Evaluation was made of the
linear relationship between the absorbances of the complex at wavelengths
of 242 nm and 490 nm, in order to ensure use of a band that
was directly related to the complex. The coefficient of determination
(R2) obtained was 0.998, with standard deviation of the residuals
equal to 0.024. The analytical sensitivity at 242 nm was 31.4-fold that
obtained at 490 nm, so the wavelength of 242 nm was selected for use
during method development. The effect of the presence of interferents
that might absorb in this region of the ultraviolet spectrum could be
eliminated using a blank solution obtained before formation of the complex
with Mn(III). The EDTA spectrum showed no absorption bands in
this region.