Amperometric sensor for cyanide utilizing cyanidase and formate dehydrogenase

An amperometric sensor for the detection of cyanide integrated in a flow injection analysis (FIA) system is presented. The specificity of the sensor for cyanide is achieved by a reaction cascade involving two enzymes, cyanidase (EC 3.5.5.1) and formate dehydrogenase (FDH, EC 1.2.1.2). The limit of detection (LOD) and the limit of quantification (LOQ) were determined to be in the low micromolar range. The sensor showed very good long term stability and the linear range of detection extends from 0.7 up to 800 μM. The sensor’s ability to measure cyanide in complex matrices, such as plant extracts, is demonstrated. Although the sensor is susceptible to formate and to a lesser extent to thiocyanate, sulfide does not interfere significantly.