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Biomedical subjects

C M Selavka

Publications and source records attributed to C M Selavka.

11 recordsLinked to original sources
PubMed1991

Poppy seed ingestion as a contributing factor to opiate-positive urinalysis results: the Pacific perspective.

The possible contribution of poppy seed foods to positive opiate urinalysis results, especially from foods available in the Pacific Rim area, has recently become an issue for the U.S. Army Forensic Toxicology Drug Testing Laboratory in Hawaii. To assess the likelihood of this possible contribution, seven different poppy seed food products were consumed by male and female volunteers, and urine specimens were collected at time increments up to either 24 or 72 h. Specimens were evaluated for opiates using Roche Abuscreen radioimmunoassay (RIA), and all RIA positive specimens were analyzed for morphine and codeine using gas chromatography/mass spectrometry (GC-MS). Poppy seed cake, bagels, muffins, and rolls did not contain sufficient quantities of poppy seeds to give rise to opiate positive specimens by U.S. Department of Defense (DOD) GC-MS cutoff levels (morphine = 4000 ng/mL, codeine = 2000 ng/mL), although a number of specimens were positive by National Institute on Drug Abuse (NIDA) cutoff levels (morphine and codeine = 300 ng/mL). However, ingestion of poppy seed streusel or Danish pastry led to confirmed morphine and codeine positive specimens, irrespective of the use of DOD or NIDA confirmation cutoff values. In addition, significant amounts of codeine were observed in a number of these specimens. These findings argue against the unqualified application of previously published quantitative guidelines for eliminating poppy seed ingestion as a possible cause for a positive opiate urinalysis result.

Codeine↗
PubMed1990

Determination of deoxynivalenol (DON, vomitoxin) in wheat by high-performance liquid chromatography with photolysis and electrochemical detection (HPLC-hv-EC).

Deoxynivalenol (DON, vomitoxin) is a naturally occurring toxic fungal metabolite found in grains such as wheat, corn, rye, and barley. Current methods of analysis for DON and related trichothecene mycotoxins involve gas chromatography with electron capture detection, thin-layer chromatography, and high-performance liquid chromatography with ultraviolet detection. Improved sensitivity and selectivity for DON, as well as for the related compounds nivalenol and fusarenon-X, are made possible by the use of high-performance liquid chromatography with online, postcolumn photolysis and oxidative amperometric detection (HPLC-hv-EC). Conditions are optimized with respect to residence time in the photolytic reactor, applied potentials, mobile phase pH, and chromatographic parameters for the separation of DON, nivalenol, and fusarenon-X, and the technique is found to be linear over a range of 10 ppb-2 ppm with minimum detection limits on the order of 1-2 ng on-column (10-20 ppb). Since these compounds are not electroactive in the absence of photolysis, an additional mode of specificity is realized in addition to the chromatographic retention time and the dual-electrode response ratio. Some market samples of wheat naturally contaminated with DON are analyzed by this method, and the results are in agreement with those obtained by HPLC-UV and TLC analyses of the same samples.

Chromatography, High Pressure Liquid↗
PubMed1987

Precolumn derivatization for improved detection in liquid chromatography-photolysis-electrochemistry.

Precolumn, homogeneous chemical derivatization with Sanger's reagent (2,4-dinitrofluorobenzene) is utilized to improve the chromatographic and detection properties of amino alcohols and amino acids. The 2,4-dinitrophenyl derivatives are separated using reversed-phase liquid chromatography and are detected using the hybrid photolysis-electrochemical (hv-EC) detector in tandem with UV absorbance detection. Following optimization of reaction, chromatographic, and detection variables, the derivatization-detection approach provides limits of detection in the low parts-per-billion range, with a linearity of roughly three orders of magnitude. Selectivity is based on retention times as well as dual electrode response ratios and a "lamp on/off" responsiveness criterion unique to the hv-EC detector. The method is applied to the determination of serine in beer.

Amino Acids↗
PubMed1986

An improved method for the rapid screening of illicit cocaine preparations using high performance liquid chromatography with electrochemical detection.

Electrochemical detection in HPLC offers a very sensitive and selective alternative to UV detection for a number of classes of compounds. While there have been no reports of the use of electrochemical detection for the determination of cocaine in illicit preparations or biological fluids, it is now possible to use on-line, continuous post-column photolytic derivatization to generate electroactive species from cocaine which may then be detected downstream using a conventional electrochemical detector operated at oxidative working electrode potentials. In this manuscript the construction, optimization and characterization of system parameters are discussed, and the sensitive and highly selective nature of this novel detection method is demonstrated to be uniquely suited to the rapid identification and quantitation of cocaine in simulated illicit preparations.

Chromatography, High Pressure Liquid↗
PubMed1985

Photolytic derivatization for improved LCEC determinations of pharmaceuticals in biological fluids.

Although electrochemical (EC) methods have been demonstrated to be sensitive and selective, wide use of EC detection in high performance liquid chromatographic (HPLC) assays in forensic and clinical toxicology laboratories has not been forthcoming. This fact is due to the general difficulty involved with the use of reductive EC detection methods, as well as to the lack of EC response in either the oxidative or reductive mode, for a number of classes of drugs having substantial clinical and forensic importance. The use of an on-line, post-column, continuous photolytic derivatization step, followed by conventional oxidative amperometric detection, alleviates many of these problems. In this report, the use of HPLC-photolysis-EC (HPLC-h nu-EC) for the trace determination of a number of controlled substances in biological fluids is presented. Following system optimization, the determination of phenobarbital, cocaine, methylphenidate, and several 1,4-benzodiazepines (and metabolites) is linear over three orders of magnitude. In addition, HPLC-h nu-EC offers a sensitive approach for these compounds, in that limits of detection (LODs) are all below 1 microgram/ml, ranging from 1 ng/ml to 750 ng/ml. The validity of this newer method is demonstrated in collaborative studies involving the trace determinations of phenobarbital in human serum, and chlordiazepoxide and its major metabolite, norchlordiazepoxide, in human urine. Finally, the authors' view of the role of HPLC-h nu-EC in the clinical and forensic toxicology laboratory is presented.

Anti-Anxiety Agents↗