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Determination of isobutyraldehyde in air application of thermal desorption instrument

2020-07-23 13:50:02 Practical analysis twenty-nine

Determination of isobutyraldehyde in air application of thermal desorption instrument

Isobutyraldehyde in the air was collected by silica gel tube Thermal desorption After injection, the samples were separated by FFAP column and detected by flame ionization detector.

The retention time was used for qualitative analysis and peak height was used for quantification.

instrument

Silica gel sampling tube: put 200 mg, 40-60 mesh silica gel into a 150 mm long glass tube with an inner diameter of 3.5-4.0 mm and an outer diameter of 5.5-6.0 mm. Both ends of the tube are fixed with glass wool, covered with plastic caps or fused and sealed.

Air sampler: flow rate 0 ~ 1L / min.

Syringe: 100ml, 1ml.

Dynamic gas distributor.

Constant temperature water bath: ± 0.1 ℃.

Domestic thermal desorption It is mainly composed of heater, controller, thermometer and gas flow control parts. The temperature control range is 100 ~ 350 ℃, and the desorption gas flow control range is 50 ~ 100ml / min.

Gas chromatograph, flame ionization detector.

Chromatographic column: column length 2m, inner diameter 3 ~ 4mm, stainless steel column.    

FFAP:ChromosorbWAW=10:100;

Column temperature: 90 ℃

Temperature of vaporizer: 150 ℃;

Detection room temperature: 150 ℃

Carrier gas (nitrogen): 50ml / min.

    

sampling

Open the silicone tube at the sampling site, connect the sampler and place it vertically, and collect 2L air at the speed of 0.2l/min. After sampling, put plastic caps on both ends of the tube for analysis within three days.

   

Analysis steps

Control test: take the silica gel tube which has not been sampled to the sampling point, and other operations are the same as the sample, as the blank control of the sample.

Sample treatment: remove the plastic caps at both ends of the silicone tube, connect a 100ml syringe, place it in the thermal desorption device, and use nitrogen to desorb to 100ml at the speed of 50ml / min at 300 ℃.

Standard curve drawing: 5.0, 10.0, 20.0, 50.0 mg / M isobutyraldehyde standard gas was prepared by diffusion tube dynamic gas distribution method (or static large syringe method).

Adjust the instrument to the best state according to the operating conditions, inject 1ml gas, and determine the standard series respectively. Each concentration is measured three times to calculate the average peak height.

The standard curve was drawn with the mean value of peak height as ordinate and isobutyraldehyde content as abscissa. Retention time is a qualitative indicator.

Determination: under the same conditions of standard curve determination, determine the sample and blank control respectively; after subtracting the reading of blank control from the measured sample reading, the quality (PG) of isobutyraldehyde in the sample can be obtained from the standard curve.