改进的流动注射催化光度法测定啤酒中微量甲醛

Determination of Formaldehyde in Beers by Flow Injection Coupled with Kinetic Spectrophotometry

甲醛对KBrO3氧化结晶紫的催化作用可用来测量甲醛的含量,但该反应往往需要较高温度才能有效进行。当采用流动注射光度法测量时,加热产生的气泡使管路液体不连续。本实验通过自制的三通管,借助蠕动泵可将气泡在线地抽出而保证管路不断流,并将此方法用于啤酒中微量甲醛含量的测定。经优化发现,当V(1.0mol/LH3PO4)∶V(0.04mo1/LKBrO3)=1∶2的混合溶液与3.5×10-4mol/L结晶紫反应时,在90℃温度下反应60s可使催化体系和非催化体系的吸光度差值(ΔA)达到最大。甲醛浓度在0.05～2mg/L范围内与ΔA值有良好的线性关系(r>0.999);检出限为2.49μg/L;加标回收率为93.3%～102%。所测的5种不同品牌的啤酒样品中甲醛含量均低于发酵酒卫生标准(GB/T5009.49-2003)中的相关规定值。

When the ordinary flow injection analytical method based on the oxidation of crystal violet by potassium bromate in the phosphoric acid medium was used for the determination of trace formaldehyde, it encounters the problem of a higher temperature bubbles emerge in the reaction tube. In the present experiment, a de-bubbling device by home-made three-way joint （T-piece） was developed in this kinetic spectrophotometric method coupled with flow injection. The trace formaldehyde in beers after being distillated could be measured. The results indicated that the most absorbance difference between the catalyst and non-catalyst systems could be obtained when the mixture of 1.0 mol/L of phosphoric acid and 0.04 mol/L of bromate at 1 ： 2 （v/v） reacted with 3.5×10^-4 mol/L of crystal violet at the temperature of 90℃ for 60 s. Under the optimization conditions, linear response of formaldehyde ranged from 0.05 to 2 mg/L （r〉0.999 ）. The detection limit meas-ured with 11 replicates of procedure blank recovery tests by standard additions ranged and estimated with 3-fold standard deviation was 2.49μg/L. The from 93.3% to 102%. The formaldehyde content in the five kinds of beers measured was lower than the limit of hygienic standard of fermented wines of China （ GB/T 5009.49-2003）. The method was suitable for the t of trace formaldehyde in beers.