2-D GC/MS and the Deans Switch: Theory and Applications. Fred Feyerherm, Agilent Technologies Inc. Houston, Tx

Transcription

1 2-D GC/MS and the Deans Switch: Theory and Applications Fred Feyerherm, Agilent Technologies Inc. Houston, Tx

2 Introduction Simplified 2-D GC can be used to accomplish the separation of specific analytes from very complex matrices. In complex sample matrices, there are often too many overlapping compounds to allow resolution of the compound(s) of interest, even with the highest resolution columns available. On any single column, the analytes co-elute with several other compounds, making their analysis difficult or impossible. This approach can solve difficult analytical problems with a relatively low cost, easy to use system that is very robust and easy to maintain.

3 Multidimensional (2-D) GC Very old (>25 yrs) but powerful separation technique. Based on cutting peak(s) from one GC column onto another with stationary phase of different selectivity (polarity). Compounds that co-elute with analyte on the first column separate from the analyte(s) of interest on the second column of different polarity. THC in Hair NIDA drugs in Oral Fluids THC in Blood Especially useful at ultra-trace concentrations (<1 ng/ml)

4 Why 2-D GC now? What s Changed? 6890 Simplified 2-D GC systems are much easier to use Micro-fluidics Deans Switch Column connections are easier, zero dead volume, inert, and reliable. Setting gas flows done with EPC and Flow Calculator. Retention time drift greatly reduced with modern oven and EPC. Inertness problems with switch hardware eliminated with surface coatings. RT control is very tight and the new switch is very quick.

5 Simplified 2-Dimensional GC 7683 Autosampler Cut FID1 FID2 Column 1 Column N GC Deans Switch

6 Deans Switch System: Used to heart cut individual peaks from DB-17ms to DB-1ms column FID T2 S/S Inlet restrictor 0.1 mm UDFS T1 purge restrictor solenoid valve PCM DB-17ms 15m x 0.25 x 0.25 um MS T3 DB-1ms 15m x 0.25 x 0.25 um Oven Wall

7 Deans Switch System Used to heart cut peak from DB-17MS to DB-1MS FID restrictor 0.3 m x.1 mm FS solenoid valve Injector PCM DB-17MS 15m x.25 x 0.25 um MSD DB-1MS 15m x.25 x 0.25 um

8 Deans Switch System Switch off, DB-17MS effluent goes to monitor FID (no cut) FID restrictor solenoid valve (off) Injector PCM 27 psi 20 psi DB-17MS MSD DB-1MS

9 Deans Switch System Switch on, DB-17MS effluent is cut to DB-1MS FID restrictor solenoid valve (on) Injector PCM 27 psi 20 psi DB-17MS MSD DB-1MS

10 Deans Switch System (after the cut) Switch off, DB-17MS effluent goes to monitor FID FID restrictor solenoid valve (off) Injector PCM 27 psi 20 psi DB-17MS MSD DB-1MS

11 EPC Backflush to save time and clean out first column! Program Inlet pressure down to 0.5 psi after the last cut, then after the last analyte elutes from column 2, program the PCM to 60 psi so heavies are backflushed out split vent. FID restrictor solenoid valve (off) S/S Inlet PCM 27 psi 0.5 psi 20 psi 60 psi DB-17ms MS DB-1ms

12 New Micro-fluidics Deans Switch

13 Deans Switch column connections

14 Simple Run Table Entry Cuts Sample onto Column 2

15 Method Developers Calculator to Tools correctly set flows and restrictor size

16 Cryo Trap Re-focuses Sample on Column 2 Sharpens peak very important for lower concentrations Adds ability to perform 2nd oven ramp FID restrictor solenoid valve (on) Injector AUX 4 27 psi 20 psi DB-17MS MSD Cryo DB-1MS

17 First Application Example 0.1 pg/mg THC in Hair DB-35ms DB-5ms 2002 at Northwest Toxicology in Salt Lake City Using Finnigan TSQ 7000 Triple Quadrupole MS Same samples analyzed with Deans switch

18 Low Level Detection Required SAMSHA guidelines set confirmatory cutoff at 0.05 pg/mg 20 mg sample size used washed, cut up, digested, extracted derivitized with PFPA/PFPOH 50 ul final extract volume (in toluene) THC-COOH concentration in final extract = 20 fg/ul

19 GC/MS Conditions Agilent 6890N N Negative chemical ionization (NCI) mode -Autotuned Source temperature 160C SIM ions (5 ions): THC-COOH 620, 492, 472 d3-thc-cooh 623, 495 Ammonia reagent (buffer) gas (5X increase in sensitivity vs methane)

20 Ideal Conditions (2 ul unextracted Abundance standard) 1200 Ion ( to ): THC-03.D Ion ( to ): THC-03.D 8.45 Ion ( to ): THC-03.D pg/mg (unextracted) Time-->

21 Abundance Hair Matrix Effect: 0.1 pg/mg Ion ( to ): THC-05.D Ion ( to ): THC-05.D Ion ( to ): THC-05.D Time-->

22 Deans Switch System (THC in Hair) Heartcut THC peak from DB-35MS to DB-5MS FID restrictor 4.2m x.1 mm FS tubing UNIS Inlet solenoid valve PCM DB-35MS 40m x.18 mm x 0.18 um MSD DB-5MS 40m x.18 mm x 0.18 um

23 Deans Switch System Switch off, DB-35MS effluent goes to monitor FID (no cut) FID restrictor solenoid valve (off) UNIS Inlet PCM 80 psi 50 psi DB-35MS MSD DB-5MS

24 Deans Switch System Switch on, DB-35MS effluent is cut to DB-5MS FID restrictor solenoid valve (on) UNIS Inlet PCM 80 psi 50 psi DB-35MS MSD DB-5MS

25 Results: 0.1 pg/mg THC-COOH in Hair Abundance 1100 Ion ( to ): THC-032.D m/e pg/mg THC-COOH in hair Time-->

26 Second Application Example THC in Oral Fluid TMS derivative DB-17ms DB1ms Both are 15m x 0.25 x 0.25

27 Deans Switch System Used to heart cut peak from DB-17MS to DB-1MS FID restrictor 0.3 m x.1 mm FS solenoid valve Injector PCM DB-17MS 15m x.25 x 0.25 um MSD DB-1MS 15m x.25 x 0.25 um

28 Method Developers Calculator to Tools correctly set flows and restrictor size

29 THC parent drug in Oral Fluid Abundance 1400 Ion ( to ): THC03.D\data.ms Ion ( to ): THC03.D\data.ms Ion ( to ): THC03.D\data.ms ng/ml Time-->

30 Third Application Example THC parent and THCA in Blood Arizona DPS TMS derivative RTX-200 DB17ms

31 Example of Inadequate Resolution DB-17ms DB-1ms Abundance Ion ( to ): 02-A.D Ion ( to ): 02-A.D Ion ( to ): 02-A.D Time-->

32 Deans Calculator

33 FID channel of the Deans Switch with no cuts to the secondary column Abundance Signal: 05B.D\FID1A.CH Time-->

34 Cut Times determined from FID

35 Abundance Signal: 05C.D\FID1A.CH THC Cut THCC Cut Abundance Time--> Ion ( to ): 05C.D Ion ( to ): 05C.D THCC-TMS Abundance 1000 Time--> TIC: 08g.D THC- TMS Co-eluting peaks from primary column THCC-TMS THC-TMS Time-->

36 0.5 ng/ml THC-TMS in Blood Abundance Ion ( to ): 011SP011.D Ion ( to ): 011SP011.D Ion ( to ): 011SP011.D THC-TMS, 0.5 ng/ml Ion Time-->

37 Summary Developments in GC hardware in recent years have made Deans switch systems easier to use and maintain. 2D GC is a powerful tool that can be used by itself or combined with other selective techniques to solve difficult separation problems. 2D GCMS (GC/GC/MS) can be used instead of GC/MS/MS in many applications.