1、 Method Overview:

With the continuous improvement of people's living standards, the requirements for living environment are becoming higher and higher, and indoor air quality is also attracting more and more attention. In order to control and monitor the indoor air quality of civil construction projects, the country has formulated GB50325-2001 "Code for Indoor Environmental Pollution Control of Civil Construction Projects", which stipulates the use of gas chromatography to determine the content of benzene and TVOC. TVOC refers to the total amount of volatile organic compounds with a boiling point lower than or equal to 250 ℃ measured in air under normal pressure conditions.

Main operating procedure: Use a dedicated atmospheric sampling instrument to sample at the location to be tested at a flow rate of 500ml/min through a Tenax tube for 20 minutes (using activated carbon tubes for benzene). This process is called adsorption. Then put this Tenax tube into the desorption instrument, and this process is called desorption. The desorbed sample is carried into the chromatographic column by the carrier gas, separated by the chromatographic column, and then enters the detector. The data is collected and processed through a dedicated chromatographic workstation.

2、 Execution standards:

GB50325-2001 "Code for Indoor Environmental Pollution Control of Civil Building Engineering" (2006 edition)

3、 GC-2001 Indoor Air Quality TVOC/Benzene Testinggas chromatographPerformance indicators:

Detection limit: When the sampling volume is 10L, the detection limit is 0.5ug/m3

Linear range: ≥ 107

4、 GC-2001 Indoor Air Quality TVOC/Benzene Detection Gas Chromatography Instrument Package:

GC-2001 gas chromatograph host

2. TVOC dedicated workstation with reverse control

3. Specialized capillary chromatography column

4. Atmospheric sampler

5. TENAX adsorbent

6. Activated carbon adsorption tube

7. TVOC specific standard samples

8. Benzene specific standard sample

5gas chromatographMain technical indicators:

1. Column box temperature index:

◎ Column box temperature range: 15 ° C to 399 ° C above room temperature (incremental 1 ° C)

◎ Column box temperature control accuracy: ± 0.1 ° C (measured at 200 ° C)

◎ Column box program temperature rise: 8-stage rise

◎ Lift rate setting: 0.1 ° C to 40 ° C/min (incremental 1 ° C), measured at 200 ° C

◎ Constant temperature time for each stage: 0-655min (increment of 1min)

2. Temperature indicators of injector, detector, and thermal desorption chamber

◎ 1) Temperature range: 15 ° C to 399 ° C at room temperature (increments of 1 ° C)

◎ 2) Temperature control accuracy: ± 0.1 ° C (measured at 200 ° C)

3. Flame ionization detector (FID)

◎ The collection adopts a cylindrical structure and a quartz nozzle

◎ Detection limit: ≤ 3 × 10-12g/s (n-hexadecane/isodecane)

◎ Baseline noise: 5 × 10-14A

◎ Baseline drift: ≤ 2 × 10-13A/30min

◎ Linear: ≥ 107

4. GC-2001 Indoor Air Quality TVOC/Benzene Detection Gas Chromatography Other Parameters:

Instrument dimensions: Width 690 x Depth 470 x Height 420

Weight: 47Kg

5. Instrument usage requirements:

◎ Power supply voltage: 220V~± 22V 50Hz ± 0.5Hz

◎ Rated power: ＜ 1800W

◎ Environmental temperature: 5 ° C to 35 ° C

◎ Relative humidity: ≤ 85%

The instrument placement site must not have corrosive gases or electric or magnetic fields that affect normal operation. The instrument placement workbench should be stable and free from vibration. There shall be no electric furnace or spark within 2 meters of the hydrogen cylinder.

Indoor air dedicated chromatography workstation

Software Description:

(1) Reference peak function: It can automatically count unrecognized peaks as toluene without the need for manual calculation

(2) Calibration function for temperature and atmospheric pressure: Directly input the temperature and atmospheric pressure of the sampling point during sampling, and the system will automatically convert the concentrations of each group in the air sample into the concentration under standard conditions, without the need for manual calculation

(3) Blank deduction function: can directly deduct the amount of air blank sample

(4) Multiple calibration curve functions: Double logarithmic calibration curve can be selected

Hardware performance:

◆ Communication interface: COM interface ◆

◆ Resolution: ± 1 μ v ◆ Input level range: -5mv to 1v

◆ Sampling frequency: high 20 times/second ◆ Dynamic range: 106

◆ Integral sensitivity: 1 μ v · sec ◆ Linearity: ＜ ± 0.1%

◆ Reproducibility: 0.06%

Software operation interface

Application examples of methods

Analysis conditions: desorption temperature 250 ℃, desorption time 5 minutes, sweeping gas flow rate 50ml/min, carrier gas N2

Gas chromatograph analysis conditions:

Vaporization temperature 250 ℃ Detection temperature 250 ℃

The column furnace temperature is maintained at 50 ℃ for 10 minutes, and then raised to 250 ℃ at a rate of 5 ℃/min. The chromatographic column is 50m × 0.53mm × 1.0 μ m

TVOC standard curve chart (taking undecane as an example)

Standard curve graph of benzene

Standard sample spectrum

1 # Standard sample direct injection spectrum 1 # Standard sample desorption absorption spectrum

Sample spectrum