Sample preparation procedure using extraction and derivatization of carboxylic acids from aqueous samples by means of deep eutectic solvents for gas chromatographic-mass spectrometric analysis
The paper presents a new procedure for the determination of organic acids in a complex aqueous matrixusing ultrasound-assisted dispersive liquid–liquid microextraction followed by injection port derivati-zation and GC–MS analysis. A deep eutectic solvent (choline chloride: 4-methylphenol in a 1:2 mol ratio)was used both as an extracting solvent and as a derivatizing agent to yield ion pairs which were next con-verted to methyl esters of organic acids in a hot GC injection port. The procedure was optimized in termsof selection of a deep eutectic solvent, disperser solvent, and the ratio of their volumes, pH, salting outeffect, extraction time, injection port temperature and time of opening the split valve. The developed pro-cedure is characterized by low LOD (1.7–8.3 g/L) and LOQ (5.1–25 g/L) values, good repeatability (RSDranging from 4.0 to 6.7%), good recoveries for most of the studied analyte (81,5–106%) and a wide linearrange. The procedure was used for the determination of carboxylic acids in real efﬂuents from the pro-duction of petroleum bitumens. A total of ten analytes at concentrations ranging from 0.33 to 43.3 g/mLwere identiﬁed and determined in the efﬂuents before and after chemical treatment. The study revealedthat in efﬂuents treated by hydrodynamic cavitation an increase in concentration of benzoic acid andrelated compounds was observed.
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