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Water content determination of biodiesel by Karl Fischer Titration according to EN ISO 12 937
Water content as a quality parameter The water content of biodiesel determines the calorific value and, above all, the storage life of the fuel. Biodiesel with a high water content has a clearly lower oxidation stability. The lower the oxidation stability, the greater the probability that oxidation products will be formed during a longer storage period. These could damage the motor, in particular the fuel injection system, by forming deposits. In order to avoid this, DIN EN 14 214 limits the water content of biodiesel to 500 ppm. (Read more)
Coulometric Karl Fischer Titration by Metrohm The EN ISO standard 12 937 «Petroleum products – Determination of water – Coulometric Karl Fischer titration method» describes the coulometric Karl Fischer titration for determining the water content. The 756 and 831 KF Coulometers from Metrohm easily meet all the specifications stipulated in the standard and are outstandingly suitable for this application. In most cases the sample can be injected directly into the reaction solution. In order to improve the solubility of the samples, xylene (dimethylbenzene) is added to the KF reagent. Get rid of side-reactions and contaminations Many biodiesel fuels contain additives that could participate in side-reactions during the direct coulometric Karl Fischer titration. In such cases Metrohm recommends that the biodiesel sample is not injected directly into the reaction solution. Instead the water contained in the biodiesel should be driven off in a Karl Fischer oven. The 860 KF Thermoprep oven is suitable for this. The water is driven off at 120 °C and transported to the titration cell of the KF Coulometer in a stream of carrier gas (dry air or inert gas). This process can be completely automated with the 774 Oven Sample Processor. An additional option is reagent exchange using an automated dosing device. The KF vessel does not have to be opened during this procedure. This means that no hazardous reagents have to be handled, which results in increased operator safety. Product information Coulometric KF Titration: KF Oven: |
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