FLOW-INJECTION SPECTROPHOTOMETRIC DETERMINATION OF AMINO-ACIDS BY USING 1,2-NAPHTHOQUINONE-4-SULFONATE IMMOBILIZED ON AN ION-EXCHANGE RESIN

A spectrophotometric flow-injection method based on the immobilization of 1,2-naphthoquinone-4-sulfonate reagent in an anion-exchange Amberl ite IRA 904 packed reactor is proposed for the determination of amino acids. The reagent was attached on this solid bed by electrostatic bin ding between the sulfonate and the ammonium quaternary groups. This so lid-phase reactor was used as a source of reagent since it could be de sorbed by means of a hydrochloric acid solution. The reagent liberated to the flow system reacts with the amino acids in a thermostated reac tion coil to give the corresponding derivatives. The spectrophotometri c detection was performed at 480 nm. For glycine, the response was lin ear up to 1.5 x 10(-3) M the detection limit was 5.3 x 10(-4) M, the r epeatability 0.4% and the reproducibility 5.4%. The method was applied to the analysis of some amino acids in several pharmaceutical samples . Results obtained were ill good agreement with those from the standar d method for amino acid analysis.