SP-3420A Indoor Air Quality TVOC/Benzene Detection Gas Chromatography Detailed Information:
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、 Thermal desorption system flowchart:

3、 Execution standards:
GB50325-2001 "Code for Indoor Environmental Pollution Control of Civil Building Engineering" (2006 edition)

4、 Performance indicators:
Detection limit: When the sampling volume is 10L, the detection limit is 0.5ug/m3
Linear range: ≥ one hundred and seven

5、 Instrument completeness:
1. SP-3420A gas chromatograph host 2 TVOC dedicated workstation 3. Dedicated capillary chromatography column 4 Atmospheric sampler 5. TENAX adsorbent 6. Activated carbon adsorption tube 7 TVOC specific standard sample 8. Benzene specific standard sample 9 Temperature and humidity meter 10. Empty box table 11. Thermal analyzer
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 ◆ High precision: 24 bit high-precision A/D
◆ Resolution: ± 1 μ v ◆ Input level range:- 5mv to 1v
◆ Sampling frequency: up to 20 times per 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


■ Sample spectrum