The precision of the method was estimated using triplicate analyses. The intra- and inter-day repeatabilities were estimated by analyzing spiked samples at three different concentrations (10, 50 and 100 ng/mL) in a single day and for three days,respectively. For evaluating the accuracy of the analytical method,the recoveries were determined by spiking known amounts of standards in known real samples in triplicate at two concentration levels, 10 and 100 ng/mL.