Spectrophotometric determination of phosphate using lanthanum chloranilate

The spectrophotometric determination of phosphate using lanthanum chloranilate has been investigated. It is possible to determine 3–300 ppm of phosphate with an accuracy of ±2%, if suitable conditions are chosen. Chloride or nitrate ions do not interfere up to 400 ppm. Interference from sulphate ion can be compensated for by adding a large amount of sulphate both to the sample and to the standard solutions. This method is simpler, has less critical reaction conditions, and develops a much more stable coloration than the conventional heteropolyacid methods.