Abstract
A monitoring tape for hydrogen cyanide gas in air has been developed by using Cu (II) and N, N-diethyl-pphenylenediamine (DPD) sulfate. It is based on color change of the tape when reacting with hydrogen cyanide. The tape, which contains silicagel as an absorbent and is impregnated with a processing solution that includes copper (II) acetate, DPD sulfate and glycerin, was found to be a highly sensitive means of detecting hydrogen cyanide gas. When an air sample including hydrogen cyanide gas was passed through the tape, hydrogen cyanide was absorbed on the surface of the tape. The cyanide ion reacted with the copper (I) ion producing Cu CN, then the DPD was oxidized by the copper (II) ion to form a stain. The intensity of the stain was proportional to the concentration of hydrogen cyanide at a constant sampling time (70s) and the flow rate (400ml/min). The intensity of the stain could be recorded by measuring the intensity of reflecting light (555nm). The detection limit was 0.20ppm for HCN. No response was observed from various other gases, with an exception of oxidizing gases (ex Cl2). However, the influence of oxidizing gases in the sample gas was completely eliminated by passing the sample gas through an elimination column packed with DPD.
