新近处理了一批样品,其中质控样是GSB-5.采用
压力消解罐法消解:称取约0.5g,加4ml硝酸浸泡过夜,再加3ml双氧水,135度,6小时,未赶酸,无离子水定容至25ml。2%磷酸二氢铵为基体改进剂。分别测定了铅、镉。结果是镉的数据较好,基本全部进入了标值范围;而铅的含量却高了近一倍。具体数据如下:
Analyte | Cd 228.8 | | | | ID: | Corr. Abs. | Conc (ug/L) | weight(g) | result(ug/g) | Manual Furnace Cycle | -0.0003 | | | | Calib Blank 1 | 0.0009 | 0.0 | | | Calib Std 1 | 0.0398 | 1.0 | | | Calib Std 2 | 0.0837 | 2.0 | | | Calib Std 3 | 0.1199 | 3.0 | | | Calib Std 4 | 0.1599 | 4.0 | | | Calib Std 5 | 0.1915 | 5.0 | | | Reagent Blank 1 | 0.0018 | -0.016 | | | K-1 | 0.0012 | -0.016 | | | K-2 | 0.0014 | -0.011 | | | K-3 | 0.0008 | -0.025 | | | GSB-5 | 0.0303 | 0.737 | 0.5028 | 0.0366 | GSB-5 | 0.0277 | 0.671 | 0.5021 | 0.0334 | GSB-5 | 0.0286 | 0.692 | 0.5029 | 0.0344 | | | | | | Analyte | Pb 283.3 | 2011/12/08 | | | ID: | Corr. Abs. | Conc (ug/L) | weight(g) | result(ug/g) | | -0.0004 | | | | Calib Blank | 0.0021 | 0.0 | | | Calib Std 1 | 0.0029 | 1.0 | | | Calib Std 2 | 0.0058 | 2.0 | | | Calib Std 3 | 0.0094 | 3.0 | | | Calib Std 4 | 0.0126 | 4.0 | | | Calib Std 5 | 0.0157 | 5.0 | | | Reagent Blank 1 | 0.0106 | 3.389 | | | K-1 | 0.0090 | -0.499 | | | K-2 | 0.0328 | 6.929 | | | K-3 | 0.0143 | 1.145 | | | GSB-5 | 0.0360 | 7.920 | 0.5028 | 0.394 | GSB-5 | 0.0142 | 1.111 | 0.5021 | 0.055 | GSB-5 | 0.0342 | 7.365 | 0.5029 | 0.366 | | | | | |
从以上结果来看,三个GSB-5测镉的平行样数值都进入镉标准值范围(0.035±0.006ug/g),而它们测铅的平行样却与镉大不相同,不仅三个平行中有一个不平行,而且那两个比较接近的平行样的数值也几乎是铅标准值(0.19±0.03ug/g)的2倍,空白的表现也跟镉不同。请教各位大师:这是怎么回事?问题出在何处? | | | | |
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(由于计算失误,致使铅标曲浓度范围过窄,这一点我已认识到,请大家在此不必再议。)
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