In October 2017 the CORESTA Tobacco and Tobacco Products Analytes Sub-Group (TTPA) initiated a proficiency study for the determination of water activity in smokeless tobacco products, ground tobacco, cigarette filler, and cigar filler. The intent of the study was to assess the capability of the participating laboratories to measure water activity and to support laboratory accreditation.

Participating laboratories used water activity meters equipped with one or more of the following sensor types: tunable diode laser (TDL), chilled mirror, or capacitance hygrometer. Water activity measured using a TDL sensor provided consistent results from one lab to another for all products. The chilled mirror or capacitance sensors can be affected by volatile constituents found in certain tobacco products.

The TTPA Sub-Group recommended that a future collaborative study be conducted focusing on the use of water activity meters equipped with TDL sensors and that a CRM be drafted.