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Browsing by Subject "mikropilarisähkösumutussiru"

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  • Backman, Nina (2011)
    Screening of drugs of abuse has to combine sensitivity, selectivity and repeatability. The conventional screening methods include immunoassay screening followed by a more sensitive confirmation method. The aim of the study was to develop a simple, yet sensitive sample preparation method for screening of benzodiazepines and amphetamine derivatives in urine samples with silicon micropillar array electrospray ionization chip (µPESI) coupled to mass spectrometric analysis. Another aim was to evaluate the suitability of µPESI in biological sample analysis. Ideally, the developed method would provide an alternative to immunoassay screening method in forensic urine analysis. The sample preparation methods were separately optimized for benzodiazepines and amphetamine derivatives. Methods used included solid- phase extraction with Oasis HLB cartridge and C18-phase containing ZipTip®-pipette tip, liquid-liquid extraction, and dilution and filtering without prior extraction. Optimization focused, however, on ZipTip®-extraction. The compounds were spiked in blank urine to their cut-off levels, 200 ng/ml for benzodiazepines and 300 ng/ml for amphetamine derivatives. For benzodiazepines, every extraction phase was optimized. The sample pH was adjusted to 5, the ZipTip® phase was conditioned with acetonitrile and washed with a mixture of water (pH 5) and acetonitrile (10 % v/v) and the sample was eluted with a mixture of acetonitrile, formic acid and water (95:1:4 v/v/v). For amphetamine derivatives, pH values of sample and solvents were optimized. The sample pH was adjusted to 10, the ZipTip® phase was conditioned with a mixture of water and ammoniumbicarbonate (pH 10, 1:1 v/v), washed with a mixture of water and acetonitrile (1:5 v/v) and the sample was eluted with methanol. The optimized methods were tested with authentic urine samples obtained from Yhtyneet Medix Laboratories and compared to the results of quantitative GC/MS analysis. Benzodiazepine samples were hydrolyzed prior to extraction to improve recovery. All samples were measured with Q-TOF Micro apparatus and hydrolyzed benzodiazepine samples additionally with microTOF apparatus in Yhtyneet Medix Laboratories. Based on the results the developed method needs more optimization to function properly. The main problems were lack of reproducibility and poor sample ionization. Manual sample preparation and adding to the chip sample introduction spot increased variation. Authentic benzodiazepine samples gave false negative and authentic amphetamine derivative samples false positive results. False negatives may be due to the lack of sensitivity and false positives due to the contamination of sample cone, chips or solvents.