The indirect determination of amino acids is carried out in a flow-injection assembly by means of a solid-phase reactor containing cupric salts, immobilized in polyester resin beads. A pharmaceutical substance is forced through the reactor and the released cupric ions (complexed by the pharmaceutical substance) act as a catalyst for the subsequent reaction between Fe(III) and sodium thiosulfate. The calibration graph is linear over the range 0.1-3.0 µg mL-1 glycine, the RSD was 2.3%, and the sample throughput was 28 h-1. The influence of foreign substances was studied and the method was applied to the determination of glycine in two different pharmaceutical formulations.
Cu(II) catalyst; spectrophotometry; glycine, amino acids; flow analysis; solid-phase reactors
