Application of high-performance liquid chromatography/laser spray mass spectrometry to legal medicine.

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Mass spectrometry (MS) is a useful tool for detecting and identifying drugs and poisons ; recent progress of interfaces has enabled high-performance liquid chromatography (LC) to couple as LC/MS or LC/MS/MS. Electrospray ionization (ESI) is widely used as an ionization method for LC/MS, but softer ionization methods with higher efficiency are needed. In this project, we have tried to apply laser ionization (LSI), a new soft ionization method to forensic toxicological analyses. In LSI, target compounds are ionized by infrared laser beam.In this project, one of the most difficult problem is the appropriate adjustment of laser beam onto the tip of the capillary ; the elongation of light path and the monitoring of the capillary using a CCD camera, were useful for fee adjustment of the laser focus on the capillary tip.We used a time-of-flight (TOF) MS as a LC/MS system, and TOF-MS has higher mass resolution ; we have developed a sensitive and specific method for identifying and quantitating Aconitum alkaloids in human body fluids and Aconitum tubers, which will be published in the Journal of Mass Spectrometry.By LSI, some drugs-of-abuse, e.g.cocaine, morphines and amphetamines were ionized with 5 to 10 times higher intensities, compared to those by the conventional ESI. In the negative mode, propionic acid derivative analgesic-antipyretic compounds were ionized with 20 to 30 times higher intensities, compared to those by ESI. All those compounds were applied direct infusion mode. However, the ion intensities were quite unstable ; thus it seems difficult for the on-line analysis of target compounds.In the future project, this LSI ionization should be applied to a nanoscale LC system to obtain more stable ionization.