ISO 14714 pdf download.Essential oils and aromatic extracts — Determination of residual benzene content
1 Scope
This International Standard describes a method for determining the residual traces of benzene in essential oils and aromatic extracts, using static headspace gas chromatography. It applies to residual contents of around 1 0 31 0 26 (1 0 ppm) in the analysed product.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 356, Essential oils — Preparation of test samples. ISO 7609, Essential oils — Analysis by gas chromatography on capillary columns — General method.
3 Principle
Analysis by gas chromatography of the static headspace on a capillary column, either by flame ionization detector or by detection by means of mass spectrometry. Determination of residual benzene content using external standard method (by calibration).
4 Reagents
4.1 Reference substance: benzene, of minimum purity 99 %, as determined by gas chromatography. 4.2 Diethyl phthalate, free from any traces of benzene, to be verified under test conditions.
5 Apparatus
5.1 Chromatograph, recorder and integrator See ISO 7609. 5.2 Capillary column, with the following characteristics: – length: 30 m to 60 m; – internal diameter: 0,20 mm to 0,5 mm; – stationary phase: methyl silicone type is recommended. 5.3 Flame ionization detector or mass detector 5.4 Headspace sampling device, for the injection of headspace vapours, comprising either 5.4.1 or 5.4.2. 5.4.1 Gas syringe system (manual), with leaktight locks. 5.4.2 Automatic injector equipment
7 Operating conditions
7.1 Chromatographic operating conditions 7.1.1 Injector temperature shall be 1 50 °C. 7.1.2 Oven temperature shall be maintained constant at between 40 °C and 60 °C for 1 5 min, followed by rapid temperature programming to elute any less volatile product. 7.1.3 Temperature of flame ionization detector shall be between 200 °C and 250 °C. 7.1.4 For flow rate of carrier gas and auxiliary gases, see ISO 7609. 7.2 Operating conditions for headspace sampling device 7.2.1 The sample shall be thermostatted at a temperature of between 70 °C and 75 °C. 7.2.2 This temperature shall be maintained for a minimum of 30 min.
8 Quantitative analysis method
8.1 External calibration curve 8.1.1 Preparation of standard solutions Weighing to the nearest 0,0001 g, prepare a stock solution of benzene in the diethyl phthalate (4.2) containing a mass fraction of benzene of 1 %. By means of successive gravimetric dilutions, prepare a range of standard 8.1.2 Injection of vapour phase of standard solutions The test specimen is placed in the headspace sampling flask (5.4) and shall be:  identical in all cases (calibration and quantitative analysis); – between one-tenth and one-half of the total volume of the flask. 8.1.3 Plotting the external calibration curve Record the areas of the benzene markers obtained for the successive injections into the headspace of the standard solutions. Plot the curve of the areas as a function of the concentrations. 8.1.4 Validation of the external calibration curve Before each analysis, validate the calibration curve by preparing, by weighing afresh, a benzene solution containing a mass fraction of between 0 and 25 3 1 0 26 (25 ppm). Injection of the vapour phase of this validation solution under the same conditions as used for calibration shall give a point which is on the calibration curve. If not, it is necessary to carry out a complete determination of a new calibration curve, with new weighing and new validation.