CHEMOMETRICS ASSISTED UV-SPECTROPHOTOMETRIC ...

If Beer’s Law is satisfied for the zero-order spectrum the relationship between concentration
and amplitude can be shown as:
Zero order A = ∈bc.......................... [10]
First order ..................... [11]
n th order ................... [12]
Where A is absorbance, ∈ is the extinction coefficient, b is the sample path length and C is
the sample concentration [45].
Many types of analyses would be improved by using this principle because the use of an
absorbance spectrum is no more difficult than the use of derivative spectrum. The amplitude
between the minimum and maximum on the n th derivative curve is more proportional to the
values of the absorbance of the solution. A calibration curve can be obtained from several
standard solutions of varying concentrations to which the same mathematical principles are
applied [46].
1.4.1. Characters of Derivative Spectrophotometer
1. Increase of spectra resolution
The most prominent feature of DS is the improvement of the resolution of overlapping
spectral bands. It gives due attention to sharp features of a spectrum at the expense of broad
bands [45, 47, 48].
Fig.5. Effect of derivative order (zeroth, second and fourth) on the relative amplitudes of two
coincident Gaussian bands, X and Y, of equal intensity but with a band- width ratio 1:3 [47].
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