The hydroperoxide levels of two commercial types of crosslinked poly (vinylpolypyrrolidinone) (or crospovidone) disintegrants were studied as a function of time and temperature using the titanyl sulfate titration method. It was noted that the two crospovidone types exhibited significantly different rates of hydroperoxide buildup and that this difference increases with increasing temperature. While the chemical and physical structures of these commercial types are essentially the same, they are known to be different with respect to their crosslinkers which represent nominally 2% of the total mass. These crosslinkers are 3-ethylidene-N-vinyl-2-pyrrolidinone and N,N'-divinylimidazolidinone. While both contain lactam type rings, the latter possesses two nitrogen atoms versus one in the former. It was hypothesized that this difference in the number of heteroatoms results in a greater susceptibility to oxidative attack at carbon positions vicinal to these nitrogen atoms. To test this hypothesis, model compounds representing the two crosslinker ring structures were subjected to oxidative attack and analyzed for hydroperoxide buildup over time and at several temperatures. The results of the model compound study were consistent with the observations made for hydroperoxide buildup in the corresponding crospovidone types thereby supporting this hypothesis. (c) 2007 Wiley Periodicals, Inc.