Online isotope dilution and inductively coupled plasma mass spectrometry: from elemental to species quantification

Abstract

Apresentam-se sistemas de análises em fluxo propostos para a quantificação de elementos e espécies por diluição isotópica (ID) utilizando espectrometria de massas com fonte de plasma acoplada indutivamente (ICP-MS). Detalham-se os esquemas para adicionar em linha a solução isotopicamente enriquecida à amostra. São relatadas as aplicações em meio aquoso e outras com transferência do analito para a fase vapor, seja por processo de vaporização eletrotérmica, geração de vapor ou ablação por laser. Apresentam-se as aplicações com quantificação de espécies por ID caracterizadas pela adição do isótopo enriquecido, antes ou após a separação das espécies, seja por cromatografia a líquido, a gás ou por eletroforese capilar acoplada a ICP-MS. As principais equações envolvidas na quantificação por ID e as principais fontes de erro são descritas. São discutidas as mudanças introduzidas na estratégia de quantificação temporal por ID de elementos e espécies pela calibração do fluxo de massas da amostra e do isótopo enriquecido adicionado.Flow analysis has been utilized for elemental and species quantification by online isotope dilution inductively coupled plasma mass spectrometry (ICP-MS). Online isotope dilution (ID) herein refers to strategies promoting the addition of enriched isotopic solutions to the samples while flowing towards the plasma. Applications of online ID's are commonly performed in aqueous media, however, in some processes the analyte transference to the vapor phase using electrothermal vaporization, vapor generation or laser ablation is also required. Flow diagrams to perform online pre or post-column spiking with the enriched isotope for quantification by ID in speciation analysis by liquid chromatography, gas chromatography or capillary electrophoresis devices coupled to ICP-MS are presented. The main figures of merit and equations applied to elemental and species quantification by ID in flowing schemes are assessed.

Strategies to overcome interferences in elemental and isotopic geochemical analysis by quadrupole inductively coupled plasma mass spectrometry: A critical evaluation of the recent developments

“…The concentration of the element in the sample can be calculated using the following equation: where A S and B S are the atom fractions of isotopes A and B in the sample; A Sp and B Sp are the atom fractions in the spikes; C S and C Sp are the concentrations of the elements in the sample and spike; m Sp is the spike mass; V s is the sample volume; R b is the measured isotope ratio of the blended sample corrected for mass discrimination; and K is the ratio of the atomic mass of the element to that of the spike. Considering R b as the enriched to natural isotope ratio, the K factor will have values slightly above or below unity depending on whether the spike is enriched in the heavy or light isotope 98 . Calibration of the isotopic abundances and the concentration of the spike is required to achieve accurate concentration data by isotope‐dilution MS.…”

Atomic spectrometry update. Elemental speciation

“…A third review paper in this area covers online IDMS for both total elemental and speciation measurements. 179 The article covers the history, principles and recent applications of online IDMS. The use of 'gas phase' generation systems, LA, ETV and HG as well as liquid phase systems, HPLC and CE and different types of ICP-MS, e.g.…”

CE of inorganic species – A review of methodological advancements over 2009–2010

“…Three reports on using CE as a self‐contained speciation tool were prepared for mercury species 47, metalloproteins 48, and – in combination with MS – the analysis of biological samples 49. Separately scrutinized were online isotope dilution strategies for species quantification by CE devices hyphenated with ICP‐MS 50. Juang and Armstrong 51 summarized recent applications of CE‐based methods for the evaluation of association between metal ions and pharmacological complexes with biological molecules.…”