The use of solid phase reactors as the source of a catalytic solution. The indirect flow-injection spectrophotometric determination of amino acids

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 mu g 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.