3.2.1. Specificity
RA, A1 and IS chromatograms obtained from processed blank plasma samples
were examined to determine the degree of interference by endogenous
plasma components. Fig. 4(a)–(c) shows typical chromatograms of blank
plasma, plasma spiked with IS and plasma samples with A1 and RA. The
retention times of PPD (IS), RA, and A1 were 1.15, 1.38, and 1.53
minutes, respectively, with no endogenous interference or matrix
effects.