Shpotyuk O, Bujňáková Z, Baláž P, Ingram A, Shpotyuk Y
Institute of Physics of Jan Dlugosz University in Czestochowa, 13/15, Al. Armii Krajowej, Czestochowa 42200, Poland; Vlokh Institute of Physical Optics, 23, Dragomanov Str., Lviv 79005, Ukraine.
Institute of Geotechnics of Slovak Academy of Sciences, 45, Watsonova Str., Košice 04001, Slovakia.
J Pharm Biomed Anal. 2016 Jan 5;117:419-25. doi: 10.1016/j.jpba.2015.09.030. Epub 2015 Sep 30.
Positron annihilation lifetime spectroscopy was applied to characterize free-volume structure of polyvinylpyrrolidone used as nonionic stabilizer in the production of many nanocomposite pharmaceuticals. The polymer samples with an average molecular weight of 40,000 g mol(-1) were pelletized in a single-punch tableting machine under an applied pressure of 0.7 GPa. Strong mixing in channels of positron and positronium trapping were revealed in the polyvinylpyrrolidone pellets. The positron lifetime spectra accumulated under normal measuring statistics were analysed in terms of unconstrained three- and four-term decomposition, the latter being also realized under fixed 0.125 ns lifetime proper to para-positronium self-annihilation in a vacuum. It was shown that average positron lifetime extracted from each decomposition was primary defined by long-lived ortho-positronium component. The positron lifetime spectra treated within unconstrained three-term fitting were in obvious preference, giving third positron lifetime dominated by ortho-positronium pick-off annihilation in a polymer matrix. This fitting procedure was most meaningful, when analysing expected positron trapping sites in polyvinylpyrrolidone-stabilized nanocomposite pharmaceuticals.
正电子湮没寿命谱被用于表征在许多纳米复合药物生产中用作非离子稳定剂的聚乙烯吡咯烷酮的自由体积结构。平均分子量为40,000 g mol(-1)的聚合物样品在单冲压片机中于0.7 GPa的外加压力下压片。在聚乙烯吡咯烷酮颗粒中揭示了正电子和正电子素捕获通道中的强烈混合。根据无约束的三项和四项分解对在正常测量统计下积累的正电子寿命谱进行了分析，后者也是在真空中与仲正电子素自湮没适当的固定0.125 ns寿命下实现的。结果表明，从每次分解中提取的平均正电子寿命主要由长寿命的正电子素成分决定。在无约束三项拟合中处理的正电子寿命谱明显更受青睐，给出了由聚合物基质中的正电子素拾取湮没主导的第三正电子寿命。在分析聚乙烯吡咯烷酮稳定的纳米复合药物中预期的正电子捕获位点时，这种拟合程序最有意义。
