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System and method for measuring content of 57 volatile organic compounds in ambient air

A volatile organic compound, ambient air technology, applied in measurement devices, instruments, scientific instruments, etc., can solve the problems of difficulty in simultaneous enrichment and analysis, low sensitivity, complex structure, etc., to avoid false positive results, improve analytical sensitivity, The effect of high method sensitivity

Active Publication Date: 2019-08-30
SHANDONG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] The physical and chemical properties of the 57 volatile organic compounds vary greatly. From ethylene (-104°C) with the lowest boiling point to dodecane (217°C) with the highest boiling point, the boiling point spans more than 300°C, making it difficult to enrich and analyze at the same time; and ethylene, Ethane, acetylene, and propane have low boiling points and small molecular weights, making column separation difficult
[0005] Among the 57 kinds of volatile organic compounds, there are many isomers. If gas chromatography-flame ionization detection and analysis are used only, there are many pairs of co-eluting component pairs, and it is impossible to accurately quantify each compound; if mass spectrometry is used to analyze , requires cold column temperature for sample injection, and ethylene, acetylene, and ethane have low sensitivity
Although the device can analyze all volatile organic compounds at the same time through a single sample injection, the structure is complex. Disadvantages: complex structure, difficult installation and maintenance
Can only analyze C 6 The above components, C 2 -C 5 The components cannot be analyzed, and the analysis of all components cannot be realized; this sampling method has no sample focusing link, and peak tailing is prone to occur

Method used

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  • System and method for measuring content of 57 volatile organic compounds in ambient air
  • System and method for measuring content of 57 volatile organic compounds in ambient air
  • System and method for measuring content of 57 volatile organic compounds in ambient air

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Experimental program
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Embodiment 1

[0054] This embodiment carries out the analysis of 57 kinds of volatile organic compounds in ambient air

[0055] (1) Preparation of mixed standard gas

[0056]Dilute the standard mixed gas with a concentration of 1.00 μmol / mol to the intermediate standard gas of 40.0 nmol / mol through a gas dilution device and high-purity nitrogen (≥99.999%) at a volume ratio of 1:25; then dilute the 40.0 nmol / mol The intermediate standard use gas and high-purity nitrogen (≥99.999%) are diluted to a concentration of 2.00nmol / mol in a volume ratio of 1:20 to obtain a mixed standard use gas, which is stored until cleaned and evacuated for sampling tank (the first vacuum sampling tank). The sampling tank is heated, humidified, cleaned and vacuumed (<10Pa) by the cleaning device. The gas dilution device adopts devices of various existing structures, which is a prior art.

[0057] (2) Preparation of internal standard using gas

[0058] The internal standard gas containing bromochloromethane, p-...

Embodiment 2

[0073] In this embodiment, the method of the present invention is investigated methodologically.

[0074] Prepare the mixed standard use gas of concentration 0.5nmol / mol, sample size 100ml, do 7 groups in parallel according to the method of the present invention, calculate each component method detection limit (MDL) according to formula (1); Prepare 2.00nmol with high-purity nitrogen / mol, 10.0nmol / mol, and 18.0nmol / mol low, medium, and high-concentration standard gases, the injection volume is 100ml, and the method precision experiment is carried out 6 times in parallel according to the method of the present invention, and the addition is calculated according to the blank addition. Recycled for accuracy determination. See Table 3 for the detection limit and lower limit of determination of the method; for the results of precision and accuracy.

[0075] MDL=t(n-1,0.99)×S (1)

[0076] In the formula: n is the number of sample measurements; t is the t-distribution (one-sided) w...

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Abstract

The invention provides a system and a method for measuring the content of 57 volatile organic compounds in ambient air. The system comprises a four-way valve, a gas chromatograph and a three-stage cold trap preconcentrator; the four ports of the four-way valve are respectively connected with a pre-separation column, a first secondary separation column, a second secondary separation column and a helium gas source; and the gas chromatograph is provided with a flame ionization detector and a mass spectrometry detector. The method comprises the following steps: (1) preparing a mixed standard use gas; (2) preparing an internal standard use gas; (3) collecting an ambient air sample; (4) establishing a standard curve of a target component; and (5) taking the ambient air sample to be tested, removing interfering substances through the three-stage cold trap preconcentrator, performing gas chromatography-mass spectrometry analysis in the mass spectrometry detector after focusing is performed, obtaining the content of each component according to a peak area and the standard curve established in the step (4), and calculating the concentration of the sample to be tested according to a sample injection volume of the sample to be tested. By adopting the method provided by the invention, the simultaneous analysis of two detectors is achieved by once sample injection, thereby avoiding the influence of the interfering substances on the measurement result simply and effectively.

Description

technical field [0001] The invention relates to a method for measuring volatile organic compounds (57 kinds) in ambient air. The method is a combination of gas chromatography-hydrogen flame ionization detection / mass spectrometry detection and belongs to the technical field of volatile organic compounds. Background technique [0002] The 57 kinds of volatile organic compounds (VOCs) are a branch of volatile organic compounds. The molecular structure only includes two kinds of atoms, carbon and hydrogen, and the number of carbon atoms is in C 2 ~C 12 Among them, including alkenes, alkanes, aromatic hydrocarbons and alkynes, are considered as ozone-generating precursor substances (PAMS) due to their strong photochemical activity. Many countries use the substances that exist in large amounts in urban ambient air and play a major role in ozone generation, that is, the substances in the original PAMS list, as monitoring indicators. The 57 kinds of volatile organic compounds are ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N30/02G01N30/72G01N30/68G01N30/04G01N30/06G01N30/14G01N30/86G01N30/08G01N30/24G01N30/10
CPCG01N30/02G01N30/04G01N30/06G01N30/08G01N30/10G01N30/14G01N30/24G01N30/68G01N30/72G01N30/8634G01N2030/045G01N2030/047G01N2030/085
Inventor 曹方方李红莉王艳段修宇岳太星张凤菊王桂勋聂晓玲宋永超杜丽丽
Owner SHANDONG UNIV
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