Gas-Thermo Extraction and Rapid Determination of Trace Amounts of Cyanide in Liquid Samples

Trace amounts of cyanide in water samples and foodstuff were extracted by reaction with the CN^--pretreatment reagents in the self-made portable multi-functional sample processor under the gas-thermo-condition of air flow-rate of 0.5 L·min^-1 and time of heating of 20 min, by which the concentration of CN^- in water sample could be enriched and concentrated to the extent of 5 times. The extract containing CN^- was transferred to the coloration tube and after one drop of 1 mol·L^-1 H₂SO₄ was added, volume of the solution was made up to 5.0 mL, and the CN^--reagent Ⅰ was added, shaken well and stood for 2 min. The CN^--reagent Ⅱ was added and after shaking well and standing for 20 min, value of c.v. was measured by the water-quality determinator. Detection limit of the method was found to be 0.003 mg·L^-1, and RSDs (n=6) found were all less than 3.5%. Values of recovery found by standard addition method were in the range of 92.5%-103%. The proposed method was advantageous to be used for rapid analysis at field or testing site.