SPECTROSCOPIC STABILITY OF CHLOROPHYLLS a AND b AND CERTAIN ANALYTICAL CONSIDERATIONS

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Abstract
The effects of longtime storage at low temps, on the absorption curves of chlorophylls a and b were studied. Purified prepns. of chlorophyll a in ether soln. are stable for a week or more, after which deterioration is evident; the behavior of dried samples is less predictable. Chlorophyll in crude extracts in ether appears more stable than in purified prepns. Satis-factory analytical results were obtained on ether extracts from tomato leaves after 14 weeks at[long dash]20[degree] C. Storage of fresh corn leaves at[long dash]20[degree] C for one month did not influence analytical results but chlorophyll deteriorated during longer periods. Storage of leaves in acetone has some advantages for long storage periods (7 months or more). Small amts. of ethanol, methanol, or acetone in ether eolns. and 20% water in acetone solns. caused absorption changes; hexane produced no change in ether solns. Spectroscopic effects of solvent impurities and of acids are discussed in relation to chlorophyll analysis. The subject of standards for spectroscopic analysis is considered in relation to stability factors. Comparisons are made from the viewpoint of practical application to plant materials.