P. J. Apps

Volatile components of anal gland secretion of aardwolf (Proteles cristatus).

Volatile constituents of the anal gland secretion and of scent marks of the aardwolf were identified using dynamic solvent effect sampling, capillary gas-liquid chromatography, and mass spectrometry. Both scent marks and gland contents consisted mainly of short- to medium-chain fatty acids, a complex series of medium- and long-chain esters, indole, and hexanol. There were marked individual differences in the relative concentrations of the various components.

Manufacture, by electroforming, of thin-walled nickel capillary columns for gas—liquid chromatography

Abstract A process is described for manufacturing nickel capillary tubing, in lengths up to 100 m, with an internal diameter between 100 and 500 μm and a wall thickness of 50 μm. Steel wire is continuously plated in a bath, 5 m long, containing the plating solution. The wire is cathodic and a nickel anode is used. The nickel-coated wire is cut to suitable lengths, e.g. , 25–100 m, and the wire core is removed by stretching the wire. The nickel capillary tubing is normally springy but may be softened by annealing at 450°C. In this state it may be bent or flattened to form a precise flow restrictor. End-sealing for deactivation, or static coating with stationary phase, is simply effected by crimping the tube. The inner surface of the nickel tubing is smooth and lends itself to a variety of deactivation strategies.

Chromatographic analysis of species specific odor profiles inMastomys natalensis andM. coucha (Rodentia: Muridae)

Whole-body volatiles from males of the cryptic multimammate mouse speciesMastomys natalensis andM. coucha were analyzed by dynamic solvent effect sampling and capillary gas chromatography. One compound, 3-nonene-2-one, was always present, sometimes as the major component, in volatiles fromM. coucha and absent, or present only at low levels, in volatiles fromM. natalensis. The mean ±SD of the 3-nonen-2-one peak area forM. coucha was 8599 ±9630 and forM. natalensis 148 ±486. Chromatographic analysis was more reliable in identifying a males species than were a females in a two-choice olfactorium.

High-precision sampling of trace gas-borne volatiles by the dynamic solvent effect with a comparative review of alternative techniques

Abstract The precise determination of traces of organic volatiles is particularly challenging in semiochemistry and clinical chemistry, where specimen sizes are intrinsically limited and amounts of trace components correspondingly very small. This demands a sampling technique that is fully compatible with the ability of capillary columns and gas chromatographic detectors to separate and quantify nanogram and sub-nanogram amounts from complex mixtures. The quantitative precision of dynamic solvent-effect sampling of low parts per billion (10 9 ) aqueous carbonyl compounds, high ppb and low parts per million aqueous phenols, low ppb and high parts per trillion (10 12 ) airborne hydrocarbons and the volatiles from wine, human urine and a slow-release pesticide was tested with specimen sizes that yielded amounts of volatiles down to the sub-nanogram level. Provided that sources of variability, such as temperature changes, adsorption on containers, incomplete peak resolution and changes in the specimens themselves, were adequately controlled, dynamic solvent-effect sampling consistently provided coefficients of variation in peak areas, peak percentage areas and peak-area ratios of less than 10% at nanogram and sub-nanogram levels. The literature was surveyed for data on the performance of other sampling systems. None of them have been demonstrated to match the precision of the dynamic solvent effect with such small amounts from such a wide range of materials.

Salute focusing by means of the solvent effect: formation of the film

Abstract Solute focussing using the solvent effect is usually carried out in an open tube. Under such circumstances the sample film can be unstable and this leads to peak distortion. It is shown that when the sample film is formed in a packed bed, the film is much more stable, even when polar solvents are used. A further advantage of packed beds is that large sample volumes can be handled.

Comparison between the conditions for solute focussing by the static and dynamic solvent effects under ideal conditions

Abstract In capillary gas chromatography static and dynamic solvent effect inlets provide quantitatively precise methods of sample introduction of solutes which fulfill the conditions for solute focussing. Equations are derived for the conditions for focussing on static and dynamic films. In the case of a static film a solute will be focussed if the sum of its partition coefficient between the gas phase and the film and the phase ratio are greater than the partition coefficient of the solvent. On dynamic solvent films solutes whose partition coefficients are larger than those of the solvent are focussed.

A versatile cryo-focussing flow switching gas chromatography inlet for trace analysis of intractable compounds

A wide variety of samples that can be analysed by gas chromatography do not lend themselves to the usual preparation of solvent extracts for split-splitless injections, and are best handled by purge and trap or equilibrium headspace sampling. A cryo-focussing, flow switching gas chromatography inlet system that handles different types of sample without the need for hardware changes has been prototyped. It provides excellent repeatability and linearity with liquid injections, purge and trap, and equilibrium headspace samples, in both split and splitless modes. The performance of the system was tested with sub-nanogram quantities of challenging analytes such as free carboxylic acids, alcohols, diols, phenols and aldehydes, and volatiles purged from contaminated soil, mammal faeces, a pesticide formulation, and a spice. Repeatability RSDs for peak areas were consistently below 11% and repeatabilities of retention times below 0.05%, independently of sample type (liquid or gas phase) and nature or quantity of compound. Regression coefficients of peak areas vs. quantity were typically ≥ 0.999 over two orders of magnitude ranges extending down to below 0.01 ng, also independently of sample and analyte. Limits of quantitation were robustly below 0.1-0.2 ng. Peak shapes and resolution are the same with use of the cryo-trap and flow switch as they are with conventional injections. Performance is robust to flow rate and, for most compounds, to trapping and desorption temperature. The cryo-trapping flow switching inlets performance parameters match those of other sample introduction systems, and are achieved with sub-nanogram quantities of intractable analytes.

High-precision sampling of sub-nanograms, low-parts-per-billion solutes from liquids using the dynamic solvent effect

Abstract The quantitative precision of dynamic solvent-effect sampling from solvent specimens is reported. For sub-nanogram amounts of a range of solutes at a concetration of 5:109 the coefficients of variations of peak areas, peak percentage areas and peak-area ratios are consistently below 10%. The dynamic solvent effect allows high-precision sampling of much smaller amounts of solute than do alternative sampling methods.

High precision air sampling using the dynamic solvent effect: a possible sampling method for atmospheric carcinogens

The analysis of organic air pollutants using gas chromatography—mass spectrometry (GC‐MS) invariably involves some form of preconcentration of the sample which can substantially decrease the precision of the analysis. A relatively new sampling technique—solute focusing using the dynamic solvent effect—has been investigated for analysing organic air pollutants. Using the technique together with GC‐MS and industrial grade compressed air as a sample, it is shown that a coefficient of variation of less than 5% may be obtained for a wide variety of compounds ranging in concentration from 1.7–95.3 /μg/m3. This represents a significant improvement on established concentration techniques and suggests that the method holds considerable promise for studying air pollution problems.