MICROBIAL SENSOR FOR SELECTIVE DETERMINATION OF SULFIDE

A microbial sensor consisting of immobilized Thiobacillus thiooxidans, a gas-permeable membrane, and an O-2 electrode was prepared for the d etermination of sulphide. When a sample solution containing sulphide w as passed into the flow cell, the output of the microbial sensor decre ased markedly with time until a steady state was reached. The total ti me required for an assay was 20-30 min by the steady-state method. In the pulse method, the total time required for an assay was about 5 min . A linear relationship was obtained between the sensor output and the concentration of sodium sulphide below 0.40 mM. The minimum detectabl e concentration of sodium sulphide was 0.02 mM. Selectivity of the sen sor was satisfactory. The microbial sensor was applied to the determin ation of sulphide in spring water. A good agreement was obtained betwe en the microbial sensor and the methylene blue method. The regression coefficient was 0.97 for five experiments. The activity of the microbi al membrane was stable for more than 25 days. The response was reprodu cible with 2.5% of the relative standard deviation when a sample solut ion containing 0.2 mM sodium sulphide was employed.