Simultaneous determination of 4-substituted cathinones (4-MMC, 4-MEC and 4-FMC) in human urine by HPLC-DAD.

This study developed a selective and rapid high-performance liquid chromatography-diode array detection method for the confirmation of different cathinone derivates in human urine. Samples were prepared by solid-phase extraction (SPE) using procaine hydrochloride as the internal standard. The chromatographic separation was performed on a Kinetex PFP column using isocratic elution. The mobile phase was composed of a mixture of acetonitrile (33%, v/v) and 0.005M ammonium trifluoroacetate buffer (67%, v/v; pH 4.93 ± 0.03) with a flow rate of 0.350 mL/min. The diode array detection was performed at 262 nm. The method was linear over the concentration range of 25-2,400 ng/mL. Intra-day and inter-day precision values for cathinones were less than 1.26% (relative standard deviation). The limit of detection for any compounds extracted from human urine by the optimized SPE method was 40 ng/mL and the limit of quantification was 100 ng/mL in the urine. The recovery rate of SPE was between 71 and 82% with a lower relative standard deviation than 2.35%.

Detection of tinuvin 770, a light stabilizer of plastic materials from dialysis membranes, by high-performance liquid chromatographic analysis.

Tinuvin 770 [bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate] is a pharmacologically active agent used worldwide as a light stabilizer for plastic materials. In vitro studies show that it is an L-type Ca(2+) channel and neuronal nicotic acethylcholine receptor blocker. Hypotension, vegetative dysfunction, and neurological symptoms are frequently observed during a haemodialysis treatment. The release of Tinuvin 770 from plastic materials applied in haemodialysis may play a part in the development of clinical signs. In our study, four different commonly used haemodialysis membranes (polysulphon, cuprophan, and two types of hemophan) are examined. The polymers are soaked for 72 h in physiological saline solution. Isolation is carried out using a Waters Oasis SPE column for solid-phase extraction and by high-performance liquid chromatography (HPLC) with electrospray ionization-mass spectrometric detection. Tinuvin 770 release is detected from all examined membranes. Validation studies show a satisfactory selectivity, linearity, accuracy, and recovery of this method. Our results suggest that Tinuvin 770 could have specific toxicological and therapeutic importance related to haemodialysis treatment. The developed HPLC method is suitable for the detection of Tinuvin 770.