Bermejo-Barrera P, Muñiz-Naveiro O, Moreda-Piñeiro A, Bermejo-Barrera A
Department of Analytical Chemistry, Nutrition and Bromatology, Faculty of Chemistry, University of Santiago de Compostela, Spain.
Forensic Sci Int. 2000 Jan 10;107(1-3):105-20. doi: 10.1016/s0379-0738(99)00155-3.
Experimental designs were used for the optimisation of acid-leaching procedures assisted by ultrasonic energy for the extraction of Ca, Cu, Fe, Mg, Mn and Zn from human hair samples. A Plackett-Burman 2(7) x 3/32 design for seven factors ([HNO3], [HCl], [H2O2], acid/oxidant solution volume, exposure time to ultrasounds, temperature of the ultrasonic bath and hair particle size) was used in order to choose the variables affecting the acid-leaching process. The variables [HNO3], [HCl] and temperature of the ultrasonic bath were found to be the most important parameters for the acid-leaching procedure, and these variables were optimised by a response surface design (central composite design 2(3) + star) which involved 16 experiments. Optimum values in the 3.7-4.2 M range were found for [HNO3], while optimum values between 3.0 and 3.5 M were found for [HCl]. The optimum temperature of the ultrasonic bath was between 80 and 90 degrees C. An acid digestion induced by microwave energy (details given) was used to obtain the total metal concentration and also for comparative purposes. Ca, Cu, Fe, Mg and Zn were measured by flame atomic absorption spectrometry (FAAS) using a conventional air/acetylene flame, while Mn was determined by electrothermal atomic absorption spectrometry (ETAAS) under optimised conditions. Two different reference materials, IAEA-085 International Atomic Energy Agency, Monaco) and NIES No. 13 (National Institute for Environmental Studies, Japan), with certified metal contents for some of the elements investigated, were used in order to verify the accuracy of the methods.
采用实验设计方法优化了超声辅助酸浸提程序，用于从人发样品中提取钙、铜、铁、镁、锰和锌。为了选择影响酸浸提过程的变量，对七个因素（硝酸浓度、盐酸浓度、过氧化氢浓度、酸/氧化剂溶液体积、超声暴露时间、超声浴温度和毛发粒径）采用了Plackett-Burman 2(7)×3/32设计。结果发现，硝酸浓度、盐酸浓度和超声浴温度是酸浸提程序中最重要的参数，并通过响应面设计（中心复合设计2(3)+星点设计）对这些变量进行了优化，该设计涉及16个实验。硝酸浓度的最佳值在3.7 - 4.2 M范围内，而盐酸浓度的最佳值在3.0 - 3.5 M之间。超声浴的最佳温度在80至90摄氏度之间。采用微波能量诱导的酸消解方法（给出了详细信息）来获得总金属浓度，并用于比较目的。钙、铜、铁、镁和锌采用火焰原子吸收光谱法（FAAS），使用常规空气/乙炔火焰进行测定，而锰则在优化条件下通过电热原子吸收光谱法（ETAAS）进行测定。为了验证方法的准确性，使用了两种不同的标准物质，即国际原子能机构（摩纳哥）的IAEA - 085和日本国立环境研究所的NIES No. 13，它们对部分所研究元素的金属含量进行了认证。
