Product category:
Liquid Analysis: Titration, HPLC, IC
News Release from: Metrohm UK | Subject: Bioethanol QC measurement
Edited by the Processingtalk Editorial
Team on 19 February 2008
Quality control of bioethanol
The EU standard for bioethanol is EN 15376: under this standard there are a number of parameters that the bioethanol must meet
These include a minimum percentage of pure bioethanol and maximum water, acidity, chloride and sulphur contents A too high water content and have a negative effect on the fuel quality and can damage the fuel system of the vehicle
This article was originally published on Processingtalk on 2 Jul 2008 at 8.00am (UK)
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With the aim of avoiding these problems, the manufacturers of biofuels and motor vehicles have developed quality standards in which testing methods and quality parameters for biofuels are defined.
Metrohm provide analytical equipment for the quality control of bioethanol, namely, moisture content, acidity, chloride and sulphur content.
* Water content determination in bioethanol by Karl Fischer titration.
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The problem is the bioethanol affinity with water - when petrol containing bioethanol comes in contact with water, the latter leaches out the ethanol and forms an aqueous layer at the bottom of a tank.
Motor vehicles taking on this fuel can stop a short distance from the garage Bioethanol is mixed with gasoline in various ratios in order to reduce both the demand for gasoline and environmental pollution.
The gasoline-alcohol blend is known in the USA as gasohol and in Brazil as Gasolina Tipo C.
In the USA the mixtures E10 and E85, which contain 10% and 85% bioethanol respectively, are widespread.
In Brazil the bioethanol content of most blends lies between 21% and 23%.
The ASTM standard E 1064 Standard Test Method for Water in Organic Liquids by Metrohm 831 Coulometric Karl Fischer Titration describes the coulometric Karl Fischer titration for determining the water content.
For a water content >2% the recommended test method is volumetric titration as per ASTM E 203.
The 870 volumetric KF titrator from Metrohm meet all the specifications required by the standard and is therefore extremely suitable for this application.
* pH measurement.
The pH value is an important quality criterion for bioethanol.
A combined pH glass electrode with ground-joint diaphragm is recommended for measuring the pH in organic solvents.
Because of the expected low conductivity of the sample, the electrode should be particularly well shielded in order to suppress electrostatic influences.
The Solvotrode with separable ground-joint diaphragm is particularly suitable for measuring the pH of biofuels.
The pH meter used for the measurement should possess the following GLP functions, among others: (1) Three-point calibration with automatic buffer recognition; (2) Temperature compensation; (3) Calibration data monitoring; (4) Automatic measured value recording; (5) Result memory with identification.
The pH meter 827 pH lab for laboratory use and the handy, battery-operated 826 pH mobile offer all these functions with extremely comfortable operation.
* Chloride in bioethanol.
The chloride content in bioethanol fuels is the subject of ASTM D 512.
Determinations can be carried out by mercurimetric or argentometric titration or by direct titration with a Cl-sensitive electrode.
Argentometric determination (with silver nitrate) is the method of choice because of its environmental advantages and very high precision.
A defined volume of the sample is pipetted into the titration cell, treated with 5 mL of 2M nitric acid and then titrated against 0.01M silver nitrate solution.
* Sulphate in bioethanol.
A proven method for sulphate determination is potentiometric titration with lead nitrate using a Pb-sensitive electrode.
The pH of the sample is adjusted to pH 3...5 with perchloric acid and the sulphate is then precipitated out with lead nitrate solution.
The Pb-selective electrode detects the first excess of lead ions at the equivalence point.
The wide range of potentiometric applications for bioethanol requires a highly flexible titrator.
No other titration system offers more flexibility than the Metrohm Titrando.
Very importantly, the determinations can be carried out with excellent reproducibility due to the range of high specification electrodes provided by Metrohm.
For the pH measurement and acidity titration the well shielded Solvotrode (6.0229.100) non-aqueous electrode is used; for the chloride determination, the low maintenance Silver Titrode (6.0431.100) is used and for the sulphate determination, the Pb-selective ion Selective Electrode is used.
Metrohm UK has a large network of service and support personnel throughout the UK including dedicated training staff for each product and an application/support laboratory.
They have a lot of expertise in the measurement of biofuels and offer Application Bulletins and periodic seminars. Request a free brochure from Metrohm UK ...
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