1、 Instrument Introduction

There are many definitions of volatile organic compounds (VOCs), such as the American ASTM D3960-98 standard which defines VOCs as any organic compound that can participate in atmospheric photochemical reactions. The definition of volatile organic compounds by the US Environmental Protection Agency (EPA) is any carbon compound that participates in atmospheric photochemical reactions, except for carbon monoxide, carbon dioxide, carbonic acid, metal carbides, metal carbonates, and ammonium carbonate.

There are various definitions of Total Volatile Organic Compounds (TVOC), which generally refer to various measured VOCs. Formaldehyde does not belong to the category of TVOC. The World Health Organization (WHO, 1989) defines TVOC as a general term for volatile organic compounds with a melting point below room temperature and a boiling point range between 50 and 260 ℃; The definition of TVOC in GB/T18883 is: volatile organic compounds that are sampled using Tenax GC/TA, analyzed on a non-polar chromatographic column (polarity index less than 10), and retained between n-hexane and n-hexadecane.

Due to the complexity of indoor air, the TVOC spectrum contains hundreds of peaks, making it difficult to quantitatively analyze all standard samples one by one. Therefore, 9 highly toxic organic compounds (benzene, toluene, para/meta xylene, o-xylene, styrene, ethylbenzene, ethyl acetate, undecane) were selected for qualitative and quantitative analysis, while the remaining unknown compounds were calculated using toluene.

Shanghai Kechuang Chromatography Instrument Co., Ltd. has accumulated more than ten years of experience in specialized gas chromatographs for environmental air analysis, and continuously improves and optimizes the instruments. It can be directly inserted into the heating block for rapid and uniform heating, with good desorption effect.

Customers can choose between a single thermal desorption or a secondary thermal desorption sampling method. One thermal desorption is achieved by directly desorbing and injecting the sample through an adsorption tube; Secondary thermal desorption refers to the adsorption of samples through adsorption tubes and secondary cold focusing, resulting in high recovery rates, good peak shapes of components, and high separation efficiency.

The HL-800 secondary thermal desorption analyzer produced by the company can be used in conjunction with various types of domestic and imported gas chromatographs or gas chromatographs, and can also be retrofitted with existing scientific and technological gas chromatographs.

2、 Detection limit

When the sampling volume is 10L, the detection limit of the method is 0.5 μ g/m³.

3、 Execution standards

Details specified in the standard

4、 Instrument features

4.1. LCD screen or 5.7-inch color touch screen;

4.2. A fully computerized reverse control system, with a single computer capable of controlling up to 253 chromatography instruments and 7 temperature control channels; 8-channel external event time program;

4.3. The instrument is equipped with a dedicated chromatography workstation for indoor environmental monitoring (TVOC), which has functions such as intelligent peak identification/automatic processing, multi-channel spectrum integration and exchange, automatic application of toluene to calculate unknown peak content, automatic conversion of sampling volume to standard state based on environmental temperature and pressure, and automatic calculation of the content of each component and the whole in the unit sampling volume. It can also deduct the peak area of each component in the solvent and the content of each component in the outdoor air sample to obtain the final result;

4.4. The instrument adopts RJ45 Ethernet interface, which makes signal output and control acquisition simple and convenient, and can realize remote control, remote data transmission, processing and supervision of the instrument. Can be connected to unit supervisors and higher-level supervisors for easy supervision by supervisors;

4.5. Large capacity column box with automatic rear opening door, capable of 8-step programmed heating, and column box with near room temperature control function (5 ℃ above room temperature);

4.6. Equipped with fault self diagnosis function, displaying the location and nature of the fault at any time; Equipped with over temperature protection function, any temperature exceeding the set temperature will automatically stop heating.

Note: For other parameters of the instrument, please refer to the introduction of the gas chromatography host.

5、 Instrument configuration

Configuration of a thermal analysis instrument

Secondary thermal analysis instrument configuration

Note: The gas chromatography host can be selected from GC9800 or GC2002 models

5、 Instrument gas path diagram

6、 Workstation operation interface

7、 Analyze the graph and conditions

Analysis spectrum of air TVOC samples