[Determination: of citrus red 2 in navel orange by ultra performance liquid chromatography-tandem mass spectrometry].

An ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/ MS) method was developed for the determination of citrus red 2 (CR2) in navel orange. The sample was extracted with acetonitrile, cleaned-up by an NH2 solid phase extraction cartridge. Then, the analyte was separated on a Waters Acquity UPLC BEH C18 column (50 mm x 2.1 mm, 1.7 microm) in gradient elution with the mobile phases of water and acetonitrile. The separated compounds were detected with a Waters Xevo TQ MS tandem quadrupole mass spectrometer operated in multiple reaction monitoring (MRM) mode via positive electrospray ionization (ESI+). The linearity of the method was good (r2 = 0.996 5) over the concentration range from 0.1 to 100 microg/L for CR2. The limit of detection (LOD) was 0.05 microg/kg, and the limit of quantification (LOQ) was 0.1 microg/kg. The average recoveries of CR2 at the three levels of 1.0, 10.0 and 100.0 microg/kg were between 84.2% and 94.0% with the relative standard deviations (RSDs) between 2.86% and 10.15%. Finally, a total of 18 navel orange samples randomly collected from different markets were detected by the proposed method, and two samples contained CR2. The sensitivity, accuracy, and precision of this method can meet the requirements of the CR2 analysis.