1. The Right GC Column - Selection Essentials

2. Cylinders or Generators Typical Gas Chromatographic System Picking the appropriate stationary phase and optimum dimensions for the column will give the greatest resolution in the shortest analysis time.

3. Four Primary Selection Areas Stationary Phase Type Column Internal Diameter Stationary Phase Film Thickness Column Length

4. Resolution N =  (gas, L, r c ) k =  (T, d f, r c )  =  (T, phase) Efficiency Retention Selectivity L = Length r c = column radius d f = film thickness T = temperature

5. Resolution Efficiency Retention Selectivity L = Length r c = column radius d f = film thickness T = temperature N =  (gas, L, r c ) k =  (T, d f, r c )  =  (T, phase)

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

7. Liquid Phase Carrier Gas Porous Layer Open Tube (PLOT) Wall Coated Open Tube (WCOT) Solid Particles Carrier Gas Capillary Column Types

8. HH HO --C-C-O -- H H H n Polyethylene glycol backbone Stationary Phase Polymers

9. k 2 = partition ratio of 2nd peak k 1 = partition ratio of 1st peak Why Is Stationary Phase Type Important?  = k2k2 k1k1  Influence of

10. 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

11. 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

12. Compounds - Properties CompoundsPolarAromatic Hydrogen Bonding Dipole Toluenenoyesnoinduced Hexanolyesnoyes Phenolyes Decaneno Naphthalenenoyesnoinduced Dodecaneno

13. 100% Methyl Polysiloxane (boiling point column?) Strong Dispersion No Dipole No H Bonding 0246810121416 1 2 3 4 5 6 1. Toluene 110 o 2. Hexanol 156 o 3. Phenol 182 o 4. Decane (C10) 174 o 5. Naphthalene 218 o 6. Dodecane (C12) 216 o

14. 5% Phenyl Strong Dispersion No Dipole Weak H Bonding 0246810121416 0246810121416 100% Methyl 1 2 3 4 5 6 5% Phenyl 1 2 3 4 5,65,6 Strong Dispersion No Dipole No H Bonding 1. Toluene 2. Hexanol 3. Phenol 4. Decane (C10) 5. Naphthalene 6. Dodecane (C12) CompoundsPolarAromatic Hydrogen Bonding Dipole Toluenenoyesnoinduced Hexanolyesnoyes Phenolyes Decaneno Naphthaleneno yes noinduced Dodecaneno ?

15. 50% Phenyl Strong Dispersion No Dipole Weak H Bonding 50% Phenyl 0246810121416 100% Methyl 1 2 3 4 5 6 0246810121416 1 2 4 3 6 5 Strong Dispersion No Dipole No H Bonding 1. Toluene 110 o 2. Hexanol 156 o 3. Phenol 182 o 4. Decane (C10) 174 o 5. Naphthalene 218 o 6. Dodecane (C12) 216 o CompoundsPolarAromatic Hydrogen Bonding Dipole Toluenenoyesnoinduced Hexanolyesnoyes Phenolyes Decaneno Naphthaleneno yes noinduced Dodecaneno ?

16. 14% Cyanopropylphenyl Strong Dispersion None/Strong Dipole (Ph/CNPr) Weak/Moderate H Bonding (Ph/CNPr) 0246810121416 0246810121416 100% Methyl 1 2 3 4 5 6 1 2 4 6 3 5 14% Cyano- propylphenyl Strong Dispersion No Dipole No H Bonding 1. Toluene 2. Hexanol 3. Phenol 4. Decane (C10) 5. Naphthalene 6. Dodecane (C12) CompoundsPolarAromatic Hydrogen Bonding Dipole Toluenenoyesnoinduced Hexanolyesnoyes Phenolyes Decaneno Naphthaleneno yes no induced Dodecaneno ?

17. 50% Cyanopropyl Strong Dispersion Strong Dipole Moderate H Bonding 0246810121416 0246810121416 100% Methyl 1 2 3 4 5 6 4 1 6 2 5 3 50% Cyanopropyl Strong Dispersion No Dipole No H Bonding 1. Toluene 2. Hexanol 3. Phenol 4. Decane (C10) 5. Naphthalene 6. Dodecane (C12) CompoundsPolarAromatic Hydrogen Bonding Dipole Toluenenoyesnoinduced Hexanolyesnoyes Phenolyes Decaneno Naphthalenenoyesnoinduced Dodecaneno ?

18. 100% Polyethylene Glycol Strong Dispersion Strong Dipole Moderate H Bonding 0246810121416 4 1 6 2 5 3 100% PEG 0246810121416 100% Methyl 1 2 3 4 5 6 Strong Dispersion No Dipole No H Bonding 1. Toluene 2. Hexanol 3. Phenol 4. Decane (C10) 5. Naphthalene 6. Dodecane (C12) CompoundsPolarAromatic Hydrogen Bonding Dipole Toluenenoyesnoinduced Hexanolyesnoyes Phenolyes Decaneno Naphthalenenoyesnoinduced Dodecaneno ?

19. Selectivity is important but not everything… Inertness and Bleed can be critical factors in column selection. Temperature limits will play a role as well.

20. Stationary Phase Bleed A thermodynamic equilibrium process that occurs to some degree in all columns, and is proportional to the mass amount of stationary phase inside the capillary tubing/carrier gas flow path Polysiloxane backbone releases low molecular weight, cyclic fragments Is negligible in low temperature, O2-free, clean GC systems Increased by increased temperature, oxygen exposure, or chemical damage

21. Bleed: Why Does It Happen? “Back Biting” Mechanism of Product Formation + Repeat Si OOOO O O OH CH 3 OHSi O O O CH 3 Si O O O CH 3 H3CH3C H3CH3C H3CH3C Si CH 3 O OOOO O Si HO H3CH3C CH 3 Si CH 3 Cyclic products are thermodynamically more stable!

22. DB-5ms Structure CH 3 3 3 3 3 3 Si O O O O DB-5 Structure DB-5 5% Phenyl CH 3 3 3 3 3 3 3 3 Si O O DB-5ms Structure DB-5ms 1.Increased stability 2.Different selectivity 3.Optimized to match DB-5

23. Solid line:DB-5ms 30 m x.25 mm I.D. x.25  m Dashed line:DB-5 30 m x.25 mm I.D. x.25  m Oven:60 o C isothermal Carrier gas: H 2 at 40 cm/sec 1: Ethylbenzene 2: m-Xylene 3: p-Xylene 4: o-Xylene Difference in Selectivity

24. Four Types Of Low Bleed Phases Phases tailored to “mimic” currently existing polymers -Examples: DB-5ms, DB-35ms, DB-17ms, DB-225ms Phases unrelated to any previously existing polymers -Examples: DB-XLB Optimized manufacturing processes -DB-1ms, HP-1ms, HP-5ms Hand selected columns

25. Benefits of Low Bleed Phases PAH Sensitivity Using DB-35MS 1. Naphthalene 2. Acenaphthylene 3. Acenaphthene 4. Fluorene 5. Phenanthrene 6. Anthracene 7. Fluoranthene 8. Pyrene 9. Benz[a]anthracene 10. Chrysene 11. Benzo[b]fluoranthene 12. Benzo[k]fluoranthene 13. Benzo[a]pyrene 14. Indeno[1,2,3,- c,d]anthracene 15. Dibenz[a,h]anthracene 16. Benzo[g,h,i]perylene Columns: 30 m x 0.32 mm x 0.35 um. Carrier: H2, constant flow, 5 psi at 100 o C. Injector: 275 o C, splitless, 1 ul, 0.5-5ppm. Oven: 100 o C to 250 o C (5 min.) at 15 o C/min.,; then to 320 o C (10 min.) at 7.5 o C/min. Detector: FID, 320 o C. 510152025 min. DB-35MS 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Commercially Available 35% phenyl column Benzo[ghi]perylene S/N = 120 Benzo[ghi]perylene S/N = 15

26. Benefits of Low Bleed Phases DB-35ms vs Standard 35% Phenyl Benzo[g,h,i]perylene, 1ng

27. M/Z -> Abundance 50 78 96 135 157 207 223 253 276 331 346 377 405 439 50100150200250300350400 0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 110000 120000 130000 140000 150000 Scan 1118 (20.560 min): 3901004.D Standard 35% Phenyl M/Z -> Abundance 78 119 138 207 239 274 276 315 377 50100150200250300350400 0 10000 20000 30000 40000 50000 60000 70000 80000 Scan 1138 (20.640 min): 3901004.D DB-35ms Higher Spectral Purity

28. Polarity vs Stability/Temperature Range Polarity Stability Temperature Range

29. Stationary Phase Selection Existing information Selectivity/Polarity Critical separations Temperature limits Application designed Examples: DB-VRX, DB-MTBE, DB-TPH, DB-ALC1, DB-ALC2, DB-HTSimDis, DB-Dioxin, HP-VOC, etc. Choose the column phase that gives the best separation but not at the cost of robustness or ruggedness.

30. Resolution N =  (gas, L, r c ) k =  (T, d f, r c )  =  (T, phase) Efficiency Retention Selectivity L = Length r c = column radius d f = film thickness T = temperature

31. Resolution N =  (gas, L, r c ) k =  (T, d f, r c )  =  (T, phase) Efficiency Retention Selectivity L = Length r c = column radius d f = film thickness T = temperature

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

33. 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

34. Diameter Summary If you decrease the inside diameter: EfficiencyIncrease ResolutionIncrease PressureIncrease CapacityDecrease Flow rateDecrease

35. Film Thickness and Retention: Isothermal Constant Diameter Normalized to 0.25 µm Thickness (µm)Retention Change 0.100.40 0.251.00 1.04.00 3.012.0 5.020.0

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

37. Film Thickness and Capacity 0.32 mm I.D. Like Polarity Phase/Solute Thickness (µm)Capacity (ng) 0.10 50-100 0.25 125-250 0.50 250-300 1500-1000 31500-3000 52500-5000

38. Film Thickness and Bleed More stationary phase = More degradation products

39. Film Thickness and Inertness 1.0 active inactive active inactive 3.0 active inactive 0.25

40. Film Thickness Summary If you increase the film thickness: RetentionIncrease Resolution (k<5)Increase Resolution (k>5)Decrease CapacityIncrease BleedIncrease InertnessIncrease EfficiencyDecrease

41. Resolution N =  (gas, L, r c ) k =  (T, d f, r c )  =  (T, phase) Efficiency Retention Selectivity L = Length r c = column radius d f = film thickness T = temperature

42. Resolution N =  (gas, L, r c ) k =  (T, d f, r c )  =  (T, phase) Efficiency Retention Selectivity L = Length r c = column radius d f = film thickness T = temperature

43. Column Length and Resolution Length X 4 = Resolution X 2 R  n  L t  L

44. Column Length and Cost 15m 30m 60m £ £ £ £ £ £ £

45. Length Summary If you Increase Length: EfficiencyIncrease ResolutionIncrease Analysis TimeIncrease PressureIncrease CostIncrease

46. Summary - Four Primary Selection Areas Stationary Phase Type Column Internal Diameter Stationary Phase Film Thickness Column Length

47. Still Can’t Decide Which Column to Use????? …Get in touch with us!!! TECHNICAL SUPPORT t: 01357 522961 e: enquiries@crawfordscientific.com