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 Band 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 mu g/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 mu g/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 mu g/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.