Hexafluoroisopropanol-induced coacervation in aqueous mixed systems of cationic and anionic surfactants for the extraction of sulfonamides in water samples.

Abstract

Hexafluoroisopropanol (HFIP)-induced coacervation in aqueous mixed systems of catanionic surfactants of dodecyltrimethylammonium bromide (DTAB) and sodium dodecyl sulfate (SDS) was described in detail, and its application in the extraction of strongly polar sulfonamides (SAs) was investigated. With 10% (v/v) HFIP inclusion, coacervation formation and two-phase separation occur in a wide range of SDS/DTAB mole ratios (88:12∼0:100mol/mol) and total surfactant concentrations (10∼200mmol/L). The interactions between HFIP and DTAB play an important role in coacervation formation. The HFIP-induced SDS-DTAB coacervation extraction proves to be an efficient method for the extraction and preconcentration of SAs. Both hydrophobic interaction and polar interactions (hydrogen-bond, electrostatic, and π-cation) contribute to the distribution of SAs into coacervate phase. The proposed HFIP-induced SDS-DTAB coacervation extraction combined with HPLC-UV was employed for the extraction and quantitative determination of SAs in environmental water samples. Limits of detection were 1.4∼2.5ngmL(-1). Excellent linearity with correlation coefficients from 0.9990 to 0.9995 was obtained in the concentration of 0.01∼10μgmL(-1). Relative recoveries were in the range of 93.4∼105.9% for analysis of the lake, underground, and tap water samples spiked with SAs at 0.01, 1.0, and 10μg/mL, respectively. Relative standard deviations were 0.7∼3.2% for intraday precision and 1.3∼4.6% for interday precision (n = 3). Concentration factors were 17∼49 for three water samples spiked with 0.01μg/mL SAs. The results demonstrate that the proposed extraction method is feasible for the preconcentration and determination of trace SAs in real water samples.