EN 14538 Fat and oil derivatives - Fatty acid methyl ester (FAME) - Determination of Ca, K, Mg and Na content by optical emission spectral analysis with inductively coupled plasma (ICP OES)
4 Chemicals
Unless otherwise stated, only chemicals of recognized analytical quality shall be used.
4.1 Paraffin oil, low viscosity, Pharmacopeia (EUPHARM EP5), e.g. Merck 107174
4.2 Kerosene, boiling range included between 150 °C and 325 °C, e.g. Aldrich 32.946-0
4.3 Element Standard solutions, dissolved in oil, 500 mg/kg per element. These are available as single element standards, like e.g. Merck 115053 (Ca), 115057 (Mg), 115054 (K) and 115058 (Na), or also at least partially as multi-element standards, (e.g. Spex).
4.4 Argon, with minimum purity w (Ar) = 99.996 % (V/V)
5 Apparatus
Commercial laboratory and glass equipment, in conjunction with the following:
5.1 100 ml bottles with cap, preferably made of Polyethylene (PE), brown
5.2 250 ml bottles with cap, preferably made of Polyethylene (PE), brown
NOTE In order to minimize pollution of the solutions, it is recommended to prepare all the determination solutions in polyethylene bottles. Do not touch surfaces that could come in contact with working solutions. New glassware should be filled with sodium-free water and to be left for two days before use to remove soluble sodium. This is especially important when this procedure is used for the determination of sodium and/or potassium.
5.3 ICP OES spectrometer
5.3.1 General
ICP OES spectrometers (simultaneous or sequence devices) equipped for the analysis of organic liquids are suitable. Both setup and operation of the ICP OES spectrometer shall be done in accordance with operating instructions of the manufacturer.
NOTE 1 Depending on the type and construction of the ICP OES spectrometer (radial, axial, detectors sensitivity, etc.), it may sometimes be necessary to select wavelengths different from those listed here. In such cases, a separate optimization of the instrument parameters and possibly also of the optimal dilution (see 9.1) is strongly recommended.
NOTE 2 The calibration solution with an element content of 1 mg/kg (7.4) can be used to check the correct instrument performance.
5.3.2 Recommended wavelengths for Calcium and Magnesium
The following wavelengths are recommended for the analysis, because they have been found to exhibit minimal interference in daily practice:
Calcium 422,673 nm;
Magnesium 279,553 nm.
Depending on the ICP OES spectrometer's optical configuration also other specific wavelengths can be selected, like 317,933 nm, 393,366 nm or 396,847 nm for Calcium and 285,213 nm for Magnesium, if these lines are free from interferences (see also Note 1 under 5.3.1).
5.3.3 Recommended wavelengths for Sodium and Potassium
The following wavelengths are recommended for the analysis, because they have been found to exhibit minimal interference in daily practice (see also Note 1 under 5.3.1).
Sodium 588,995 nm or 589,592 nm;
Potassium 769,897 nm or 766,490 nm.
