Faculty of Chemistry, Biological and Chemical Research Centre, University of Warsaw, Zwirki i Wigury 101, 02-093 Warsaw, Poland.
National Research Council Canada, 1200 Montreal Road, K1A 0R6 Ottawa, Ontario, Canada.
Anal Chem. 2020 Dec 15;92(24):16097-16104. doi: 10.1021/acs.analchem.0c03768. Epub 2020 Nov 23.
In this work, a method for the accurate and precise determination of Se/Se isotope ratio in natural samples of environmental and biological origin, using multicollector inductively coupled plasma mass spectrometry in a wet plasma mode without using neither hydride generation nor separation of Se, was developed. It was based on the optimized regression model with standard-sample bracketing (ORM-SSB) to efficiently correct instrumental isotopic fractionation/mass bias and matrix effects. In addition, three mass bias correction models of SSB alone, SSB combined with internal standard (IS-SSB), and ORM-SSB were compared for the Se isotope ratio measurements. NIST SRM 987 Sr was used as an internal standard, and the reproducibility of the results obtained with the proposed method was verified by measuring NIST SRM 3149 standard over different days (nine independent measurement sessions). Delta values of the Se/Se isotope ratio were measured in selenium-enriched yeast-certified reference material SELM-1, natural selenomethionine samples, and model solutions of artificial seawater. Solutions obtained after thiol resin treatment were measured to demonstrate the applicability of the proposed method in eliminating matrix effects due to residual of thiol resin in the sample solutions. Among three mass bias correction models, ORM-SSB correction model proved to be the best to eliminate the matrix effects and instrumental drift. IS-SSB model offered also a good precision but was slightly less accurate. Both models showed good robustness against effects of different sample matrices. Finally, the SSB alone could not be recommended for Se isotope analysis as it produces inaccurate and imprecise results.
本工作开发了一种无需使用氢化物发生或硒分离，在湿等离子体模式下使用多接收电感耦合等离子体质谱仪，精确测定环境和生物来源天然样品中硒/硒同位素比的方法。该方法基于带有标准-样品内标（ORM-SSB）的优化回归模型，可有效地校正仪器同位素分馏/质量偏差和基质效应。此外，还比较了 SSB 单一、SSB 与内标（IS-SSB）结合以及 ORM-SSB 三种质量偏差校正模型在硒同位素比测量中的应用。使用 NIST SRM 987 Sr 作为内标，通过在不同天数（九次独立测量）测量 NIST SRM 3149 标准来验证所提出方法的结果重现性。在硒富集酵母标准参考物质 SELM-1、天然硒代蛋氨酸样品和人工海水模型溶液中测量了硒/硒同位素比的 Delta 值。对经过巯基树脂处理后的溶液进行了测量，以证明所提出的方法在消除因巯基树脂在样品溶液中的残留而产生的基质效应方面的适用性。在三种质量偏差校正模型中，ORM-SSB 校正模型被证明是消除基质效应和仪器漂移的最佳模型。IS-SSB 模型也提供了良好的精密度，但准确性略低。两种模型均表现出对不同样品基质效应的良好稳健性。最后，由于产生不准确和不精确的结果，因此不建议单独使用 SSB 进行硒同位素分析。
