was partially modified. For measuring chlorophyll a and b concentrations in plant extracts, the equation
A(
)/ 
a() = Ca + [b()/ a()]Cb is considered, where A() is the absorbance spectrum of the extract analyzed, Ca and Cb are concentrations of chlorophylls a and b, and
a() and b() are respective wavelength dependen-cies of the molar extinction coefficients. This equation meets the criterion for a two-component system. In the
presence of additional light-absorbing components, this function deviated from linearity in the region 550–
670nm, as was the case in the extracts containing products of chlorophyll pheophytinization and photodegra-
dation. This approach makes it possible to estimate the analytical error and to assess the spectral range of light
absorption by impurities. Our data showed that, in some samples (extracts from pea, sorrel, or senescing maple
leaves), the conventional two-wavelength photometry can lead to significant errors in pigment assays. The
aforementioned criterion showed that, in extracts from wheat seedlings or green leaves of maple and stinging
nettle, chlorophyll content can be measured with reasonably high accuracy. Additional qualitative and quanti-
tative information on the compounds present in extracts was obtained by subtracting chlorophyll absorbance
spectra from the initial absorbance spectrum. This was demonstrated with extracts containing carotenoids,
anthocyanins, and long-wavelength UV-absorbing compounds.