title: Determination of kojic acid in a skin-whitening cosmetic by high-performance liquid chromatography coupled with ultraviolet detection after pre-column derivatization with 4-fluoro-7-nitro-2,1,3-benzoxadiazole.
abstract: Various methods for the determination of kojic acid (KA), a skin-whitening agent, have been reported by high-performance liquid chromatography (HPLC). In this study, the concentration of KA in a skin-whitening cosmetic was analyzed by HPLC with ultraviolet detection (380 nm) after pre-column derivatization with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) in order to improve the sensitivity. The HPLC column was 150 mm x 3.0 mm i.d., containing 5 microm particles of C18 packing material. The mobile phase was prepared by the addition of acetonitrile (550 ml) to 450 ml of Milli-Q water containing trifluoroacetic acid (0.1 v/v%). The samples were eluted from the column at room temperature at a flow rate of 0.35 ml/min. The retention time of NBD-KA was 7.8 min. A standard curve was obtained after derivatization with NBD-F in borate buffer (pH 9.0) at 40 degrees C for 7 min. The calibration plot was linear, in the range of 0.25-5 microg/ml with an r2 value of 0.9982, and the lower limit of detection was 0.06 microg/ml (at a signal-to-noise ratio of 3:1; absolute amount of 0.4 ng/20 microl injection). The coefficient of variation was less than 9.6%. It was found that the amount of KA in a skin-whitening cosmetic was 237 +/- 14 microg/ml (range: 219-255 microg/ml). Recovery in addition-recovery tests was within the range of 83.4% to 98.1%.
authors.affiliation: Department of Analytical Chemistry, Faculty of Pharmaceutical Sciences, Hokuriku University, Ho-3, Kanagawa-machi, Kanazawa 920-1181, Japan. y-higashi@hokuriku-u.ac.jp
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Higashi
authors.forename: Youichi
authors.initials: Y
authors.lastname: Fujii
mesh_terms: D009327:4-Chloro-7-nitrobenzofurazan / Q000031:analogs & derivatives* / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006801:Humans; D011753:Pyrones / Q000032:analysis* / Q000737:chemistry; D015203:Reproducibility of Results; D062327:Skin Lightening Preparations / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D011753:Pyrones; D062327:Skin Lightening Preparations; C032930:7-fluoro-4-nitrobenzo-2-oxa-1,3-diazole; C011890:kojic acid; D009327:4-Chloro-7-nitrobenzofurazan