT OFF MULTIPLIER OFF SZ 7 LPT1 SLOCATE COLOUR 10FALET pole mass spectrometer and said vacuum pump 3 The system as claimed in claim 1 wherein said vacuum pump is a turbomolecular pump 4 The system as claimed in claim 1
53. o said mass spectrometer 2 concurrently evacuating said spectrometer by a source of high vacuum 3 placing a mass correction lens having an aperture in the flow of substances between the mass spectrometer and the source of vacuum and 4 preselecting the area of said aperture to optimize the detection limit of a particular substance to be detected 17 The method as claimed in claim 16 wherein said source of vacuum is a turbomolecular pump and an ion pump is also used prior to analysis to obtain a high vacuum in said mass spectrometer 18 The method as claimed in claim 16 wherein the mass spectrometer has an ion source an electron multi plier and a mass filter placed along an axis between said ion source and said electron multiplier and wherein said sample is admitted to the mass filter and removed along said axis from said ionizer by said source of vac uum 19 The method as claimed in claim 16 wherein the area of said aperture in said mass correction lens is variably adjustable and wherein said method further comprises setting said area to a predetermined optimum for the substance to be detected prior to mass analysis for that substance i 20 The method as claimed in claim 19 further com prising the steps of adjusting an operating value for said electron multiplier to different preselected values for the analysis of different fragment ions for said substance to be detected in order to optimize the signal to noise ratio o
54. p 17 optimal functioning of the modified system was evaluated according to the following criteria a Tightness of the entire system was determined by means of the time dependent increase of pressure allow ing a maximum leak rate of 1x 10 5 torr l s and b Sensitivity measurements of the quadrupole spec trometer 13 were made using benzene acetylacetone and chloroform achieving a detection limit of at least 100 ppb By these improvements the operating pressure of the mass analyzer was reduced to 10 9 torr so that the background noise could not be measured any longer Since the sensitivity increased enormously the detec tion and determination of ppb and ppt concentrations of chemicals was made possible Since the background could not be measured spectras from pure samples were obtained The separator system 3 is placed between manifold 1 and mass analyzer system 2 and an optional selector valve 21 may be placed between the separator system 3 and the sampling manifold 1 to obtain gas phase samples from locations not shown other than the sampling manifold 1 The separator system 3 further shown in FIG 2 consists of three needle valves 18 20 which can be combined in parallel or in series Usually valve 18 is closed i e the pressure in the manifold is higher than 40 45 50 55 65 6 10 6 torr and the concentrations of the chemicals to be examined are high Valves 19 and 20 control the flow into the
55. quadrupole mass analy zer of increased sensitivity A quadrupole mass analyzer is provided with a nee dle valve to permit the introduction of the sample into the vacuum chamber of the analyzer an ion pump for obtaining a reduced pressure in the vacuum chamber and a secondary electron multiplier for providing in creased sensitivity Preferably the test sample passes directly through a separator system of needle valves from a vacuum con trollable sampling manifold to a modified quadrupole mass analyzer the secondary electron multiplier is a Channeltron 6 electron multiplier and a turbomolecu lar pump used during mass analysis is combined with a mass correction lens These modifications to the system reduced background noise such that organic com pounds could be detected and concentration deter mined in the range of from ppb to high ppt in the gas phase using direct mass spectroscopical analysis with out preliminary enrichment procedures It has been found that the location and orientation of the gas inlet and outlet to the quadrupole mass sensing unit and specifically the placement and aperture of the mass correction lens have a critical effect on the detec tion limit Although the precise mechanism for the im provement of the detection limit is not clearly under stood at this time it appears to be related to an ongoing cleansing of the quadrupole sensing unit during analysis which preferentially increases the duration which th
56. ragment ions for the different substances During operation of the mass analyzer with the mass correction lens having an optimum aperture area it was found that the noise level or baseline of the Channel tron 6 electron multiplier deviated from its optimum minimum level as a function of the mass of the ions to be detected In accordance with another aspect of the present invention the operating characteristics of the Channeltron amp are readjusted for the detection of ions of different mass In particular the value of the high voltage supplied to the Channeltron for effecting electron multiplication is variably selected as a function of ion mass This variable selection of the voltage sup plied to the Channeltron 8 preferably is coordinated with automatic selection of the altenuator gain in the electrometer responsive to the direct Channeltron output so that the dynamic range of sensing the ion current of the selected mass is not exceeded Associated with prestored Channeltron amp voltage control settings are corresponding gain factors and therefore the actual ion current is readily computed from the digitized elec trometer output value the prestored gain factor having been set for the mass being analyzed and the electrome ter altenuator gain having been automatically reset if necessary to avoid limiting of the electrometer output in the event of a high ion concentration at the mass selected for analysis Accord
57. rm remote control of the UTI 100C 02 quadrupole spec trometer scanning and collection of the spectrometer data The computer program is listed in the Appendix to the present specification The microcomputer 4 transmits a precise voltage to the spectrometer 13 to select the mass of the ions which are detected by the electron multiplier 14 This precise voltage is generated by a 16 bit digital to analog con verter having a 0 10 V range a dynamic impedance less than 1 kOhm noise level less than 1 mV and drift less than 0 000546 to insure a spectrometer resolution of 0 01 AMU The microcomputer also has an output for selecting whether the electron multiplier is reading a multiplied ion concentration signal or a non multiplied Faraday cup signal received for determining the multi plier gain by comparison of the two signals and an output activating an analog switch for feeding either the signal from the electron multiplier or the signal from a pressure gauge to a twelve bit analog to digital con verter for input to the microcomputer In this fashion the microcomputer can read the electron multiplier for ion current within the picoammeter range from 10 5 to 10 12 amperes and the total pressure from 10 3 to 10 8 torr The ionizer filaments in the mass spectrome ter are automatically shut down in the event of extreme conditions such as loss of vacuum indicated by the elec tron multiplier signal or the pressure gauge signal The microcomputer
58. sample of the substance to be determined with appropriate correction for fragment ions which are common to more than one of the known substances The scanning process with the analyzer 2 of FIGS 8 9 requires approximately 2 minutes for scanning a mass spectrum ranging from 0 to 300 AMU After scan ning is done the ion pump 16 is turned back on At night the heat wrap 85 is turned on for example by a diurnal timer so that it will have baked out the system at night and the system will have cooled to operating temperatures in the morning To service the ion pump 16 and the turbomolecular pump 17 without breaking vacuum to the spectrometer unit 13 respective gate valves 88 89 are provided for 45 i the spectrometer unit The gate valves 88 89 are Model i No SVB 1 53 VM supplied by Torr Vac Products Van Nuys Calif manually closing off the connections of the pumps to In view of the above an economical and portable mass analyzer has been described which uses a quadru greatly improved for the substances to be detected Preferably the aperture area of the mass correction lens is variably adjustable and is set to a perdetermined opti mum area for each substance under analysis It is also preferred to adjust the electron multiplier high voltage value to a predetermined value for each ion mass to optimize the signal to noise ratio of detection The small size and low cost of the mass analyzer enables it to
59. t 132 in FIG 3 and the high voltage supply to the Channeltron electron multiplier 14 The computer 4 and its associated printer 87 may be turned on at this time for automatic rather than manual control of the mass spectrum scanning For analysis of a sample from a source the source is connected to the sample inlet 71 After checking the numeric indicator 73 to ensure that the variable leak valve 72 is closed the inlet valve 74 is opened Then the variable leak valve is slowly opened until a pressure of 1076 to 10 7 torr is indicated on the control console 76 At this time a constant stream of the substances to be analyzed is passing through the mass spectrometer 13 to the turbomolecular pump 17 and the mass analysis process may begin for scanning a range of mass values or if scanning for determining the concentration of known substances the discrete mass values of the char acteristic fragment ions of each substance Although a mass correction lens 15 having a fixed aperture area is shown in FIG 9 if the variable aperture lens 15 of FIG 6 were used the aperture of the lens would prefer ably be readjusted 10 an optimum area for each known substance The total intensity of each known substance to be determined is then obtained by a weighted aver age of the measured currents of its fragment ions the weighing factors being determined by the relative inten sities of the fragments obtained during analysis of a standard
60. upole mass analyzer is provided with a highly sensitive electron multiplier a turbomo lecular pump and a mass correction lens placed be tween the quadrupole sensor unit and the turbomolecu lar pump These components are arranged and selected to provide a substantial increase in sensitivity permitting the direct analysis of organic compounds in the gas phase in the ppb and high ppt concentration range The placement of the mass correction lens and the area of its aperture has a pronounced effect on the detection limit the optimum aperture area is a function of the mass of the molecules to be detected and preferably an iris diaphragm is used to permit manual of automatic adjust ment of the aperture area to a predetermined optimum for each of the different substances to be detected Pref erably the electron multiplier voltage is also variably selected and reset during the scanning of each fragment ion to optimize the signal to noise ratio of the electron mutiplier The mass analyzer is sufficiently compact and economical to provide on site analysis and the continu ous monitoring or control of industrial processes 20 Claims 6 Drawing Sheets lt CONTROL DATA SYSTEM MICROCOMPUTER KLECTRON Po QUADRI E MASS SPECTROMETER Sheet 1 of 6 4 757 198 Jul 12 1988 U S Patent INI 227 77022 02 VOIA SILIWOYLIIAS SSW 0020100070100 E YH TILL Zur NWONLIF TF
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