BS ISO 20424:2019 pdf download – Fatty acid methyl esters (FAME) — Determination of sulfur content — Inductively coupled plasma optical emission spectrometry (ICP-OES) method
This document specifies a test method for inductively coupled plasma optical emission spectrometry(ICP-OES) for the detection of the sulfur content from 2 mg/kg to 21 mg/kg in fatty acid methylesters (FAME).
NOTE 1 For the purposes of this document, the term “% (m/m)” is used to represent the mass fraction (1) ofthe material.
NOTE2 The method can also be used for the determination of concentrations outside the given limits. Theprecision statement, however, is only valid for the concentration range given in the scope.
NOTE3 The method described in the document was tested with FAME derived from soybean oil and beeftallow.FAME derived from other feedstock, in particular aged oils, may behave different due to the differentnature of sulfur compounds.
2Normative references
The following documents are referred to in the text in such a way that some or all of their contentconstitutes requirements of this document. For dated references, only the edition cited applies.Forundated references, the latest edition of the referenced document (including any amendments) applies.ISo 3170, Petroleum liquids —Manual sampling
ISO 3171, Petroleum liquids — Automatic pipeline sampling
ISO 12185,Crude petroleum and petroleum products — Determination of density — OscillatingU-tube method
3Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
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An exactly weighed test portion is diluted with kerosene to allow the proper introduction of the aerosolinto the plasma.The resulting solution is directly injected into the plasma of the ICP-OES spectrometer.
7 sampling
Samples shall be taken as described in ISo 3170 or lSO 3171.
8Preparation of stock solution and calibration solution8.1Stock solution
Sulfur solution with a concentration of 50 mg/kg:add to an appropriate conical flask(6.4) approximately3,0 g of the standard sulfur solution (5.3), fill up to 30 g with diluent(5.1).
Weigh the masses with an accuracy of 0,000 1 g and homogenize the solution.Calculate the exactconcentration of this solution, which shall be used to prepare the calibration solutions.
lt is also permitted to prepare the dilution on volumetric basis. In this case, use appropriate pipettes(6.5) to transfer the volumes.In this case the concentration is expressed as mass/volume.
Other concentrations and quantities can be used for the stock solution but the precision data inClause 10 were obtained from analysis with the given concentration above.
8.2Preparation of the calibration solutions
The calibration solutions are prepared from an organic sulfur compound which is commerciallyavailable. The sulfur compound is diluted in a mixture of diluent (6.1) and base oil (6.2). The additionof the base oil has the objective to reduce the differences in viscosity between the samples and thecalibration solutions.
8.2.1 Blank solution for sulfur
Prepare an adequate amount of a solution of 10 % (m/m) low viscosity oil (5.2) in the solvent (5.1).WARNING — When using other oils (see Note to 5.2) the concentration of low viscosity oil in theblank solution shall be calculated as described in Annex A.
8.2.2Calibration sample set
Table 1 shows the recommended calibration set for sulfur (0,0 mg/kg,1,0 mg/kg, 2,5 mg/kg,5,0 mg/kgand 10 mg/kg).
Weigh the masses with an accuracy of 0,000 1 g into the flask and fill up to the given amount with blanksolution (8.2.1).Stir the samples until the homogenization is complete.
Calculate the exact concentrations of the calibration solutions for given in Table 1.
When the concentrations of the solutions are expressed in mass/volume percentages (8.1), thecalibration solutions shall be expressed in the same way.
For each calibration, freshly prepared calibration samples shall be used.
9 Calibration
Run the measurements of the calibration solutions, with at least three readings of each one.
Calculate the arithmetic average of the three measurements, for each solution. From these averages,associate the intensity values to the respective concentration values for the calibration solutions,expressed in milligrams per kilogram, using a linear regression to obtain the calibration curve.
In the case of using a mass/volume relationship, express the concentration values for the calibration solutions in mg/l.
NOTE In the ILS, each calibration sample was measured three times.BS ISO 20424 pdf download.