Search

The current work describes the implementation of electro membrane extraction (EME) into an autosampler for high-throughput analysis of samples by EME-LC-MS. The extraction probe was built into a luer lock adapter connected to a HTC PAL autosampler syringe. As the autosampler drew sample solution, analytes were extracted into the lumen of the extraction probe and transferred to a LC-MS system for further analysis. Various parameters affecting extraction efficacy were investigated including syringe fill strokes, syringe pull up volume, pull up delay and volume in the sample vial. The system was optimized for soft extraction of analytes and high sample throughput. Further, it was demonstrated that by flushing the EME-syringe with acidic wash buffer and reverting the applied electric potential, carry-over between samples can be reduced to below 1%. Performance of the system was characterized (RSD, <10%; R2, 0.994) and finally, the EME-autosampler was used to analyze in vitro conversion of methadone into its main metabolite by rat liver microsomes and for demonstrating the potential of known CYP3A4 inhibitors to prevent metabolism of methadone. By making use of the high extraction speed of EME, a complete analytical workflow of purification, separation, and analysis of sample could be achieved within only 5.5 min. With the developed system large sequences of samples could be analyzed in a completely automated manner. This high degree of automation makes the developed EME-autosampler a powerful tool for a wide range of applications where high-throughput extractions are required before sample analysis. [ABSTRACT FROM AUTHOR]

Heterocyclic amines (HCAs) are mutagenic/carcinogeniccompoundsformed at ng/g levels during frying meat or fish. The effect of thenormal intake of dietary HCAs in humans and their involvement in theetiology of cancer are currently unknown. In this work, a new extractionmethod, liquid phase microextraction (LPME) with hollow fibers, andLC-MS/MS have been used for the first time to determine HCAs and metabolitesin nonspiked human urine following a single meal of chicken cookedat 180 °C for 6 min. The total intake of HCAs was estimated tobe 6 μg, of which 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) accounted for about 1 μg. The concentrationsof PhIP in nonhydrolyzed urine samples ranged from 11.7 to 59.4 pg/g.The total amount of PhIP in urine ranged between 9.3 and 21.1 ng,which corresponds to 0.91–2.1% of the ingested PhIP. In addition,the urine levels of 4′-OH-PhIP (2-amino-1-methyl-6-(4′-hydroxy)phenylimidazo[4,5-b]pyridine) and 5-OH-PhIP (2-amino-1-methyl-6-(5-hydroxy)phenylimidazo[4,5-b]pyridine) also showed a narrow variation between the samples.The analysis of urine samples after acid hydrolysis did not give additionalinformation but showed a notable increase in norharman in some cases.The obtained results suggest PhIP in urine as a possible biomarkerof exposure to HCAs and the LPME and LC-MS/MS method as an appropriatestrategy to biomonitor HCAs in urine. [ABSTRACT FROM AUTHOR]