微波消解—浓度直读法快速测定食品中微量钙的含量

Rapid determination of micro-calcium in food by microwave digestion-concentration direct reading method

目的建立微波消解-浓度直读法快速测定食品中的微量钙含量。方法采用硝酸-过氧化氢混合酸进行微波消解,采用p Ca-1钙离子选择性电极快速测定钙含量,同时研究了钙在不同食品组织中的分布。结果最佳条件为：硼砂-硼酸缓冲剂加入量为3.5 m L,p H为7.4,1 mol/L三乙醇胺-盐酸离子强度调节剂加入量为5 m L。所用电极性能良好,平行测定的相对标准偏差小于2.3%（n=5,干基）,回收率为89.6%-96.0%,所测定干基样品中钙的含量为0.09-2.64 mg/g,同一样品中的钙含量呈现由外至内逐渐减小的趋势。结论该法快速简便、成本低廉、读数直观准确,有利于现场即时测定。

Objective To establish a method for the rapid determination of micro-calcium by microwave digestion-concentration direct reading method. Methods Nitric acid-hydrogen peroxide solution was used for microwave digestion, and calcium was determined rapidly by pCa-1 calcium selective electrode. Meanwhile the calcium distribution was studied in different food organizations. Results Optimal conditions were as follows： the amount of borax and boric acid buffer was 3.5 m L, p H was 7.4, and the amount of ionic strength regulator of triethanolamine and hydrochloric acid（1 mol/L） was 5 m L. The performance of electrode was good. The relative standard deviations were less than 2.3%（n=5, dry basis）, recoveries were ranged from 89.6% to 96.0%, and the calcium content of samples were ranged from 0.09 mg/g to 2.64 mg/g. Calcium content in the same sample presented decreasing trend from outside to inside. Conclusion This method is rapid, simple, inexpensive, intuitive and accurate in reading, which is beneficial to on-site determination.