Simultaneous determination of triazine-based UV absorbers by first-order derivative spectrophotometry in different media

The simultaneous determination of individual components in mixtures of UVA- and UVB-type triazine-based UV absorbers, including bis-ethylhexyloxyphenol methoxyphenol triazine (BEMT), diethylhexyl butamido triazone (DBT), and ethylhexyl triazone (EHT), presents significant challenges due to the strong spectral overlap in their UV absorption profiles. In this study, we explored the feasibility of employing first-derivative spectrophotometry for the simultaneous quantitative determination of these UV absorbers in a variety of organic solvents, such as chloroform, diethyl ether, ethyl acetate, acetonitrile, dimethyl sulfoxide (DMSO), 1,4-dioxane, isopropanol, etc. Focusing on quality control analysis during sunscreen formulation, a first-order derivative spectrophotometric method was developed for quantifying binary mixtures in dioctyl carbonate, a commonly used solvent in sunscreens. For the binary mixture BEMT-DBT and BEMT-EHT, the optimal wavelengths for quantification were identified as 372 nm for BEMT, 316 nm for DBT, and 318 nm for EHT, respectively. This method demonstrated a linear relationship within the concentration range of 1 to 9 mg L
-1
for both systems. In the BEMT-DBT mixture, the mean recoveries were documented at 98.96±1.54% for BEMT and 100.84±2.28% for DBT. The average relative standard deviations (RSD) for both intra-day and inter-day precision remained below 2.47%. In the binary mixture BEMT-EHT, the mean recoveries for BEMT and EHT were 98.43±2.10% and 99.85 ± 1.68%, respectively. Additionally, the average RSD values for both intra-day and inter-day precision remained below 1.46%. To facilitate quantitative analysis of triazine-based UV absorber mixtures for the studies concerning their sorption behavior and ecotoxicity in aqueous environments, this method was successfully adapted in a DMSO/H₂O (4:96, v/v) mixed solvent system. This adaptation enabled effective simultaneous determination of both BEMT-DBT and BEMT-EHT binary systems within this medium.