Development and Application of a Nonaqueous Capillary Electrophoresis System for the Analysis of Porphyrins and Their Oligomers (PHOTOFRIN)

PHOTOFRIN is a complex porphyrin mixture used in the photodynamic therapy of cancer. A nonaqueous buffer with a polyether additive is used in the development of a capillary electrophoresis method for the analysis of this type of compound. This method achieves partial separation of 60 peaks for PHOTOFRIN in 30 min. A methanol-based buffer is used to improve the efficiency of the separation by decreasing the aggregation of porphyrin, and the resolution is improved by using the electroosmotic flow (EOF) to counterbalance the electrophoretic migration of the analytes. This counterbalancing EOF holds the analytes in the electric field longer, thereby improving the resolution. Brij 35 is used as a complexation reagent to adjust the selectivity and improve the efficiency of the separation. The effects that Brij 35 concentration has on the separation of both monomeric and oligomeric porphyrins are discussed. The polarity of the solvent is adjusted through the addition of water and its effect is rationalized. A qualitative fingerprinting method for characterizing PHOTOFRIN is developed, and different batches and stressed samples are studied.