Abstract: This article introduces the gas chromatography analysis method for naphthalene content in coal tar. GC2010 gas chromatography was used to determine the naphthalene content in coal tar, and satisfactory results were achieved.
Keywords: coal tar naphthalene gas chromatography
1. Preface
The gas chromatography method for determining the naphthalene content in coal tar complies with GB3704-83. The principle is: based on the fact that alkanes do not dissolve asphaltene in coal tar, but have a greater ability to dissolve naphthalene, alkanes are used as extractants to remove asphaltene and other impurities, and then the extraction solution is analyzed and quantified by external standard method.
2. Experimental section
2.1 Instruments and reagents:
Instrument: Zhongkepu GC2010 gas chromatograph (equipped with hydrogen flame ionization detector, packed column or capillary column injection system), N2000 chromatography workstation.
Reagents: Naphthalene (analytical grade), n-Dodecane (analytical grade)
2.2 Chromatographic conditions
Capillary: Carrier gas pressure: 0.06Mpa Supplementary gas (high-purity nitrogen) flow rate: 30ml/min Air flow rate: 300ml/min Hydrogen flow rate: 30ml/min Split flow rate: 30ml/min
Filling: Carrier gas (high-purity nitrogen) flow rate: 30ml/min Air flow rate: 300ml/min Hydrogen flow rate: 30ml/min
Column box temperature: 180 ° C Sample injector: 200 ° C Detector: 200 ° C (both filling and capillary are the same)
2.3 Preparation of External Standard Samples and Samples
2.3.1 Preparation of external standard samples:
Weigh a certain amount of naphthalene, then weigh a certain amount of n-dodecane, dissolve it in a volumetric flask, shake well, and store. The naphthalene content of the external standard sample required to be prepared is generally similar to the naphthalene content in the sample preparation described below.
2.3.2 Sample Preparation:
*Secondary extraction: Weigh about 1.5g of evenly mixed coal tar sample, accurate to 0.0002g, and place it in a volumetric flask. Then add 3-4g of n-dodecane and slightly heat it on an electric heater or other heating device, with the temperature controlled at around 80 degrees. Stir for 2-3 minutes while heating, then take it off and let it stand. After cooling to room temperature, pour the extraction solution into another volumetric flask of known weight and cover it tightly.
Second extraction: Take another 3-4g of n-dodecane and add it to the volumetric flask containing the residue. Perform the second extraction according to the * extraction method, merge the second extraction solution into the * extraction solution, and seal tightly.
Third extraction: Perform the third extraction using the same method as described above. Mix the third extraction solution with the previous two extraction solutions, and weigh the extraction solution to the nearest 0.001g. Cover tightly and shake well for later use.
2.4: Experiment:
Adjust the GC2010 chromatograph to a stable state, introduce 0.2ul of external standard sample, and calculate the calibration factor. Under the same conditions, add 0.2ul of sample and calculate the concentration of the sample using the external standard method;
3. Experimental results and calculations:
After calculating the sample concentration using the external standard method, calculate the naphthalene content in coal tar according to the following formula:
C sample * G test 100
Naphthalene%=------------- X---------
G 100-Wf
In the formula: C sample - the concentration of the sample calculated by external standard method,%;
G-test - the weight of the extracted liquid obtained after extraction, g；
G - weight of coal tar sample, g；
Moisture content in Wf coal tar analysis sample,%----