Certification of the reference material of water content in water saturated 1-octanol by Karl Fischer coulometry,Karl Fischer volumetry and quantitative nuclear magnetic resonance

Certified reference materials (CRMs) of water content are widely used in the calibration and validation of Karl Fischer coulometry and volumetry. In this study, the water content of the water saturated 1-octanol (WSO) CRM was certified by Karl Fischer coulometry, volumetry and quantitative nuclear magnetic resonance (Q NMR). The water content recovery by coulometry was 99.76% with a diaphragm-less electrode and Coulomat AG anolyte. The relative bias between the coulometry and volumetry results was 0.06%. In Q NMR, the water content of WSO is traceable to the International System (SI) of units through the purity of internal standard. The relative bias of water content in WSO between Q NMR and volumetry was 0.50%. The consistency of results for these three independent methods improves the accuracy of the certification of the RM. The certified water content of the WSO CRM was 4.76% with an expanded uncertainty of 0.09%.     

Vaporisation coulometric Karl Fischer titration: A perfect tool for water content determination of difficult matrix reference materials

Volumetric Karl Fischer titration (V-KFT) is the reference method to determine the water content in a whole range of organic and inorganic matrices. The method has several important drawbacks e.g. a high solvent consumption and a rather large measurement uncertainty when determining the water content in reference and candidate reference materials containing starch (e.g. maize, toasted bread, etc.). It is also labour intensive for routine measurements. In order to overcome these disadvantages, a relatively new method of coulometric Karl Fischer titration, equipped with a fully automated oven system, has been established and optimised.