The Metrohm 852 dual Karl Fischer (KF) analyser can measure low-level moisture in finished biodiesel and higher levels in raw materials on the same instrument.
As of the 15 April 2008, all petrol and diesel that is sold at UK pumps had to include at least 2.5 per cent biofuels.
This obligation extended to 3.25 per cent in 2009.
The idea behind the Renewable Transport Fuels Obligation (RTFO) is to reduce climate change emissions from transport, which produced more than a quarter of overall greenhouse gases in the UK, by using renewable fuels instead of fossil fuels.
These renewable fuels have been added to fuel sold around the country.
Biodiesel is obtained from vegetable oils by esterification with methanol.
Biodiesel is a mixture of fatty acid methyl esters (Fame).
Minimum requirements for the quality of biodiesel were defined in 2003 by the European Standard DIN EN 14214.
The amount of water in biodiesel determines the calorific value and, above all, the shelf 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 long storage periods.
These can cause engine problems due to deposits, particularly with the injection system.
In order to avoid this, DIN EN 14214 limits the maximum water content to 500ppm.
The ISO standard 12937 petroleum products - determination of water - coulometric Karl Fischer titration method describes the Karl Fischer coulometric titration for determining the water content.
The range of KF Coulometers from Metrohm meet all the specifications demanded by the standard.
In most cases, the sample can be injected directly into the reaction solution with a syringe.
In order to improve the solubility of the samples, xylene (dimethyl benzene) is added to the KF reagent.
Annex B of the standard also describes the volumetric determination.
Using the 852 dual KF system from Metrohm means that one instrument can be used for low-level moisture determination finished products via the KF Coulometer cell (1ppm to 0.1 per cent), and the volumetric KF cell can be used for quick checks and in oils and raw materials with suspected higher levels of moisture (less than 0.1 per cent).
