An innovative technology for "random-access" sampling.

A major instrumental limitation to rapid, "random-access" clinical analysis has been cross-contamination at sampling and reagent probes. Use of an immiscible, nonreactive fluid as a positive barrier between the liquid sample and reagent and the interior and exterior surfaces of their respective probes provides an inert, deformable surface that both prevents carryover and ensures accurate delivery. Being totally nonreactive under clinical chemistry conditions, the fluid does not affect the ensuing analysis. Application of this technology to the Technicon RA-1000 (trademark of Technicon Instruments Corp.) system allows transfer of a liquid sample and any of 14 liquid reagents to the reaction vessel with a carryover of less than 1/10(6) with a precision (CV) of 0.5%. Its use provides for a rapid analysis rate of 240 tests per hour, and for transfer of microliter quantities of serum, with carryover of less than 1/8000, again at an average CV of 0.5%.