Simultaneous determination of epirubicin, doxorubicin and their principal metabolites in human plasma by high-performance liquid chromatography and electrochemical detection.

A high-performance liquid chromatographic method with electrochemical detection has been developed for the simultaneous determination of epirubicin, 13-S-dihydroepirubicin, doxorubicin and 13-S-dihydrodoxorubicin in human plasma. An aliquot of 200 microl plasma, spiked with internal standard, was extracted by solid-phase extraction using polymeric adsorbent columns. Chromatography was performed using a C18 reversed-phase column with a mobile phase consisting of water-acetonitrile (71:29, v/v) containing 0.05 M Na2HPO4 and 0.05% v/v triethylamine adjusted to pH 4.6 with citric acid. Linearity of the method was obtained in the concentration range of 1-500 ng/ml for all the analytes. Analytical recoveries of the analytes ranged from 89 to 93%. The assay can be used for the simultaneous determination of the four analytes, or for epirubicin and its metabolite or doxorubicin and its metabolite, using the other parent drug as an internal standard. The method was applied to analyze human plasma samples from patients treated with epirubicin using doxorubicin as an internal standard.

Methodological issues in biomonitoring of low level exposure to benzene.

Data from a pilot study on unmetabolized benzene and trans,trans muconic acid (t,t-MA) excretion in filling station attendants and unexposed controls were used to afford methodological issues in the biomonitoring of low benzene exposures (around 0.1 ppm). Urinary concentrations of benzene and t,t-MA were measured by dynamic head-space capillary GC/FID and HPLC, respectively. The accuracy of the HPLC determination of t,t-MA was assessed in terms of inter- and intra-method reliability. The adequacy of urinary t,t-MA and benzene as biological markers of low benzene exposure was evaluated by analysing the relationship between personal exposure to benzene and biomarker excretion. Filling station attendants excreted significantly higher amounts of benzene, but not of t,t-MA, than controls. Adjusting for occupational benzene exposure, smokers excreted significantly higher amounts of t,t-MA, but not of unmetabolized benzene, than nonsmokers. A comparative analysis of the present and previously published biomonitoring surveys showed a good inter-study agreement regarding the amount of t,t-MA and unmetabolized benzene excreted (about 0.1-0.2 mg/l and 1-2 micrograms/l, respectively) per unit of exposure (0.1 ppm). For each biomarker, based on the distribution of parameters observed in the pilot study, we calculated the minimum sample size required to estimate the population mean with given confidence and precision.

Simultaneous determination of heroin 6-monoacetylmorphine, morphine, and its glucuronides by liquid chromatography--atmospheric pressure ionspray-mass spectrometry.

A new analytical technique has been developed for the simultaneous determination of heroin, 6-monoacetylmorphine, morphine, morphine-6- and 3-glucuronides, and codeine in serum using liquid chromatography coupled with ionspray mass spectrometry. The analytes and the internal standard, nalorphine, were subjected to solid-phase extraction (SPE) using ethyl SPE columns before chromatography. The chromatographic separation of the analytes was achieved using a normal phase column and a water-methanol-acetonitrile-formic acid mobile phase at a flow rate of 230 microL/min. The mass spectrometer was operated in selected-ion monitoring mode. Under these conditions, the limit of quantitation was 0.5 ng/ml for heroin, 4 ng/ml for 6-monoacetylmorphine, 4 ng/ml for morphine, 1 ng/ml for morphine-3-glucuronide, 4 ng/ml for morphine-6-glucuronide, and 4 ng/mL for codeine. Serum levels of heroin metabolites were determined in C57BL/6 inbred mice after a dose of 20 mg/kg heroin administered subcutaneously. 6-monoacetylmorphine showed a peak concentration of 0.93 micrograms/mL serum at 3 min, whereas morphine and morphine-3-glucuronide achieved their peak concentrations of 9.6 and 2.9 micrograms/mL serum at 10 and 20 min, respectively. Finally, the absence of morphine-6-glucuronide and codeine excluded the possibility of their formation from morphine in this animal model.