Electrolytic enrichment and liquid scintillation determination of low-level tritium in high-salinity seawater with correction for salinity matrix effects

Abstract Low-level tritium determination in seawater remains analytically demanding because electrolytic enrichment, liquid scintillation counting and matrix-dependent quench correction must all remain stable at activities close to environmental background. This study developed and statistically validated an integrated alkaline electrolytic enrichment-liquid scintillation counting procedure for high-salinity waters from 0 to 60 PSU. Nine water matrices, including low-background water, artificial seawaters, coastal seawater, estuarine high-salinity water and desalination brine, were processed across 72 independent enrichment measurements. Ion chromatography, ICP-OES, conductivity, pH, ORP, TOC, UV-visible turbidity, FTIR/Raman spectroscopy, XRD, SEM-EDS, XPS and electrochemical impedance spectroscopy were combined with tSIE-based quench tracking to identify matrix-sensitive terms. The uncorrected method showed a progressive negative bias at salinities above 35 PSU, reaching a mean bias of −15.2 % in the 60 PSU matrix. A matrix correction model using salinity, major-ion load, tritium retention and quench index reduced the overall mean absolute bias from 9.4 % to 4.3 %, with mean recoveries of 93.5–102.2 % and expanded uncertainties of 0.026–0.211 Bq L −1 . Minimum detectable concentrations were 0.031–0.044 Bq L −1 after enrichment. Mixed-effects modeling showed that batch-to-batch variance was small compared with salinity-associated quench and retention terms, while PCA separated high-brine matrices through conductivity, tSIE and retention loadings. The workflow therefore provides a practical correction framework for radioanalytical monitoring of low-level tritium in saline marine waters.