Fast and accurate moisture analysis

Moisture analysis is a critical parameter during the manufacture of solid pharmaceutical bulk products. But oven methods can be slow and inaccurate because they tend to measure all volatiles rather than just water, while Karl Fischer techniques cannot be used with absolute accuracy because opening up the KF cell to the atmosphere during the addition of the solid allows moisture into the cell, which will be titrated giving spurious results.

To overcome these problems, Metrohm UK has launched the 774 oven sample processor in conjunction with the 756 coulometer. The sample is weighed into a vial and placed in an oven where it is heated. The moisture generated is transferred to the coulometer cell via a flow of dry nitrogen and the resulting water titrated using the Karl Fischer technique.

Typical analysis time is 3-5min and more than 30 samples can be measured automatically. The instrument can also measure bound and unbound moisture in the samples, using the temperature ramping function.