Rapid analysis of methylated xanthines in teas by an improved high-performance liquid chromatographic method using a polyvinylpolypyrroridone pre-column

We have developed a new high-performance liquid chromatography (HPLC) metho d for the analysis of methylated xanthines in tea by removing polyphenols u sing a polyvinylpolypyrroridone (PVPP) pre-column. The PVPP pre-column was connected with the upstream of analytical column to remove catechins in tea extract. Using this pre-column, caffeine and theobromine in tea, which bel ong to methylated xanthines, could be rapidly determined in less than 10 mi n with an isocratic solvent system. RSDs of standard solutions of caffeine and theobromine were about 0.3 and 0.3% for the retention time, and were ab out 1.6 and 2.5% for the peak area. The quantitation curves of caffeine and theobromine were linear from 5 to over 1000 ng. (C) 1999 Elsevier Science B.V. All rights reserved.