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Determination of total volatile organic compounds (VOCs) in benzene and toner by thermal desorption gas chromatography

2020-08-03 16:05:59 Practical thermal analysis thirty-five

Determination of total volatile organic compounds (TVOC), benzene and styrene in toner by thermal desorption gas chromatography

principle

Install the thermal desorption tube filled with toner sample into the Thermal desorption apparatus With the inert carrier gas, the volatile organic compounds in the sample enter into a low-temperature trap, and the trap is heated to high temperature rapidly. The vaporized organic compounds enter the gas chromatograph with the carrier gas for detection and analysis, and the external standard method is used for quantitative calculation.

    

Desorption tube: stainless steel or glass material desorption tube, PTFE pipe matched with desorption tube, desilicated glass wool.

Adsorbent: Tenax TA or other equivalent adsorbent.

Pipette or pipette: 1ml, 5ml, 10ml; volumetric flask: 100ml.

Carrier gas: helium or nitrogen, the purity of which meets the analysis requirements of gas chromatography or gas chromatography-mass spectrometry, and needs to be purified before use.

Hydrogen: the purity meets the requirements and needs to be purified before use.

Air: it should be free of corrosive impurities and should be purified before use.

   


Instrument and equipment

Gas chromatograph or GC-MS

Detector: FID or Ms.

Capillary column.

Data processing system or equivalent system used to collect and process gas chromatographic signals.

Thermal desorption instrument is also called thermal desorption instrument

It has secondary desorption function.

The precision of the balance is 0.00001 G.

   

Sample tube preparation

Standard tube filling

Each tube is filled with Tenax TA adsorbent of 0.20g ~ 0.26g, and the filling length is determined according to the metal indicator strip on the outside of the tube, and glass wool is plugged at both ends for fixation. Commercial standard tubes can also be purchased.


Aging of standard tube

Please use a steady aging instrument

The aging temperature was 300 ℃, and each tube was aged for 1 h ~ 2 h under the flow rate of 100 ml / min nitrogen or other inert gases. Aging can be carried out directly on thermal desorption instrument or equipped with aging device alone.

Note: service conditions recommended by manufacturer.

   

Sample tube filling

Fill the PTFE tube with 5mg ~ 10mg (accurate to 0.01mg) toner sample, fix both ends with glass wool, and install the filled PTFE tube in the thermal desorption tube. Or the ink sample is directly filled into the thermal desorption tube, and the two ends of the thermal desorption tube are fixed with glass wool. The compactness of toner sample and glass wool should be appropriate. Toner should not fall off and glass wool should not affect VOC volatilization.

   

Instrument reference conditions

Conditions of thermal desorption apparatus

The results showed that the sample tube desorption temperature was 130 ℃, the desorption time was 30min, the desorption flow rate was 30ml / min, the TRAP-1 was 30 ℃ ~ 280 ℃, the inlet flow was 0 ml / min, the outlet flow was 5 ml / min, and the column flow rate was 2 ml / min.

   


Chromatographic conditions

Chromatographic column: coated with 100% polydimethylsiloxane, 60m in length, 0.32mm in inner diameter and 1.0pm in film thickness.

Detector temperature: 280 ℃, or other suitable temperature recommended by the manufacturer.  

Heating program: 50 ℃, 5 ℃ / min to 200 ℃, 10 ℃ / min to 280 ℃, holding for 22 min.

Carrier gas: helium.

Flow rate of FID gas and auxiliary gas: hydrogen, 30ml / min; air, 300ml / min.

Note: users can also choose other suitable instrument conditions within the scope of use specified by the manufacturer.

   


testing procedure

Standard curve drawing

Pipette a certain amount of standard solution (3.2) into methanol (3.1) to prepare standard series with target concentrations of 25mg / L, 50mg / L, 100mg / L, 200mg / L and 300mg / L respectively. Set the flow rate of nitrogen or other inert gas at 100ml / min. 1 pl of the above-mentioned standard solution was transferred with a micro syringe and injected into the standard tube for 5 min. The syringe was quickly pulled out to make standard tubes with target content of 25ng, 50NG, 100ng, 200ng and 300ng respectively.

    

Standard chromatogram

 Solid thermal desorption