Simple Run Table Entry Cuts Sample onto Column 2. Method Developers Calculator to Tools correctly set flows and restrictor size

Transcription

1 Introduction 2-D GC/MS and the Deans Switch: Theory and Applications 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. Fred Feyerherm, Agilent Technologies Inc. Houston, Tx Multidimensional (2-D) GC Why 2-D GC now? What s Changed? Very old (>25 yrs) but powerful separation technique. 689 Simplified 2-D GC systems are much easier to use Based on cutting peak(s) from one GC column onto another with stationary phase of different selectivity (polarity). Micro-fluidics Deans Switch Compounds that co-elute with analyte on the first column separate from the analyte(s) of interest on the second column of different polarity. Column connections are easier, zero dead volume, inert, and reliable. THC in Hair Setting gas flows done with EPC and Flow Calculator. Retention time drift greatly reduced with modern oven and EPC. NIDA drugs in Oral Fluids THC in Blood Especially useful at ultra-trace concentrations (<1 ng/ml) Inertness problems with switch hardware eliminated with surface coatings. RT control is very tight and the new switch is very quick. Simplified 2-Dimensional GC Cut 7683 Autosampler : Used to heart cut individual peaks from DB-17ms to DB-1ms column 1 T2.1 mm UDFS 2 S/S Inlet T1 purge DB-17ms 15m x.25 x.25 um Column 1 Column 2 689N GC MS T3 DB-1ms 15m x.25 x.25 um Oven Wall Deans Switch 1

2 Used to heart cut peak from to Switch off, effluent goes to monitor (no cut).3 m x.1 mm FS 15m x.25 x.25 um 27 psi 2 psi 15m x.25 x.25 um Switch on, effluent is cut to (after the cut) Switch off, effluent goes to monitor (on) 27 psi 2 psi 27 psi 2 psi EPC Backflush to save time and clean out first column! Program Inlet pressure down to.5 psi after the last cut, then after the last analyte elutes from column 2, program the to 6 psi so heavies are backflushed out split vent. New Micro-fluidics Deans Switch S/S Inlet 27 psi.5 psi 2 psi 6 psi DB-17ms MS DB-1ms 2

3 Deans Switch column connections Simple Run Table Entry Cuts Sample onto Column 2 Method Developers Calculator to Tools correctly set flows and size Cryo Trap Re-focuses Sample on Column 2 Sharpens peak very important for lower concentrations Adds ability to perform 2nd oven ramp (on) AUX 4 27 psi 2 psi Cryo First Application Example Low Level Detection Required.1 pg/mg THC in Hair DB-35ms DB-5ms 22 at Northwest Toxicology in Salt Lake City Using Finnigan TSQ 7 Triple Quadrupole MS Same samples analyzed with Deans switch SAMSHA guidelines set confirmatory cutoff at.5 pg/mg 2 mg sample size used washed, cut up, digested, extracted derivitized with PFPA/PFPOH 5 ul final extract volume (in toluene) THC-COOH concentration in final extract = 2 fg/ul 3

4 GC/MS Conditions Ideal Conditions (2 ul unextracted standard) Ion 62. (619.7 to 62.3): THC-3.D Ion 492. (491.7 to 492.3): THC-3.D 8.45 Ion 472. (471.7 to 472.3): THC-3.D Agilent 689N N Negative chemical ionization (NCI) mode -Autotuned Source temperature 16C SIM ions (5 ions): THC-COOH 62, 492, 472 d3-thc-cooh 623, 495 Ammonia reagent (buffer) gas (5X increase in sensitivity vs methane) pg/mg (unextracted) Hair Matrix Effect:.1 pg/mg Ion 62. (619.7 to 62.3): THC-5.D 2 Ion 492. (491.7 to 492.3): THC-5.D Ion 472. (471.7 to 472.3): THC-5.D (THC in Hair) Heartcut THC peak from DB-35MS to DB-5MS m x.1 mm FS tubing UNIS Inlet DB-35MS 4m x.18 mm x.18 um DB-5MS 4m x.18 mm x.18 um Switch off, DB-35MS effluent goes to monitor (no cut) Switch on, DB-35MS effluent is cut to DB-5MS (on) UNIS Inlet 8 psi 5 psi DB-35MS UNIS Inlet 8 psi 5 psi DB-35MS DB-5MS DB-5MS 4

5 Results:.1 pg/mg THC-COOH in Hair Second Application Example Ion 62. (619.7 to 62.3): THC-32.D m/e pg/mg THC-COOH in hair THC in Oral Fluid TMS derivative DB-17ms DB1ms Both are 15m x.25 x Used to heart cut peak from to Method Developers Calculator to Tools correctly set flows and size.3 m x.1 mm FS 15m x.25 x.25 um 15m x.25 x.25 um THC parent drug in Oral Fluid Third Application Example Ion 371. (37.7 to 371.7): THC3.D\data.ms Ion 386. (385.7 to 386.7): THC3.D\data.ms Ion 33. (32.7 to 33.7): THC3.D\data.ms ng/ml THC parent and THCA in Blood Arizona DPS TMS derivative RTX-2 DB17ms

6 Signal: 5B.D\1A.CH Signal: 5C.D\1A.CH Ion 371. (37.7 to 371.7): 5C.D Ion 33. (32.7 to 33.7): 5C.D Example of Inadequate Resolution DB-17ms DB-1ms Deans Calculator 11 Ion 371. (37.7 to 371.7): 2-A.D Ion 386. (385.7 to 386.7): 2-A.D Ion 33. (32.7 to 33.7): 2-A.D channel of the Deans Switch with no cuts to the secondary column Cut Times determined from.5 ng/ml THC-TMS in Blood THC Cut THCC Cut Ion 33. (32.7 to 33.7): 11SP11.D Ion 371. (37.7 to 371.7): 11SP11.D Ion 386. (385.7 to 386.7): 11SP11.D 45 THC-TMS,.5 ng/ml THCC-TMS TIC: 8g.D THC- TMS Ion Co-eluting peaks from primary column THCC-TMS THC-TMS

7 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. 7