Potentiometric determination of chlorides with an "Air-Gap" cyanide sensor.

A new electroanalytical method for determining chloride ions with an Air-Gap cyanide sensor system is described. The method is based on the reaction of chloride with mercury(II) cyanide in dilute sulphuric acid. This reaction leads to hydrogen cyanide which can be determined with an Air-Gap cyanide sensor. Optimum concentrations of mercury(II) cyanide and sulphuric acid were established and an analytical curve was prepared for 1 x 10(-1)-1 x 10(-5)M Cl(-). The slope of the calibration curve was equal to 62.8 mV/log C. The correlation coefficient (R) was equal to 0.9992. The method can determine chloride with good results in high saline solutions and in the presence of surfactants, which is in contrast to direct potentiometry with a chloride electrode. The method was applied for chloride determination in fuses used for initiating explosions. The chlorides were determined both in the raw materials used to prepare the fuse braids and in the other fuse components. Chloride was also determined in drinking water and river water. In dependence of source, chloride amount analyzed in drinking water was in the range 2.18-182.6 mg/l. and 25.8 mg/l. in river water. A comparative analysis was carried out. In the first case, chloride was determined by a turbidimetric method, whereas in the second one by potentiometric titration against a chloride-ISE.