Application of Gas Chromatography in Detection

With the continuous improvement of the social economy, people's living standards have been improved and pollution has increased. The health of our country is declining. Indoor pollution is one of the reasons. The gas chromatograph is an instrument that analyzes and analyzes each component in the mixed gas. It also helps in the detection of indoor environmental pollutants.

The construction of luxurious buildings and the increasing number of disputes caused by renovations have increased the interest and attention of the country, and active and effective measures have been taken to organize relevant experts to formulate national standards GB50U5-2001, which were jointly promulgated by relevant ministries and commissioned in recent years. The regulations stipulate indoor air quality as an important indicator of the quality of civil construction projects, of which a modification was made in 2006 and was recently revised on the basis of the previous two amendments and issued as a new national mandatory standard, namely GB503M-2010, At the same time, GB503M-2001 was abolished.

The standard stipulates that all newly-built, reconstructed and expanded civil building projects must be tested for indoor air quality when they are completed and inspected. Qualified inspections are acceptable for acceptance and delivery. In addition, more stringent requirements are imposed on building materials. Construction site use. However, due to various reasons, the management of the current market is still not perfect, and the propaganda of relevant departments at all levels is not enough, so consumers are not familiar with the pollutant indicators of various materials in the market during the purchase of houses and renovations. The blinding of unscrupulous merchants, often spending money has led to the "invisible killer", resulting in a variety of decoration disputes occur from time to time. In addition, the number of testing organizations is relatively large, and the quality of their testing services is uneven. Therefore, in light of the above situation and the situation that the author has encountered in recent years, the inspection focused on the complexity of the five indicators that must be tested in national standards. The methods for the detection of TVOCs and the issues that should be noted in the testing process are briefly described. It is hoped that they will help the relevant personnel to communicate.

Experimental Experimental Instruments and Reagents Instruments: GC-2010 chromatograph (equipped with FID detector), Shimadzu instrument; thermal desorption instrument; chromatographic workstation (1pL injection needle).

Standard solution: (National Standard Material Center) Standard solution concentration 1.0mg/mL (including benzene, toluene, butyl acetate, ethylbenzene, styrene, o-xylene, and undecane are all 1.0 mg/mL. Toluene 2.0 mg/mL).

Chromatographic conditions capillary column: 50mmx0.32mmx1^m; (2) temperature program: column temperature: 50T/min; holding time: 10min; heating rate: 5T/min; final temperature: 250; holding time: 10min; detector temperature: 250T;

Injection chamber temperature: 250; sensitivity: 1010; gas flow ratio: air/hydrogen/nitrogen = 30:1:1; split ratio: 5:1.

Thermal Desorption Condition Adsorbent: Tenax-TA 200 mg; desorption temperature: 300 T; desorption tube intruded into the chromatograph time: 40 s; thermal desorption time: 10 min; injection time: 40 s; desorption backflush activation time: 15 min.

Adsorption and Desorption of Standard Samples for Adsorption and Desorption of Standard Samples: Different volumes of standard solutions were injected into a T^nax-TA tube with a 1 pL sample and spectra of different sample volumes were obtained. Inject 0.0-L, 0.2-L, 0.4-L, 0.6-L, and 0.8^L of the standard solution into the Tenax-TA tube and immediately place it in the desorption instrument to desorption for 10 minutes. After the time expires, the desorber automatically opens the solenoid valve. The sample was injected into the chromatogram for 40s. The desorption instrument carrier gas flow rate was 30 mL/min and the insufflation flow rate was 60 mL/min. After the air injection is completed, the solenoid valve automatically shuts off, and the time program of the chromatography station and chromatograph is turned on at the same time. The desorption instrument automatically blows at a nitrogen flow (60 mL/min) for 15 minutes to allow the aging of the rTenax-TA tube for use in the next analysis.

Connection between thermal desorption instrument and chromatograph The thermal desorption instrument has a steady flow valve and the flow rate can be adjusted from 0 to 100 mL/min. The six-way valve and solenoid valve control the thermal desorption state of the thermal desorption device and the injection tailing state. The heating system is supplied by the thermal desorption device itself. Two gas lines are available, one is always supplied with a thermal desorption instrument and chromatograph, and the other is a routed six-way valve and solenoid valve-controlled supply desorber for sample purging and tail blowing. Connect the end of the desorption tube to the solenoid valve and connect the other end directly to the inlet of the chromatograph with a connecting line. Both the thermal desorption state and the injection state can be set in the desorption instrument. The desorber automatically opens the solenoid valve to start desorption and sample injection. The degree of automation is high and the working time and labor intensity are greatly reduced.

With the introduction of the national standard GB50U5-2001, government departments have attached great importance to the promotion of indoor environmental testing from the beginning of the promotion to the subsequent requirements of 2008, all civil construction projects must carry out indoor environment testing mandatory regulations, and then to 2010 The revision of GB50325 can be seen that this standard has been widely used in practice and has been continuously improved, so that the material and other specifications have been effectively controlled in terms of standards, and materials used for improving people's living conditions, comfort, etc. have been guaranteed at the source. Inflow into the market, and then into the interior decoration, bringing indoor environmental pollution, but the level of various testing agencies are mixed, so only strengthen the management of inspection agencies, supervision, improve their service levels and technical quality, so that we can effectively make our consumption Those who receive high-quality, standardized testing services are guaranteed for the living environment.