Hooton Jennifer C, German Caroline S, Allen Stephanie, Davies Martyn C, Roberts Clive J, Tendler Saul J B, Williams Philip M
Laboratory of Biophysics and Surface Analysis, School of Pharmacy, University of Nottingham, NG7 2RD, United Kingdom.
Pharm Res. 2004 Jun;21(6):953-61. doi: 10.1023/b:pham.0000029283.47643.9c.
To understand differences in particle adhesion observed with increasing humidity between samples of salbutamol sulfate prepared by two different methods.
Atomic force microscopy (AFM) force measurements were performed as a function of humidity (<10% to 65% RH) using two systems. The first system used clean AFM tips against compressed disks of micronized and solution enhanced dispersion by supercritical fluid (SEDS) salbutamol. The second system involved particles of both salbutamol samples mounted onto the apexes of AFM cantilevers, and force measurements being performed against a highly orientated pyrolytic graphite (HOPG) substrate. Following these measurements, the contact asperities of the tips were characterized.
The first system showed a maximum in the observed adhesion at 22% relative humidity (RH) for the SEDS salbutamol compared to 44% RH for the micronized salbutamol. The second system showed a mix of peaks and continual increases in adhesion with humidity. The predicted Johnson-Kendall-Roberts forces were calculated and divided by the actual forces in order to produce a ratio.
By relating the nature of the asperities to the force measurements, we propose a model in which adhesion scenarios range from single asperity nanometer-scale contact in which peaks in the adhesion were observed, to multiasperity contact where a continuous increase in adhesion was seen with humidity.
了解两种不同方法制备的硫酸沙丁胺醇样品在湿度增加时观察到的颗粒附着力差异。
使用两个系统进行原子力显微镜（AFM）力测量，测量结果作为湿度（<10%至65%相对湿度）的函数。第一个系统使用清洁的AFM针尖接触超临界流体增强分散法（SEDS）制备的微粉化硫酸沙丁胺醇和溶液的压缩盘。第二个系统是将两种沙丁胺醇样品的颗粒安装在AFM悬臂的尖端，并对高度取向热解石墨（HOPG）基底进行力测量。在这些测量之后，对针尖的接触粗糙情况进行了表征。
第一个系统显示，SEDS硫酸沙丁胺醇在相对湿度为22%时观察到的附着力最大，而微粉化硫酸沙丁胺醇在相对湿度为44%时附着力最大。第二个系统显示出附着力随湿度呈现出峰值和持续增加的混合情况。计算预测的约翰逊-肯德尔-罗伯茨力，并将其除以实际力以得出一个比率。
通过将粗糙情况的性质与力测量相关联，我们提出了一个模型，其中附着力情况范围从观察到附着力峰值的单粗糙纳米级接触，到随着湿度增加附着力持续增加的多粗糙接触。
