An improved and validated solid-phase extraction and liquid chromatography-coupled mass spectrometry method for the simultaneous analysis of organic UV-filtering compounds in surface waters

Organic UV-filters in surface waters have gained increasing attention, yet their analytical detection and quantification remain challenging. In this study, we developed an analytical method involving optimized solid phase extraction (SPE) and UHPLC-MS/MS to simultaneously analyze selected top UV-filter compounds commonly used in Europe and/or listed in the 5th Watch List (2025) under the Water Framework Directive: avobenzone (AVO), iscotrizinol (DBT), octinoxate (EHMC), ethylhexyl triazone (EHT), and octocrylene (OC). The validation criteria included the evaluation of selectivity, linearity, accuracy, LOD, and LOQ. Plackett-Burman design as a compherensive and high-level approach was applied to evaluate robustness. Among the UHPLC-MS/MS variables tested, the most influential factors were the mobile phase pH, oven temperature, and mobile phase flow rate. Instead of using the commonly applied C18 and C8 HPLC columns, a pentafluorophenyl column was used to achieve a better and optimal chromatographic separation. The validated method achieved accuracies from 85.9 % to 123.4 % and LOD/LOQ values from 0.76/2.29 ng/L to 3.16/9.58 ng/L. With the optimized SPE protocol using Phenomenex Si-1 cartridges, the recoveries ranged from 45.2 % to 73.4 %. The method was applied for the analysis of Lake Balaton's surface freshwater, detecting all targeted UV-filters at the following concentrations: c(AVO) = 590.5 ± 17.5 ng/L, c(DBT) = 136 ± 9.7 ng/L, c(EHMC) = 776.8 ± 19.2 ng/L; c(EHT) = 55.2 ± 4.2 ng/L, and c(OC) = 141.8 ± 7.2 ng/L. Our study provides the first analytical protocol for DBT and EHT measurements. This study reflects the continuously evolving nature of UV-filters in sunscreens, emphasizing the need for new and adaptive analytical approaches. Our method innovatively evaluates and optimizes multiple parameters, ensuring robust and reliable quantification of five top organic UV-filters in environmental samples. • A robust UHPLC-MS/MS method for determination of organic UV-filters was developed. • The first analytical method for measuring DBT and EHT in freshwater was provided. • A novel SPE method using Phenomenex Si-1 cartridges was introduced. • Low LOD/LOQ values demonstrating high method sensitivity was achieved. • The method was applied to Lake Balaton's water, detecting all targeted UV-filters.