Flow-through sensor for the fluorimetric determination of cyanide.

A fluorimetric method for the determination of cyanide, based on its reaction with pyridoxal-5-phosphate and the use of an anion-exchange resin (QAE Sephadex) located in the detector flow-cell, is proposed. The merging-zone flow-injection manifold used allows simultaneous injection of the sample and reagent, development of the reaction along the transport system, and retention of the reaction product in the flow-cell. The calibration graph for cyanide is linear over the range from 50 ng/ml to 3.0 mug/ml and the relative standard deviation and sampling frequency are 1.4% (for 2 mug/ml cyanide) and 10 per hr, respectively. The selectivity of the method is much better than that of the conventional fluorimetric and photometric flow-injection methods for cyanide.