Semipreparative separation and fractionation of sulfonamides via supercritical fluid chromatography

Three protocols with two different apparatus setups are evaluated to obtain a pure fraction from a supercritical fluid chromatographic separation of three sulfonamides. Results show that the addition of a rinse pump to flush the lines after the detector can decrease cross-contamination of the fractions. However, the location of the rinse pump in the system is a major factor. It is demonstrated that it is better to place the rinse pump immediately after the detector in order to obtain pure fractions. Evaluation of three collection protocols shows that collection at a constant interval can result in the isolation of a pure fraction. Minifractions collected every 0.2 min through the analyte peak show purities of 97, 92, and 73% for sulfamethazine (SMZ), sulfadimethoxine (SDM), and sulfaquinoxaline (SQX), respectively. However, collection of fractions at 0.5-min intervals throughout the entire chromatogram without regard to the onset of the peak shows purities of 92, 82, and 86% for SMZ, SDM, and SQX, respectively.