Chemical analyser

Abstract

A liquid sample is analysed for a target chemical. A sample solution is added to a measurement cell of known volume and a reagent is incrementally added to the cell until a detectable change is observed. A reference compound, of a known concentration, that does not take part in the reaction between the target chemical and reagent, is added to the reagent and by measuring the concentration of the reference compound the amount of reagent used may be determined. A single mechanism introduces a sample, adds reagent mixes cleans and flushes the measurement cell which incorporates a longitudinal chamber having a number of fluid inlets for sample and reagent and an outlet for measured sample/reagent mixtures, a detector being located in or adjacent to said chamber between the inlets and said outlet and a piston movable in said chamber carrying a series of seals such that movement of the piston sequentially opens the inlets and expels the fluid. The analyzer also includes a device for delivering a volume of reagent into a measurement cell incorporating a first port to introduce sample fluid; a second port to allow injection of fluid reagent; and a third port to allow expulsion of sample and sample/reagent mixtures to waste which includes a compressible reservoir of reagent which is positioned within a rigid container, and is surrounded by a fluid which substantially fills the space between said reservoir and the inside wall of said container and means for pressurising said fluid surrounding said reservoir to effect partial collapse of said reservoir in order to inject reagent into said measurement cell.

Dependencies are inferred from the claim text.