da Silva Alessandra Furtado, Borges Daniel L G, Lepri Fábio Grandis, Welz Bernhard, Curtius Adilson J, Heitmann Uwe
Departamento de Química, Universidade Federal de Santa Catarina, 88040-900 Florianópolis-SC, Brazil.
Anal Bioanal Chem. 2005 Aug;382(8):1835-41. doi: 10.1007/s00216-005-3327-9. Epub 2005 Jun 18.
This work describes the development of a method to determine cadmium in coal, in which iridium is used as a permanent chemical modifier and calibration is performed against aqueous standards by high-resolution continuum source atomic absorption spectrometry (HR-CS AAS). This new instrumental concept makes the whole spectral environment in the vicinity of the analytical line accessible, providing a lot more data than just the change in absorbance over time available from conventional instruments. The application of Ir (400 microg) as a permanent chemical modifier, thermally deposited on the pyrolytic graphite platform surface, allowed pyrolysis temperatures of 700 degrees C to be used, which was sufficiently high to significantly reduce the continuous background that occurred before the analyte signal at pyrolysis temperatures <700 degrees C. Structured background absorption also occurred after the analyte signal when atomization temperatures of >1600 degrees C were used, which arose from the electron-excitation spectrum (with rotational fine structure) of a diatomic molecule. Under optimized conditions (pyrolysis at 700 degrees C and atomization at 1500 degrees C), interference-free determination of cadmium in seven certified coal reference materials and two real samples was achieved by direct solid sampling and calibrating against aqueous standards, resulting in good agreement with the certified values (where available) at the 95% confidence level. A characteristic mass of 0.4 pg and a detection limit of 2 ng g(-1), calculated for a sample mass of 1.0 mg coal, was obtained. A precision (expressed as the relative standard deviation, RSD) of <10% was typically obtained when coal samples in the mass range 0.6-1.2 mg were analyzed.
本工作描述了一种测定煤中镉的方法的开发，其中铱用作永久性化学改进剂，并通过高分辨率连续光源原子吸收光谱法（HR-CS AAS）针对水溶液标准进行校准。这种新的仪器概念使得分析线附近的整个光谱环境均可获取，提供了比传统仪器仅随时间变化的吸光度更多的数据。将400微克铱作为永久性化学改进剂热沉积在热解石墨平台表面，使得能够使用700℃的热解温度，该温度足够高，可显著降低在低于700℃热解温度下分析物信号之前出现的连续背景。当使用高于1600℃的原子化温度时，在分析物信号之后也会出现结构化背景吸收，这是由双原子分子的电子激发光谱（具有旋转精细结构）引起的。在优化条件下（700℃热解和1500℃原子化），通过直接固体进样并针对水溶液标准进行校准，实现了对七种有证煤标准物质和两个实际样品中镉的无干扰测定，在95%置信水平下与有证值（如可获得）具有良好的一致性。对于1.0毫克煤样，计算得到的特征质量为0.4皮克，检测限为2纳克/克。当分析质量范围为0.6 - 1.2毫克的煤样时，通常可获得<10%的精密度（以相对标准偏差，RSD表示）。
