氧弹燃烧-离子选择性电极法测定豆类中的钙

Determination of Calcium Content in Beans with Oxygen Bomb Combustion-Ion Selective Electrode

采用氧弹燃烧-离子选择性电极法测定了豆类中的钙含量.首先对pCa-1-01型钙离子选择性电极的性能进行测试,此电极对钙离子浓度在0.1~100 mmol·L-1范围内有较理想的能斯特响应,斜率为-29.33mV/pCa（25℃）;然后用氧弹燃烧技术对样品进行预处理,酸液吸收燃烧所得产物;最后在样品液中加入离子强度调节溶液KCl及pH值为10的NH4Cl-NH3·H2O缓冲溶液后定容,用钙离子选择性电极测定溶液的电动势,再计算不同豆类中钙的含量.结果表明,黄豆中钙的含量最高,花豇豆中钙的含量最低,回收率为96.12%~98.06%,相对标准偏差在0.44%~1.19%之间.

The calcium content in beans was determined by Oxygen Bomb Combustion-Ion Selective Electrode. First, the quality of pCa-1-01-type calcium ion selective electrode was studied, and it was found that excellent Nernst response to calcium ion was in the range of 0.1 - 100 mmol· L-1 with slope of - 29.33 mV/pCa （ 25 ℃ ）. Then the sample was burned in the oxygen bomb, and the combustion products were absorbed by the acid solution. Finaily KCl （ISA） and NH4C1-NH3 · H2O（pH10） was added to the sample solution, and the calcium content in different beans was determined by ion selective electrode. The results showed that the calcium content in soybeans was the highest,the calcium content in mix coloured cowpea was the lowest. The recoveries were in the range of 96.12% -98.06% , and RSD was 0.44% - 1.19%.