Abstract: Contamination between successive aqueous samples in a continuous-flow analytical system is eliminated by the careful and precise application of a thin, uniform film of immiscible fluid upon the outer surface of an aspirating probe of a metering system. The immiscible fluid is selected to preferentially wet the inner and outer probe surfaces and the inner wall surfaces of the conduits of such system, to the substantial exclusion of the aqueous samples. The immiscible fluid is aspirated, along with an air segment, between aspirations of successive samples, each aspirated air and sample segments are encapsulated by such immiscible fluid while passed through such system. A selective valve is utilized to isolate and transfer each fluid sample from the probe to such system.

Abstract: A sample analyzing system features a number of discrete sample segments continuously conveyed along a conduit. Each sample segment receives a precise aliquot of one or more reagents on a selective basis, and in any particular sequence. Selective injection of the reagent into the moving stream of sample segments allows for an increase in the efficiency and throughput of the sample processing.