Reducing Helium Costs more than 10
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1. Help W Manual Tune 5975 BACKCHEK u E _ Oj i File Execute Calibrate MoreParams View Scan 10 00 100 00 108 peaks lon Pol Pos MassGain f 692 Base 28 10 Abundance 6257 Emission 34 6 MassUffs 36 100 ElErnrgy 693 9 AmuGain 1210 Filament 1 Amulffs 122 88 Wid219 0 065 Repeller 26 44 DC Pol Pos lonFcus 85 4 EntLens 19 0 HEDEnab On EntOffs 19 07 EM olts 1082 PFTIBA Closed 40 60 60 Temperatures and Pressures MS Source 230 Turbo Speed 100 MS Quad 150 Hi ac 9 75e 06 Abund Rel Abund 1161 100 00 6257 579 61 597 50 55 Emission O 0 to 315 2 34 6 p E Mass spectrometer is of Profile Scan Ramp Stop MS Off i Cancel Help Figure 6 MS background with 1 5 mL min helium carrier and no flow contribution from front split splitless injection port Upper panel at time zero and lower panel at 72 hours later No change in the 18 28 or 32 background is detected over the period Note a small air leak does exist in this system Conclusions The PCT configuration provides a number of features that improve GC MS operation These include rapid backflushing to protect the column and MS source and increase productivity and quick ventless servicing of the column and inlet to maintain data quality The PCT Gas Saver mode is an additional capability which archives the GC MS system with extremely low helium carrier gas use This allows the MS ana lyzer to remain at temperature2. Reducing Helium Costs more than 10 fold with the PCT Gas Saver mode Harry Prest Technical Overview This note describes a technique for minimizing helium carrier flow when the GC MS system is not in use Helium has become expensive and costs of operation are always a concern Using the G14 2A Rapid amp Universal GC MS Backflushing kit in the Pressure Controlled Tee PCT configuration total helium use can be lowered to lt 3 mL min while the GC MS is dormant The MS analyzer is still under vacuum at operating temperatures and can be rapidly called into use Total helium savings over the course of a month or year are substantial using this mode Introduction Recently the price of helium carrier for gas chromatography has dramatically increased and supply has become limited Many instrument users have become concerned about saving this gas whenever possible Saving helium carrier by cool ing and venting GC MS instruments single quadrupole and triple quadrupole is not an efficient approach because air and water enter the vacuum manifold Although the instruments can rapidly reach analyzer operating temperatures the removal of chemisorbed water is a slow process therefore the time necessary to reach stable operation is lost analytical time In addition the frequent venting and pumpdown cycles wear out the pump system components and tend to be time consuming The optimum situation has always been to keep an MS system under vacuum and at
3. maintenance including liner change and septum change e Simple column servicing or the more efficient approach of guard or coated precolumn exchange to restore compound chromatographic performance and maintain compound retention times PCT operation is simple to understand Figure 1 During GC analysis the pressure applied at the Purged Ultimate Union Pope is Just a little higher than that needed to prevent backflow into the electronic pneumatic control EPC module After the GC MS analysis is completed the pressure is raised at the tee Purged Ultimate Union and lowered in the front section of column to push matrix out the split vent This is Post Run backflushing mode In Concurrent backflushing mode after the last ana lyte of interest has passed through the front column and the tee Purged Ultimate Union and entered the second section of column the head pressure at the inlet can be dropped P et so that the later eluting components will begin to retreat in column 1 The last analytes then proceed to column 2 and enter the MS detector The MS system can be any of the Agilent systems including diffusion pumped sys tems Details and evidence of PCT performance are given in several application notes 1 4 and instructions for the installation and operation are given in the Agilent G1472A Rapid Universal GC MS Backflushing Kit Pressure Controlled Tee manual G1472 90001 For simplicity this note describes work performed with the midpoi
4. temperature to allow the system background to continuously improve or at least remain stable This philosophy is also true for other GC detectors Employing GC instrument parameters to minimize gas use such as standby methods using low split ratios with low column flows and septum purge settings risk air intrusion with consequent damage to the inlet or column These methods can produce a gas usage rate of about 7 to 10 mL min at best While this is lower than the typical use of greater than 24 mL min during operations it still represents a substantial quantity of helium expended that is not available for analysis This note describes a state of the GC instrument enabled by the Pressure Controlled Tee PCT and the Agilent Rapid Universal GC MS Backflushing Kit G1472A in which total helium carrier gas use is lt 3 mL min during the archived state of the GC MS instrument This state is referred to as the PCT Gas Saver mode and while saving helium the MS system remains under vacuum and at temperature and rapidly can be brought into operation In terms of helium carrier savings nearly every hour the instrument is placed in this PCT Gas Saver mode is equal to a saved Agg Agilent Technologies hour of analysis when compared to typical default operating conditions 24 mL min Over the course of a year this can result in considerable helium gas savings For example archiving a GC MS instrument with the PCT Gas Saver through every weekend i
5. 53 mL min Figure 5 This shows column flow is back from the Purged Ultimate Union into the inlet pe COLUMN 1 VIME Ins 1LONs Pressure Flow Actual Setpoint Figure 5 Column 1 Inlet gt Aux conditions pressure OFF the flow calculation result is shown and the negative sign indicates flow is back into the injection port To return the system back to use 1 Set the Column 2 flow to 3 mL min for diffusion pump systems or 8 mL min for turbo systems See the PCT User s Manual 2 Reseal the injection port and set the inlet pressure to 2 psi 3 Set the septum purge to ON at 23 mL min and gas saver on with a split flow of gt 20 mL min 4 Turn on the injection port temperature The Column 1 flow will be negative 1 7 mL min in 15 m x 0 25 mm id configura tion and as the port warms up to operating temperature contaminants accumulat ed during the idle period will be backflushed out the split vent and not transferred into the analytical column Results Comparing the air water background in the mass spectrometer reveals no measure able increase due to air intrusion between the operating state and this PCT Gas Saver mode even when compared over a gt 2 hour weekend period Figure 6 Total gas use Is about 2 6 mL min for this configuration The default 7890 Gas Saver mode is a split flow of 20 mL min an additional flow used by the septum purge is 3 mL min minimum and the column flow of about 1 2 mL min mea
6. as reached room temperature it can be turned OFF to save power 2 Set the Column 2 flow to 1 5 mL min constant flow Figure 3 Note for columns narrower than the 0 25 mm id used in this example set the pressure at Column 2 to 3 psi For example a 10 m x 0 18 mm id Column 2 would only require a flow of 0 6 mL min which results in even higher gas savings COLUMN 2 He Dimensions 15 0 m 250 u Pressure PS 3 2K Flow 1 500 Actual Setpoint Figure 3 Column 2 AUX MSD conditions column flow setpoint 1 5 mL min 3 When the injection port and oven have cooled set the inlet pressure to OFF The port must then be opened by either removing the septum and septum nut or rotating the twist top to release the liner connection Figure 4 This releases the pressure inside the port and the inlet The Column 1 display should read zero or close to It Alternatively if the user does not want to open the injection port then set the 7890 Gas Saver to OFF the inlet pressure to 0 total flow to 0 and septum purge to 0 The 7890 system will beep as it can not achieve the setpoints Figure 4 When the injection port is cold loosen the injection twist top by counter clockwise rotation of the yellow handle Make sure to lift the top slightly to insure the seal is broken 4 In this 15 m x 15 m column configuration the calculated flow displayed on the GC panel for Column 1 near the inlet should be negative and approximately 0
7. n a year will result in a helium savings equivalent to more than an additional 100 days or almost half of year of analytical operating time This technical overview contains specific directions for enabling this PCT Gas Saver mode for PCT with the GC MS The approach can be easily generalized to other PCT configurations to enable carrier gas savings on all GC systems Why the PCT for GC MS Operation A simple schematic and an illustration of the PCT configuration are shown in Figures 1 and 2 The analytical capillary column is split into two sections by a tee called the Purged Ultimate Union Many configurations of the PCT are possible because the column sections do not need to be of equal lengths Using the PCT improves GC MS operation by providing rapid backflushing and rapid GC servicing Rapid backflushing removes late eluting matrix contaminants to e Avoid fouling the MS source thereby increasing instrument uptime and eliminat ing frequent source cleaning e Avoid carryover baseline rise and compound retention time shifts over the course of sample sequences The PCT enables both post acquisition or Post Run backflushing and Concurrent backflushing modes to minimize run time and cycle time Concurrent backflushing takes place while sample data acquisition is still underway Rapid servicing without venting the MS system allows e Quick capillary analytical column cutbacks to quickly restore chromatographic performance e Fast inlet
8. ns that the minimum use in operation is 24 mL min If the user were to apply this PCT Gas Saver mode over only weekends from Friday at 6 pm to 8 am Monday morning 62 hours they would gain about 55 hours of operation every week If this is applied every weekend of a year the helium savings is over 2600 hours or 100 days of oper ation each year Even overnight from 6 pm to 8 am saves helium carrier equivalent to 12 5 hours of operating time or more than an additional 8 hour day of operation Also worth noting is that PCT Gas Saver mode unlike 7890 Gas Saver mode causes a very small backward flow through the port Therefore trace carrier contaminants do not accumulate as rapidly as they would at higher split flow This is similar to the PCT Standby mode where the system is in backflush and column is kept clean 5 W Manual Tune 5975 BACKCHEK u ee Ioj xi File Execute Calibrate MoreParams wiew Scan 10 00 100 00 110 peaks lon Pol Pos MassGain f 692 Base 28 10 Abundance 6779 Emission 34 6 MassUifs 36 100 ElEnrqy 69 9 AmuGain 1210 Filament 1 AmuDffs 122 88 wid219 0 065 Repeller 26 44 DUC Pol Fos lonF cus 95 EntLens 19 0 HEDEnab On EntOfts 19 07 EMolts 1082 PFT BA Closed T 40 60 oO Temperatures and Pressures MS Source 230 Turbo Speed 100 MS Quad 150 Hi ac 9 7 72 06 Abund Rel Abund 1167 100 00 6779 530 69 635 54 41 Emission 0 0 to 315 2 34 6 w Frofile Scan Ramp 0 i Cancel
9. nt PCT configura tion in which the Purged Ultimate Union is inserted between two 15 m columns 0 25 mm id The concept is easily generalized to other column arrangements Injection Port wr SS P inlet Agilent MS System Purged Ultimate Union PUU 9975C MSD 7000A QQQ Z mL min OO Column 1 Column 2 Agilent 7890A GC Figure 1A The PCT configuration schematically shown in the forward flow mode operating during analy sis The EPC device supplies just enough pressure to prevent backflow into the connecting EPC device line P Pane inlet Injection Port Agilent MS System Purged Ultimate Union PUU 9975C MSD 7000A QQQ x mL min Column 1 Column 2 Agilent 7890A GC Figure 1B The PCT configuration schematically shown in backflush mode After completing the analysis the EPC pressure has been raised to send flow back through the forward section of the col umn into the inlet and out the split vent P _ lt Feng Figure 2 Picture of an installed PCT Column 1 connects dash dot dash the injection port to the Purged Ultimate Union at right and Column 2 connects dash the MS system to the Purged Ultimate Union Procedure for PCT Gas Saver Mode To put the system in PCT Gas Saver mode 1 Set the injection port temperature to OFF and allow it to cool to room temperature The port will cool faster with the GC oven set to 20 C After the oven h
10. on descriptions and specifications in this publication are subject to change with out notice Agilent Technologies Inc 2010 Printed in the USA April 1 2010 5990 5444EN i j Agilent Technologies
11. ow Technology for GC MS A Simple Tee Configuration for Analysis at Trace Concentrations with Rapid Backflushing for Matrix Elimination Agilent Technologies publication 5989 8664EN Capillary Flow Technology for GC MS Efficacy of the Simple Tee Configuration for Robust Analysis Using Rapid Backflushing for Matrix Elimination Agilent Technologies publication 5989 9359EN Maintaining Compound Retention Times with the Backflush enabled Pressure Controlled Tee Configuration for Agilent 7890A GCs with Agilent 5975 Series MSD and Agilent 7000 Series Triple Quadrupole MS Systems Agilent Technologies publication 5990 4643EN Implementation of the Pressure Controlled Tee for Backflushing for the 7000 Series Triple Quadrupole Mass Spectrometer Implications for Sensitivity Agilent Technologies publication 5990 4504EN User Quick Guide to Pressure Controlled Tee PCT Operation Post Run Backflushing Agilent Technologies publication 5990 5484EN Acknowledgements The author is grateful for many helpful discussions with Bruce Quimby and Bob Henderson at Agilent Technologies Wilmington DE For More Information For more information on our products and services visit our Web site at www agilent com chem www agilent com chem Agilent shall not be liable for errors contained herein or for incidental or consequential dam ages in connection with the furnishing performance or use of this material Informati
12. s where the background and stability of the system improves or maintains its integrity The GC system can be quickly called into use so there is less time required than in venting the system and returning it to service PCT Gas Saving Mode uses carrier at lt 3 mL min When compared to typical GC MS use every hour the system is in PCT Gas Saver Mode is an additional hour of analytical time and carrier saved Routinely archiving the system in this mode for every weekend of a year equates to more than 100 days of analytical time recovered Since the PCT can be enabled on any GC MS or GC system an entire laboratory can employ these savings to dramatically reduce one of the major costs of opera tion Table 1 shows a summary of the additional analytical time that can be provided by PCT Gas Saver mode over various durations Table 1 Additional Operating Analytical Time Days Supplied by the PCT Gas Saver Mode as a Function of the Duration Applied and Period of Consistent Use PCT Gas Saver Mode Use Period Every night Only weekends Evening and weekends 1 Week 3 6 days 2 3 days 4 4 days 1 Month 14 6 days 9 2 days 17 5 days 1 Year 174 6 days 110 5 days 210 3 days Note For example using PCT Gas Saver Mode only on the weekends will add an additional 110 days year of operation compared to the default Gas Savers Settings of 20 mL min plus column and septum flows of 1 2 mL min and 3 mL min respectively References 1 Capillary Fl
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