BS EN 14109:2003 – Fat and oil derivatives — Fatty Acid Methyl Esters (FAME) — Determination of potassium content by atomic absorption spectrometry
1 Scope
This European Standard specifies a method for the determination of potassium contents equal to or greater than 0,5 mg/kg. This method is applicable to fatty acid methyl esters intended for addition to mineral oils.
WARNING — The use of this method may involve hazardous equipment, materials and operations. This method does not purport to address to all of the safety problems associated with its use, but it is the responsibility of the user to search and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
2 Principle
The vegetable oil methyl ester sample is diluted with a xylene solution and a stabilizer. The potassium content in the sample is directly determined by flame atomic absorption spectrometry at the wavelength of 766,5 nm. The calibration solutions used are prepared from a potassium organometallic salt dissolved in a mixture of xylene and stabilizer.
The addition of a stabilizer to the calibration solutions is necessary in order to improve their storage (the low element contents are unstable) and the linearity of the calibration. WARNING — The ester sample shall be diluted at least ten times with xylene so that the comparison of the measurements of the sample solution and standards is valid.
NOTE Xylene can be replaced by cyclohexane or light petroleum in those laboratories which are not authorized to use aromatic solvents.
3 Reagents Use only reagents of recognized analytical grade, unless otherwise specified.
3.1 Recommendations for washing glassware The glassware used for the preparation of the solutions shall be washed at least twice with an approximate 5 mol/l solution of hydrochloric acid, rinsed with distilled water then dried in order to avoid potassium pollution.
3.2 Xylene, mixture of isomers. WARNING — Inflammable and noxious.
3.3 Stabilizer, supplied by CONOSTAN 1) . 3.4 Stabilizer solution in xylene, 100 g/l. Dilute in a 200 ml polypropylene volumetric flask, 20 g of stabilizer (3.3) with xylene. Store this solution in a polypropylene bottle. 3.5 Potassium, solution in oil, 5 000 mg/kg. Ready-to-use solution of a potassium organometallic salt in stock oil, having a certified titre 2) .
BS EN 14109:2003 – Fat and oil derivatives — Fatty Acid Methyl Esters (FAME) — Determination of potassium content by atomic absorption spectrometry