Simultaneous quantification of sulfamethoxazole and trimethoprim in whole egg samples by column-switching high-performance liquid chromatography using restricted access media column for on-line sample clean-up

This work reports the application of restricted access media (RAM) column, in a multidimensional configuration, for simultaneous analysis of sulfamethoxazole (SMX) and trimethoprim (TMP) in whole eggs with ultraviolet detection. The proteins were partially precipitated by adding 0.5 mL of acetonitrile into 1.0 mL of blended egg followed by centrifugation. The supernatant was injected (250 μL) directly into the muldimensional system. At the first dimension, a restricted access medium (RAM) bovine serum albumin (BSA) octadecyl column (100 mm × 46 mm I.D., Luna® silica, 10 μm particle size and 100 Å pore size), was used for extraction and concentration of the analytes and at second dimension, an octadecyl column (150 mm × 46 mm I.D., Luna® silica, 10 μm particle size and 100 Å pore size), for analysis. The developed method showed good selectivity, accuracy and precision for quantification of these different compounds in eggs, and the limits of quantification were 80 ng/mL, for both compounds. The validated method is reliable and sensitive for monitoring residues in whole eggs samples and thus, to determine withdraw period for laying hens using veterinary medicine having SMX–TMP combination.