Determination of trace levels of parabens in real matrices by bar adsorptive microextraction using selective sorbent phases

In the present work, the development of an analytical methodology which combines bar adsorptive microextraction with microliquid desorption followed by high performance liquid chromatography-diode array detection (BA mu E-mu LD/HPLC-DAD) is proposed for the determination of trace levels of four parabens (methyl, ethyl, propyl and buthyl paraben) in real matrices. By comparing six polymer (P1, P2, P3, P4, P5 and P6) and five activated carbon (AC1, AC2, AC3, AC4 and AC5) coatings through BA mu E, AC2 exhibited much higher selectivity and efficiency from all the sorbent phases tested, even when compared with the commercial stir bar sorptive extraction with polydimethylsiloxane. Assays performed through BA mu E(AC2, 1.7 mg) on 25 mL of ultrapure water samples spiked at the 8.0 mu g/L level, yielded recoveries ranging from 85.6 +/- 6.3% to 100.6 +/- 11.8%, under optimized experimental conditions. The analytical performance showed also convenient limits of detection (0.1 mu g/L) and quantification (0.3 mu g/L), as well as good linear dynamic ranges (0.5-28.0 mu g/L with remarkable determination coefficients (r(2) > 0.9982). Excellent repeatability was also achieved through intraday (RSD < 10.2%) and interday (RSD < 10.0%) assays. By downsizing the analytical device to half-length (BA mu E(AC2, 0.9 mg)), similar analytical data was also achieved for the four parabens, under optimized experimental conditions, showing that this analytical technology can be design to operate with lower volumes of sample and desorption solvent, thus increasing the sensitivity and effectiveness. The application of the proposed analytical approach using the standard addition methodology on tap, underground, estuarine, swimming pool and waste water samples, as well as on commercial cosmetic products and urine samples, revealed good sensitivity, absence of matrix effects and the occurrence of levels of some parabens. Moreover, the present methodology is easy to implement, reliable, sensitive, requiring low sample and minimized desorption solvent volume, having the possibility to tune the most selective sorbent coating, according to the target compounds involved. (C) 2014 Elsevier B.V. All rights reserved.