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

Practical Faster GC Applications with High-Efficiency GC Columns and Method Translation Software. Paul Barton Product Specialist Consumables Division Agilent Technologies. Questions to Ask. What information do you need from your analysis?

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

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  1. Practical Faster GC Applications with High-Efficiency GC Columns and Method Translation Software Paul BartonProduct SpecialistConsumables DivisionAgilent Technologies

  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?

  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

  4. N = ¦ (gas, L, rc) k = ¦(T, df, rc) a =¦(T, phase) Resolution L = Length rc = column radius df = film thickness T = temperature Efficiency Retention Selectivity

  5. Plates: 5000 10000 15000 20000 25000 Alpha: 1.10 1.35 1.60 1.85 2.1 k’: 2.0 4.5 7.0 9.5 12.0 Typical Method Development Parameters - Effects of Selectivity, Efficiency, and Retention on Resolution Selectivity Impacts Resolution Most Rs = N½/4  (-1)/  k’/(k’+1)

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

  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

  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

  9. DB-1 15m x 0.32mm, 0.25µm Oven: 40°C for 2 min 40-120°C at 5°C/min 0 2 4 6 8 10 12 14 Time (min.) DB-Wax 15m, 0.32mm, 0.25µm Oven: 80-190°C at 20°C/min 0 1 2 3 4 5 Time (min.) Start with the Right Phase

  10. N = ¦ (gas, L, rc) k = ¦(T, df, rc) a =¦(T, phase) Resolution L = Length rc = column radius df = film thickness T = temperature Efficiency Retention Selectivity

  11. Column Length and Efficiency (Theoretical Plates) N Length (m) 15 69,450 30 138,900 60 277,800 0.25 mm IDn/m = 4630 (for k = 5)

  12. R=1.16 R=0.84 R=1.68 2.29 min 8.73 min 4.82 min Column Length VS Resolution and Retention: Isothermal 15 m 30 m 60 m Double the plates, double the time but not double the the resolution

  13. 4 2 3 1 5 1.0 2.0 3.0 4.0 5.0 6.0 DECREASE THE LENGTH DB-5 30 m 0.53 mm I.D., 0.5 µm 1 4 2 3 5 .5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 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

  14. If you Decrease Length: Efficiency Decrease Resolution Decrease Analysis Time Decrease Pressure Decrease Cost Decrease Length Summary

  15. N = ¦ (gas, L, rc) k = ¦(T, df, rc) a =¦(T,phase) Resolution Efficiency Retention Selectivity L = Length rc = column radius df = film thickness T = temperature N = 1 r [11k2+6k+1]/[3(k+1)2]

  16. i.d. (mm) N/m 0.05 23,160 5 m 0.10 11,580 10 m 0.18 6,660 20 m 0.20 5830 0.25 4630 0.32 3660 30 m 0.45 2840 0.53 2060 Column Diameter - Theoretical Efficiency Total Plates N ~ 112,000 N ~ 112,000 N ~ 112,000 N ~ 112,000 k = 5

  17. β = PHASE RATIO ()Film Thickness • Column DimensionsPhase Ratio β • 30 m x .53 mm x 3.0 m 44 • 30 m x .32 mm x 1.8 m 44 KC = k β r 2df

  18. Column : DB-624 30 0.53 3 m, mm, m 0 5 10 15 20 Time (min) Different Column I. D. Equal Phase Ratios (cm/sec) Carrier: Helium, 40 Oven: 65° C Injection: Split Detector: FID Column : DB-624 30 0.32 1.8 m, mm, m

  19. Column Diameter and Capacity I.D. (mm) Capacity (ng) 0.05 1-2 0.10 6-13 0.18 25-55 0.20 35-70 Like Polarity Phase/Solute 0.25 µm film thickness 0.25 80-160 0.32 110-220 0.45 600-800 0.53 1000-2000

  20. Column Diameter - Inlet Head Pressures (Helium) I.D (mm) Pressure (psig) 0.05 275-400 0.10 90-130 0.18 30-45 0.20 25-40 0.25 15-25 30 metersHydrogen pressures x 1/2 0.32 10-20 0.45 3-7 0.53 2-4

  21. 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

  22. If you decrease the inside diameter: Efficiency Increases Resolution Increases Pressure Increases Capacity Decreases Flow rate Decreases Diameter Summary

  23. Carrier Gas ConsiderationsBest 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

  24. Carrier Gas Considerations Golay Plots Excessive Diffusion 1.00 He 0.75 h Poor Mass Transfer 0.50 H 2 0.25 ū OPGV opt 10 20 30 40 50 60 u (cm/sec)

  25. 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!)

  26. Easy Options with Method Translation Software • Different Column Dimensions • Switch He to H2 Carrier Gas and Try Faster Velocities • Same Column & Gas Type but Faster Velocities • Combination of all of the above

  27. Agilent Method Translation Software

  28. Location for Method Translation Software and Flow Calculator http://www.agilent.com/chem Technical Support Downloads and Utilities Software Utilities • GC Method Translation Software • GC Pressure/Flow Calculator Software generates a translated method (new temperature program), which attempts to maintain the resolution and selectivity of the original method

  29. 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 2µL, 50ppb Oven: 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 5,6 2 δ-BHC / heptachlor 3 7 10 9 12 1 13 8 11 21 15 18 14 16 <16 minutes 4 19 22 17 20

  30. Input Original Method Parameters

  31. Same Column and Gas TypeFast Analysis (OPGV) Transfer same dimensions New Velocity New Temp. Program

  32. Before Same Column and Gas TypeFast Analysis (OPGV) No Real Changes in Resolution! Only Time! <14 minutes

  33. Same Column and Gas typeNone mode, Try higher velocities New calculated temp. program

  34. Same Column and Gas typeNone mode, Higher velocities Before Co-elution (poorer) 80 cm/sec <8 minutes Co-elution (poorer) 65 cm/sec <10 minutes Close elution (similar) 50 cm/sec

  35. Same Column, Hydrogen Carrier GasTranslate Only

  36. Same Column, H2 Carrier GasTranslate Only Before No Real Changes in Resolution 33% faster! 11 minutes

  37. Same Column, H2 Carrier Gas, Higher Velocities

  38. Same Column, H2 Carrier Gas, Even Higher Velocities Before Co-elution 85 cm/sec 7 minutes Co-elution 80 cm/sec <8 minutes Co-elution 70 cm/sec

  39. New Column Dimensions, H2 Gas, Translate Only Input NEW dimensions Close enough New Velocity New Temp. Program

  40. New Column Dimensions, H2 Gas, Translate Only

  41. New Column Dimensions, H2 Gas, Translate Only 5 10 11 6

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

  43. New Column Dimensions, H2 Gas, Fast Analysis Better Resolution and Faster Analysis!

  44. New Column Dimensions, H2 Gas, Higher Velocities

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

  46. 2 5 12 3 7 10 9 1 8 13 21 11 19 22 6 14 15 16 18 4 17 20 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/min2 to 3mL/min 2mm i.d. liner 0.5µL, 50ppb Oven: 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 Final Method Used at EPA

  47. 2 5 3 12 7 DB-XLB 10 1 8 9 13 11 21 19 22 6 15 14 18 16 4 17 20 2 10 7 9 12 21 3 5 8 DB-17ms 13 1 19 11 22 6 14 16 15 17 18 4 20 Final Method Used at EPA

  48. 10.6 min Δ -16.8 min (0.18 mm, H2 Carrier) 17.7 min Δ -9.7 min (0.18 mm, He Carrier) (0.25 mm, He Carrier) 27.4 min Time (min) Spearmint Oil

  49. Δ -16.8 min (0.18 mm, H2 Carrier) 10.6 min Δ -9.7 min (0.18 mm, He carrier) 17.7 min (0.25 mm, He Carrier) 27.4 min Spearmint Oil – Resolution Check

  50. Resolution Maintained

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