Open AccessSelective Diffusive Gradients in Thin Films (DGT) for the Simultaneous Assessment of Labile Sr and Pb Concentrations and Isotope Ratios in Soils
Author(s) -
Stefan Wagner,
Jakob Santner,
Johanna Irrgeher,
Markus Puschenreiter,
Steffen Happel,
Thomas Prohaska
Publication year - 2022
Publication title -
analytical chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.117
H-Index - 332
eISSN - 1520-6882
pISSN - 0003-2700
DOI - 10.1021/acs.analchem.2c00546
Subject(s) - chemistry , diffusive gradients in thin films , soil water , fractionation , membrane , elution , matrix (chemical analysis) , bioavailability , ionic strength , analytical chemistry (journal) , phosphoric acid , environmental chemistry , chromatography , aqueous solution , bioinformatics , biochemistry , environmental science , organic chemistry , soil science , metal , biology
A method using diffusive gradients in thin films (DGT) for the accurate quantification of trace-level (μg L -1 ) Sr and Pb concentrations and isotope ratios [ δ SRM 987 ( 87 Sr/ 86 Sr) and δ SRM 981 ( 207 Pb/ 206 Pb)] in labile, bioavailable element fractions in soils is reported. The method is based on a novel poly(tetrafluoroethylene) (PTFE) membrane binding layer with combined di(2-ethyl-hexyl)phosphoric acid (HDEHP) and 4,4'(5')-bis- t -butylcyclohexano-18-crown-6 (crown-ether) functionality with high selectivity for Sr and Pb (TK100 membrane). Laboratory evaluation of the TK100 DGT showed linear uptake of Sr over time (2-24 h) up to very high Sr mass loadings on TK100 membranes (288 μg cm -2 ) and effective performance in the range of pH (3.9-8.2), ionic strength (0.001-0.1 mol L -1 ), and cation competition (50-160 mg L -1 Ca in a synthetic soil solution matrix) of environmental interest. Selective three-step elution of TK100 membranes using hydrochloric acid allowed us to obtain purified Sr and Pb fractions with adequate (≥75%) recovery and quantitative (≥96%) matrix reduction. Neither DGT-based sampling itself nor selective elution or mass loading effects caused significant isotopic fractionation. Application of TK100 DGT in natural soils and comparison with conventional approaches of bioavailability assessment demonstrated the method's unique capability to obtain information on Sr and Pb resupply dynamics and isotopic variations with low combined uncertainty within a single sampling step.