Measurements for assessing environmental exposures to children using small amounts of serum and urine: state-of-the-art.

This paper addresses the recent advances in gas chromatographic (GC)-based instrumentation for the analytical determination of environmental toxicants using small samples. One-dimensional GC/time-of-flight mass spectrometry (TOFMS) and comprehensive two-dimensional GC (GCxGC) are shown to drastically improve sample component resolution, sensitivity and overall analytical throughput. A presentation of the concepts behind the new state-of-the-art, and results highlighting the advantages of the emerging technologies are presented.

Gas chromatography in space.

Gas chromatography has proven to be a very useful analytical technique for in situ analysis of extraterrestrial environments as demonstrated by its successful operation on spacecraft missions to Mars and Venus. The technique is also one of the six scientific instruments aboard the Huygens probe to explore Titan's atmosphere and surface. A review of gas chromatography in previous space missions and some recent developments in the current environment of fiscal constraints and payload size limitations are presented.

Improvement of Gas Chromatographic Performance of Cyclic Siloxane Bonded Phases by Incorporation of n-Alkyl Groups.

Cyclic siloxane-based silica columns of high retention capacity for light hydrocarbons were prepared by incorporation of octyl and octadecyl groups on the siloxane skeleton. Spectroscopic studies revealed the presence of the alkyl groups on the silica surface, which results in high surface coverage of the packing materials. The retention characteristics of the columns are significantly higher than those of cyclic siloxane phases due to their high surface coverage and better solute-stationary phase interactions. In agreement with previous data for micropacked columns, the H vs u curves, on passing through the optimum region, remained substantially constant at high linear gas velocities, indicating their usefulness for fast analysis of light hydrocarbons at high flow rates without any appreciable loss in column performance. Presumably due to greater availability of the bonded alkyl groups for interactions, a 10-component mixture of C(1)-C(4) saturated and unsaturated hydrocarbons was sufficiently separated on the hexamethylcyclotrisiloxane-octadecylsilyl phase compared to the conventional octadecyldimethylsilyl phase, irrespective of the high carbon content of the latter.

Gas chromatographic column for the storage of sample profiles.

The concept of a sample retention column that preserves the true time profile of an analyte of interest is studied. This storage system allows for the detection to be done at convenient times, as opposed to the nearly continuous monitoring that is required by other systems to preserve a sample time profile. The sample storage column is essentially a gas chromatography column, although its use is not the separation of sample components. The functions of the storage column are the selective isolation of the component of interest from the rest of the components present in the sample and the storage of this component as a function of time. Using octane as a test substance, the sample storage system was optimized with respect to such parameters as storage and readout temperature, flow rate through the storage column, column efficiency and storage time. A 3-h sample profile was collected and stored at 30 degrees C for 20 h. The profile was then retrieved, essentially intact, in 5 min at 130 degrees C.