The use of shape-selective stationary phases in GC. Part 1: Cyclodextrin phases

ABSTRACT -Cyclodextrin phases are one of the most interesting geometry selective stationary phase in GC. 'beyare outstanding in their ability to separate isomeric and enantiomeric compounds. Two examples of the separation of cyclic compounds on cyclodextrins are given. The combination of chiral and achiral phases in series coupled columns is a useful tool for complicate separation and identification problems

Ambient air analysis of volatile organic compounds using adsorptive enrichment

This review summarizes a presentation on ambient air analysis of volatile organic compounds given at the “Trace enrichment for GC and HPLC analysis” workshop at the ISC'02. Adsorptive enrichment of volatile organic compounds has become an important technique in ambient air analysis. The paper focuses on the use of adsorptive enrichment for sampling volatile organic compounds. Different techniques for sampling and desorption are reviewed and an overview of commonly used adsorbent materials is given. Furthermore, strategies for managing interferences, such as moisture, are discussed

Adsorbent materials commonly used in air analysis for adsorptive enrichment and thermal desorption of volatile organic compounds

A review is given dealing with commonly used adsorbent materials in ambient air analysis of volatile organic compounds (VOCs). The adsorbents covered in the paper are selected in consideration of their compatibility with thermal desorption. Initially, we discuss the requirements that an adsorbent should fulfill, and useful parameters for the selection and evaluation of an appropriate material. Then, the most important materials are presented considering their properties, advantages, and drawbacks. A few applications are given, but a complete review of sampling techniques and applications dealing with adsorptive enrichment and thermal desorption is beyond the scope of this paper

Determination of perfume oil in household products by geadspace solid-phase microextraction and fast capillary gas chromatography

Headspace solid-phase microextraction (HS-SPME) has been successfully applied to the determination of perfume components in scented candle wax, liquid laundry detergent, and fabric softener. Different fiber coatings (100 μm polydimethylsiloxane, 50/30 μm divinylbenzene/Carboxen/polydimethylsiloxane, 70 μm Carbowax/divinylbenzene, and 85 μm polyacrylate) were tested and the extraction conditions were optimized. For most compounds extraction efficiency, reproducibility, and long-term stability were highest for polydimethylsiloxane. The compatibility of SPME with fast gas chromatographic separation was investigated. The speed of conventional gas chromatography was increased by a factor of 2.5, without loss of separation efficiency, simply by reducing the column length and inner diameter and adjusting the separation conditions by use of method translation software. It was demonstrated that SPME is a suitable sample-introduction technique for fast GC if split injection is used

Stability of reactive low boiling hydrocarbons on carbon based adsorbents typically used for adsorptive enrichment and thermal desorption

In the context of evaluating air sampling methods, laboratory experiments were performed to investigate the stability of eleven selected low boiling hydrocarbons (e.g. 1,3-butadiene, isoprene) adsorbed on four different carbon based adsorbents. The carbon molecular sieves Carboxen 569, Carboxen 1003, Carbosieve SIII and the graphitized carbon black Carbotrap X were tested. The influence of storage duration on the recovery of the analytes was examined by loading the adsorbent tubes with the test compounds via a sample loop under inert gas. Furthermore, the influence of sampling the hydrocarbons continuously from air on the recovery of the analytes was investigated using a simple experimental set-up providing a flow of synthetic air spiked with the hydrocarbons. Analysis of the loaded adsorbent tubes was performed by thermal desorption and capillary gas chromatography. Losses up to 80% of 1,3-butadiene and isoprene were observed for the carbon molecular sieves, occurring even immediately after the sampling step. In contrast, no significant losses of these reactive constituents were detected for Carbotrap X over a storage time of seven days. The laboratory investigations were confirmed in a field experiment

Studies of thermally assisted hydrolysis and methylation-GC-MS of fatty acids and triglycerides using different reagents and injection systems

This work describes methodical studies of thermally assisted hydrolysis and methylation (THM) of fatty acids (FA) and triglycerides comparing different derivatization reagents, such as tetramethylammonium hydroxide (TMAH), tetramethylammonium acetate (TMAAc), trimethylsulfonium hydroxide (TMSH), trimethylphenylamine hydroxide (TMPAH), and (m-trifluoromethylphenyl) trimethylammonium hydroxide (MethPrep 2). The performance of these reagents using different injection techniques, such as pyrolysis, hot split injection, and programmed temperature vaporization (PTV) has been investigated. It was found that the PTV-injection can be used for quantitative in-situ methylation of free fatty acids. THM of triglycerides in a PTV injector is less effective than THM in a pyrolyzer. The highest yields of fatty acid methyl esters (FAMEs) were obtained using TMPAH as reagent. Generally, THM of unsaturated triglycerides did not result in complete trans-methylation

Adsorptive enrichment and thermal desorption of low-boiling oxygenated compounds—possibilities and limitations

Laboratory experiments have been performed to examine the potential of adsorptive enrichment thermal desorption and gas chromatography for the analysis of low molecular-weight oxygenated compounds in gaseous samples. The experiments were conducted with test atmospheres containing, for example, acetaldehyde, propionaldehyde, acrolein, methacrolein, and acetone. The suitability of the graphitized carbon blacks Carbotrap X and Carbograph 5 for sampling these compounds was tested. In this context the influence of humidity on the recovery of the analytes and on the storage stability of the loaded adsorbent tubes over a period of seven days under different storage conditions was investigated. Losses of up to 60% propionaldehyde and acrolein were observed for Carbotrap X, even immediately after sampling. In contrast Carbograph 5 seems promising for the sampling of low molecular-weight oxygenated compounds, although with some limitations. The laboratory investigations were proved by use of an interlaboratory experiment