3.2. Method validation
3.2.1. Linearity and ranges
Serial dilutions of the studied drugs over the concentration
ranges stated in Table 1 were prepared in triplicates and analyzed
as previously described. The average peak areas of each drug were
plotted versus the corresponding concentrations and the calibration
curve was constructed using the least squares regression
model. From the values gathered in Table 1, good linearity can be
verified from the close to unity correlation coefficient
(rP0.9994) and the low values of the relative standard deviation
of the slope (Sb% < 1.7%). The standard deviation of the residuals is
another important statistical tool to assess method linearity. In the
developed method, low values of Sy/x were obtained which designate
the negligible difference between the calculated and the
found y-values and hence, the closeness of the experimental points
to the best fitted regression line. Furthermore, the regression equations
showed high F values which indicate steeper regression lines,
and low significant F values which confirm the less scattered
experimental points around the regression line.