Simultaneous determination of 7 rhodamine dyes in hot chili products by high performance liquid chromatography-tandem mass spectrometry

A credible method was developed for the simultaneous determination of 7 rhodamine dyes in hot chili products based on high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The samples were extracted with hexane or methanol-water (1:1, v/v) and then cleaned up by a solid phase extraction cartridge. The target analytes were separated on an SB-C18 column with gradient elution using acetonitrile and water (containing 0.1% (v/v) formic acid for both) as mobile phases. The identification and quantification were achieved by using ESI-MS/MS in positive ion mode and with multiple reaction monitoring (MRM). The linear ranges were from 0.0005 to 1.0 mg/L with the correlation coefficients (r2) above 0.997 for all the 7 rhodamine dyes. The limits of detection (LOD) in chili powder and chili oil were from 0.21 to 51 microg/kg and 0.19 to 25 microg/kg, respectively. The relative standard deviations of intra-day and inter-day were both less than 20%. The recoveries of the method were between 85.0% and 106%. The method is simple, rapid, highly sensitive and suitable for the simultaneous determination of 7 rhodamine dyes in foods.