Mobile Navigation

Chemical Engineering

View Comments PDF

Focus on Analyzers

| By Gerald Ondrey

Technique approved for water content in petrochemicals

Since they can be poorly soluble, viscous and often highly contaminated, determining the water content in lubricants, hydraulic oils and other petrochemical samples can challenging. Addressing these challenges, ASTM has revised standard method D6304. The revised standard now includes the Karl Fischer (KF) oven technique. Users can conveniently and accurately determine water content in up to 35 samples automatically by coulometric Karl Fischer titration (photo). Using the KF oven technique, the oil matrix does not come into contact with the titration cell at all. Instead, the samples are introduced in single-use vials, which are put on the rack of an oven sample processor. Heating vial by vial, the water contained in the samples is evaporated. A constant stream of an inert carrier gas is used to bring the water fraction into the titration cell, where it is determined coulometrically. The sample matrix stays in the vials, which are disposed of after the titration. The benefits of this method are considerable, including: no contamination of the KF titration cell; no matrix interferences; less solvents needed; and better reproducibility of results. — Metrohm AG, Herisau, Switzerland