]>

(a)

(b)

Figure 3: The plot of absorbance changes in the spectrum (a) means that the value of the absorbance difference for the $j$th-wavelength of the $i$th-spectrum ${\mathrm{\Delta }}_{ij}=A_{ij}-A_{i,\text{acid}}$ is divided by the instrumental standard deviation $s_{\text{inst}}(A)$ and the resulting ratios $SER=\mathrm{\Delta }/s_{\text{inst}}(A)$ are plotted as a function of wavelength λ for all absorbance matrix elements where $A_{i,\text{acid}}$ means the limiting spectrum of the acid form of the drug measured. This ratio is compared to the limiting SER value for silybin to test if the absorbance changes ${\mathrm{\Delta }}_{ij}$ are significantly larger than the instrumental noise $s_{\text{inst}}(A)$. The plot of the ratio $e/s_{\text{inst}}(A)$, that is, the ratio of residuals divided by the instrumental standard deviation $s_{\text{inst}}(A)$ as a function of wavelength λ for all residual matrix elements (b) for silybin tests if the residuals e are of the same magnitude as the instrumental noise $s_{\text{inst}}(A)$.