QUANTITATION OF INDIVIDUAL PHOSPHOLIPID MOLECULAR-SPECIES BY UV ABSORPTION-MEASUREMENTS

To validate the utility of on-line measurements of UV absorption for t he direct quantitation of individual phospholipid molecular species is olated by reverse-phase HPLC, we synthesized 37 different individual m olecular species of diradyl choline glycerophospholipids. UV absorbanc e response factors (integrated UV absorbance/nmole phospholipid) were calculated for all diacyl, alkenylacyl, and alkylacyl species by injec ting varying amounts of the purified molecular species in the 2-100 nm ole range and integrating the UV absorbance al 203 nm. There was excel lent agreement between the results of the quantitation of individual m olecular species determined by measurements of phospholipid mass in HP LC fractions with that based on measurements of total integrated UV ab sorption and the use of absorbance response factors. The on-line quant itation of individual phospholipid molecular species by UV absorption measurement should prove useful as an adjunct to other techniques of p hospholipid quantitation, as a means to assist in the identification o f individual molecular species in complex biologic mixtures, and as a stand-alone approach to phospholipid quantitation to facilitate studie s of the metabolism of individual species particularly when coupled wi th radiolabeling techniques.