Use of Thermogravimetric Analysis for Moisture Determination in Difficult Lyophilized Biological Samples

Residual moisture is a key quality control parameter for lyophilized biologicals, as high moisture can correlate with poor stability. Coulometric Karl Fischer titration is the most widely used technology to determine residual water content; some chemicals are known to cause problems with Karl Fischer titration, but these chemicals do not usually occur in biologics. Three biological samples, of fibrinogen, heparin and Haemophilus influenza b polysaccharide, have caused particular issue in our hands by routine Karl Fischer analysis, illustrating different limitations with this method. The use of thermogravimetric analysis, with evolved gas mass spectrometric monitoring, is described here as a successful alternative for moisture analysis in these materials.