Determination of formic acid content in industrial glacial acetic acid by gas chromatography
Glacial acetic acid for industrial use-Determination of formic acid content-Gas chromatographic method
1 Scope This standard specifies the gas chromatography method for the determination of formic acid content in industrial glacial acetic acid.
This standard applies to the determination of formic acid content in industrial glacial acetic acid products.
2 Method summary The components of industrial glacial acetic acid were separated on sebacic acid / GDX 103 column, detected by thermal conductivity detector, ethyl acetate was used as internal standard, and quantified by internal standard method.
3 Reagents and materials
3.1 Hydrogen: purity 99.9% V / V.
3.2 Reagent
3.2.1 Formic acid: chromatographically pure.
3.2.2 Ethyl acetate: chromatographically pure.
3.2.3 Glacial acetic acid: pure grade.
3.2.4 Potassium permanganate: analytically pure.
3.2.5 Absolute ethanol: analytically pure.
3.2.6 Fixative: Sebacic acid.
3.2.7 Carrier: GDX103, aperture 0.18 ～ 0.25mm.
4 Instruments
4.1 Gas chromatograph.
4.2 Detector: Thermal conductivity detector.
4.3 Recorder: 1mV full scale, or chromatographic data processor.
4.4 Column
4.4.1 Column tube: 1.5 ～ 2.0m, stainless steel tube or borosilicate glass tube with inner diameter of 2 ～ 3mm.
4.4.2 Filler fixing solution: carrier = 7: 100.
Method of applying fixative solution: Weigh 0.28g sebacic acid, place it in a 200mL beaker, add about 23mL of absolute ethanol to dissolve, then add 4.0g carrier to completely immerse the carrier, stir a little, and slowly evaporate the solution on the water bath To dry, and then moved to 100 ℃ electric thermostat drying oven for 2h.
4.4.3 Packing method Put the glass wool at the outlet end (connected to the detector end) of the chromatographic column, connect to the vacuum pump, and connect the funnel to the other end. Turn on the vacuum pump, install the stationary phase under gentle vibration, fill evenly and tightly. The filling amount is about 2g. Then plug it with glass wool.
4.4.4 Chromatographic column aging Install the packed gas chromatographic column in the chromatograph column box, the outlet is disconnected from the detector, and aging at 120 ℃ for more than 8h until the baseline is stable.
4.5 Micro glass syringe of the injector: capacity 10μL, minimum graduation 0.2μL.
5 Analysis steps
5.1 Chromatograph operating conditions Adjust the instrument according to the following conditions, allowing appropriate changes according to different instruments and obtaining appropriate resolution.
5.1.1 Temperature of vaporization chamber: 150 ℃.
5.1.2 Temperature of testing room: 150 ℃.
5.1.3 Oven temperature: 110 ℃.
5.1.4 Bridge current: 135mA.
5.1.5 Carrier gas flow rate: 50mL / min.
5.2 Quantitative method internal standard method.
5.2.1 Preparation of standard samples
5.2.1.1 Glacial acetic acid without formic acid: Add 1g of potassium permanganate to 1000mL of glacial acetic acid reagent to decompose formic acid, then distill to remove formic acid.
5.2.1.2 Preparation of standard samples: Pipette 20mL of glacial acetic acid without formic acid into clean and dry 4 to 5 milled glass bottles, add the formic acid standard sample and ethyl acetate standard sample with a micro syringe (add more than formic acid) , So that the peak areas of the two components are close to each other), weighed by incremental method, accurate to 0.0002g, and mix. Prepared during measurement.
5.2.2 Determination of correction factor After the operating conditions of the instrument are stable, draw 5μ respectively, each standard sample is injected, and the first needle saturates the column. After the peak is completed, the correction factor is calculated. The measurement result is based on the 95% confidence level, and the average value is calculated. The correction factor should be calibrated regularly.
5.2.3 Calculation of correction factor The relative correction factor fi of formic acid is calculated according to formula (1):
As • mi
fi = ——————
Ai • mi
In the formula: fi——the relative correction factor of the mass of formic acid and the internal standard ethyl acetate;
As——peak area of ​​ethyl formate, cm2;
mi——the quality of formic acid standard sample, g;
This article is derived from the determination of formic acid content in industrial glacial acetic acid by gas chromatography | Scientific Instrument Online Original Link: http: //
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