SPECTROPHOTOMETRIC PHOSPHATE DETERMINATION IN URINE BY LIGAND-EXCHANGE EXTRACTION

A new spectrophotometric method for the determination of phosphate in urine is proposed, based on the ligand exchange extraction produced by phosphate solution at pH 7.5 when it is shaken with a solution of Fe( III) indole-2-carboxylate in iso-amyl alcohol. The organic layer decol oration is measured at 400 nm and the phosphate indirectly determined. The sensitivity of the method is 1.07 x 10(3) 1 mol(-1) cm(-1), the l inear working range 1-15 x 10(-5) mol/l of phosphate and the relative standard deviation 5%. It does not require previous treatment of the s ample and it is free from interferences by other normal or pathologica l constituents of the urine samples. The results agreed closely with t hose obtained by using a Sigma Diagnostics procedure for inorganic pho sphorus, based on the Fiske-SubbaRow method. The method does not requi re special instrumentation and is not expensive.