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Biomedical subjects

T J Siek

Publications and source records attributed to T J Siek.

16 recordsLinked to original sources
PubMed1997

Computer-aided identifications of thin-layer chromatographic patterns in broad-spectrum drug screening.

We have developed a systematic thin-layer chromatographic (TLC) technique for detecting and identifying drugs and drug metabolites on 10-cm-long silica-gel plates with organic binder (fluorescent indicator); a computer program (SPOT CHEK) assists in matching the data from a particular chromatogram with those obtained for known drugs recovered from serum, urine, or other specimens. The plates are developed in a single mobile phase. Visualization and detection reagents used to characterize unknowns include fluorescamine, ferric chloride/perchloric acid/nitric acid, Dragendorff, Marquis, Mandelin, and iodinated Dragendorff solutions, 254 nm ultraviolet light, and vapor from chlorine or hydrochloric acid. Detection limits of 5-200 ng per sample spot were obtained for drugs in the database. The computer program database is based on nine reaction responses plus the plate zone locations for 243 drug substances but requires entry of only one TLC property to generate a matching list. We ran the program with an IBM-compatible 386/486 PC using an MS-DOS operating system (version 6.2).

Chromatography, Thin Layer↗
PubMed1993

Documentation of a doxylamine overdose death: quantitation by standard addition and use of three instrumental techniques.

To answer the question, "Is this death due to a drug overdose?" requires at least that the drug be unequivocally identified and a blood concentration reliably determined. The approach taken in this case as standard addition technique and use of three different chromatographic techniques-high performance liquid chromatography (HPLC), high performance thin-layer chromatography (HP-TLC) and gas chromatography/mass spectrometry (GC/MS). Each of the chromatographies was carried out on the same extract by splitting the residue three ways. HPLC provided a quantitative result which was 1.2 mg/L in blood and HP-TLC and GC/MS confirmed this result with additional quantitative data, information about two metabolites (nordoxylamine and dinordoxylamine) and conclusive identification. Blood nordoxylamine was 0.52 mg/L and doxylamine plus metabolites in urine was 25 mg/L.

Calibration↗
PubMed1984

Determination of carboxyhemoglobin in the presence of other blood hemoglobin pigments by visible spectrophotometry.

The convenience of the spectrophotometric method for the determination of carboxyhemoglobin has been tempered by the observation that the analysis of postmortem bloods is often biased by the presence of pigments other than oxyhemoglobin, carboxyhemoglobin, and reduced hemoglobin. These other pigments include most prominently methemoglobin and sulfhemoglobin. Using a microprocessor-controlled spectrophotometer, a method was developed depending on absorbance difference measurements at isosbestic points for oxyhemoglobin, carboxyhemoglobin, and reduced hemoglobin that is accurate down to 2% carboxyhemoglobin in fresh blood. A correction for the error caused by methemoglobin is part of the method. Qualitative confirmation of carboxyhemoglobin by examination of spectra details, sodium dithionite reduction, and first derivative spectra is described. The analysis of denatured and autolyzed bloods is examined in the context of postmortem case reports. A number of spectra are shown in detail, including methemoglobin, sulfhemoglobin, alkaline hematin, acid hematin, and mixtures of blood pigments containing varying concentrations of carboxyhemoglobin. The method has been shown to be precise, accurate, and reliable for fresh bloods. While accuracy for denatured bloods is diminished, reliability of carboxyhemoglobin identification is maintained. The analysis time is about 5 min for routine blood samples and the method is easily implemented with a precise microprocessor-controlled spectrophotometer.

Carboxyhemoglobin↗
PubMed1978

Effective use of organic solvents to remove drugs from biologic specimens.

While studies on the extraction of drugs by various organic solvents are numerous, very few direct comparisons of all the commonly used extraction solvents have been made. Review of the literature and some specific studies undertaken by the author show that the solvents more frequently used in toxicology are not all alike but vary with respect to type of drug being extracted. Hexane, 1-chlorobutane, dichloromethane, chloroform, isopropyl ether, ethyl ether, ethyl acetate, and 1-butanol all extract nonpolar drugs quite efficiently; drugs which have polar functional groups such as alcohols, phenols, carboxylic acids, imides, amides, esters, and sulfonamides require more polar solvents for their removal from aqueous solution in high yield. Ethyl ether and other ethers, ethyl acetate, and ketones are hydrogen bond acceptor molecules and therefore extract electron donor solutes more readily than chloroform, the most commonly used electron donor solvent. Alcohols such as 1-butanol are excellent general drug extractors but pose other problems such as odor and emulsion formation. Hexane, on the other end of the polarity scale, extracts polar solutes very poorly. Thus, chloroform and ethyl ether are the most versatile solvents, although dichloromethane and 1-chlorobutane are finding more use. Solvent costs and health hazards vary within the group of solvents discussed. 1-Chlorobutane and chloroform are relatively expensive, while ethyl ether, hexanes, and dichloromethane are less expensive. No solvent is 100% safe with respect to fire, explosion, and health hazard. While chloroform has the lowest TLV, a safety limit, some of the other solvents have higher vapor pressures. The most useful solvent for small volume extractions is chloroform or chloroform with a small percentage of an alcohol. Although poor recoveries are obtained for many drugs by the small volume extraction technique, more and more use of this approach is expected in the future.

Animals↗
PubMed1976

Identification of drugs and other toxic compounds from their ultraviolet spectra. Part III: Ultraviolet absorption properties of 22 structural groups.

The ultraviolet absorption spectra of 22 different chemical (structural) groups of drugs and toxic compounds were studied. This paper completes a three-part series in which more than 500 individual compounds have been grouped according to structure as it pertains to characteristics of the ultraviolet absorption scan. Each group has a typical absorption profile with respect to the number of bands between 200 and 340 nm, the intensity of the band(s), and the changes in absorption pattern with solvent and pH changes. Phenothiazines, xanthines, coumarins, quinolines, naphthalene derivatives. O-alkyl benzene derivatives, opiates, ergot alkaloids, benzodiazepines, and various heterocyclic compounds are among the groups of compounds covered in this paper.

Forensic Medicine↗
PubMed1975

Identification of drugs and other toxic compounds from their ultraviolet spectra. Part II: Ultraviolet absorption properties of thirteen structural groups.

The ultraviolet absorption spectra of 13 different chemical classes of drugs and toxic organic compounds were studied. A classification system has been developed in which compounds with the same conjugated molecular system and auxochrome substituents are grouped together. Each of these groups has characteristic absorption spectra, showing similarities in the number of major bands, position of maximum absorbance, pH effects, and solvent effects. The absorption maxima and molecular absorptivities are tabulated for approximately 100 compounds, and characteristic spectra of each designated group are illustrated. Classes of drugs included in this study are pyridine derivatives, hydrazines, pyridylamine derivatives, variously substituted phenols, barbiturates, ureides, imides, hydantoins, and conjugted ketones (enones).

Amines↗
PubMedDate not supplied

Determination of trazodone in serum by instrumental thin-layer chromatography.

A simple and specific method for trazodone that uses high-performance thin-layer chromatography (TLC) plates for chromatography and the Camag TLC Scanner for fluorescence-reflectance measurements is described. The quantitative method employs quinidine as an internal standard and the calibration line is linear between 0.2 and 2.0 mg/L serum, the usual range encountered in patients treated with the drug. Replicate analyses of single serum specimens demonstrated reproducibility of better than +/- 3% coefficient of variation for concentrations of trazodone in the midrange of the test line.

Antidepressive Agents, Tricyclic↗
PubMedDate not supplied

A rapid, sensitive, and specific screening technique for the determination of cyanide.

A colorimetric method for the screening of cyanide in biological specimens is presented. Cyanide in a 200-microL sample is diffused in a Conway 3 compartment dish into the center well where it catalyzes the reaction between p-nitrobenzaldehyde and o-dinitrobenzene. The resulting blue-violet color intensity is proportional to cyanide concentration. The reaction is specific for cyanide, and concentrations as low as 0.05 mg/L can readily be detected.

Body Fluids↗
PubMedDate not supplied

A report of a suicide involving digoxin and doxepin.

In this report we give details on an overdose fatality involving both digoxin and doxepin. There have been numerous reported fatalities, both accidental and suicidal, involving digoxin and many more reports of fatalities involving doxepin. We believe that this is the first time a fatality from this drug combination has been reported in the literature.

Adult↗
PubMedDate not supplied

Formation of 2-(4-chlorophenoxy)-2- methylpropanamide from a clofibrate metabolite during extraction of urine.

Drug isolation from urine by solvent extraction after alkalinization suffers the potential disadvantage of chemically altering desired isolates by hydrolytic reactions. This paper reports a reaction which results in the formation of an amide substance when urine from individuals ingesting clofibrate is treated with ammonium hydroxide or sodium hydroxide and ammonium ion. The amide formed in urine has been compared to synthetically prepared 2-(4-chlorophenoxy)-2-methylpropanamide by gas chromatography, thin layer chromatography, ultraviolet spectrophotometry, infrared spectrophotometry, and mass spectrometry with complete correspondence of chemical properties. Conditions under which this amide, the major clofibrate-related entity, formed in urine are those routinely employed in analytical toxicology.

Chemical Phenomena↗