Abstract
Ratios of Fourier function coefficients to their analogous orthogonal function coefficients are proposed as purity indices during spectrophotometric analysis. Hence,
a
1
/
p
2
(where
a
1
= coefficient of cos
x
and
p
2
is the coefficient of
P
2
) calculated for a set of absorbances is independent of concentration and is sensitive to the presence of interferents. The concentration of tetraenes in amphotericin B has been determined by this ratio, calculated from absorbances measured at 6-nm intervals from 264 to 294 nm.