Secrets of GC Column Dimensions

Transcription

1 Secrets of GC Column Dimensions GC Columns and Consumables Simon Jones Application Engineer May 20, 2008 Slide 1

2 Secrets of GC Column Dimensions Do I have the right column phase? Resolution Equation Changes in Dimensions: Length Diameter Film Thickness Method Translation Software Carrier gas (if time) Slide 2

3 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.) Slide 3

4 Variables that affect chromatography Stationary Phase Temperature Programming Carrier Gas: type and linear velocity Column Length Film Thickness Internal Diameter There s no such thing as a free lunch Slide 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 Slide 5

6 Column Dimensions Length Diameter Film Thickness Slide 6

7 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 Slide 7

8 Column Length and Efficiency (Theoretical Plates) Length (m) N 15 69, , , mm ID n/m = 4630 (for k = 5) Slide 8

9 Column Length and Resolution R α N α L Length X 4 = Resolution X 2 t α L Upside = Cut a bunch off during routine inlet maintenance and not lose a lot of Resolution Slide 9

10 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 resolution Slide 10

11 Column Length and Cost 15m 30m 60m $ $ $ $ $ Slide 11

12 Length Summary If you Increase Length: Efficiency Resolution Analysis Time Pressure Cost Increase Increase Increase Increase Increase Slide 12

13 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 Slide 13

14 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 Slide 14

15 Column Diameter Capillary Columns I.D. (mm) Common Name 0.53 Megabore 0.45 High speed Megabore 0.32 Widebore Narrowbore 0.18 Minibore 0.10 Microbore 0.05 Nanobore Slide 15

16 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 = Slide 16

17 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) Slide 17

18 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 Slide 18

19 High Resolution Megabore (0.45 mm diameter) Same outer diameter as the Megabore No special hardware required Smaller inner diameter (0.45mm) Maintain phase ratio (Beta) Methods are easy to translate!

20 High Resolution Megabore Column Dimensions Phase Ratio β 30 m x.53 mm x 3.0 μm m x.45 mm x 2.55 μm 44

21 High-SPEED Megabore Same Resolution - Faster Analysis! DB-5 30 m, 0.53 mm I.D., 0.5 µm 1 2 R = cm/sec DB-5 30 m, 0.45 mm I.D., 0.42 µm 45.9 cm/sec 1 2 R = Benzene 2. Toluene 3. Ethylbenzene 4. m,p-xylene 5. o-xylene BTEX Carrier: Helium Oven : 40 C for 3 min, 5 /min to 100 C

22 High SPEED Megabore Same Resolution - Faster Analysis! Increasing Sample Throughput With High-Speed Megabore Application note EN

23 Column Diameter and Capacity I.D. (mm) Capacity (ng) Like Polarity Phase/Solute 0.25 µm film thickness Slide 23

24 Column Diameter - Inlet Head Pressures (Helium) I.D (mm) Pressure (psig) meters Hydrogen pressures x 1/ Slide 24

25 Diameter Summary If you decrease the inside diameter: Efficiency Resolution Pressure Capacity Flow rate Increase Increase Increase Decrease Decrease Slide 25

26 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 Slide 26

27 Film Thickness and Retention: Isothermal Thickness (µm) Retention Change Constant Diameter Normalized to 0.25 µm Slide 27

28 Film Thickness and Resolution When solute k < 5 d f R (early eluters) or T When solute k > 5 (later eluters) d f or T R Slide 28

29 Other Retention - Adsorption Analysis of Noble & Fixed Gases Using HP PLOT MoleSieve Column: Carrier: Oven: Sample: HP-PLOT/MoleSieve 30 m x 0.53 mm x 50 m HP part no P-MS0 Helium, 4 ml/min 35 C(3min) to 120 C (5 min) at 25 C/min 250 l, split (ratio 50:1) Neon 2. Argon 3. Oxygen 4. Nitrogen 5. Krypton 6. Xenon Time (min) Slide 29

30 Film Thickness and Capacity Thickness (µm) Capacity (ng) mm I.D. Like Polarity Phase/Solute Slide 30

31 Film Thickness and Bleed More stationary phase = More degradation products Slide 31

32 Film Thickness and Inertness active inactive active inactive active inactive Slide 32

33 Film Thickness Summary If you increase the film thickness: Retention Increase Resolution (k<5) Increase Resolution (k>5) Decrease Capacity Increase Bleed Increase Inertness Increase Efficiency Decrease Slide 33

34 GC Column Dimensions Examples. Slide 34

35 Method m x 0.25mm ID, 0.50 μm 25 min run time Slide 35

36 Fast 8270 Semivolatile Analysis 12.5m X 100 μm ID HP-5ms column 7.5 min run time But.is this practical? See Agilent application note # EN for more details. Slide 36

37 Running Samples on 100 μm ID Columns Practical? Environmental type samples = high contaminant residue potential. Smaller ID columns have reduced capacity for matrix contaminants due to lower surface area, shorter length (less forgiving). Less surface area a 10 m x.10 mm column has 7.5X less overall surface area than a 30 m x 0.25 mm ID column. A more robust solution might be to switch to a 20 m x 0.18 mm ID column (nice middle-ground between 0.25 and 0.10). These columns could be used in splitless or in split mode, whereas the 0.10 mm ID columns are practically limited to split introduction. Slide 37

38 Fast 8270 Semivolatile Analysis 20m x 0.18mm ID x 0.36um, DB min run time Flow program or faster temperature program? Slide 38

39 What this method optimization means to your lab Before Optimization GC/MS 1 GC/MS 2 GC/MS 3 19 Spls/day 19 Spls/day 19 Spls/day After Optimization GC/MS 1 GC/MS 2 GC/MS 3 29 Spls/day 28 Spls/day Idle Slide 39

40 Regular Unleaded Gasoline California Phase I Normal Column: DB-PETRO m x 0.25 mm I.D., 0.5 µm Carrier: H 2, 24 psig, 31 cm/s Oven: 35 C// 9.5 min// 13.3 /min// 45 // 11 min// 1.4 /min// 60 // 11min// 2.7 /min// 220 // 3.6 min Injector: Split 1:200, 0.2 µl Detector: 300 C Time (min.) High Speed Column: DB-1 40 m x 0.10 mm I.D., 0.20 µm Carrier: H 2, 78 psig, 34.8 cm/s Oven: 35 C// 3.6 min // 36.1 /min// 45 C// 4.15 min // 3.91 /min// 60 C// 4.15 min//6.9 / min// 220 C// 1.38 min Injector: Split 1:400, 250 C, 0.2 µl Detector: 300 C Time (min.)

41 OK, Test Time Fusel Oil Simple Standard 1 2 DB m x.53 mm I.D. x 3.0 μm Inlet: FID: Carrier: Oven: 250 o C, split 300 o C H 2, 50 cm/sec 40 o C for 5 min. 10 o C/min to 250 o C 1. acetaldehyde 2. methanol 3. 3-methyl-butanol (isoamyl alcohol) 4. 2-methyl-butanol (active amyl alcohol) How would you try to get better R for this? k, α, N? 3 4 C Time (min) Slide 41

42 Need Plates? Length AND Column Diameter Column Dimensions Theoretical Plates 25 m x.53 mm x 3.0 μm 34, m x.25 mm x 1.4 μm 181,860 Slide 42

43 Fusel Oil Standard DB m x.25 mm I.D. x 1.4 μm Inlet: FID: Carrier: Oven: 250 o C, split 300 o C H 2, 50 cm/sec 40 o C for 5 min. 10 o C/min to 250 o C acetaldehyde 2. methanol 3. ethanol 4. acetone 5. 1-propanol 6. ethyl acetate 7. isobutanol 8. 1-butanol 9. 3-pentanol (IS) methyl-butanol (isoamyl alcohol) methyl-butanol (active amyl alcohol) 12. hexanol 13. phenylethanol Rs = C Time (min) Slide 43

44 Method Translation Software Input Screen Available at or use the key words GC Method Translator in the quick search box at the Agilent.com website. Slide 44

45 CARRIER GAS Carries the solutes down the column Selection and velocity influences efficiency and retention time Slide 45

46 RESOLUTION VS. LINEAR VELOCITY Helium Resolution of 1.5 = baseline resolution R = 1.46 R = 1.31 R = cm/sec 35 cm/sec 40 cm/sec 4.4 psig 5.1 psig 5.8 psig DB-1, 15 m x 0.32 mm ID, 0.25 um 60 C isothermal 1,3- and 1,4-Dichlorobenzene Slide 46

47 VAN DEEMTER CURVE OPGV = Optimum Practical Gas Velocity 1.00 H u opt OPGV u (cm/sec) Slide 47

48 μ opt and OPGV μ opt : Maximum efficiency OPGV: Optimal practical gas velocity Maximum efficiency per unit time 1.5-2x u opt Slide 48

49 COMMON CARRIER GASES Nitrogen Helium Hydrogen Slide 49

50 VAN DEEMTER CURVES 1.00 N 2 H Small 0.25 Large He H u (cm/sec) Page 50 Group/Presentation Title Agilent Restricted Month ##, 200X

51 CARRIER GAS Helium vs. Hydrogen Helium (35 cm/sec) Hydrogen (73 cm/sec) Time (min.) Time (min.) DB-1, 15 m x 0.25 mm i.d., 0.25 µm 50 C for 2 min, C at 20 /min 10.5 min 7.8 min Slide 51

52 CARRIER GAS Gas Advantages Disadvantages Nitrogen Cheap, Readily available Long run times Helium Good compromise, Safe Expensive Hydrogen Shorter run times, Cheap Explosive* *Hydrogen is difficult to explode under GC conditions Slide 52

53 Conclusions Make sure what you are doing make sense Try not to make a big change in diameter; take small steps A good place to start is to switch from 0.53 to 0.45 mm id, or 0.32 to 0.25 mm Remember that with a decrease in diameter you will also have a decrease in capacity and flow Avoid mm id columns unless you are proficient in 0.18 mm id Use Method Translator Utilize Technical Support! Slide 53

54 Thank you! Agilent technical support can be reached at: Questions? Slide 54

55 Wrap-up E-Seminar Questions Thank you for attending Agilent e-seminars. Our e-seminar schedule is expanding every week. Please check our website frequently at: Or register for Stay current with e-notes to receive regular updates Slide 55

56 Upcoming GC e-seminars Techniques for Making Your GC Analysis More Repeatable and Robust June 20, :00 p.m. EDT Techniques, Tips and Tricks of Troubleshooting Capillary GC Systems July 15, :00 p.m. EDT