Simultaneous Determination of 24 Acid Industrial Dyes in Food by Solid Phase Extraction-Ultrahigh Performance Liquid Chromatography-Tandem Mass Spectrometry

A method based on solid phase extraction (SPE) combined with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established for the determination of 24 acid industrial dyes in food. The sample was extracted with ammonia-ethanol solution (ammonia: absolute ethyl alcohol:water=2:7:1, v/v), the extracting solution was condensed to 1 mL under a stream of nitrogen, then dissolved by 10 mL 5% methanol-water solution. The solution was purified by Agela Cleanert PWAX SPE column. The eluant was dried with nitrogen and dissolved by ammonium acetate acetonitrile solution (10 mmol/L ammonium acetate water:acetonitrile =1:1, v/v), the analytes were separated by the Agilent ZORBAX Eclipse RRHD C₁₈ (3.0 mm×150 mm, 1.8 μm) column using mobile phase gradient with acetonitrile and 10 mmol/L ammonium acetate. The analytes were ionized with negative electrospray ionization (ESI⁻) and analyzed by multiple reaction monitoring (MRM) mode, then quantified by external standard method. The linearity of 24 acid industrial dyes displayed good linearities in the range from 20～300 ng/mL, the correlation coefficients higher than 0.999. The limits of detection (LOD) and quantification (LOQ) were 10 μg/kg and 25 μg/kg. The recoveries at three level spiked levels (25、100、250 μg/kg) were 91.0%～112.7% with the relative standard deviations (n=6) between 0.42% and 4.39%. The method was applied to determine 40 batches of bean products, condiments, aquatic products and meat products each, the acid orange Ⅱ was detected in 2 batches of braised meat samples, the content was 138±2.8 μg/kg and 179±3.7 μg/kg, the red 2G was detected in 2 batches of sausage samples, the content was 320±8.6 μg/kg and 230±6.2 μg/kg. The method is rapid, sensitive and reliable, it can be applied to determine 24 acid industrial dyes in food.