Determination of Parabens in Cosmetics by Liquid-Phase Microextractions and High-Performance Liquid Chromatography–Diode Array Detection

Abstract

To deal the stubborn problem arising from oily matrix of cosmetics in the chromatography of parabens, an efficient, rapid, and economic sample preparation method is proposed involving separation of matrix material by extraction with 1 mL of isooctane/1-octanol (50:50, v/v) in the presence of 1 mL of 1 mol/L sodium hydroxide, and centrifugation. Then, parabens in the alkaline solution were preconcentrated, after acidification, by liquid–liquid–liquid microextraction using 200 µL of isooctane/1-octanol (50:50, v/v) as organic solvent and 5 µL of 0.1 mol/L of sodium hydroxide as the acceptor drop. Using the optimized procedure, the method provided a rectilinear graph for 0.01–8 mg/kg of parabens with correlation coefficient (r) in the range 0.9982–0.9990, limit of detection in the range 1.7–4.3 µg/kg, and enrichment factor in the range 79–118. Intra-day (and inter-day) RSD at 0.01 and 5 mg/kg spiked levels of parabens were found as 7.7% (9.2%) and 4.7% (5.6%), respectively. Average recovery of spiked amounts of parabens to cosmetics was 98.9% with an average RSD of 6.1%. A distinct superiority of the present method in terms of sensitivity attained for parabens was evident over HPLC and CE methods that used UV detection, and some others where mass spectrometric detection was used.

Keywords:

• 3-phase microextraction
• cosmetics
• HPLC-DAD
• liquid–liquid microextraction
• matrix removal
• parabens

Notes

^a The abbreviations used are UAE, ultrasonic-assisted extraction; SFVCDME, solidified floating vesicular coacervative drop microextraction; SPE, solid-phase extraction; SCN, sonication; FIA, flow injection analysis; CL, chemiluminescence; MWCNTs, multi-walled carbon nanotubes; CAD, chared aerosol detection; SFE, supercritical fluid extraction; ELPME, emulsification liquid-phase microextraction; LLLME, liquid-liquid-liquid microextraction; CZE, capillary zone electrophoresis; MEKC, micellar electrokinetic chromatography; FI, flow injection; SPME, solid-phase microextraction; SDME, single-drop microextraction; PA, polyacrylate; BSA, N,O-bis(trimethylsilyl)acetamide; BSTFA/TMCS, N,O-bis(trimethylsilyl)trifluoroacetamide/trimethylchlorosilane.

^b EF, enrichment factor; (-) indicates data not reported in the original work.

^c LOD of the method calculated using the molar mass of 4-hydroxybenzoic acid.

^a All results are the average of six replicate analyses; standards were prepared by spiking known amounts to cosmetic sample.

^b RSD (%) obtained on standard spikes given for intra-day and inter-day (in parentheses) analyses.

^a All results are the average of five replicate analyses.

^b Recovery (%) takes into account the amount already found in the sample.

^c Intra-day RSD (%) obtained are given.

Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/ljlc.