RUGGEDNESS TESTS ON THE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY ASSAY OF THE UNITED-STATES PHARMACOPEIA-23 FOR TETRACYCLINE-CENTER-DOT-HCL -COMPARISON OF DIFFERENT COLUMNS IN AN INTERLABORATORY APPROACH

Ruggedness tests were performed on the United States Pharmacopeia assa y for tetracycline . HCl to examine problems previously reported in th e literature. The experiments were performed on nine different columns . The effects of four factors selected from the procedure were examine d on qualitative responses by performing half-fraction factorial desig ns at three different ages on each column. The influence of column age ing was separately evaluated by injections under nominal method condit ions at different ages. The C-8 columns gave a separation that was as good as, or better than, the C-18 ones and were less influenced by age ing. The normalized effects of each of the factors on a response were compared and found to be more or less equal for most of the columns an d to remain constant with time. The responses were most affected by th e pH of the mobile phase and by the content of the organic modifier. I n general it was found that C-8 columns were preferred for this assay.