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Rob Vreeken

Publications and source records attributed to Rob Vreeken.

2 recordsLinked to original sources

Generic solid phase extraction-liquid chromatography-tandem mass spectrometry method for fast determination of drugs in biological fluids.

A generic method was developed for the fast determination of a wide range of drugs in serum or plasma. The methodology comprises generic solid-phase extraction, on-line coupled to gradient HPLC with tandem mass spectrometric detection (SPE-LC-MS/MS). The individual components of the SPE-LC-MS/MS system were optimized in an integrated approach to maximize the application range and minimize the method development time. The optimized generic SPE-LC-MS/MS protocol was evaluated for 11 drugs with different physicochemical properties. Good quantification for 10 out of 11 of the pharmaceuticals in serum or plasma could be readily achieved. The quantitative assays gave recoveries better than 95%, lower quantification limits of 0.2-2.0 ng/ml, acceptable precision and accuracy and good linearity over 2-4 orders of magnitude. Carry-over was determined to be in the range of 0.02-0.10%, without optimization.

Chromatography, High Pressure Liquid↗

Determination of oxytetracycline and its degradation products by high-performance liquid chromatography-tandem mass spectrometry in manure-containing anaerobic test systems.

This paper describes the development of a HPLC-MS-MS (ESI) method with baseline separation of oxytetracycline, 4-epi-oxytetracycline, alpha-apo-oxytetracycline and beta-apo-oxytetracycline using an XTerra column and an MeOH-MilliQ-water (containing 8 mM formic acid) mobile phase. Limits of quantification for aqueous standards were in the range of 0.004 to 0.008 microM. The linear range tested was 0.003 to 0.5 microM and in one case up to 17 microM. An experiment simulating the degradation of oxytetracycline in manure was set up and free concentrations of the four antibiotics were determined during 6 months. Oxytetracycline (>0.02 microM) was observed up till 6 months after spiking. No important increase in free concentrations of the degradation products was observed.

Anaerobiosis↗