Determination of cannabinoids in plasma using salting-out-assisted liquid-liquid extraction followed by LC-MS/MS analysis.

The detection of the markers of Cannabis consumption in biological specimens is an important task for drug testing laboratories in varous contexts. A simple assay combining salting-out assisted liquid-liquid extraction sample preparation and LC-MS/MS analysis was applied to the measurement of Δ9 -tetrahydrocannabinol, 11-nor-9-carboxy-Δ9 -tetrahydrocannabinol (THC-COOH), 11-hydroxy-Δ9 -tetrahydrocannabinol, cannabinol and cannabidiol concentrations in 100 µl plasma specimens. The assay had linearity of 1-100 ng ml-1 for THC-COOH and 0.5-50 ng ml-1 for the other tested cannabinoids. Assay validation criteria were fulfilled. Extraction yields (88.7-97.3%) and internal-standard correct matrix effects (-9.6 to +5.4%) were acceptable. The assay was applied to 238 clinical specimens from trauma patients, with 19 samples presenting quantifiable concentrations of at least one of the target compounds. The developed assay is a simple and efficient strategy for simultaneous measurement of Δ9 -tetrahydrocannabinol, THC-COOH, 11-hydroxy-Δ9 -tetrahydrocannabinol, cannabinol and cannabidiol concentrations in plasma specimens.

Determination of meropenem in capillary plasma microsamples using LC-MS/MS.

Background: The measurement of meropenem plasma concentrations is employed for dosing regimen individualization. The aim of this study was to develop and validate a LC-MS/MS assay for quantification of meropenem in capillary plasma microsamples. Methods: Samples were prepared by protein precipitation with acetonitrile, followed by clean-up with dichloromethane. The method was validated and applied to 12 paired samples of venous and capillary plasma. Results: The method was linear in the range of 0.5-50 µg/ml. Matrix effects were minimal. Inter- and intra-assay were 3.8-7.9% and 2.7-5.5%, respectively, while accuracy was 91.7-100.6%. Concentrations in capillary and venous plasma were highly correlated. Conclusion: An assay for the quantification of meropenem in capillary plasma microsamples was fully validated, showing potential for clinical application.

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Determination of cortisol in hair using UHPLC-MS/MS: application to patients admitted for ethanol dependence treatment.

Aim: Cortisol hair levels can be used to evaluate chronic stress status. In this context, an improved UHPLC-MS/MS assay for the determination of cortisol in hair was developed and validated. Materials & methods: Hair was extracted with methanol for 4 h at 25°C. Chromatographic run time was 5.5 min. The assay was linear in the range of 1-250 pg mg-1. Precision was 3.6-12.2% and accuracy 97.1-103.8%. The method was applied in hair from 19 volunteers admitted at a rehabilitation clinic, with ethanol consumption classified using ethyl glucuronide hair levels. Conclusion: Abstinent/chronic moderate ethanol consumers had significantly lower cortisol hair levels than chronic excessive consumers. This is the first study evaluating cortisol hair levels in ethanol abuse patients using an objective marker for ethanol consumption.