chlorophyll
NOTES AND COMMENT 343
DETERMINATION OF CHLOROPHYLL AND PHEO-PIGMENTS :
SPECTROPHOTOMETRIC EQUATIONS~
It has been shown that chlorophyll degradation products may at times constitute a significant fraction of the total green pigments present in seawater (Yentsch and
Menzel 1963; Lorenzen 1965; Yentsch 1965).
These degraded forms, or inactive chlorophyll, absorb light in the red part of the spectrum; if they are present in concentrations significant relative to chlorophyll a, a serious error may be introduced into chlorophyll data using the present spectrophotometric techniques ( Richards with
Thompson 1952; Parsons and Strickland
1963), because the absorption of light by the degraded forms is not distinguished from that absorbed by active chlorophyll.
Chlorophyll a can readily be converted to pheophytin simply by the addition of a weak or dilute acid, either oxalic acid or
1 N HCl, and when the reaction is carried out on a specific sample the absorbancy of the solution is reduced (Vernon 1960). The pheo forms of chlorophyll, both pheophytin and pheophorbide, do not show a reduction in absorbancy when treated with an acid, although the chlorophyllide apparently does ( unpublished data). This reduction in absorbancy by acid is probably the result of the removal of the bound Mg atom in the porphyrin ring.
This simple property, brought about by the conversion of chlorophyll to pheophytin, could be used in a method for the determination of chlorophyll a in samples containing pheo-pigments. The fluorometric technique for pigment determination (Yentsch and Menzel 1963; Holm-Hansen et al.
1965) has been used extensively in this laboratory, and its precision and the recovery of both chlorophyll and pheophytin from prepared solution is excellent; but the presence of chlorophyll b may interl
Contribution from the Scripps Institution of
Oceanography, University of California, San Diego.
This investigation was part of the Scripps
DETERMINATION OF CHLOROPHYLL AND PHEO-PIGMENTS :
SPECTROPHOTOMETRIC EQUATIONS~
It has been shown that chlorophyll degradation products may at times constitute a significant fraction of the total green pigments present in seawater (Yentsch and
Menzel 1963; Lorenzen 1965; Yentsch 1965).
These degraded forms, or inactive chlorophyll, absorb light in the red part of the spectrum; if they are present in concentrations significant relative to chlorophyll a, a serious error may be introduced into chlorophyll data using the present spectrophotometric techniques ( Richards with
Thompson 1952; Parsons and Strickland
1963), because the absorption of light by the degraded forms is not distinguished from that absorbed by active chlorophyll.
Chlorophyll a can readily be converted to pheophytin simply by the addition of a weak or dilute acid, either oxalic acid or
1 N HCl, and when the reaction is carried out on a specific sample the absorbancy of the solution is reduced (Vernon 1960). The pheo forms of chlorophyll, both pheophytin and pheophorbide, do not show a reduction in absorbancy when treated with an acid, although the chlorophyllide apparently does ( unpublished data). This reduction in absorbancy by acid is probably the result of the removal of the bound Mg atom in the porphyrin ring.
This simple property, brought about by the conversion of chlorophyll to pheophytin, could be used in a method for the determination of chlorophyll a in samples containing pheo-pigments. The fluorometric technique for pigment determination (Yentsch and Menzel 1963; Holm-Hansen et al.
1965) has been used extensively in this laboratory, and its precision and the recovery of both chlorophyll and pheophytin from prepared solution is excellent; but the presence of chlorophyll b may interl
Contribution from the Scripps Institution of
Oceanography, University of California, San Diego.
This investigation was part of the Scripps