Determination of kojic acid in foods using high performance liquid chromatography-tandem mass spectrometry

The quantification method for the determination of kojic acid in foods using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was developed. For solid samples, the kojic acid was extracted with acetonitrile; for liquid samples, they were diluted with water, then deproteinized by the deposition with zinc acetate and potassium ferrocyanide. The analytes were determined by HPLC-MS/MS on a C18 column with 5 mmol/L ammonium acetate/formic acid solution as mobile phases. The analysis of kojic acid was performed under selected reaction monitoring (SRM) mode by selecting one parent ion and two daughter ions as qualitative ions with [13C6]-kojic acid as the internal standard, and the most abundant daughter ion as quantitative ion. The limits of quantification (S/N > 10) were 0.1 mg/kg for the solid samples, and 2.5 mg/kg for the liquid samples. The good linearity (r > 0.99) was achieved for the target compound over the range of 0.1 - 2.0 mg/L. The recoveries at three levels for kojic acid were from 72.6% to 114% with the relative standard deviations no more than 11.4%. The method is simple and practical, and can be applied to most of matrices which may contain kojic acid as food additives. It can meet the qualitative and quantitative requirements for import and export foods.