Phenolic compounds can be readily phosphitylated with 1,3,2-dioxaphospholanyl chloride. (9; Scheme 1) directly in an NMR tube. Using P-31 NMR Spectroscopy different phenols can be easily discriminated. Using this technique we have developed a facile qualitative and quantitative method for the determination; of phenolic functional groups in PPO resin. On the basis of the developed technique, we were able to obtain the hydroxyl concentration of normal phenolic ends, hydrogen-bonded phenolic ends, and phenolic groups on the backbone, as well as the number-average molecular weight of the polymers. In addition, based on nitrogen content analyses and quantitative P-31 NMR, the Mannich type ends were also determined; The precision of the method was determined to be +/-15 ppm for the determination of individual hydroxyl functionalities. The results of quantitative P-31 NMR when compared to those obtained by applying traditional analytical techniques were in excellent agreement.