关于降低AFS-930型原子荧光光度计汞检出限的方法研究

氢化物发生-原子荧光光谱法(HG-AFS)是测试环境样品汞(Hg)的高灵敏度方法，但是为了适应污染物形态分析的需要，其灵敏度需要作进一步的提升和改善。通过提高光电倍增管负高压至280 V和空心阴极灯的灯电流至30 mA，原子化器高度设为10 mm，并降低KBH₄溶液到0.5%(KOH 0.2%)等调整措施大大改善了仪器对Hg的灵敏度，仪器检出限从原来的8 ng·L-1降至2 ng·L-1(n=6)。在优化的条件下，可以获得线性良好的0～10 ng·L-1浓度Hg标准曲线，能够实现对Hg浓度约为4 ng·L-1的水溶液的准确测定，其测试相对标准偏差<5%;选用低吸附的聚四氟乙烯器皿和优级纯以上级别试剂可将仪器的检出限降低为1 ng·L-1(n=10)，使Hg的灵敏度得到进一步提升。

A Study on Decreasing the Instrument Detection Limit of Atomic Fluorescence Spectrometry(AFS-930)for Hg

In the present study, the detection limit of atomic fluorescence spectrometry (AFS-930) was decreased to 2 ng·L-1 (n=6) based on several optimizing modifications, including that the sub-high voltage of photomultiplier tube and the current of hollow-cathode lamp were elevated to 280 V and to 30 mA, respectively, and the height of atomization cell was set as 10 mm; In addition, the concentration of KBH4 was decreased to 0.5% (KOH 0.2%). With the optimized parameters, a good standard curve of Hg concentration versus intensity of fluorescence (If) could been obtained readily, after that, a 4-ng·L-1-Hg water samples was measured accurately with a little relative standard deviation (RSD) of <5%, while for approximately 2-ng·L-1-Hg waters the RSD varied within a wide range of 10.9%-27.2%, likely due to the absorption of Hg by polyethylene vessels used in this study and/or due to the contamination by analysis grade reagents used in this study. By using low-absorption polytetrafluoroethylene (PTFE) materials and the guaranteed reagents, the instrument detection limit was further decreased to 1 ng·L-1(n=10).