• Gačnik, Jan
• Hudobivnik, Marta Jagodic
• Andron, Teodor-Daniel
• Ali, Saeed Waqar
• Nair, Sreekanth Vijayakumaran
• Živković, Igor
• Božič, Dominik
• Horvat, Milena
• Kocman, David

Abstract

<jats:title>Abstract</jats:title><jats:p>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 SnCl<jats:sub>2</jats:sub>, and collected in a 2.25 mL concentrated inverse aqua regia (3:1 HNO<jats:sub>3</jats:sub>: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 <jats:sup>197</jats:sup>Hg radiotracer showed recoveries averaging 99 ± 1.7% and 100 ± 3.0%, respectively. Mercury at concentrations as low as 1.83 ng g<jats:sup>−1</jats:sup> 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 δ<jats:sup>202</jats:sup>Hg 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.</jats:p><jats:p><jats:bold>Graphical abstract</jats:bold></jats:p>

Topics

• impedance spectroscopy
• fractionation
• Mercury
• inductively coupled plasma mass spectrometry