How to Measure Water in Lubricating Oil in ppm with the KFT-50C

Can Karl Fischer titration measure water in oil?

Yes. ASTM D6304 describes coulometric Karl Fischer procedures for measuring water in lubricating oils and other petroleum products. The procedure still needs to match the sample and the laboratory’s method requirements.

When should I use direct injection or an oven?

Direct injection may suit an oil that is compatible with the KF reagent and dissolves adequately. For viscous, poorly soluble or matrix-sensitive samples, an oven method may be considered. Confirm that the oven and interface are included in the selected setup.

What does the KFT-50C offer?

The KFT-50C has 0.1 μg resolution and a 3 μg–200 mg absolute water measurement range. Listed functions include automatic titration, oven titration and oven blank measurement. The range is an amount of water, not a universal ppm detection limit.

How do I calculate water content in ppm?

For water content by mass, divide the measured water in μg by the sample mass in g. The numerical result is mg/kg, or ppm.

Example: 50 μg of water in a 1 g oil sample equals 50 ppm.

What helps keep results consistent?

Homogenize the oil, weigh the sample accurately, limit exposure to humid air, and monitor the reagent, blank and drift. For formal ASTM testing, verify the method and instrument configuration for the specific oil.