A validated LC-MS/MS determination method for the illegal food additive rhodamine B: Applications of a pharmacokinetic study in rats

Rhodamine B is an illegal and potentially carcinogenic food dye. The aim of this study was to develop a convenient, rapid, and sensitive UHPLC-MS/MS method for pharmacokinetic studies in rats. Rat plasma samples were deproteinized with acetonitrile and separated by UHPLC on a reverse-phase C18e column (100 mm x 2.1 mm, 2 mu m) using a mobile phase consisting of methanol-5 mM ammonium acetate (90:10, v/v). Detection was performed using a triple quadrupole tandem mass spectrometer in the selected reaction monitoring mode at [M](+) ion m/z 443.39 -> 399.28 for rhodamine B and [M+H](+) ion m/z 253.17 -> 238.02 for 5-methoxyflavone as the internal standard. This method was specific and produced linear results over a concentration range of 0.5-100 ng/mL, with a lower limit of quantitation of 0.5 ng/mL. All validation parameters, including the inter-day, intra-day, matrix effect, recovery, and stability in rat plasma, were acceptable according to the biological method validation guidelines developed by the FDA (2001). This method was successfully applied to a pharmacokinetic study in rats; oral administration of 1 mg/kg of rhodamine B yielded a time to maximum concentration (T-max) of 1.3 +/- 0.4 h and an elimination half-life of 8.8 +/- 1.4 h, with a clearance of 229.7 +/- 19.4 mL/h/kg. These pharmacokinetic results provide aconstructive contribution to our understanding of the absorption mechanism of rhodamine B and support additional food safety evaluations. (C) 2016 Elsevier B.V. All rights reserved.