ISO 2561:2012 pdf download – Plastics – Determination of residual styrene monomer in polystyrene (PS) and impact-resistant polystyrene (PS- I) by gas chromatography

03-05-2022 comment

ISO 2561:2012 pdf download – Plastics – Determination of residual styrene monomer in polystyrene (PS) and impact-resistant polystyrene (PS- I) by gas chromatography
8.3 Preparation of sample solution for method A
Weigh 0,5 g of sample, to the nearest 1 mg, into a volumetric flask (6.6) having a volume between 25 ml and 100 ml. Using a syringe or a pipette, add 20 ml of the internal standard solution prepared in 8.2. Then stopper tightly and mix until dissolved.
8.4 Preparation of sample solution for method B
Weigh 0,5 g of sample, to the nearest 1 mg, into a volumetric flask (6.6) having a volume betwen 50 ml and 100 ml. Using either a syringe or a pipette, add 20 ml of the internal standard solution prepared in 8.2. Then stopper tightly and dissolve the sample (shake well, if necessary). After completely dissolving the sample, add 10 ml of precipitator (5.3) with a pipette. After vigorous shaking, allow the precipitate to settle. The supernatant solution is used for injection into the gas chromatograph using a micro-syringe (6.4).
8.5.1 General
The range of concentrations which can be analysed by gas chromatography using the internal-standard method is determined by the amounts of measured styrene and other aromatic hydrocarbons to be measured and the dilutions (see Table 1). A series of calibration solutions are prepared for each aromatic hydrocarbon to be analysed. The solutions are kept for injection into the gas chromatograph.
8.5.2 Calibration solutions for method
A Weigh, to the nearest 0,1 mg, into separate volumetric flasks (6.6) (for the volume of the flasks, refer to Annex B) at least four of the amounts indicated in Table 1 of styrene and, if necessary, other aromatic hydrocarbons such as ethylbenzene, cumene or α-methylstyrene. Add internal-standard solution (8.2) to each flask, dissolve and make up to the mark with internal-standard solution.
8.5.3 Calibration solutions for method B
Measure to the nearest 1 ml, 1 000 ml internal-standard solution (8.2) into a 2 000 ml flask. Then add 500 ml of precipitator (5.3), stopper tightly and mix well (this solution is hereafter called the precipitator solution). Weigh, to the nearest 0,1 mg, into separate 1 000 ml volumetric flasks (6.6) at least four of the amounts indicated in Table 1 of styrene and, if necessary, other aromatic hydrocarbons such as ethylbenzene, cumene or α-methylstyrene. Add the precipitator solution to each flask, dissolve and make up to the mark with precipitator solution. NOTE For safety and economic reasons, there has been the case in which a smaller size glass container has been used instead of the 2 000 ml flask.
8.6.1 Gas-chromatograph operating conditions
Select the gas-chromatographic conditions, solvent and internal standard to give sufficient separation of styrene and the other eluted materials. If it is difficult to separate the peak corresponding to the internal standard from that corresponding to a target component, except styrene, use the standard addition method for analysis. If it is difficult to separate the peak corresponding to the internal standard from those due to impurities, increase the concentration of the internal standard to a level at which the peaks due to impurities become negligible. Prepare a chromatogram satisfying the following requirements. The resolution R e between the peaks corresponding to styrene, the internal standard and any other aromatic hydrocarbons (such as ethylbenzene, cumene or α -methylstyrene) and the peaks corresponding to the target components appearing just before or just after the former peaks shall be more than 1,0 and preferably 1,5 if possible.

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