Instrumentation for the high speed analysis of gas samples using a small and portable gas chromatograph (Micro GC) is described. Several components in the Micro GC are based upon silicon micromachining which allows for miniaturization, ruggedness and modular design. Applications of the technology include analysis of natural gas, chemical process streams, permanent gases and many others. Typical analysis times are on the order of 30 - 160 seconds.

Capillary Electrochromatography in Columns Packed with Fluoropolymer Particles

Affiliation: Dept. of Chem., State University of N. Y. at Buffalo

Capillary electrochromatography (CEC) is a hybrid of high performance liquid chromatography (HPLC) and capillary electrophoresis (CE) that can be performed in open tubes or packed columns. Packing materials traditionally used for HPLC have been used in CEC. We are investigating the use of ethylene chlorotrifluoroethylene (ECTFE) as a support material for CEC. Our initial studies of ECTFE for CEC show that electroosmotic flow can be generated in this material using acetonitrile-water mixtures as the mobile phase. We will present results using ECTFE for CEC. Some unique electrochromatographic parameters of this material will be discussed.

Rapid Quantification of Trace Organics in Complex Matrices by Solid-Phase Microextraction Gas Chromatography

Authors: Janet A. Cosgrove and Janet M. Barilla

Presenter: Janet A. Cosgrove

Affiliation: Eastman Kodak Company

In chromatography, the utilization of automated sample preparation technology has become increasingly important over the years due to greater sample matrix complexity and the need for lower detection limits, increased precision, and faster analytical turnaround. Automated solid-phase microextraction (SPME) has been evaluated for the routine quantification of ppb-levels of residual organic analytes in polymer latex suspensions. With many existing solvent-free extraction techniques, thermally unstable polymers and addenda or the presence of water have hampered our ability to quantify low-level, semi-volatile analytes by general headspace techniques. SPME provides the ability to selectively extract analytes from solution of headspace onto a fiber for subsequent desorption in the GC inlet. This unique sample introduction capability has overcome several existing analytical challenges. This presentation will review several practical considerations encountered during optimization using the Varian SPME III autosampler, as well as general information regarding SPME methodology and capabilities.

Using non-invasive methodology allows for the assessment of a person’s health in a painless, low-risk, and convenient manner. However, sampling substances noninvasively, while reliably reflecting the content of blood is not a trivial task. Sampling techniques must be thoroughly evaluated in terms of feasibility before clinical studies can be initiated. To accomplish this, we are using capillary electrophoretic techniques to characterize and optimize our sampling procedures. We have chosen glucose as our model sampling analyte, because of its biological importance. Our studies have progressed to the point where sampling is executed in-vivo, such that we can make initial comparisons to blood concentrations. Presented here will be the most recent developments of our investigations.

A gas chromatographic method is presented for determining from 1 to 100 m g/mL 1,4-dioxane in toluene with purities ranging from commercial to high-purity grades. This method relies on extracting 1,4-dioxane from toluene into water. The water extract is analyzed for 1,4-dioxane content by gas chromatography/ flame ionization detection using splitless-injection and a capillary column coated with a bonded polyethylene glycol stationary phase. Purging extracts with nitrogen after an initial analysis is suggested as a means to confirm the identification of 1,4-dioxane and to improve baseline resolution of toluene and 1,4-dioxane when its concentration is near the method detection limit.

Reversed-phase HPLC column research strives to fulfill needs in chromatographic performance that are not met with conventional C18 and other hydrocarbon phases. Although these packings are used for a wide variety of separations, there are still many samples that can not be easily run on common reversed-phase columns. Examples include very polar analytes that are not retained on C18 phases, or those solutes that require high aqueous mobile phases for solubility or other reasons. Under high aqueous conditions, most C18 phases and many C8 phases collapse, resulting in loss of retention. Mixtures containing compounds with similar lipophilicity may also be difficult to isolate on C18 phases since the hydrophobic separation mechanism may not distinguish between the molecules. Another shortcoming of C18 packings is that peak shape for very basic compounds is not always symmetrical, resulting in possible qualitative and quantitative problems.

Some relatively new types of reversed-phase packings are the, "intrinsically Base Deactivated" (IBD) phases, which address many of the concerns that surface regarding the use of C18 phases. These packings are characterized as having a polar group within, or intrinsic to, the hydrocarbon bonded phase. The polar group has been shown to assist in 1) retaining very polar solutes, 2) preventing chain collapse under high aqueous mobile phase conditions, 3) furnishing unique selectivity for compounds of similar global lipophilicity, 4) providing symmetrical peak shape of basic compounds. In addition, IBD columns can be good choices for LC-MS, and for complex mixtures containing acids, bases and zwitterions. Applications demonstrating these attributes are presented as well as some precautions for the proper use of IBD HPLC packings.

Chronic exposure to cancer chemotherapy can modify DNA in target cells by metabolic activation. If uncorrected, genetic error during replication can ultimately produce malignant phenotype. The building blocks of DNA can be released enzymatically. Digestion of modified DNA nuclease P1 excises both normal and modified nucleotides. HPLC could be a powerful technique to detect the formation of modified nucleotides in exposed DNA. Reversed-phase HPLC analysis of DNA modification induced by Tamoxifen (an anti-estrogenic compound used in breast cancer) and its inhibition by antioxidants as chemopreventitive agents will be discussed.

With the need to reduce costs per sample, environmental methods should take advantage of fast chromatography using small internal diameter columns, and should take advantage of large volume injection techniques, which minimizes solvent use and extraction time.

This presentation will focus on how to reduce costs per sample using Fast GC and Large Volume Injection. It will encompass optimizing detection limits with GC/MS.

We will present equivalent methods on how to decrease the time of analysis using GC/MS specifically for pesticides and PCBs - methods 525 and 508.

Application of Headspace Gas Chromatography to Forensic Chemistry

Author: Dr. Thomas Brettell

ABSTRACT

Headspace gas chromatography (HGC) is used for the analysis of a variety of samples submitted to the crime laboratory. An overview of HGC in Forensic Science will be presented, along with case examples. Toxic volatiles resulting from solvent abuse have been detected in biological specimens from both living and postmortem specimens. Toxic gases and volatiles from drugs of abuse have also been detected evidential materials and biological fluids. Volatiles are used to characterize the origin of drug specimens as well as in the determination of the synthetic route of clandestine-synthesized drugs of abuse. GC/MS coupled with passive headspace sampling procedures have become the method of choice for the analysis of fire debris for ignitable liquid residues. Although static headspace sampling is most commonly employed in the analyses of these evidential materials, passive headspace sampling methods have been adopted for some unique applications.