Quantification of Phthalate Esters in Carbonated Soft Drinks by Hollow Fiber-Microporous Membrane Liquid-Liquid Extraction and 96-Well Plate System Using Natural Deep Eutectic Solvents Based on Fatty Acids

Abstract

This study introduces a green approach to sample preparation by applying natural deep eutectic solvents (NADES) to determine phthalates in carbonated soft drinks using high-performance liquid chromatography with diode array detector (HPLC-DAD). The method employs hollow fiber-microporous membrane liquid-liquid microextraction combined with a 96-well plate system, utilizing fatty-acid-based DES in the pores of the membranes. This methodology substantially reduces the use of organic solvents, and its efficiency is comparable to or better than conventional methods. Fatty acids with chain lengths ranging from 6 to 12 carbons were investigated for the determination of dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), and benzyl butyl phthalate (BBP). The optimized approach used a NADES of decanoic and nonanoic acids (2:3 molar ratio), with 60 min of extraction and 30 min of desorption in acetonitrile:methanol (1:1 ratio). Limits of detection were reported as 8.2 µg/L for DMP, 7.6 µg/L for DEP and DBP, and 3.0 µg/L for BBP. Intraday precision ranged from 2.2% to 18.6% and inter-day precision from 8.8% to 18.8%. Relative recovery across 3 levels ranged from 83.1% to 113.5%. The methodology was evaluated by two tools with green metrics to indicate sustainability. Analytes are extracted, quantified, and confirmed as phthalates in two brands of carbonated soft drinks.