Analytical & Testing Center, Sichuan University, Chengdu, Sichuan, 610064, China.
Key Lab of Green Chemistry & Technology of MOE, and College of Chemistry, Sichuan University, Chengdu, Sichuan, 610064, China.
Anal Chim Acta. 2021 Jun 8;1163:338502. doi: 10.1016/j.aca.2021.338502. Epub 2021 Apr 10.
A tungsten coil (W-coil) as an electrothermal vaporizer (ETV) was interface-free integrated with a point discharge (PD) microplasma as an excitation source for a miniaturized optical emission spectrometer (OES). The PD microplasma and the W-coil ETV were vertically arranged in one quartz tube, and the W-coil was directly placed just under the PD without any physical interface. Working gas flow could sweep them successively to carry analytes released from the W-coil to the PD microplasma, and exhaust out of the quartz tube. The W-coil firstly acted as an ETV for sampling, on which pipetted with a tiny amount of sample solution (typically 10 μL), followed by a heating program for eliminating sample moisture and matrix. Vapor of analytes was subsequently released from the W-coil at a high temperature and immediately swept into the PD microplasma for excitation of atoms to obtain their optical emission spectra. Due to the high temperature of the W-coil, the released analyte species from the W-coil probably had been already atomized/excited partly and partially maintained prior to entering into the PD microplasma, thus saving the energy in the PD for sample evaporation and dissociation. In other words, the W-coil indirectly provided extra energy to the PD microplasma, thus its excitation capability was intensified. Under optimal experimental conditions, simultaneous determination of Ag, As, Bi, Cd, Cu, In, Pb, Sb and Zn was achieved, with LODs of 0.6, 45, 40, 0.08, 15, 8, 8, 41 and 5 μg L, respectively, and RSDs all less than 4.5% (n = 3, at corresponding concentrations of 5, 250, 250, 0.5, 100, 50, 50, 250 and 25 μg L). The accuracy validation of the proposed technique was demonstrated by successfully analyzing Certified Reference Materials (CRMs, including water, soil, stream sediment and biological samples), and preliminarily analyzing one CRM with direct slurry injection, both with satisfactory results, which had no significant difference with the certificated values at a confidence level of 95% by t-test.
作为一种电热蒸发器（ETV）的钨丝线圈（W-coil）与作为激发源的点放电（PD）微等离子体无界面集成，构成了一个小型化的光学发射光谱仪（OES）。PD 微等离子体和 W-coil ETV 垂直排列在一个石英管中，W-coil 直接放置在 PD 下方，两者之间没有物理接口。工作气体流可以依次吹扫它们，将从 W-coil 释放的分析物带到 PD 微等离子体中，并从石英管中排出。W-coil 首先作为取样的 ETV，其上用微量的样品溶液（通常为 10μL）进行点样，然后进行加热程序以去除样品中的水分和基质。随后，分析物的蒸汽在高温下从 W-coil 中释放出来，并立即被吹扫到 PD 微等离子体中，以激发原子获得它们的发射光谱。由于 W-coil 的高温，从 W-coil 中释放的分析物物种可能已经部分原子化/激发，并在进入 PD 微等离子体之前部分保持，从而为 PD 节省了用于样品蒸发和离解的能量。换句话说，W-coil 间接地为 PD 微等离子体提供了额外的能量，从而增强了其激发能力。在最佳实验条件下，实现了 Ag、As、Bi、Cd、Cu、In、Pb、Sb 和 Zn 的同时测定，其检出限分别为 0.6、45、40、0.08、15、8、8、41 和 5μg L，相对标准偏差均小于 4.5%（n=3，对应于 5、250、250、0.5、100、50、50、250 和 25μg L 的浓度）。通过成功分析认证参考物质（包括水、土壤、溪流沉积物和生物样品），以及通过直接浆进样初步分析一个 CRM，验证了该技术的准确性，结果令人满意，通过 t 检验，与认证值在 95%置信水平下无显著差异。
