BIOANALYTICAL METHOD BY COLUMN-SWITCHING WITH DIRECT INJECTION OF HUMAN PLASMA FOR DETERMINATION OF SULPHONYLUREAS

Sulphonylureas are widely used in the treatment of Diabetes mellitus, one of the main causes of death in human population. Their determination is essential in pharmacological research and in the development of new drugs. Generally, determination of sulphonylureas in biological matrices is performed using conventional sample preparation techniques, which frequently leads to an increase of analysis time and errors. In this context, a bioanalytical method for the simultaneous determination of sulphonylureas by direct injection of human plasma was developed and optimized. An automated column-switching high performance liquid chromatographic system with a restricted access media (RAM) column coupled to a fused-core column was employed. At the first dimension, a RAM column with mobile phase of ultrapure water pH 6.0 at a flow-rate of 1.0 mL min-1 was used. The valve switching time was 3 minutes. At the second dimension, a C18 guard-column coupled to a C18 fused core column with mobile phase of acetonitrile and 10 mM phosphate buffer pH 3.0 (54:46 v/v) at a flow-rate of 0.8 mL min-1 were employed. The column switching system was performed in backflush configuration with an analyte elution time of 1 minute. Flufenamic acid was used as the internal standard. The mean plasma protein exclusion percentage by the RAM-column was 104.5%. The developed and optimized method showed to be fast and simple, allowing the direct injection of biological sample into the chromatographic system and the simultaneous determination of three sulphonylureas in only 12 minutes, including the sample treatment, separation and detection.