1 研究背景
中药是我国的传统医药,是中华民族的瑰宝。随着中药产业的发展,中药的安全性问题日益受到国内外的普遍关注[1-2]。近年来,在我国中药安全性方面,中药材重金属含量超标是一个比较突出的问题[3]。中药材重金属含量超标不仅降低了中药的质量,影响了用药的安全性,而且严重影响了我国中医药在国际上的形象和声誉,制约了中药的出口,成为中药贸易的壁垒[4]。汞、砷、铅、镉等元素是目前已被报道的中药中常见的有毒有害元素[5]。在这些元素中,砷是中药中最常见和最具毒性的污染物之一。近些年,对中药中砷化物的安全性评价研究已成为毒理学、中药药理学、生物无机化学的研究热点。因此,精确测定中药中的砷具有重要意义[6]。
目前砷的检测技术有很多种,包括原子发射光谱法(AES)、原子荧光光谱法(AFS)、原子吸收光谱法(AAS)、电感耦合等离子体质谱法(ICP-MS)、荧光和紫外可见光谱法等[7-10]。这些技术虽然具有较高的灵敏度,但仍然有局限性,如分析仪器高能耗、体积大、价格昂贵等。近年来,基于微等离子体的原子发射光谱法,由于其具有体积小、气体需求量小、功率能耗小、重量轻、制造成本低等优点,受到研究者的广泛关注[11-13]。微等离子体包括尖端放电(PD)、介质阻挡放电(DBD)、电晕放电(CD)和辉光放电(GD)等多种放电方式,将这些微等离子体搭配微型光谱仪使用,即成为一种新型的小型化便携式原子光谱分析仪器。
本文以尖端放电微等离子体为激发源,建立了一个小型化氢化物发生原子发射光谱分析系统(简称PD-HG-AES分析系统),用于中药中砷的高灵敏分析。该方法采用氢化物发生(HG)实现样品引入,其具体过程为:当含砷样品与硼氢化钾(KBH4)发生反应时,生成砷化氢气体(AsH3),生成的AsH3通过气液分离器即可实现与基体的有效分离,通过载气引入空心电极进入尖端放电激发原子化,最后将产生的砷原子发射信号通过CCD光谱仪进行检测。PD-HG-AES分析系统利用中空电极将氢化物发生于尖端放电耦合,大大降低了光谱发射背景,提高了分析的灵敏度和选择性。
2 中药中砷的测定
3 讨论与结果
4 结语
基于微等离子体原子发射光谱法在痕量元素分析中的应用,本文建立了PD-HG-AES分析系统,用于中药中痕量砷的高灵敏分析。该方法采用空心电极进样,使得氢化物发生产生的AsH3气体完全进入放电区,保证了微等离子体中AsH3气体充分引入和激发。PD-HG-AES分析系统具有体积小、功耗低、气体消耗少、进样效率高、灵敏度高等特点,其较宽的线性范围有助于检测砷浓度差异大的中药样品。PD-HG-AES分析系统与最新的萃取技术相结合,可进一步提高分析的灵敏度,可以预见,PD-HG-AES分析系统在中药分析检测中具有较好的发展前景。
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杨海燕 余秋月 廖静 黄科 四川师范大学化学与材料科学学院 |