Validation of the dew point chilled mirror method for the measurement of water activity on solid pharmaceutical products, testing the effect of different temperatures, sample preparations, and environment exposure times

Abstract

Objective The objective of this investigation is to validate the dew point chilled mirror method for quantifying water activity in tablets and capsules, evaluating the effects of different temperatures, sample preparations, and local environmental exposure times. Key findings The validation of an acute and precise water activity measurement method has become an important goal in the pharmaceutical industry, because it may help to predict the microbiological bioburden on solid products, since most xerophilic and osmophilic microorganisms are unable to grow at water activity levels below 0.60, to safely reduce the frequency of routine microbiological analysis using conventional methods. For all the solid samples tested, a suitability of method was carried out, considering the sample preparation, environmental exposure times, and different measuring temperatures. Following USP guidelines, essential parameters such as precision (SD < 0.5), accuracy (% recovery in the 95%–105% range), linearity (R2 > 0.99), ruggedness (ANOVA, P < .05), robustness, operative range (aw 0.17–1), limits of detection (aw = 0.17), and limit of quantification (aw = 0.25) were met by the dew point methodology. Conclusion The dew point chilled mirror method was proven to yield accurate, precise, and robust data, making it an outstanding methodology to be implemented in the pharmaceutical industry for measuring the water activity status in tablets and capsules as a direct assessment of the microbial burden.