Practical Faster GC Applications with High-Efficiency GC Columns and Method Translation Software

Transcription

1 Practical Faster GC Applications with High-Efficiency GC Columns and Method Translation Software GC Columns and Consumables Mark Sinnott Application Engineer January 8 th, 2008 Page 1

2 Questions to Ask What information do you need from your analysis? Do you have more baseline than you need between your peaks? Do you need to resolve all of the components? Page 2

3 Variables for Shortening Run Times Stationary Phase Temperature Programming Carrier Gas: type and linear velocity Shorten Column Length Decrease Film Thickness Decrease Internal Diameter Page 3

4 Resolution N k α 1 R = s 4 k + 1 α Efficiency Retention Selectivity N = ƒ (gas, L, r c ) k = ƒ (T, d f, r c ) α = ƒ (T, phase) L = Length r c = column radius d f = film thickness T = temperature Page 4

5 Resolution N k α 1 R = s 4 k + 1 α Efficiency Retention Selectivity N = ƒ (gas, L, r c ) k = ƒ (T, d f, r c ) α = ƒ (T, phase) L = Length r c = column radius d f = film thickness T = temperature Page 5

6 Stationary Phase - Common Types Siloxane polymers Poly(ethylene) glycols Porous polymers Page 6

7 Selectivity Relative spacing of the chromatographic peaks The result of all non-polar, polarizable and polar interactions that cause a stationary phase to be more or less retentive to one analyte than another Page 7

8 Optimizing Selectivity Match analyte polarity to stationary phase polarity - like dissolves like(oil and water don t mix) Take advantage of unique interactions between analyte and stationary phase functional groups Page 8

9 Start with the Right Phase DB-1 15m x 0.32mm, 0.25µm Oven: 40 C for 2 min C at 5 C/min Time (min.) DB-Wax 15m, 0.32mm, 0.25µm Oven: C at 20 C/min Time (min.) Page 9

10 Resolution N k α 1 R = s 4 k + 1 α Efficiency Retention Selectivity N = ƒ (gas, L, r c ) k = ƒ (T, d f,r c ) α = ƒ (T, phase) L = Length r c = column radius d f = film thickness T = temperature Page 10

11 Column Length and Efficiency (Theoretical Plates) Length (m) n 15 69, , , mm ID n/m = 4630 (for k = 5) Page 11

12 Column Length and Resolution R α n α L Length X 4 = Resolution X 2 t α L Page 12

13 Column Length VS Resolution and Retention: Isothermal R= min R= min R= min 15 m 30 m 60 m Double the plates, double the time but not double the the resolution Page 13

14 DECREASE THE LENGTH DB-5 30 m 0.53 mm I.D., 0.5 µm DB-5 15 m 0.53 mm I.D., 0.5 µm 1. Benzene 2. Toluene 3. Ethylbenzene 4. m,p-xylene 5. o-xylene BTEX Carrier: Helium, 36 cm/sec at 40 c Oven : 40 C for 3 min, 5 /min to 100 C Page 14

15 Column Length and Cost 15m 30m 60m $ $ $ $ $ $ $ Page 15

16 Length Summary If you Decrease Length: Efficiency Resolution Analysis Time Pressure Cost Decrease Decrease Decrease Decrease Decrease Page 16

17 Resolution N k α 1 R = s 4 k + 1 α Efficiency Retention Selectivity N = ƒ (gas, L, r c ) k = ƒ (T, d f, r c ) α = ƒ (T, phase) L = Length r c = column radius d f = film thickness T = temperature Page 17

18 Column Diameter - Theoretical Efficiency Total Plates I.D. (mm) n/m 5 m N ~ 112, , m N ~ 112, , , m N ~ 112, m N ~ 112, k = Page 18

19 Different Column I. D. Equal Phase Ratios Column: DB m, 0.53 mm, 3 m Carrier: Oven: Helium, 40(cm/sec) 65 C Injection: Split Detector: FID Column: DB m, 0.32 mm, 1.8 m Time (min) Page 19

20 PHASE RATIO (β) Film Thickness Column Dimensions Phase Ratio β 30 m x.53 mm x 3.0 μm m x.32 mm x 1.8 μm 44 K C = k β β = r 2d f Page 20

21 Column Diameter and Capacity I.D. (mm) Capacity (ng) Like Polarity Phase/Solute 0.25 µm film thickness Page 21

22 Column Diameter - Inlet Head Pressures (Helium) I.D (mm) Pressure (psig) meters Hydrogen pressures x 1/ Page 22

23 Column Diameter and Carrier Gas Flow Lower flow rates: Smaller diameter columns Higher flow rates: Larger diameter columns Low flow rates : GC/MS High flow rates: Headspace, purge & trap Page 23

24 Diameter Summary If you decrease the inside diameter: Efficiency Resolution Pressure Capacity Flow rate Increase Increase Increase Decrease Decrease Page 24

25 Combining a Change in Length With a Change in Diameter Decrease Length Decrease Diameter Efficiency Analysis Time Page 25

26 Carrier Gas Considerations Best velocity? Optimal range of velocities Too low or high results in loss of resolution Balance resolution and analysis time BUT... there is no LAW against going FASTER Page 26

27 Carrier Gas Considerations Van Deemter Curve 1.00 Excessive Diffusion h He Poor Mass Transfer 0.25 ū opt H 2 OPGV u (cm/sec) Page 27

28 Carrier Gas Considerations Utilizing Computer Controlled Flow Ramping (EPC) Lonely Late Eluters? = P Decrease retention and overall run time by increasing pressure (speed up the gas!) Page 28

29 Easy Options with Method Translation Software Different Column Dimensions Switch He to H 2 Carrier Gas and Try Faster Velocities Same Column & Gas Type but Faster Velocities Combination of all of the above Page 29

30 CLP-Pesticides - Original Improved Method 0.32mm I.D., Helium Carrier Gas , Column: DB-XLB 30m x 0.32mm i.d., 0.25µm Carrier: He, constant flow, 38 cm/s at 120 C Injector: Pulsed Splittless, 220 C Pulse pressure & time: 35psi for 1.15min Oven: µL, 50ppb 120 C for 1.17min 120 C to 160 C at 25 /min 160 C to 260 C at 10 /min 260 C to 300 C (4min) at 15 /min Detector: µ-ecd, 320 C Ar/CH4 (P5) makeup gas at 60mL/min <16 minutes Page 30

31 Input Original Method Parameters Page 31

32 Same Column and Gas Type Fast Analysis (OPGV) Transfer same dimensions New Velocity New Temp. Program Page 32

33 Same Column and Gas Type Fast Analysis (OPGV) Before No Real Changes in Resolution! Only Time! <14 minutes Page 33

34 Same Column and Gas type None mode, Try higher velocities New calculated temp. program Page 34

35 Same Column and Gas type None mode, Higher velocities Before Co-elution (poorer) cm/sec Co-elution (poorer) <8 minutes 65 cm/sec <10 minutes Close elution (similar) 50 cm/sec Page 35

36 Same Column, Hydrogen Carrier Gas Translate Only Page 36

37 Same Column, H 2 Carrier Gas Translate Only Before No Real Changes in Resolution % faster! 11 minutes Page 37

38 Same Column, H2 Carrier Gas, Higher Velocities Page 38

39 Same Column, H2 Carrier Gas, Even Higher Velocities Co-elution Before cm/sec Co-elution 7 minutes 80 cm/sec Co-elution <8 minutes 70 cm/sec Page 39

40 New Column Dimensions, H 2 Gas, Translate Only Input NEW dimensions Close enough (got lucky) New Velocity New Temp. Program Page 40

41 New Column Dimensions, H2 Gas, Translate Only Page 41

42 New Column Dimensions, H2 Gas, Translate Only Page 42

43 New Column Dimensions, H2 Gas, Fast Analysis New Velocity New Temp. Program Page 43

44 New Column Dimensions, H2 Gas, Fast Analysis Better Resolution and Faster Analysis! Page 44

45 New Column Dimensions, H2 Gas, Higher Velocities Page 45

46 New Column Dimensions, H2 Gas, Higher Velocities 105 cm/sec? 5.5 minutes! 95 cm/sec <6 minutes 85 cm/sec Page 46

47 Final Method Used at EPA Column: DB-XLB 20m x 0.18mm i.d., 0.18µm Carrier: H2, constant flow, 77.3cm/s at 120 C Injector: Pulsed Splittless, 220 C Pulse pressure & time: 35psi for 0.5min Flow ramp at 6.25min of 99mL/min 2 to 3mL/min 2mm i.d. liner Oven: µL, 50ppb 120 C for 0.49min 120 C to 160 C at 59.4 /min 160 C to 260 C at 23.7 /min 260 C to 300 C (1.69min) at 35.6 /min Detector: µ-ecd, 320 C Ar/CH4 (P5) makeup gas at 60mL/min Page 47

48 Final Method Used at EPA DB-XLB DB-17ms Page 48

49 Food/Fragrance Method translation Page 49

50 Food/Fragrance Method translation Page 50

51 Spearmint Oil 10.6 min Δ min (0.18 mm, H 2 Carrier) 17.7 min Δ -9.7 min (0.18 mm, He Carrier) (0.25 mm, He Carrier) 27.4 min Time (min) Page 51

52 Spearmint Oil Resolution Check Δ min (0.18 mm, H 2 Carrier) 10.6 min Δ -9.7 min (0.18 mm, He carrier) 17.7 min (0.25 mm, He Carrier) 27.4 min Page 52

53 Resolution Maintained Compound s Compound Resolution 0.25 mm 0.18 mm 0.18 mm Helium Helium Hydrogen Sabinene β-pinene α-terpinene p-cymene Speed Gain N/A 35% 61% Page 53

54 CONCLUSIONS Stationary Phases Chosen for optimized selectivity Diameter Smaller allows shorter length but has less capacity Make Small Changes Again think capacity Carrier Gas Hydrogen, high velocity, but can still go fast with He Temperature Program Scale properly to preserve elution pattern Method Translation Software FREE, reliable Flow Ramp Increase at end of run for late eluters (if necessary) Page 54

55 Thank you! TECHNICAL SUPPORT Agilent #4, #1 Page 55

56 Thank you for attending Agilent Technologies e-seminar today. For a full listing of our e-seminar offerings as well as our hands-on training classes, please go to our website at: Or register for Stay current with e-notes to receive regular updates Page 56 Slide 56

57 Upcoming e-seminars NEW! Carrier Gases in Capillary GC - Series 1 January 15, :00 p.m. EST Introduction to Capillary GC - Series 2 February 20, :00 p.m. EST Selection of a Capillary GC Column - Series 3 March 13, :00 p.m. EST Page 57 Sli de

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59 New On Demand Webinar: Utilizing Sub-Two Micron Particles to Optimize HPLC Methods A Four Part Workshop on Managing Chemistry and Pressure for Faster and More Efficient HPLC Separations Be sure to register after today s s event. Our measure is your success. Page 59