An automated method of sample preparation of biofluids using pierceable caps to eliminate the uncapping of the sample tubes during sample transfer

Biological samples are normally collected and stored frozen in capped tubes until analysis. To obtain aliquots of biological samples for analysis, the sample tubes have to be thawed, uncapped, samples removed and then recappe d for further storage. In this paper, we report an automated method of samp le transfer devised to eliminate the uncapping and recapping process. This sampling method was incorporated into an automated liquid-liquid extraction procedure of plasma samples. Using a robotic system, the plasma samples we re transferred directly from pierceable capped tubes into microtubes contai ned in a 96-position block. The aliquoted samples were extracted with methy l-tert-butyl ether in the same microtubes. The supernatant organic layers w ere transferred to a 96-well collection plate and evaporated to dryness. Th e dried extracts were reconstituted and injected from the same plate for an alysis by liquid chromatography with tandem mass spectrometry. (C) 2000 Els evier Science B.V. All rights reserved.