Evaluation of Functional Characteristics of Lactose by Inverse Gas Chromatography

The work was focused on the analysis of different batches of the common pharmaceutical excipient lactose using inverse gas chromatography (IGC). Several batches of amorphous (spray dried) and crystalline form of lactose were studied. Surface properties represented by the surface energy and specific (acid-base) interactions between probes and analyzed samples shows batch variations and significant differences between manufacturers and technological processes. The second part of this work was focused on effect of relative humidity and temperature on stability of lactose. The variations of surface energy and specific interactions over time were studied. The changes in surface properties of two batches of lactose-amorphous and crystalline caused by higher relative humidity were measured by IGC. From measured values are obvious different chemical and physical properties of both lactose forms. Negative effect of higher temperature and air humidity lead to changes in surface energy and mainly rapid changes of electron–acceptor and electron-donor surface sites. Lactose monohydrate shows dramatic decrease in the surface energy and in the strength of electron-accepting sites on the contrary of spray dried where the acidity of surface increased.