Determination of glycolic acid in cosmetics by online liquid chromatography–Fourier transform infrared spectrometry

Abstract

An isocratic online liquid chromatography Fourier transform infrared procedure has been developed for the determination of glycolic acid in cosmetics. The method involves the ultrasound-assisted extraction of glycolic acid from the samples with an acetonitrile:phosphate buffer (25 mM, pH 2.7) (3:97 v/v). The extracts were centrifuged and filtered before their injection into the chromatography system, which was equipped with a C18 column and used a flow rate of 150 microL min(-1). FTIR spectra were acquired using a time-resolved rapid scan mode. To calculate the chromatograms, the spectral area was integrated between 1288 and 1215 cm(-1), with baseline correction established between 1319 and 1150 cm(-1), after correcting for the eluent spectral background. Peak area values of the extracted sample chromatograms were interpolated from an external calibration curve. The method provided a limit of detection of 0.034 mg mL(-1) and a relative standard deviation of 6% for five measurements at the 0.174 mg mL(-1) concentration level. Recovery values obtained by spiking 400 mg of three commercially available samples with amounts of glycolic acid from 3.7 to 9.8 mg ranged between 99.6 and 101%. The results obtained for the commercial samples agree well with their declared concentrations. An attempt to directly determine glycolic acid by attenuated total reflectance measurements using partial least squares calibration showed that results were strongly influenced by compounds coextracted from the matrix.

On-Line Fourier Transform Infrared Spectrometric Detection in Gradient Capillary Liquid Chromatography Using Nanoliter-Flow Cells

“…For example, Schulte-Ladbeck et al reported limits of detection for triacetonetriperoxide (TATP) and hexamethylenetriperoxide diamine (HMTD) of 4440 and 2080 ng on-column using a LiChroSpher RP18 column (250 × 3 mm, 5 μm) and an isocratic mobile phase of acetonitrile/H 2 O (75:25) for the separation and a CaF 2 flow cell with 25 μm path length for FT-IR detection. More recently, Kuligowski et al reported a limit of detection of glycolic acid by isocratic on-line LC-FT-IR in rapid scan acquisition mode of 680 ng on-column using a RP18 column (250 × 2 mm, 5 μm) and an isocratic mobile phase of acetonitrile/phosphate buffer (25 mM, pH 2.7) (3:97) for the separation and a CaF 2 flow cell with 14 μm path length and a volume of 1.7 μL for FT-IR detection. In short, limits of detection are dependent on the analyte but are typically in the range of 50 ng μL −1 by using micromachined nL-IR flow cells in capillary LC, and in the low μg μL −1 range or higher using standard flow cells.…”

“…Previous studies in isocratic on-line LC-IR provided detection limits in the mg mL −1 range using attenuated total internal reflectance infrared microspectroscopy, , or a conventional internal reflection element mounted in a flow cell, as well as standard IR flow cells. − ,− Whereas these reports show the usefulness of on-line IR detection for the analysis of sugars, organic acids, and peroxides (explosives), an increase in sensitivity is needed to broaden the problem solving capabilities of this hyphenation. When assessing the instrumental constraints of on-line LC-IR several reasons can be identified being responsible for the apparent low sensitivity of on-line FT-IR detection as compared to UV−vis spectrometric detection in LC using 4.6 mm columns.…”

Current trends in liquid–liquid and solid–liquid extraction for cosmetic analysis: a review

“…82,88 Other solvents such as ethyl acetate, acetonitrile, acetic acid and acetone have been used to a lesser extent. 32,81,83,91,96,100 Volumes between 0.15 and 250 mL are used.…”