Abstract: A multichamber cuvette for maintaining in independent and separate condition at least two reactants until such time that it is desired to mix them for reaction with each other and a reactant liquid sample while in the cuvette for analysis in the cuvette, and a method of use of such cuvette. There is provided a cuvette body of a suitable plastic defining at least two chambers interconnected by a passageway of relatively small cross section having at least the end portions thereof of capillary size to prevent under many circumstances, as by surface tension, accidental mixture of liquid reactants in the chambers. If there is a substantial head of liquid in one chamber and/or a risk of impact of the cuvette with an external foreign object, sufficient to break such surface tension, an air lock in the passageway when the latter is below the liquid levels in the chambers prevents such accidental mixture. A baffle in the passageway enhances separation of liquids and/or solid substances in the chambers.

Abstract: A quantitative liquid sample analysis system exhibiting improved light transmission along the sight path of a flowcell and greater optical stability for significantly more accuracy of analytical results. There is provided in such a system a source of treated liquid having a first index of refraction, means for flowing the liquid along a conduit, the conduit including a flowcell having a tubular wall structure with a second index of refraction, the second index of refraction being less than the first index of refraction.