How To Select the Correct GC Column Simon Jones Application Engineer

Things to Consider… • Is it Volatile enough to chromatograph by GC? • Is it a Gas or a Liquid? • How are we getting the Sample Injected? • What is the sample Matrix? – Can we do sample clean up? • Is it an established method? -- EPA, ASTM, USP • What do we Know about the analytes? • What else ‘MAY’ be present in the sample? Group/Presentation Title Agilent Restricted Page 2

CAPILLARY COLUMN TYPES Porous Layer Open Tube (PLOT) Carrier Gas Solid Particles Wall Coated Open Tube (WCOT) Carrier Gas Liquid Phase Group/Presentation Title Agilent Restricted Page 3

Packed Columns 1950 Introduction with the first gas chromatographs Packed Column Designs and Materials

Packed Column Anatomy • Packed Columns • 1 – 12 m length • Internal Diameter 0.5 – 4mm • Tubing – Stainless Steel, UltimetalTM SS, Glass, Nickel, Teflon • Packing – Coated packing WCOT Capillary • Inert, solid support (diatomaceous earth) coated with liquid stationary phase (e.g. OV-1, SE-30, Carbowax 20M, FFAP) – Porous packing PLOT Capillary • Porous polymers (PoraPak Q, N, HayeSep Q, R, S, etc.) • Porous carbons (Carboxens, Carbosieves, Carbotraps)

STATIONARY PHASE POLYMERS R Si O n R R=methyl, phenyl, cyanopropyl, trifluoropropyl Siloxane R R R R Si Si Si Si O R n R O O R R m Siarylene backbone HO CH2 CH2 O n Polyethylene Glycol Group/Presentation Title Agilent Restricted Page 6

Stationary Phase % Substitution -- polysiloxanes % = # of sites on silicon atoms occupied Balance is methyl R Si R=methyl, phenyl, cyanopropyl, trifluoropropyl O R n Siloxane Group/Presentation Title Agilent Restricted Page 7

Stationary Phase Poly(ethylene) Glycol HO CH2 CH2 O n H 100% PEG (DB-WAX) Less stable than polysiloxanes Unique separation characteristics Group/Presentation Title Agilent Restricted Page 8

Poly(Ethylene) Glycol Modified •Base deactivated (CAM) •Acid Modified (DB-FFAP) •Extended Temperature Range Group/Presentation Title Agilent Restricted Page 9

Mill Polarity High Polarity

PLOT Column Types PLOT columns are primarily, but not exclusively, used for the analysis of gases and low boiling point solutes (i.e., boiling point of solute is at or below room temperature). • Agilent J&W PLOT columns begin with the designation of – GS (Gas Solid) or – HP-PLOT followed by a specific name – 10 stationary phases • GS-OxyPLOT • GS-Alumina • HP-PLOT Al2O3 “M” • HP-PLOT Al2O3 “S” • HP-PLOT Al2O3 “KCl” • HP-PLOT MoleSieve • GS-OxyPLOT: oxygenates • HP-PLOT Molesieve: O2, N2, CO, Methane • GS-CarbonPLOT • HP-PLOT Alumina and GS-Alumina: complex hydrocarbon gas matrices, ethylene and...

Specialty Phases Columns developed for particular applications Examples: DB-VRX, DB-MTBE, DB-TPH, DB-ALC1, DB-ALC2, DB-HTSimDis, DBDioxin, Select Low Sulfur, CP-Volamine, Select PAH, DB-EUPAH, DB-CLP1 & 2, DB-Select 624 UI 467, CP-LowOx, Select Permanent Gases………. Group/Presentation Title Agilent Restricted Page 12

Ultra Inert Phases DB-1msUI HP-1msUI DB-5msUI HP-5msUI DB-17msUI DB-624UI DB-Select 624UI 467 Same Selectivity, more Inertness! Group/Presentation Title Agilent Restricted Page 13

Three Types Of Low Bleed Phases •Phases tailored to “mimic” currently existing polymers Examples: DB-5ms, DB-35ms, DB-17ms R R R R Si Si Si Si O R n R O O R R m Siarylene backbone •New phases unrelated to any previously existing polymers Examples: DB-XLB •Optimized manufacturing processes DB-1ms, HP-1ms, HP-5ms Group/Presentation Title Agilent Restricted Page 14

What is Column Bleed??? “Back Biting” Mechanism of Product Formation CH3 H3C Si HO O CH3 CH3 CH3 CH3 CH3 CH3 CH3 Si O Si O Si O Si O Si CH3 CH3 CH3 CH CH3 CH3 CH3 CH3 Si O Si O Si O Si O Si O Si O Si OH CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 Si O Si O Si O Si OH CH3 CH3 CH3 CH3 + 3 CH3 H3C CH3 Si O O CH3 Si H3C Si O CH 3 H3C Si O CH3 CH3 CH3 Cyclic products are thermodynamically more stable! Repeat Group/Presentation Title Agilent Restricted Page 15

DB-5ms Structure O CH3 DB-5 Structure DB-5ms Structure O O CH3 Si Si CH3 CH3 O CH3 Si CH3 Si CH3 O CH3 Si Si Si DB-5 5% Phenyl CH3 CH3 CH3 O CH3 Si CH3 DB-5ms 1.Increased stability 2.Different selectivity 3.Optimized to match DB-5 Group/Presentation Title Agilent Restricted Page 16

Why is stationary phase type important? Influence on α k2 k1 k2 = partition ratio of 2nd peak k1 = partition ratio of 1st peak Group/Presentation Title Agilent Restricted Page 19

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 Group/Presentation Title Agilent Restricted Page 20

Optimizing Selectivity () Match analyte polarity to stationary phase polarity -’like dissolves like’ Take advantage of unique interactions between analyte and stationary phase functional groups Group/Presentation Title Agilent Restricted Page 21

Analyte Polarity Nonpolar Molecules - generally composed of only carbon and hydrogen and exhibit no dipole moment (Straight-chained hydrocarbons (n-alkanes)) Polar Molecules - primarily composed of carbon and hydrogen but also contain atoms of nitrogen, oxygen, phosphorus, sulfur, or a halogen (Alcohols, amines, thiols, ketones, nitriles, organo-halides, etc. Includes dipole-dipole interactions and H-bonding) Polarizable Molecules - primarily composed of carbon and hydrogen, but also contain unsaturated bonds (Alkenes, alkynes and aromatic compounds) Group/Presentation Title Agilent Restricted...

Selectivity Interactions • Dispersion • Dipole • Hydrogen bonding Group/Presentation Title Agilent Restricted Page 23