Removing the challenges of blank values and side reactions using the new Aquamax KF Pro Oil for ppm water in oil and fuels

There are a number of problems which have been identified when titrating oil and fuel samples using direct injection coupled with the coulometric Karl Fischer method. Additives used in lubricating oils and fuels, plus mercaptans in crude oils, are known to cause detrimental side reactions when the sample is injected directly into the titration solvent, primarily resulting in lack of reproducibility and a breakdown of the solvents.

To combat this problem, an external oven is used. The industry standard is a “headspace” oven, in which the sample is heated in a sealed vial until the water is extracted and carried directly into the titration vessel via a dry carrier gas, usually nitrogen. Upon entering the vessel, the sample is titrated, without the addition of any additives or mercaptans.

Although the headspace technique combats the issues of side reactions, it is not without its own problems. A blank value for each empty vial is required. Quite simply, this is a measurement of the atmospheric moisture or water inside the empty vial. Depending on the size and storage conditions, a blank vial could contain anywhere between 30-80 micrograms of water. The blank value of each vial will change throughout the day, regular blank value checks are recommended. When using a detection technique as sensitive as coulometric Karl Fischer titration, these blank values simply do not provide true ppm accuracy.

Take insulating oils for example, these have a water content of approximately 10ppm. Having a blank value which could be 3-8 times greater means you simply cannot rely on the result, and in many cases, instruments will display 0ppm as they cannot distinguish the true water content over the blank value content as the differential value is so small.

Additionally, a problem associated with an external carrier gas is the fact that the system is regarded as “open”, meaning the methanol in the Karl Fischer solvent quickly evaporates causing immediate instability.

ECH Elektrochemie Halle have addressed all the above issues with the closed loop oil evaporator, which is available on the new Aquamax KF Pro Oil system.

Tom Gallant, of ECH Elektrochemie Halle explains how the Aquamax KF Pro Oil is the leading technology in the titration industry: “The oven is connected directly to the titration vessel via a pump and tubing which circulates the carrier gas in a “closed loop”. The sample is injected from your sample syringe directly into the oven, removing the requirement of a blank value, whilst containing the methanol meaning we can analyse over 1000+ samples without changing the reagent….All this, and just like the Headspace technique, all side reactions are eliminated. The Aquamax KF Pro Oil truly combines the best of both methods.

The ECH closed loop principle on the Aquamax KF Pro Oil ensures true 1ppm accuracy, the longest reagent life and with ECH’s patented temperature gradient program you can clearly identify the free water and the chemically bonded water in your sample, creating a true research and development tool allowing you to know everything about the water in your fuels and oils.”