Analysis of Phloxine B and Uranine in Coffee by High-Performance Liquid Chromatography and Capillary Zone Electrophoresis after Solid Phase Extraction Cleanup

A method was developed for the analysis of phloxine B and uranine, photoactive dyes being evaluated as fruit fly toxicants, in coffee cherries and green and roasted beans. The analytes were measured by high-performance liquid chromatography (HPLC) and capillary zone electrophoresis (CZE) using visible and fluorescence detectors after cleanup with disposable amino cartridges. A mixture of methanol (MeOH)/acetonitrile/ n -butylamine ( n -BA) (1/1/0.05) effectively extracted phloxine B and uranine from coffee cherries and green beans. The method yielded good recoveries of phloxine B (66−89%) and uranine (75−100%) at spike levels of 0.05−1.0 μg/g from coffee cherries. Good recoveries of phloxine B (82−95%) and uranine (95−110%) were obtained from green beans at spike levels of 0.25−1.0 μg/g. Addition of sodium hexametaphosphate in roasted beans prior to extraction with MeOH/acetone/ n -BA (1/1/0.05) yielded good recoveries of phloxine B (72−77%) and uranine (79%) at spike levels of 0.5−1.0 μg/g. HPLC and CZE are adequate for determining these analytes. The major advantages of CZE are short analysis time and use of inexpensive columns and aqueous buffer.