The validation parameters included (a) specificity of each compound;
(b) selectivity of the elution method between two peaks;
(c) limit of detection (LOD); (d) limit of quantification (LOQ);
and, (e) linearity of the calibration curves (R2). The retention times
of each standard in the mixture solution were identified and the
percentage of relative standard deviation (%RSD) was calculated
to confirm the specificity of the peaks.