Relative matrix effects: A step forward using standard line slopes and ANOVA analysis

One of the alternative methods to identify and study the matrix effect is by determination of "relative'' matrix effect. In this experiment % coefficient of variance of standard line slopes are calculated. First, six standard lines are prepared from single plasma lot. In another experiment standard line slopes are compared from six different lots of plasma. All these standard curves are prepared by using three different types of IS (internal standard). From all these experiments it is observed that using SIL-IS (stable isotope labeled-internal standard) is one of the best approach in methods having matrix effects. Alternatively, analog IS is a cost effective approach. After comparing a large number of calibration curve slopes, it can be recommended that during every bioanalytical method validation, where the sample size is >50, scientist should perform the "relative'' matrix effect experiment by standard line slope method. In selected cases, the precision of standard line slopes in six different lots of a biofluid was compared with precision values determined six times in a single lot. The results of these studies indicated that the variability of standard line slopes in different lots of a biofluid [precision of standard line slopes expressed as coefficient of variation, CV (%)] may serve as a good indicator of a relative matrix effect and, it is suggested, this precision value should not exceed 5% for the method to be considered reliable and free from the relative matrix effect liability. (C) 2014 The Author. Production and hosting by Elsevier B.V. on behalf of King Saud University.