Departamento de Química Analítica y Análisis Instrumental, Facultad de Ciencias, Universidad Autónoma de Madrid, C/ Francisco Tomás y Valiente 7, M-28049 Madrid, Spain.
Phytochem Anal. 2010 Jul-Aug;21(4):340-7. doi: 10.1002/pca.1204.
Plants can be used as bioindicators in the study of contamination processes by heavy metals. Most of the analytical methodologies used for determination of metals in plants are based on atomic techniques with previous wet digestion of the solid samples. Methodologies that allow direct metal measurements in solid samples are very attractive alternatives.
To develop a new procedure for direct analysis of copper, nickel, cadmium and lead at very low concentration levels in leaves based on electrothermal atomic absorption spectroscopy (ET-AAS) with introduction of samples as a slurry.
In order to obtain accurate and precise results even at very low concentrations, the different parameters that influence the sample slurry preparation such as acid percentage, presence of stabilising agents and ultrasonic probe operation were studied. Instrumental parameters such as chemical modifier and temperature and times for drying, pyrolysis and atomisation steps that influence ET-AAS measurement were optimised.
Optimal slurry conditions for copper and nickel determination were 0.5% Tween 85 with 5% nitric acid. For lead and cadmium analysis the best results were obtained in 5% nitric acid without stabilising agents. The achieved detection limits were 0.023 mg/kg for copper, 0.018 mg/kg for nickel, 0.0002 mg/kg for cadmium and 0.009 mg/kg for lead. For validation purposes, the method was applied to metal analysis in a pine needles reference material.
According to our knowledge, the detection limits obtained are the best reported in the literature. The methodology was successfully used in metal determinations in actual leaf samples.
植物可用作重金属污染过程的生物指示剂。大多数用于测定植物中金属的分析方法都基于原子技术，需要对固体样品进行湿法消解。直接测量固体样品中金属的方法是很有吸引力的替代方法。
开发一种新的程序，基于电热原子吸收光谱（ET-AAS），用浆体直接分析叶片中非常低浓度水平的铜、镍、镉和铅。
为了即使在非常低的浓度下也能获得准确和精密的结果，研究了影响样品浆体制备的不同参数，如酸的百分比、稳定剂的存在以及超声探头的操作。优化了影响 ET-AAS 测量的仪器参数，如化学修饰剂、干燥、热解和原子化步骤的温度和时间。
铜和镍测定的最佳浆体条件为 0.5%Tween 85 和 5%硝酸。对于铅和镉的分析，最佳结果是在 5%的硝酸中，没有稳定剂。获得的检测限为铜 0.023mg/kg，镍 0.018mg/kg，镉 0.0002mg/kg，铅 0.009mg/kg。为了验证目的，该方法被应用于松针参考材料中的金属分析。
据我们所知，所获得的检测限是文献中报道的最佳值。该方法成功地用于实际叶片样品中的金属测定。
