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Ali SW, Božič D, Vijayakumaran Nair S, Živković I, Gačnik J, Andron TD, Jagodic Hudobivnik M, Kocman D, Horvat M. Optimization of a pre-concentration method for the analysis of mercury isotopes in low-concentration foliar samples. Anal Bioanal Chem 2024; 416:1239-1248. [PMID: 38193932 PMCID: PMC10850019 DOI: 10.1007/s00216-023-05116-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 12/12/2023] [Accepted: 12/19/2023] [Indexed: 01/10/2024]
Abstract
Hg isotope analysis in samples from background regions is constrained by the presence of low Hg concentration and therefore requires a pre-concentration method. Existing Hg pre-concentration methods are constrained by long sample processing time and limited sample loading capacity. Using foliar samples as a test case, an optimized Hg pre-concentration method is presented that involves the microwave-assisted digestion of samples for Hg isotope analysis with the addition of a pre-digestion step. Microwave-digested foliar samples and CRMs were transferred to an impinger, reduced with SnCl2, and collected in a 2.25 mL concentrated inverse aqua regia (3:1 HNO3:HCl, v/v). This resulted in an optimal acid concentration in the solution ideal for analysis on MC-ICP-MS. The time for purging with Hg-free N2 was optimized to 30 min and the efficiency of the pre-concentration method was tested using a combination of approaches. Tests performed on pure reagents and matrix of foliar samples spiked with 197Hg radiotracer showed recoveries averaging 99 ± 1.7% and 100 ± 3.0%, respectively. Mercury at concentrations as low as 1.83 ng g-1 was pre-concentrated by digesting aliquots of foliage samples in individual digestion vessels. Recoveries following their pre-concentration averaged 99 ± 6.0%, whereas recoveries of 95 ± 4.7% and 95 ± 2.5% were achieved for NIST SRM 1575a (pine needle) and reagents spiked with NIST SRM 3133, respectively. Analysis using multicollector-ICP-MS showed low fractionation of δ202Hg during sample pre-concentration with no significant mass-independent fractionation. The proposed method is a relatively simple and robust way to prepare Hg samples for Hg isotopic analysis and is suitable even for complex biological matrices.
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Affiliation(s)
- Saeed Waqar Ali
- Jožef Stefan Institute, 1000, Ljubljana, Slovenia
- Jožef Stefan International Postgraduate School, 1000, Ljubljana, Slovenia
| | - Dominik Božič
- Jožef Stefan Institute, 1000, Ljubljana, Slovenia
- Jožef Stefan International Postgraduate School, 1000, Ljubljana, Slovenia
| | - Sreekanth Vijayakumaran Nair
- Jožef Stefan Institute, 1000, Ljubljana, Slovenia
- Jožef Stefan International Postgraduate School, 1000, Ljubljana, Slovenia
| | - Igor Živković
- Jožef Stefan Institute, 1000, Ljubljana, Slovenia
- Jožef Stefan International Postgraduate School, 1000, Ljubljana, Slovenia
| | - Jan Gačnik
- Jožef Stefan Institute, 1000, Ljubljana, Slovenia
- Jožef Stefan International Postgraduate School, 1000, Ljubljana, Slovenia
| | - Teodor-Daniel Andron
- Jožef Stefan Institute, 1000, Ljubljana, Slovenia
- Jožef Stefan International Postgraduate School, 1000, Ljubljana, Slovenia
| | | | - David Kocman
- Jožef Stefan Institute, 1000, Ljubljana, Slovenia
| | - Milena Horvat
- Jožef Stefan Institute, 1000, Ljubljana, Slovenia.
- Jožef Stefan International Postgraduate School, 1000, Ljubljana, Slovenia.
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