取均质后的虾肉或蟹肉4 g,用每升中含有1 mol·L-1氢氧化钠溶液0.1 mL及甲醛-水(37+63)溶液0.1 mL的提取剂40 mL提取并离心。取上清液并经冷冻法和在线渗析系统除去其中蛋白质及脂肪,进入离子色谱仪测定其亚硫酸盐含量前,将提取液用超纯水稀释6倍。以Metrosep A supp 15色谱柱(150 mm×4 mm)为分离柱,用每升中含有0.386 g Na2CO3和0.084 g NaHCO3的丙酮-水(20+80)溶液作为淋洗液等度洗脱,用电导检测器测定。亚硫酸根的质量浓度在50 mg·L-1以内与导电率呈线性关系,测定下限(10S/N)为0.1 mg·kg-1。方法用于虾肉和蟹肉样品分析,回收率在89.5%~117%之间,测定值的相对标准偏差(n=9)在2.8%~13%之间。

Four grams of the homogenized sample of meat of shrimp or crab were extracted with 40 mL of the extractant which contains 0.1 mL of 1 mol·L-1 NaOH solution and 0.1 mL of formaldehyde-H2O (37+63) solution per 1 L, after centrifugation, the supernatant was taken and treated by freezing coagulation and on-line dialyzing to remove protein and fat. The extract was diluted 6 times with extrapure water before introduction into the IC instrument for determination of SO32- ion. Metrosep A supp 15 column (150 mm×4 mm) was used as ion-exchange column, and an acetone-H2O (20+80) solution, containing 0.386 g of Na2CO3 and 0.084 g of NaHCO3 per liter, was used as eluant, and conductivity detector was used in the detection. Linear relationship between values of conductivity and mass concentration of sulfite was kept in the range within 50 mg·L-1, with lower limit of determination (10S/N) of 0.1 mg·kg-1. The proposed method has been used in the analysis of the samples of meat of shrimp and crab, giving values of recovery and RSD′s (n=9) in the ranges of 89.5%-117% and 2.8%-13% respectively.