Lücker E, Failing K, Schmidt T
Institute of Veterinary Food Science, Justus-Liebig University, Giessen, Germany.
Fresenius J Anal Chem. 2000 Jan;366(2):137-41. doi: 10.1007/s002160050025.
In the present study the lower analytical limits of solid sampling electrothermal atomization atomic absorption spectrometry (SS-ETAAS) were characterized by means of blank measurements and--for the first time--by means of the calibration curve method, where a calibration near the range of these limits (limit of decision, detection and quantification) was performed. The limit of decision as derived from blank measurements was calculated according to the 3sigma-criterion to be 0.003 and 0.019 ng for Cd and Pb, respectively. For Pb and Cd a roughly three-fold increase of these limits was observed when the calibration method according to DIN 32 645 was applied. When solid reference material was used, only a slight increase could be observed. The analytical limits were 2 to 20 times lower than reported for sample decomposition methods. The blank measurement and conventional calibration curve method, however, do not account for factors relating to solid sampling such as sample mass and matrix. Therefore, the calibration curve model was applied to data derived from comparisons between direct solid sampling ETAAS and a compound reference method (ETAAS following sample homogenization and digestion). The observed analytical limits were not found to be substantially increased if enough samples with low element contents were available for calibration. Coupling of the calibration curve model with the comparison of methods included real test samples and thus the relevant maximum sample mass and analyte content in the range of the lower analytical limits. As validation procedures frequently include comparisons of methods, the present approach might prove to be of some general interest for the characterization of analytical quality in rapid methods.
在本研究中，通过空白测量以及首次采用校准曲线法对固体采样电热原子吸收光谱法（SS - ETAAS）的较低分析限进行了表征，其中在校准曲线法中，在校准曲线接近这些限（判定限、检测限和定量限）的范围内进行校准。由空白测量得出的判定限，根据3σ准则计算得出，镉（Cd）和铅（Pb）分别为0.003 ng和0.019 ng。对于铅和镉，当采用DIN 32 645校准方法时，这些限大约增加了三倍。当使用固体标准物质时，仅观察到轻微增加。分析限比样品分解方法所报道的低2至20倍。然而，空白测量和传统校准曲线法未考虑与固体采样相关的因素，如样品质量和基质。因此，校准曲线模型应用于直接固体采样ETAAS与复合标准方法（样品匀化和消解后的ETAAS）之间比较得出的数据。如果有足够的低元素含量样品用于校准，未发现观察到的分析限会大幅增加。校准曲线模型与方法比较相结合包括了实际测试样品，因此涉及较低分析限范围内的相关最大样品质量和分析物含量。由于验证程序经常包括方法比较，本方法可能对快速方法中分析质量的表征具有一定的普遍意义。
