Chloride-assisted microwave-assisted digestion for reliable ICP-OES determination of tin in industrial wastewater: Method development and ISO 17025 validation.

Authors

Asuhan Tepe, Elif Hatice Gürkan

Published in

Analytica chimica acta. Volume 1416. Pages 345730. Sep 22, 2026. Epub May 28, 2026.

Abstract

Accurate determination of tin (Sn) in industrial wastewater by inductively coupled plasma-optical emission spectrometry (ICP-OES) is compromised by the susceptibility of Sn⁴⁺ to hydrolysis, precipitation, and volatilization during conventional nitric acid digestion. This study presents the development and full validation of a chloride-assisted microwave digestion protocol that stabilizes tin through in situ formation of stable tin (IV) chloro-complexes (including [SnCl₆]^2- and related species), thereby suppressing analyte loss and enabling reliable quantification in complex industrial effluent matrices. A direct experimental comparison of HNO₃-only and HCl-assisted microwave-assisted digestion showed that, although the difference did not reach statistical significance (two-tailed t-test, t = 1.47, df = 12, p = 0.167), Sn concentrations were consistently lower under HNO₃ digestion across all seven replicates (48.95 vs. 51.51 μg/L), indicating a systematic negative bias attributable to the known instability of Sn⁴⁺ in oxidizing acidic media - where hydrolysis, precipitation as metastannic acid, and partial volatilization collectively compromise analyte recovery. The method was validated in full compliance with ISO/IEC 17025:2017, encompassing linearity, repeatability, intermediate precision, trueness, robustness, and measurement uncertainty. The calibration curve exhibited excellent linearity over the range 10-2500 μg/L (R² ≥ 0.999; slope = 0.8853). Precision was high across all concentration levels (RSD 0.94-6.95%). Spike recoveries in the wastewater matrix ranged from 86 to 100%. Limits of detection and quantification were 12.10 μg/L and 40.33 μg/L, respectively. Robustness assessment using a Plackett-Burman design with seven analytical factors confirmed that minor variations in instrumental and operational parameters did not significantly affect method performance (all E_x < E_crit = 4.58). To the best of our knowledge, this is among the first studies to provide a chloride-assisted microwave-assisted digestion protocol for tin determination specifically in organized industrial zone wastewater, validated in full accordance with ISO/IEC 17025:2017 and including Plackett-Burman robustness testing. The method offers a practically implementable, matrix-appropriate solution for accredited environmental laboratories engaged in regulatory monitoring of tin in industrial effluents.

PMID:
42401454
Bibliographic data and abstract were imported from PubMed on 05 Jul 2026.

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