| Abstract: | Abstract An isocratic reversed phase high performance liquid chromatographic method is described for monitoring concentrations of triphenylphosphine (TPP) and other compounds involved in an oxygen-transfer reaction catalyzed by a molybdenum complex. Using an inexpensive octadecylsilane column and a mobile phase consisting of aqueous acetonitrile, good separations and linear chromatographic responses were achieved for solutions of TPP, pyridine and each of their oxides in the mobile phase with concentrations in the range of 0.0012 – 0.12 grams/100 mL. No evidence for TPP precipitation was observed during the analysis of supersaturated solutions containing TPP at concentrations as high as 0.27 grams/100 mL. Chromatograms of more concentrated TPP solutions exhibited a second peak corresponding in retention time to TPP-oxide. Contrary to the interpretation of a similar effect in a previous study, evidence is presented indicating that this second peak is not the result of decomposition of TPP to its oxide, but rather is caused by precipitation of TPP particles which coincidentally pass through the chromatographic system at the same rate as TPP-oxide. Thus in this interpretation, the correspondence of the retention time of the early eluting peak in the chromatograms of solutions containing high concentrations of TPP with that of the oxide of TPP is coincidental, and does not indicate the decomposition of TPP during its HPLC analysis. This is consistent with the data presented here and in earlier studies. |
