Matrix effect
Matrix effects at three levels of QC concentrations (LQC, MQC and HQC) were determined by comparing the mean peak area of the samples prepared by spiking post-extracted samples with the analytes and IS in solution (without extraction) at corresponding concentrations. The %CV of the matrix effect should be within the acceptance criteria, which is less than 15%. The matrix factor (MF) was estimated based on the equation,The IS normalized MF was then calculated asThe acceptance value of IS normalized MF should be within 0.8–1.2.