Criteria for Purity of Chlorophyll Preparations*

It is inevitable that the separation in pure state of substances which cannot be purified by recrystallization or by other common methods should prove difficult, and that criteria of purity should be correspondingly less convincing. The primary purpose of this paper is to establish satisfactory criteria for several chlorophyll preparations, especially with reference to their absorption of light. This is of fundamental importance in assays of pigment mixtures by spectroscopic means. In recent years, absorption coefficients for the two chlorophyll components have been determined by Winterstein and Stein (I), Zscheile (2), Hagenbach, Auerbacher, and Wiedemann (3), and Meyer (4). The values reported in “Tabuls biologic& (5) do not indicate the startling lack of agreement which is rcvcaled by the most cursory inspection, and because of which a thorough reinvestigation becomes necessary. Several ancillary problems are thereby involved, such as preparative procedures, the possibility of more than two chlorophyll components, and the removal of impurities and degradation products. Because the preparation of chlorophyll has been fraught with much uncertainty in the past, we offer a brief description of the method employed. Although no new principle is involved, the procedure is so simplified that we believe the uncertainties to have been largely removed.