FOOD SCIENCE ›› 2020, Vol. 41 ›› Issue (4): 287-292.doi: 10.7506/spkx1002-6630-20190101-006

• Safety Detection • Previous Articles     Next Articles

Determination of Rhodamine B in Ketchup, Tomato Sauce and Chili Powder by Micellar Electrokinetic Capillary Chromatography with Laser-Induced Fluorescence Detection

DING Xiaojing, LIU Wenye, WANG Ping   

  1. (1. Beijing Key Laboratory of Diagnostic and Traceability Technologies for Food Poisoning, Beijing Center for Disease Control and Prevention, Beijing 100013, China; 2. Beijing Research Center for Preventive Medicine Research, Beijing 100013, China; 3. School of Public Health, Capital Medical University, Beijing 100069, China)
  • Online:2020-02-25 Published:2020-03-02

Abstract: A new and simple method was developed for the accurate determination of rhodamine B in ketchup, tomato sauce and chili powder samples by micellar electrokinetic capillary chromatography (MEKC) with laser-induced fluorescence (LIF) detection. The separation was performed on an uncoated fused silica capillary 75 μm × 30 cm total length (effective length: 20 cm) with a separation buffer solution consisting of 30 mmol/L sodium tetraborate, 20 mmol/L sodium dodecyl sulfonate (SDS), 20 mmol/L sodium deoxycholate (SD) and 0.2 g/L polyethyleneglycol 35000. A solution containing 10 mmol/L SDS was used for sample extraction. The analysis could be completed within 10 min. A voltage of 8 kV was used for separation. The injection time and pressure were 5 s and 3.448 kPa, respectively. The excitation and emission wavelengths were 488 nm and 520 nm, respectively. The corrected peak area and the concentration of rhodamine B displayed a good linear relationship with a correlation coefficient (r) of 0.999 9 in the ranges of 0.02–1.28 mg/L. The limit of detection (LOD; RSN = 3) and limit of quantitation (LOQ; RSN = 10) were 5 and 15 μg/L, respectively. The intra-day and inter-day precisions of the method were both no less than 2%. The average recoveries of rhodamine B at three spiked concentrations (0.04, 0.16 and 0.64 mg/L) were in the ranges of 100.9%–105.8%. When the MEKC method was used to determine the contents of rhodamine B in 3 ketchup, 3 tomato sauce and 22 chili powder samples, the results were all lower than those measured by ultra-high performance liquid chromatography-fluorescence detection (UPLC-FLR). The possible reasons for the difference were analyzed and discussed.

Key words: micellar electrokinetic chromatography, laser-induced fluorescence, rhodamine B, sauce, ketchup, chili powder

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