Determination of antipyrine in saliva using the dispersive liquid-liquid microextraction based on a stepwise injection system

A fully automated stepwise injection spectrophotometric method for determination of antipyrine in saliva (agent for non-invasive assessment of the activity of the drug metabolizing system in hepatocytes) has been developed. The method is based on the antipyrine derivatization by nitrite-ion dispersive liquid-liquid microextraction (DLLME) of formed 4-nitrosoantipyrine with subsequent UV-vis spectraphotometric detection. Under optimal experimental conditions (0.5 M sulfuric acid, 6 x 10(-3) M sodium nitrite, time 6 min) the absorbance of the colored extract at the 345 nm obeys Beer's law in the range of 3-200 mu M of antipyrine in saliva. The LOD, calculated from a blank test, based on 3 sigma, found to be 1 mu M. The relative standard deviation for the determination of 50 mu M antipyrine was 4.5% (n=10). The proposed method was successfully applied to the determination of antipyrine in saliva and the analytical results agreed fairly well with the results obtained by reference HPLC method. (C) 2014 Elsevier B.V. All rights reserved.