Nokhodchi A, Ford J L, Rubinstein M H
Pharmaceutical Technology and Drug Delivery Group, School of Pharmacy and Chemistry, Liverpool John Moores University, UK.
J Pharm Sci. 1997 May;86(5):608-15. doi: 10.1021/js960279a.
The moisture sorption and desorption profiles of four different viscosity grades of (hydroxypropyl)methylcellulose (HPMC) 2208 (HPMC K100, HPMC K4M, HPMC K15M, and HPMC K100M) of different particle size fractions were analyzed according to the Young and Nelson equations. These equations describe three locations of the sorbed moisture: monolayer adsorption, externally adsorbed moisture, and internally absorbed moisture. The effects of particle size and viscosity grade of HPMC on the three locations of moisture showed that an increase in particle size generally resulted in a reduction in the amount of internal absorption and an increase in the amount of external adsorption. These changes were more apparent for HPMC K100 and HPMC K4M than for the higher viscosity grades. The lowest values of internally absorbed moisture were obtained for HPMC K100M. Changes in tensile strengths, mean yield pressures, and elastic recoveries of HPMC K4M tablets were explained in terms of the changes produced in the internally absorbed moisture and the externally adsorbed moisture. The amounts of nonfreezing and freezing water in samples exposed to moisture were determined from melting endotherms obtained by differential scanning calorimetry. Increases in the water:HPMC ratio resulted in increases in the enthalpies of water melting for the four viscosity grades of HPMC for the < 45 and 250-350 microns particle size fractions. The amount of nonfreezable water was unaffected by change in viscosity grade or particle size.
根据扬氏方程和纳尔逊方程，分析了不同粒度级分的四种不同粘度等级的（羟丙基）甲基纤维素（HPMC）2208（HPMC K100、HPMC K4M、HPMC K15M和HPMC K100M）的吸湿和解吸曲线。这些方程描述了吸附水分的三个位置：单层吸附、外部吸附水分和内部吸收水分。HPMC的粒度和粘度等级对水分的这三个位置的影响表明，粒度增加通常会导致内部吸收量减少和外部吸附量增加。这些变化在HPMC K100和HPMC K4M中比在较高粘度等级中更明显。HPMC K100M的内部吸收水分值最低。根据内部吸收水分和外部吸附水分产生的变化，解释了HPMC K4M片剂的拉伸强度、平均屈服压力和弹性回复率的变化。通过差示扫描量热法获得的熔融吸热曲线，测定了暴露于水分的样品中的非冻结水和冻结水的含量。对于粒度小于45微米和250 - 350微米的四种粘度等级的HPMC，水与HPMC的比例增加导致水熔化焓增加。不可冻结水的量不受粘度等级或粒度变化的影响。
