Cold trapping of volatile organic compounds on fused silica capillary columns

A 30 m, 0.25 mm ID, fused silica capillary column at temperatures from –60 to –100°C has been shown to be a quantitative trap for organic compounds with volatilities ranging from that of 1, 1 -dichloroethene that of chlorobenzene. This type of “whole column cryotrapping” provided sharp peaks (peak width approximately 4–7 seconds) for all compounds at a trapping temperature of –80°C and with high carrier gas pressures and linear velocities (30 psi and 110 cm/s, respectively). Whole column cryotrapping possesses great simplicity, chromatographic efficiency (no trapping loop connections), and a built-in indicator of quality assurance for trapping efficiency (i.e., peak shape). These advantages are extremely attractive and are indicative of the fact that the potential of this approach has not yet been fully appreciated.     

Effects of trapping temperature and film thickness in purge and trap with whole column cryotrapping on fused silica columns

The effects of trapping temperature and column film thickness were investigated with respect to their ability to promote effective cryofocusing on fused silica capillary columns. The study was a further development of the purge and trap with whole column cryotrapping (P&T/WCC) method. The rates at which compounds could be thermally desorbed from a P&T unit and transferred to a column (with zero split) were first examined. A near quantitative transfer of the desorbable analytes was obtained with a 4 min, 180°C, 20 mL/min desorption. The compounds tested included naphthalene. Columns with film thicknesses from 0.12 to 3.0 μm were then investigated in P&T/WCC analyses with WCC temperatures ranging from ?80 to 0°C. The trapping took place from a transfer line gas stream initially at 175°C. The volatilities of the compounds examined varied from that of 1,1-dichloroethene to 1,1,2,2-tetrachloroethane. A higher film thickness was found to ease the WCC temperature requirements. Within each column type, the warmest WCC temperatures which allowed good cryotrapping with no significant increases in peak width were: 0.25 μm, ?70°C; 1.0 μm, ?50°C; 3.0 μm, ?20°C. In addition to being quantitative, the trapping provided good chromatography.     

Analysis of toxic anthraquinones and related compounds with a fused silica capillary column

In this study, application of a fused silica capillary column for analysis of toxic anthraquinones and related compounds found in plants was investigated.     

Analysis of mutagenic amino acid pyrolyzates with a fused silica capillary column

In this study, application of a fused silica capillary column for analysis of major mutagenic heterocyclic compounds found in cooked foods was investigated.     

Deactivation of fused silica capillary columns with phenylhydrosiloxanes

In this work, an investigation of new organosilicon hydride reagents with phenyl functional groups for deactivation and surface modification of fused silica capillary columns is described. Different reagents were tested for their ability to deactivate the fused silica surface, and actual critical surface tension measurements were made using the capillary rise method. The deactivation procedure required lower optimum temperatures than conventional methods. Deactivated capillaries and coated capillary columns were prepared and tested for reproducibility, efficiency, and surface inertness towards basic and acidic compounds at the low nanogram level.     

Deactivation of fused silica capillary columns with cyanopropylhydrosiloxanes

A method is described for surface deactivation and modification of fused silica capillary columns with a cyanopropyl-containing reagent. The deactivation procedure involved a dehydrocondensation reaction between a bis(cyanopropyl)methylhydropolysiloxane reagent and surface silanol groups at an optimum temperature of only 250°C. Actual critical surface tension measurements were made using the capillary rise method. Excellent deactivation for acidic and basic compounds at the low ng level, and wettability for nonpolar and polar polysiloxane stationary phases were obtained. A procedure was developed to remove acidic impurities that are present in polar stationary phases.     

Hydrothermal treatment of fused silica capillary columns

The activity of fused silica capillary tubing has been shown to vary considerably, which severely influences the reproducibility of column deactivation and inertness. Methods for producing a reproducible, high activity surface with maximum hydroxylation by various hydrothermal treatments were evaluated. Columns pretreated with 20% nitric acid at 200°C for 10 hours, deactivated with D₄, coated with OV-73, and crosslinked with azo-tert-butane were found to possess excellent inertness for sensitive analytes such as alcohols, amines, and alkaloid drugs.     

A study of some deactivation methods for fused silica capillary columns by CP-MAS NMR and capillary gas chromatography

The effect of deactivating a fused silica surface by silylation with 1,1,3,3-tetraphenyl-1,3-dimethylilazane (TPDMDS), triphenylsilylamine (TPSA), and octamethylcyclotetrasiloxane (D4) and by polydimethylsiloxane degradation (PSD) is studied. Rehydrated, dried, and deactivated Cab-O-Sil M5 samples are used as model materials for ²⁹Si CP-MAS NMR analysis. At about 350 °C, TPDMDS yelds mainly diphenylmethylsiloxysilane, dimethyldisiloxysilane, and triphenylsiloxysilane groups. TPSA yields phenyltrisiloxysilane, diphenyldisiloxysilane, and triphenylsiloxysilane groups. At 400°C, the products formed initially are eventually replaced by methyltrisiloxysilane or phenyltrisiloxysilane groups, while a substantial number of silanol groups still remains. The possible consequences for wettability are discussed. D4 reacts with Cab-O-Sil even at 200°C, but a large number of silanol groups remains. This number decreases gradually at higher temperatures and becomes negligible above 400°C. The formation of methyltrisiloxysilane groups, which starts at 425°C, is predominant at 490°C.     

General applications of fused silica capillary column (FSCC) chromatography to the analysis of non-priority pollutant organics in environmental samples

Further applications of fused silica capillary columns (FSCC) to the analysis of environmental samples are presented. The chromatographic behavior (RT, RRT) of organic compounds of environmental significance not listed as Consent Decree Priority Pollutants is investigated on an SE-54 FSCC. Retention indices (RRT) and mass spectral response factors (RF) are presented for a total of 28 compounds including a number of chloro- and nitro-substituted anilines, alkylpyridines, and alkylquinoline derivatives. The direct application of the FSCC/MS interface to the analysis of these compounds in actual environmental samples is presented, including vent emissions from a fungicide manufacturing process, and contaminated soil and water samples from two metropolitan Boston construction sites.     

Some improvements in the determination of volatile nitrosamines by fused silica capillary-GC in combination with a thermal energy analyzer

Summary Fused silica capillary columns of different diameters and polarities are linked to a thermal energy analyzer and a flame ionisation detector for comparison. Extra column effects are discussed. Unsymmetrical homologue nitrosamines are applied in order to assign the volatile nitrosamines most often to be determined by their linear indices rather than by their overall retention times.     

Fused silica capillary column GC/MS for the analysis of priority pollutants

Operational characteristics have been determined for fused silica capillary column (FSCC) GC/MS as applied to “extractable” priority polutants. Chromatographic data show excellent relative retention time (RRT) intralaboratory precision and interlaboratory accuracy when multiple internal standards are empolyed. Potential chromatographic problems, such as column overload and “double peaking”, are addressed. Response factor relative standard deviations (RSD) at 50 ng for most of the extractable priority pollutants over the long term indicated precise determination (i.e. RSD generally ≤ 10%). Linearity was demonstrated over two orders of magnitude for FSCC GC/MS analysis of compounds with relatively low and high RF (response factor) values. Potential quantitative problems, such as saturation, are discussed. For certain aromatic priority pollutants interlaboratory RF agreement was observed. This was noted as perhaps the most important property of FSCC GC/MS analysis when the multiple internal standard approach is utilized. Determinations of extractable priority pollutants are directly compared for paced column GC/MS and FSCC GC/MS analysis of separate and composited extracts. For six extracts analyzed in triplicate, the latter configuration was shown to produce more consistent results. In view of the superior analysis logistics of composite extract FSCC GC/MS analysis, this approach was established as the preferred method for the analysis of priority pollutants classified as extractable.     

Analysis of dust and surface swab samples for octachlorodibenzo-p-dioxin and heptachlorodibenzo-p-dioxins by fused silica capillary GC with EC detection

A method is described for the analysis of contaminated building dust samples and surface swab samples for octachlorodibenzo-p-dioxin (OCDD) and heptachlorodibenzo-p-dioxins (HpCDDs). The samples were analyzed by fused silica capillary GC combined with electron capture detection. Analysis was preceded by a short HPLC cleanup step designed to remove polychlorinated biphenyls (PCBs) and other compounds that might interfere. The method was found to work successfully on surface swab and dust samples known to contain PCBs, OCDD, and HpCDDs. The overall recovery of the analysis procedure for OCDD was found to be approximately 80%. The detection limit for the method was sample dependent, but for one typical set of surface swab samples was 0.2 μg/m² of OCDD.     

Analysis of gases containing inorganic and organic compounds using a combination of a thick-film capillary column and a packed adsorption column

A gas chromatographic system consisting of one multiport valve, two (hot-wire and flame-ionization) detectors and two analytical columns (one thick-film capillary and one packed adsorption column) is used for the analysis of gas samples containing a number of inorganic compounds (hydrogen, argon, oxygen, nitrogen, carbon monoxide, and carbon dioxide) and organic compounds. Examples include samples containing hydrocarbons up to n-nonane and benzene and toluene. The system also permits the analysis of more complicated samples containing, for example, alcohols, in addition to hydrocarbons.     

Characterization of glass,quartz, and fused silica capillary column surfaces from contact-angle measurements

Summary This paper describes the systematic characterization of glass and the newly introduced fused silica and quartz capillary columns from surface wettability measurements. Common gas chromatographic stationary phases were used in capillary-rise measurements at temperatures up to 300°C. By construction of Zisman plots and using the Cassie equation, the relative surface concentrations of wettable and non-wettable groups were determined. By application of the Fowkes equation, the dispersion force component of the surface energy was investigated. The influence of various surface treatments such as leaching, silylation, and polymeric film formation are discussed. Wettability measurements were also used to evaluate the thermostability of various treated surfaces and to compare the surface properties of glass, quartz, and fused silica. The wettability of the surfaces with selected stationary phases as a function of temperature is also discussed.     

On the stability of micro-LC columns (packed fused silica capillary columns)

The life expectancy and resistance to flow, pressure shocks, solvent gradients, and bending of packed fused silica capillary columns (Micro-LC) are discussed.     

Some applications of capillary gas chromatography in the chemical industry

About three years ago, fused silica capillary columns were introduced in the Quality Control Laboratory of the Shell refinery/chemical complex at Pernis. In general, long, thick-film, wide-bore capillary columns are used together with low split ratios and hydrogen as carrier gas. These conditions enable the analysis of relatively large sample amounts, resulting in low detection limits for the minor components without overloading by the major components, while still maintaining a satisfactory resolution. A number of applications are shown, such as the analysis of complex mixtures, the determination of trace impurities and the analysis of residual volatiles in polymers.