甲醛-酸性铬蓝K-溴酸钾体系催化动力学光度法测定痕量甲醛

Catalytic kinetic spectrophotometric determination of trace formaldehyde with formaldehyde-acid chrome blue K-potassium bromate system

基于在硫酸介质中,痕量甲醛对溴酸钾氧化酸性铬蓝K褪色反应有催化作用,且催化褪色程度与溶液中甲醛量在一定范围内成正比,建立了测定痕量甲醛的动力学光度法。讨论了反应介质、试剂用量、反应温度、反应时间及共存离子的影响,建立了最佳反应条件。测定催化反应的表现活化能为1·78kJ/mol。在选定的条件下,方法的线性范围为0·0041～0·20μg/mL,检出限为4·6×10-10g/mL。利用此法测定了废水和空气中的痕量甲醛,RSD小于2·50%(n=5),回收率在98%～99%之间。

A new kinetic spectrophotometric method for the determination of trace formaldehyde has been developed, based on the catalytic effect of trace amounts of formaldehyde on the discoloring reaction of acid chrome blue K with potassium bromate in dilute H2SO4 solution. The decrease in the absorbance has a quantitative relationship with the concertration of formaldehyde. The factor including reaction medium ,concentration of reagent, temperature and time of reaction, influence of coexisting ions on the reaction are discussed. The apparent activation energy of the reaction is 1.78 kJ/mol. Under the selected conditions,the linear range of determination is 0. 004 1-0.20 μg/mL and the detection limit is 4.6 × 10^-10 g/mL for formaldehyde. The recovery is between 98%-99% and the RSD is less than 2. 50% （n =5）. The method has been applied to the detection of trace formaldehyde in waste water and air samples with satisfactory results.