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A quantitative method was developed for valproic acid and five of its mono-unsaturated metabolites using capillary gas chromatography—mass spectrometry with selected ion monitoring. The method was applied to serum and all metabolites were measured in a single run. Methyl esters were synthesized as the derivatives suitable for gas chromatography. Calibration curves were found to be linear and the sensitivities in the order of 0.1 μg ml−1. Patients' data are presented. By this method it is possible to separate the stereoisomers of 2-n-propyl-2-pentenoic acid and of 2-n-propyl-3-pentenoic acid.

The purpose of the present work was to study the in vitro distribution of acyclovir in human skin layers after iontophoresis, applied in order to increase the amount of drug in the basal epidermis, site of Herpes simplex infections. Experiments were done with Franz diffusion cells applying, as donor, acyclovir solutions (pH values: 3.0 and 7.4) or a commercial cream. Quantification of drug at different skin depths was performed by horizontal slicing of frozen skin, and drug extraction and analysis by high-performance liquid chromatography. Seven h of transdermal iontophoresis (0.5 mA cm-2 induced an accumulation of acyclovir in epidermis and dermis ranging from 80 to 150 micrograms cm-3, characterized by homogeneous distribution of the drug in skin layers. After short current application time (30 min) however, the concentration profile of drug in skin was not significantly different from the obtained after seven h of passive diffusion, employing pH 3.0 donor solution. After 30 min of iontophoresis, the acyclovir reservoir on the skin was maintained for up to five h producing a dramatic increase of drug concentration in skin, evening out over 80 micrograms cm-3 until a depth of 300 micrograms. Acyclovir can be accumulated at target site more quickly and maintained at higher level through application of a iontophoretic pulse and by keeping the drug reservoir on skin.

This paper describes an assay procedure for acyclovir quantification in human skin after in vitro transdermal transport experiments. The procedure employs warm distilled water for acyclovir (ACV) extraction and high-performance liquid chromatography (HPLC) as analytical method. The procedure has good reproducibility, sensitivity and specificity, resulting in a reliable method for biopharmaceutical studies of ACV distribution in skin tissue. The chromatographic conditions set up, using distilled water as mobile phase, makes the analytical procedure simple and easy to perform.

The use of transient gene expression assays for the study of natural or engineered plant promoters is affected by a considerable degree of inter-experiment variability. As a means of obtaining interpretable data from a limited number of experiments, we worked out conditions for the simultaneous determi nation of the activity of two reporter genes, a “sample” and a “reference”, ona single extract of co-transformed protoplasts. s-glucuronidase (GUS) and chloramphenicol acetyl transferase (CAT) genes, both under the control of the CaMV 35S promoter, were transferred into tobacco (Nicotiana tabacum L.) protoplasts on two independent plasmids. The parallel expression of the two reporter genes in several independent co-transformation experiments was verified. Conditions for the use of a single protoplast extraction buffer and for the simultaneous assay of both reporter gene activities were set up. A HPLC method for the non-radioactive determination of both enzyme activities on a single aliquot of the reaction mixture was developed. The resulting procedure was tested using the GUS gene as “reference” and the CAT gene, under the control of either wild type or upstream-deleted (−90) CaMV 35S promoter, as “sample”. The protocol is simple and allows the fast analysis of plant promoters in the presence of a true internal standard under conditions in which assay manipulations are reduced to a minimum and both reporter gene activities are subjected to the same experimental treatments.

The Chromatographie behaviour of dibenzo-18-crown-6 complexes with mercury chloride, bromide and iodide on a Micropak CH column, with methanol— 10 -2 M phosphate or borate buffer mixtures as mobile phase, is reported. Mercury and hatides are extracted by dibenzo-18-crown-6 into methylene chloride. The detector response at 254 nm was linear in the range 0.1–10 μg of metal or halide.

HPLC method adopted in drug control laboratories for the simultaneous determination of Eterobarb and its metabolites in plasma

A method is described for the determination of oxalate in urine using flow injection analysis and fluorimetry. Oxalate is precipitated with calcium chloride at pH 4.5, redissolved in H 2 SO 4 and measured by flow injection analysis. The minimum detection limit is 6 μmol/l. The coefficient of variation is 7%. Results are in good accordance with normal values found with traditional oxalate analysis.