Extraction and determination of nicotinic acid from human plasma was performed using inverted dispersive liquid-liquid microextraction and HPLC. The parameters affecting extraction recovery such as type and volume of extracting and disperser solvents, pH of sample solution, salt addition and extraction time were optimized. Optimal extraction conditions were: 150μL tributyl phosphate as extraction solvent, 400μL methanol as disperser solvent, and pH of sample = 4.5, concentration of NaCl = 3M, without effect of extraction time. Under the optimal conditions a linear range of 30-1000 ng mL−1 (R2 = 0.9994) was obtained. Limit of detection, the extraction recovery and preconcentration factor were 10 ng mL-1, 68% and 53 respectively. The method was successfully applied for the extraction and determination of nicotinic acid in human plasma sample. ;
