试验了用氨基酸代替氨水或乙酸铵作为胺源的条件下,乙酰丙酮与甲醛反应生成有色化合物的适宜条件并提出了氨基酸-乙酰丙酮分光光度法测定水中甲醛的方法。优化的试验条件如下:① 0.12 mol·L-1甘氨酸衍生剂用量为2 mL;② 反应温度为50 ℃;③ 反应时间为15 min;④ 反应体系的pH为4.7。甲醛的质量浓度在0.2~1.0 mg·L-1范围内与吸光度呈线性关系,检出限为5 μg·L-1。加标回收率均不小于98.0%,测定值的相对标准偏差(n=6)均不大于4%。方法应用于地表水样中甲醛的测定,测定值与国标法测定结果相符。

Conditions for the color reaction of formaldehyde with acetylacetone by using amino acids instead of aq. ammonia or ammonium acetate as the donor of -NH2 group were tested and a spectrophotometric method for determination of formaldehyde in water sample with glycine and acetylacetone as reagents was proposed. The optimized conditions found were as follows: ① amount of 0.12 mol·L-1 glycine derivatizing agent: 2 mL; ② temperature of reaction: 50 ℃; ③ time of reaction: 15 min; ④ pH of reaction system: 4.7. Linear relationship between values of absorbance and mass concentration of formaldehyde was obtained in the range of 0.2-1.0 mg·L-1, with detection limit of 5 μg·L-1. Values of recovery found by standard addition method were over 98.0%,and values of RSD′s (n= 6) less than 4%. The proposed method was used in the analysis of sample of surface water, giving results of formaldehyde contents in consistency with values found by GB method.