PDF - OMICS International
Contents
1. 1 96 0 13 0 40 0 53 2 16 0 14 0 43 One day on line Average of 10 Stdev 19 05ppb 1 18ppb Note Repeated 10 times analysis of solutions containing 50 ppb each compounds and 2 ppb each compound done manually after manual calibration MDL is as 3 times of standard deviation of the 2 ppb solution measurement Table 2 Performance data of the system Analytical Performance Since no modification done on either the P amp T or GC FID the function and the measuring capabilities of these two instruments remained the same with or without the connection of the auto sampler The sensitivity and detection limit should be the same with manual sample introduction and auto sampler introduction as long as the auto sampler introduction is consistent Further auto sampler introduction needs pressurized sample reservoir and large quantity of samples It is not economically feasible to do auto sampler introduction calibration Thus the system was calibrated off line by injecting the calculated amount of calibration standard directly into the sparger After calibration the system was then in conjunction with the auto sampler Calibration curve can be adjusted based on this comparison if necessary Figure 9 is a comparison of chromatograms obtained from manual injection and from on line measurement of the same reservoir stream The validation of the system is obvious Table 2 listed the performance data for the system when it was run off line Also a comp2. are illustrated in Figure 5 With the correct user setting upon completion of the purging process the P amp T will wait for a ready signal When the GC is ready pins 5 and 9 will close briefly which momentarily short pins 3 and 4 in the P amp T communication port starting the desorbing process Since the starting point of P amp T is independent of the GC while the GC starting is triggered by the P amp T the P amp T can act as a control point Simply let the P amp T run its procedures independently except for the desorbing procedure including the preheating When the P amp T completes its purging procedure it waits for a Ready signal from the GC to desorb and start the GC analysis When the P amp T recover itself it sends a Ready Signal to the auto sampler at a predetermined time point Thus the P amp T needs to obtain two commands 1 a start command to process a loaded sample from anywhere GC computer etc and 2 a ready signal from the GC to begin desorbing Establish connection between the auto sampler and the Purge and Trap Only the water lines need to be connected between the outlet of the auto sampler and the inlet of the P amp T sparger No direct electrical connection between these two devices is needed Signal transfer is established through communication between the P amp T and the computer vial DAQ USB 6525 The connections between the P amp T and the DAQ 6525 are shown in Figure 6 When the GC is ready in this config
3. instruments have been retired from regular use but still in good working condition Keywords On line GC Purge and Trap Water treatment Introduction There is no doubt that drinking water safety is of the ultimate importance for general public water treatment plants and drinking water distributors To monitor the drinking water quality an on line GC was developed in our laboratory with existing retired equipment Volatile Organic Compounds VOCs along with other possible contaminants affect the taste of the drinking water and may present a health risk if it exceeds the acceptable level 1 For example disinfection products such as Trihalomethanes THMs are one of these VOC groups The generation of these by products greatly depend on the amount of available organic carbon in the raw water Therefore decisions for the treatment processes and chemical doses are often based on the quality of raw water 2 As a drinking water provider it is necessary to monitor the water quality including the VOC level before during and after the water treatment process Monitoring of VOCs can be done by repeatedly taking samples and analyzing them 24 hours a day all year around but it is more efficient to put an instrument in the production line let the instrument take the sample finish the analysis and automatically report the results to the operator and the quality assurance personnel To do this an on line system is required To meet th
4. with ChemStation A10 02 or higher is needed This software in turn needs the Windows XP Professional Service Pack 3 or higher operating system Finally a suitable used computer system was selected with the features satisfying these requirements Table 1 The only physical connection between the GC and the computer is between the GPIB interface on the GC and the USB port on the computer through the 82357B USB GPIB adaptor Configuration and settings of the software will not be provided in detail here Establish communication between HP GC 5890 II and P amp T Tekmar LSC 3100 The goal of the setup is to synchronize the operation between these two pieces of equipment Two key requirements have to be met First when the GC is not idle and at Ready Status the P amp T device should not desorb the compounds it collected The releasing of the compounds should only happen when the GC is at a Ready Status The GC temperature program can be started in two ways by software J Anal Bioanal Tech ISSN 2155 9872 JABT an open access journal Special Issue 12 2014 Citation Zhao YH 2014 Development of an On line GC System using Existing Retired Equipment J Anal Bioanal Tech S12 008 doi 10 4172 2155 9872 512 008 GRND Not ready Ready connector P6 LCS 3100 Figure 5 Electrical connection between the GC and P T USB 6525 push botton o Purge and Trap LCS 3100 From Tekmar 3100 or other devices
5. 08 doi 10 4172 2155 9872 512 008 Valve panel 1 2 Stream Water flow Gas flow Page 6 of 8 GPIB USB converter Control and data PC Figure 7 Block photo diagram showing the connections of the overall system Detailed sequence After all modules are initialized and synchronized after powering on both GC and P amp T are at Ready Status The following procedure takes over and runs continuously Figure 8 until it is interrupted externally 1 Start Auto sampler control program receives a start signal This can be from the push button in Figure 6 or from a pre run of the P amp T 2 Auto sampler takes sample A and loads the sample to the P amp T sparger 3 The P amp T concentrates the sample 15 minutes and waits for the HP GC to be ready if it is not 4 The P amp T receives the ready signal from GC and transfers the concentrated sample to GC and starts the GC run the transfer take 4 minutes and the GC run last 25 30 minutes depends on the column and the temperature program at the same time a signal is sent to the computer vial NI DAQ to start the time delay before taking the next sample The time delay should be long enough to let the P amp T fully recover 5 The P amp T recovers after transferring the sample to the GC 15 minutes Ensure the P amp T is recovered before the GC run ends 6 When the P amp T has recovered the auto sampler starts taking sample B and carries out the concen
6. Figure 6 Trigger signal sent out by P amp T to the computer to start the solenoid valves controlling program via the NI DAQ USB 6525 control a mouse click on the start button or by hardware remote start from an external signal For continuous operation the first approach was ruled out since one cannot click on the start button for each and every sample It has to be triggered by an external signal Additionally the run has to be started at the time point at which the compounds are injected into the GC i e when the P amp T starts desorbing The second requirement is that the P amp T must be at Ready Status when the auto sampler starts taking the next sample The auto sampler needs a Ready Signal from the P amp T to start its procedure Therefore establishing communication between the P amp T and the GC plus between the P amp T and the auto sampler is essential Page 5 of 8 The GC itself has a remote start function Specially configured connection cables are available through Agilent or other suppliers Hand shaking between the GC and the P amp T are established by an electrical connection through a Tekmar cable part number 14 6689 186 which connects the GC end to RS 232 c 25 pin and to the P amp T end 9 pin Another Tekmar cable part number 14 2991 000 connected to the communication port P T end 25 pin and the GC 12 pinremote connection to issue and receive Ready Start signals The pin configuration and interconnections
7. In another words the sample cannot be continuously introduced into the system To put this device on line an auto sampler has to be put in front of it To monitor the quality of raw and processed water and the effectiveness of individual stage of treatment process more than one stream often needs to be monitored This can be done by having one on line system for each individual stream or better having multiple streams feed into one shared instrument In order to save money for this project the second approach of having two streams share the one instrument was employed For a water treatment plant the source water often varies with the change of seasons especially during the spring run off period Sediment color turbidity dissolved and suspended material change significantly throughout the year The sample intake can become clogged very quickly by sediments in raw water of poor quality For an on line system to work properly the sample especially the raw water sample has to be filtered before being introduced into the analytical system It is hard to find a commercial auto sampler directly coupled to the P amp T without modification Also the commercially available auto samplers usually do not have stream selecting function and solid removing capability Thus we decided to build our own auto sampler in house The detailed design and construction of this device are described in the following sections Data and controller system To
8. Zhao J Anal Bioanal Tech 2014 S12 http dx doi org 10 4172 2155 9872 S12 008 Analytical amp Bioanalytical Techniques Development of an On line GC System using Existing Retired Equipment Yuhui Henry Zhao EPCOR Utilities Inc Edmonton Alberta Canada Abstract To ensure drinking water quality continual monitoring of the volatile organic compounds VOCs in the source water and the treated water is very important for any water treatment plant On line real time information is crucial to water treatment engineers and operators The concentration of VOCs provides such information For VOCs analysis gas chromatography GC is one of the best techniques due to its high sensitivity and selectivity As a result an in house on line GC System was developed for this purpose at a water treatment plant It included the following parts a stream selection device to connect two sample streams a self cleaning filter to remove sands and suspended solids a Purge and Trap P amp T device to extract and concentrate the volatile compounds a GC from Hewlett Packard equipped with a Flame lonization Detector FID to identify and quantify the compounds a computer with Windows XP plus ChemStation to control the sampling valves through a DAQ from National Instruments and to control the GC and P amp T through a GPIB USB interface from Agilent To minimize cost in the development of this system shelved GC and P amp T were used These
9. arison between the results obtained from the same stream measured by manual injection and by auto sampler introduction was also listed in the table Summary A functional On Line GC system was developed using retired existing equipment Due to the easy availability of these devices in most of the labs this system can be built by any lab which has an interest in its application With a small investment new and simplified devices can be used to replace these old devices and make the system more compact and reliable Acknowledgement The author thanks Dr Chuhong Fei from AUG Signals Inc for the assistance in developing the solenoid control References 1 Environmental and Workplace Health 2012 Guidelines for Canadian Drinking Water Quality Health Canada 2 Hammer MJ 1975 Water and Waste water Technology 4 edition Technology amp Engineering Wiley USA 3 Eaton AD Franson MAH 2005 Standard Methods for the examination of water and wastewater 21st Edition American Public Health Association USA HP 5890 Series Il and HP 5890 Series II Plus Reference Manual Tekmar 3100 manual pdf 4 5 6 NI USB 6525 National Instruments 7 http wattsupply com gclid COOi85LK8boCFSJIMgodMREA8g 8 3 Way Solenoid Valves 8320 Series ASCO 9 2 Way Solenoid Valves ASCO 10 82357B USB GPIB Interface High Speed USB 2 0 Agilent Technologies Citation Zhao YH 2014 Development of an On line GC System using Existing R
10. d valves were selected to control the stream flow and consecutively feed the P amp T LSC 3100 There is no sample pump considered in the design since in our plants the water streams are regulated to a relatively high pressure of 30 60 psi which is high enough to push the water through the solenoid and connecting tubing Referring to Figure 3 this simplified auto sampler without an internal standard addition consists of three solenoid valves V1 V3 V4 two manual mode selection valves M1 M2 the on line filter sample measuring unit and the connection tubing All the solenoid valves are electronically operated When the right voltage is applied to a valve the valve will be energized and turned ON i e changed from its normal status To turn the valve off back its normal status the voltage has to be removed from that valve All these valves and tubing are mounted on one piece of inch thick aluminum board The connections between the valves are illustrated in Figure 3 This module can be operated in two different modes either with or without filtration The sample size can be determined by the sparger size or by sample holder size in the sample measuring unit described above The valve operational sequences are described as follows e Stream 1 with filtration default sequence S1 Manual valve M1 to Left L position water flows up into the filter manual valve M2 to Right R position water from filter flows into this val
11. e requirements of water quality guidelines from relevant Helium Carrier gas Purge amp Trap iF GC with FID Helium Purging gas w Transfer line Figure 1 Schematic diagram showing the principle of a P amp T system with a GC FID system jurisdictions low detection limits are required for most of the measured organic compounds The most common method of measuring VOCs in water samples is Purge and Trap P amp T coupled with a Gas Chromatography with Flame Ionization Detector GC FID 3 This is mainly due to its high resolution simplicity reliability wide linear range and relatively high sensitivity This project uses this technique The basic principle and operation of these instruments can be found in the users manuals 4 5 and is illustrated in Figure 1 Briefly a water sample is introduced in the sparger on the P amp T device and the VOCs analytes are extracted from the water matrix by bubbling a steady flow of helium through the aqueous sample The purged organic compounds are trapped and concentrated onto an absorbent trap The analytes are then released by heating the trap onto the head of the column in a GC instrument A stream of carrier gas usually helium or hydrogen flowing through the column under a predefined temperature program separate and elute the compounds from the column The compounds eluted from the column reach the FID and are then identified by their retention times by comparing to the calib
12. e set time for a pre set length of period In this period of time a voltage of 24V is applied to the solenoid valve connected to this channel This solenoid valve will be turned on and changed from its normal status At the end of this period the channel circuit is opened the voltage is removed from this valve and the valve return to its normal status The water stream is controlled in this way Up to this point the construction of the auto sampler is finished The operation and timed events of the auto sampler are described in detail in the following section Establish computer control of HP GC 5890 II The HP 5890 II was used as a computer controlled instrument before it was retired The interface was a GPIB board with Windows NT and an old version of Chemstation However the computer is too out of date to accommodate the newly developed software Further Windows NT cannot handle USB adaptors which is most often used for connecting external devices at this time Thus a newer computer was selected For the majority of new computers there is no built in slot to accommodate a GPIB board In order to establish communication between the computer and the GC the GPIB interface in the GC has to be converted to a USB adaptor The Agilent 82357B USB GPIB adaptor is designed for this purpose Fortunately we had one of these devices already available in our lab For this device to be functional Agilent OI Library Suite 15 or higher
13. ed HP5890 II Purge amp Trap used LSC 3100 Power Supply used MW S150 24 Solenoid V1 used ASCO Redhat II Solenoid V3 used ASCO Redhat II Solenoid V4 used ASCO Redhat NI DAQ new USB 6525 GPIB USB adaptor Agilent 82357B Computer old AMD Athlon 64x2 Dual Page 2 of 8 Features Reference GPIB interface Remote control ready FID 4 DB 624 column Chemstation control or stand alone Hand held device control or computer control Single sample or scheduled run possible Input 110 120 VAC 3 2A Output 24 VDC 6 5 A 3 way 24VDC 11 6W 8 Pressure limit 100 psi 5 8 3 way 24VDC 11 6W 8 Pressure limit 100 psi 2 wayNC 12 24VDC 2W 9 Pressure limit 100 psi Individual relays built in 8 Isolated Digital Input channels 60V DC 8 Isolated Switching channels 60V DC USB connection Drive NIDAQ951f1 Programmable under MATLAB 6 10 Windows XP Professional Service Pack 3 Chemstation vA 10 02 with OI Library Suite 15 NI DAQ drive MATLAB Library Microsoft Excel Table 1 Equipment and their features used in this project equipment must be reliable readily available easy to operate of minimum capital and operational cost For the sake of developing and testing on one hand it should be operated as a stand alone instrument on the other hand it should be computer controllable for continuous analysis HP 5890 II GC retired but in good worki
14. ent a and manual injection b J Anal Bioanal Tech f ISSN 2155 9872 JABT an open access journal L a ers Citation Zhao YH 2014 Development of an On line GC System using Existing Retired Equipment J Anal Bioanal Tech S12 008 doi 10 4172 2155 9872 512 008 50 ppb Compound Average 1 1 dichloroethylene 49 08 methylene chloride 51 28 trans 1 2 dichloroethylene 53 54 cis 1 2 dichloroethylene 52 59 chloroform 49 19 1 1 1 trichloroethane 49 23 carbon tetrachloride 48 03 benzene 62 22 trichloroethylene 52 61 1 2 dichloropropane 49 39 bromodichloromethane 51 51 toluene 50 62 tetrachloroethylene 54 89 dibromochloromethane 83 40 chlorobenzene 49 94 ethylbenzene 51 51 1 4 xylene 52 50 1 2 xylene 56 26 bromoform 52 97 1 1 2 2 tetrachloroethane 55 29 1 3 dichlorobenzene 53 91 1 4 dichlorobenzene 58 12 1 2 dichlorobenzene 54 88 1 2 4 trichlorobenzene 62 31 Manual 1 measurement 22 81 ppb chloroform Page 8 of 8 2 0 ppb Stdev Average Stdev MDL 2 19 1 70 0 18 0 54 0 49 1 93 0 10 0 30 1 58 1 86 0 15 0 45 0 98 1 91 0 17 0 51 0 82 1 93 0 11 0 34 1 78 1 73 0 19 0 58 2 46 1 53 0 30 0 91 1 28 2 19 0 15 0 46 1 29 1 87 0 16 0 47 0 73 1 77 0 10 0 30 0 67 1 82 0 10 0 29 1 17 1 71 0 13 0 38 1 69 1 88 0 16 0 47 0 75 2 94 0 14 0 43 0 74 1 71 0 13 0 38 1 23 1 73 0 14 0 42 1 18 1 73 0 13 0 40 1 67 3 83 0 25 0 75 0 77 1 92 0 19 0 56 0 57 2 04 0 11 0 34 0 45 1 90 0 12 0 37 0 45 2 03 0 13 0 40 0 52
15. etired Equipment J Anal Bioanal Tech S12 008 doi 10 4172 2155 9872 S12 008 J Anal Bioanal Tech ISSN 2155 9872 JABT an open access journal Special Issue 12 2014
16. ll not be necessary Due to the limitation of this paper detailed programming cannot be given here Interested readers can contact the author to discuss in more detail If only one stream of sample to be analyzed the stream selection function is not needed The P amp T can run continuously at a schedule mode when the scheduled sequence is started Thus one can let the P amp T run independently and let the GC and auto sampler run following the trigger from the P amp T ChemStation can save the file when the GC analysis complete The file number will be automatically increase by 1 for the next sample However due to the stream selection function this is not used in this mode and all the data will be stored in one folder J Anal Bioanal Tech ISSN 2155 9872 JABT an open access journal Special Issue 12 2014 Citation Zhao YH 2014 Development of an On line GC System using Existing Retired Equipment J Anal Bioanal Tech S12 008 doi 10 4172 2155 9872 S12 008 Page 7 of 8 Streams Computer ale Data file Interruptor hand shake Manifold trigger HP GC 5890 II Figure 8 Block diagram showing the operation of the on line GC system The steps in the green loop repeat after the START command is activated until the END command is received FID1 A TEST 5890 SIG10037 D E re O fa O FID1A TEST 5890 SIG10012 D Chromoform Figure 9 Chromatograms obtained by on line measurem
17. ly The sample is ready to be purged V1 programmed OFF allows Stream 1 to pass through the sampling holder to the Drain Power supply A used power supply MW S 150 24 harvested from an old TOC analyzer was used to energize the solenoids The specification of this power supply is listed in Table 1 This power supply Page 4 of 8 has more than enough power to energize all three solenoid valves and leave enough room for future expansion i e can add up to two more valves if internal standard is needed Programmable switches To make a solenoid valve change its status at a scheduled time there must be a switch to control the power to turn the valve on or off This switch has to be programmable either through its own logic or through a computer To control all the solenoid valves a set of programmable switches have to be used After the consideration of the convenience programmability function and price a NI DAQ USB 6525 6 was selected purchased new Its features are listed in Table 1 Connections The electrical connection between the solenoid valves and the power supply via the NI DAQ 6525 is illustrated in Figure 4 7 9 The NI DAQ USB 6525 is computer controlled through an USB connection by a home developed program under MATLAB 10 The program is compiled and can be run under MATLAB Library After the control program of NI DAQ initialized the designated channel of the DAQ will be opened by closing the circuit at a pr
18. make the system run automatically the following hardware and software is necessary Hardware A PC with USB ports an Agilent GPIB USB 82357B 6 Interface a National Instruments DAQ USB 6525 Software Windows XP Professional Service Pack 3 or higher Agilent Chemstation ver A 10 02 or higher with OI Library Suite 15 0 a valve control drive programmed in house J Anal Bioanal Tech ISSN 2155 9872 JABT an open access journal Special Issue 12 2014 Citation Zhao YH 2014 Development of an On line GC System using Existing Retired Equipment J Anal Bioanal Tech S12 008 doi 10 4172 2155 9872 512 008 a e a i a ie q a q 1 Filter _ N Screen N Filter house Fix volume n Measuring ee unit house Stream out Stream in Filtered l Sample Over flow ler o a a ee es es ee J Eo a a a ae ae es ee a a b pT 1 Screen filter _ j Fix volume tubing alee 5 l com Stream 1 Drain Sparger Figure 3 The simplified auto sampler without an internal standard addition Accessories Additional accessories are also required DC power supply custom built Tester Initiator manual valves connection tubing wires Construction of the System Building the auto sampler Filter and sample volume measuring unit Raw water samples often contain large amounts of sedime
19. ng condition The gas chromatograph is the centerpiece of equipment for this project It is the most complicated and expensive component Once the decision on the selection of the GC is made the other equipment to be selected must be compatible with the GC HP now Agilent GC has a good reputation for its reliability In our laboratory and probably in every other organic laboratory in North America it is the most widely used GC instrument of choice It is often the case multiple units of these GCs in good working condition are kicking around in the lab The HP 5890 series is very common and is likely readily available The HP5890 II or HP5890 II Plus was chosen over the model HP5890 due to its computer controlling ability Configuration of the GC is listed in Table 1 Detailed specifications can be found in its user s manual 4 Tekmar LSC 3100 Purge and Trap retired but in good working condition There are many brands of P amp T devices on the market while one of the most often used is from Tekmar The obsolete LSC 3100 was chosen over newer versions such as Tekmar s Velocity or Stratum models mainly due to this P amp T s stand alone capabilities We were fortunate to have a retired unit in our lab that was still in good working condition The description and features of this instrument can be found in the user s manual 5 Auto sampler built in house Tekmar LSC 3100 P amp T is a consecutive sample processor
20. nt which will quickly clog the system unless the majority of the sediment is removed A mechanism to remove the sediment must be incorporated at the beginning of the run Page 3 of 8 This Filter Unit Figure 2a consists of three pieces of tubing a filter screen and filter housing Streaming water initially flows to the filter housing unit through the stream in tubing A small portion of this stream passes through the filter screen with the sediments removed The removed sediment is carried out by the excess stream The excess stream do not pass through the filter screen but instead exits the filter housing through the stream out tubing Figure 2a The cleaner water from within the filter screen cavity flows through the filtered tubing towards the sample holder in the Sample Volume Measuring Unit Figure 2b The Sample Volume Measuring Unit Figure 2b is also constructed in house It consists of a sample housing a bottomless cylinder as the holder and connection tubing At any given time other than filling the sparger on P amp T the sample in the holder is always at an over flowing status and thus the retained sample is always fresh with a fixed volume This volume of sample will be unloaded into the P amp T sparger at each sampling time Stream selection mechanisms Tekmar LSC 3100 can only process one sample a time Continuous feed of the water to the P amp T will make the purge process impossible Solenoi
21. ration standards Quantitation is achieved by a standard calibration For those organizations willing to invest large amount of money in analytical equipment there is commercial on line GC system available on the market for instance by WASSON Instruments However it is a relatively big financial investment to purchase install and operate In this paper a built in house unit using retired equipment is described Equipment Selected for this Project The derivation of the equipment selection is as follows The Corresponding author Yuhui Henry Zhao EPCOR Utilities Inc Edmonton Alberta T5K 0A5 Canada Tel 780 412 7612 E mail YZHAO epcor com Received November 22 2013 Accepted February 28 2014 Published March 04 2014 Citation Zhao YH 2014 Development of an On line GC System using Existing Retired Equipment J Anal Bioanal Tech 12 008 doi 10 4172 2155 9872 S12 008 Copyright 2014 Zhao YH This is an open access article distributed under the terms of the Creative Commons Attribution License which permits unrestricted use distribution and reproduction in any medium provided the original author and source are credited J Anal Bioanal Tech ISSN 2155 9872 JABT an open access journal Special Issue 12 2014 Citation Zhao YH 2014 Development of an On line GC System using Existing Retired Equipment J Anal Bioanal Tech S12 008 doi 10 4172 2155 9872 512 008 Device Model new or used GC us
22. t 3 way solenoid V1 V1 programmed OFF water flows through port 3 and 1 to the second 3 way solenoid V3 V3 programmed OFF water flows through the sample holder The overflow is discharged By now the sample is uploaded into the sample holder A signal is sent when the P amp T is ready switching both the 2 way solenoid V4 ON for releasing pressure and the 3 way solenoid V3 ON blocking water from V1 and unloads the sample from the holder into the sparger When the sample unloading is complete both V3 and V4 solenoids switch OFF automatically The sample is ready to be purged e Stream 2 default sequence S2 Stream 2 cannot be filtered Manual valve M1 to Left L position stream1 flows up into the filter manual valve M2 to Right R position Stream1 from filter get into this valve and pass to the first 3 way solenoid V1 V1 programmed ON Stream 1 blocked here by Port 3 and flows through the filter drain Stream 2 flows through V1 from Port 2 to Port 1 and reaches V3 the second 3 way solenoid V3 V1 programmed OFF water flows through the sample holder the overflow is discharged By now the sample is uploaded into the sample holder A signal is sent when the P amp T is ready switching both the 2 way solenoid V4 ON for releasing pressure and the 3 way solenoid V3 ON blocking water from V1 and unloads the sample from the holder into the sparger When the unloaded sample is complete both V3 and V4 solenoids switch OFF automatical
23. tration procedure If the concentration procedure completes before the GC is ready it will wait 7 When the GC run is finished it saves the data file on the hard drive in folder A The file should contain the following information Run date and time sample line A or B the concentration of the measured compounds 8 The GC recovers After the GC recovered and ready it sends a ready signal to the P amp T The same procedure as with line A is carried out on line B The data file has a different sample name and stored in the folder B 9 Steps 1 through 8 repeat themselves Computer controlling Depending on the requirement of the sample lines there are two ways to automatically carry out the above sequences continuously Since both the MATLAB program and ChemStation can access other Windows applications through user defined macro program this provides a channel to exchange data between the GC ChemStation and the MATLAB software One can build an Excel file which can be accessed by both software programs The file contains the time interval for the valve operation sample name and other identification time stamp of the analysis file name and path of the acquired data etc Both MATLAB program and ChemStation read and write data from into this file to alter their variables in a predefined manner Thus the entire system is under complete computer control The triggering signal from the P amp T to start the sampling wi
24. uration it sends the ready signal to P amp T and the later starts desorbing and sending a signal to the computer via the NI DAQ A time delay has to be programmed in the auto sampler control to leave time for the P amp T to desorb and recover itself before preparing for the next sample Establish connection between the Auto sampler and the HP GC 5890 II There is no water connection between the auto sampler and the HP GC 5890 II The only possible electrical connection is between the GC and the DAQ 6525 as an option not used at this time is similar to that shown in Figure 6 with the Ready signal from the GC to replace the desorb signal from the P amp T By now the construction is finished The overall diagram is shown in Figure 7 as block pictures Overall Control and Data Handling The remaining and the most difficult part of the project is the automation of the system Individually every module has been tested and works well The next step is to make them work together The overall goal is to have the system continuously sample from the water line concentrate analyze and save display the data It also requires the system handles two streams A and B alternatively The entire process is explained as the following J Anal Bioanal Tech ISSN 2155 9872 JABT an open access journal Special Issue 12 2014 Citation Zhao YH 2014 Development of an On line GC System using Existing Retired Equipment J Anal Bioanal Tech S12 0
25. ve and passes to the first 3 way solenoid V1 V1 programmed OFF sample flows through port 3 and 1 to the second 3 way solenoid V3 V3 programmed OFF water flows through the sample holder the overflow is discharged By now the sample is uploaded into the sample holder A signal is sent when the P amp T is ready switching both the 2 way solenoid V4 ON for releasing pressure and the 3 way solenoid V3 ON blocking water from V1 and unloads the sample from the holder into the sparger When the sample unloading is complete both V3 and V4 solenoids switch OFF automatically The sample is ready to be purged e Stream without filtration the only differences from the default sequence S1 are the manual valves positioning as shown in the diagram above J Anal Bioanal Tech ISSN 2155 9872 JABT an open access journal Special Issue 12 2014 Citation Zhao YH 2014 Development of an On line GC System using Existing Retired Equipment J Anal Bioanal Tech S12 008 doi 10 4172 2155 9872 512 008 USB 6525 1 2 3 4 5 6 7 8 9 1011 12 13 14 15 16 Bal CUT EERE EAA F EEE z meee ee ee Return Singnal D L Power Supply i 5 Ground i i 24VDC Figure 4 Electrical connection between the solenoid valves and the power supply via the NI DAQ Manual valve M1 to Right R position water flows down to M2 manual valve M2 to Left L position water flows from M1 directly into this valve and passes to the firs
Download Pdf Manuals
Related Search