LUMINOL CHEMILUMINESCENCE WITH HETEROPOLY ACIDS AND ITS APPLICATION TO THE DETERMINATION OF ARSENATE, GERMANATE, PHOSPHATE AND SILICATE BY ION CHROMATOGRAPHY

A flow-injection chemiluminescence (CL) method has been proposed for s ensitive determination of arsenate, germanate, phosphate and silicate, after separation by ion chromatography (IC). The post-column detectio n system involved formation of heteropoly acid in a H2SO4 medium befor e the CL reaction with luminol in an NaOH medium. For separation, hete ropoly acid formation and the CL detection reaction, pH requirements w ere not compatible. When present as a heteropoly acid complex with mol ybdenum(VI), germanium(IV) and silicon(IV) caused CL emission from oxi dation of luminol, and such a CL oxidation of luminol was observed ana logously for arsenic(V) and phosphorus(V) but with the addition of met avanadate ion to the acid solution of molybdate. Good sensitivity for the three analytes arsenic(V), germanium(IV) and phosphorus(V) could b e given by a single set of reagent conditions, chosen carefully Anothe r set was suitable for determining phosphorus(V) and silicon(IV). The minimum detectable concentrations of arsenic(V), germanium(IV), phosph orus(V) and silicon(IV) were 10, 50, 1 and 10 mu g 1(-1), respectively . Linear calibrations for arsenic(V), germanium(IV), phosphorus(V) and silicon(IV) were established over the respective concentration ranges of 10-1000, 50-25000, 1-1000 and 50-10000 mu g 1(-1). The proposed IC -CL method was successfully applied to analyses of a seaweed reference material, rice wine and water samples.