BOOK OF ABSTRACTS 89 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Tuesday, 25 August 2026 / Hall B+C Environment, Agriculture, and Forestry SL40 Sensitive Detection of Phthalate Esters in Drinking Water with Absorbance-Transmittance Excitation Emission Matrix (A-TEEM) Spectroscopy Nontokozo Magwaza1, Adam M. Gilmore2, Thabo T.I. Nkambule1 1 Institute for Nanotechnology and Water Sustainability, University of South Africa, 1st Floor, NB Pityana Building Florida, Johannesburg 1709 , Email: magwan@unisa.ac.za 2 HORIBA Instruments Incorporated, Piscataway, NJ USA 08854 The presence of phthalate esters in drinking water sources is a topic of increasing global publicity and concern for environmental regulatory agencies due to their capacity for endocrine disruption and reproductive harm [1]. Dibutyl phthalate (DBP), in particular, is a common plasticizer in poly vinyl chloride (PVC) materials, food and beverage containers. In fact, DBP has been the recent (December 2025) subject for a comprehensive risk assessment by the United States Environmental Protection Agency [2]. It is there well recognized that potential harm to human health can be observed for very low concentrations of DBP, typically less than 10 mg/L. The low concentration effects present difficulties for rapid detection and actionable responses with conventional detection methods such as Gas Chromatography Mass Spectroscopy due to complex sample preparation, capital and operational expenses and required operator experience. Recent fluorescence studies have reported DBP detection in the mg/L range but these are typically at a proof-of-concept level and often involve complex sample reagentbased assays involving derivatization or aptamers among other approaches [3]. Thus, in this study we investigated the ability to rapidly and directly measure DBP in typical drinking water matrices using A-TEEM spectroscopy without reagents. A-TEEM spectroscopy has the patented capacity to correct concentration-dependent fluorescence inner-filter effects, which is needed to separate the ubiquitous background signals of natural (or manmade) organic carbon (typically at mg/L levels) from low DBP concentrations in the mg/L range. Drinking water samples, sourced from a local tap with approximately 2 mg/L Dissolved Organic Carbon (DOC) and Type I water, were comparably spiked with varying concentrations of DBP and Diethyl phthalate (DEP) ranging from 0-765 mg/L. The A-TEEM spectra were scanned at 20° C with stirring in 3 ml quartz cuvettes in the UV region from 220-400 nm while the emission was measured from 250- 600 nm (both in 5 nm increments); the total scan required less than 5 min. DBP showed a bimodal A-TEEM fingerprint with the major excitation/emission band at 225 nm/345
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