Estimation of perimortal percent carboxy-heme in nonstandard postmortem specimens using analysis of carbon monoxide by GC/MS and iron by flame atomic absorption spectrophotometry.

In decomposed, formalin-fixed, embalmed, exhumed, and some fire-dried cases in which normal blood is unavailable, the usual methods for determination of carboxyhemoglobin saturation frequently fail. To address these specimens, a method utilizing both gas chromatography/mass spectrometric (GC/MS) determination of carbon monoxide (CO) and flame atomic absorption spectrophotometry (FAAS) determination of iron (Fe), in the same specimen, was developed. The method is reported here, along with its application to seven pertinent forsensic death investigations. The CO analytical methodology involves acid liberation of the gas from the specimen aliquot in a headspace vial. After heating and equilibrating, a sample of the headspace vapor is injected into the GC/MS system with a gastight syringe. Quantitation is achieved by standard addition comparison utilizing the ideal gas law equation. Iron is quantified by FAAS analysis of the same aliquot used for the CO determination, following nitric acid digestion. The concentration is determined by comparison to a standard curve. A formula for determining the minimum percent carboxy-heme saturation was derived by using the ratio of the amount of CO to the amount of Fe in the aliquot analyzed. Tissue types analyzed include spleen, liver, muscle, dried blood, and unspecified decomposed tissue.

Pharmacokinetics and metabolism of a 4'-methylthio derivative of propranolol in the dog.

The purpose of this study was to examine the effect of a methylthio substituent in the metabolically most active position of propranolol, i.e. the 4'-position, on the pharmacokinetics and metabolism of this drug in the dog. The kinetics of 4'-methylthiopropranolol (MTP) were compared to those of propranolol following simultaneous iv doses of labeled drug and oral doses of unlabeled drug. MTP had a significantly larger volume of distribution and a longer half-life, and demonstrated a greater accumulation by red blood cells and cardiac conductile tissue than propranolol, effects which presumably are due to a higher lipophilicity of MTP. The greatest effect was on the oral clearance, which was substantially lower for MTP (1.6 vs. 5.5 liters/min) with an associated higher bioavailability (23.1 vs. 10.9%). Studies of MTP metabolism using radiolabeled drug showed that MTP, like propranolol, was eliminated entirely by metabolism. About 70% of the urinary radioactivity was extractable into ethyl acetate at pH 9.8 and pH 2.0. The extractable metabolites were separated by HPLC and identified by GC/MS, direct probe MS, and comparison with authentic compounds. Eleven metabolites were identified as sulfoxides and, in particular, sulfones of MTP and its N-dealkylated and subsequently deaminated glycollic and lactic acid metabolites. The nonextractable urinary radioactivity (30%) was isolated by DEAE-Sephadex chromatography and identified by HPLC/MS as four glucuronic acid conjugates. In contrast to propranolol, there was no evidence of aromatic carbon oxidation for MTP. These observations suggest that the markedly decreased oral clearance of MTP compared to propranolol is due to qualitatively altered metabolism from a highly efficient aromatic carbon oxidation for propranolol to a less efficient sulfur oxidation for MTP.

Determination of codeine in plasma by high-performance liquid chromatography.

An automated, sensitive, and selective reverse-phase high-performance liquid chromatographic assay has been developed to measure codeine in plasma. The analysis requires only 1 ml plasma and is accomplished by detection of the fluorescence of codeine following extraction and concentration. The method is simple and rapid, involving a one-step extraction of codeine from alkalinized (pH 10.0) plasma into an organic layer of hexane/dichloromethane, 2/1. The organic layer was evaporated under nitrogen and the residue reconstituted with the mobile phase. The samples were chromatographed on a reverse-phase C-18 column using a mobile phase of acetonitrile-phosphate buffer, 80/20 (pH 5.80). The codeine and internal standard, N-allylnorcodeine, peaks were detected using a fluorescence detector. The retention times were 8.6 min for the internal standard and 11.3 min for codeine. Standard curves were linear from 10 to 250 ng/ml. The assay was validated by direct comparison with a gas chromatographic procedure that employed nitrogen-phosphorus detection. The assay has been employed for the analysis of several codeine studies using human, dog, and rat plasma.