Of the multiple techniques employed for moisture content determination, glow discharge mass spectrometry (GDMS) stands apart as a technique that permits direct measurement of moisture within a solid material.
In GDMS, a plasma is ignited between an anode and a cathode in an inert gas atmosphere. The sample to be analyzed is placed on the cathode, and the plasma erodes the sample’s surface. As the sample material is sputtered away, it is ionized and enters the mass spectrometer. The mass spectrometer separates the ions by their mass-to-charge ratio, and the abundance of each ion is measured. The moisture content of the sample can then be determined by measuring the abundance of the H2O+ ion.
GDMS is a powerful technique that can be used to measure moisture content in a wide variety of materials. It is a relatively new technique, but it has already been shown to be a valuable tool for researchers and industrial scientists.