石墨炉原子吸收测定高参数机组水汽中的痕量铁

Determination of trace iron in water-steam of high parameter units by graphite furnace atomic absorption spectrophotometry

针对石墨炉原子吸收分光光度法测定高参数机组水汽中小于5.0μg/L痕量铁存在的稳定性较差、空白值高的问题,从石墨炉工作状态、试剂空白、水样消解处理方式等方面进行深入考察。结果指出在标准工作曲线测定前、后均应进行试剂空白值及其重复性的测定以消除炉管残留及进样针带来的误差,当空白吸光度小于0.02、标准偏差小于0.1%时,对痕量铁测定影响不大;石墨管的损耗会降低检测灵敏度和重现性,石墨管使用次数宜控制在800次以下;采用水样酸化静置至少6 h后直接测定并与加热消解法测定值进行了对比,偏差在±0.50μg/L范围内,空白值小于0.5μg/L,有效解决了加热消解法存在空白值(1.0~3.0μg/L)高的问题,提高了水汽中小于5.0μg/L痕量铁测定的准确性。

Aiming at the problems of the high blank value and poor stability in determination of trace iron less than 5.0μg/L in normal water-steam of high parameter unit by graphite furnace atomic absorption spectrophotometry,the working state of graphite furnace,reagent blank and water sample digestion treatment were investigated in depth.The results showed that it was necessary to determine the reagent blank value and their repeatability before and after the determination of standard working curve measurement to eliminate the error caused by the furnace tube residue and the sample needle.It had hardly influence on the determination when reagent blank value was less than 0.02 abs and their standard deviation was less than 0.1%.The loss of graphite tube could reduce the detection sensitivity and reproducibility,and the use of graphite tube should be controlled below 800 times.After at least 6 hours acidification standing,the results were directly measured and compared with the measured value by standard heated digestion method,the deviation was within the range of±0.50μg/L,and the blank value was less than 0.5μg/L.The problem of high blank value(1.0-3.0 mg/L)in heated digestion method was effectively solved and the accuracy of determination of trace iron less than 5.0μg/L in water-steam was improved.