Thread Content
Analysis of 2,5-dichloro-3-nitrothiophene in o-chloro*** by gas chromatography 1. Principle: Gas chromatography. 2,5-Dichloro-3-nitrothiophene in o-nitrochlorobenzene was detected using an FPD detector equipped with a sulfur-containing filter. 2. Abstract: The sample of o-nitrochlorobenzene was dissolved in methanol and analyzed using a gas chromatograph equipped with an FPD. Since the standard sample 2,5-dichloro-3-nitrothiophene is difficult to prepare, its value was calculated using the standard working curve for 2,5-dichlorothiophene. Since determination is carried out using the standard curve method, the sample volume must be injected with high precision (precision errors arise due to different retention times); by setting the retention time of 2,5-dichlorothiophene to that of 2,5-dichloro-3-nitrothiophene, the precision errors caused by different retention times can be reduced. 3. Equipment: Gas chromatograph model: GC-SA with FPD detector equipped with a sulfur-filtering element (Shimadzu, Japan). Integrator: Chromatopa C R3A (Shimadzu, Japan). 4. Reagents: Methanol; 2,5-dichlorothiophene. 5. Analysis program: A: Analysis conditions – Column: 300 mm in length and 2.6 mm in diameter, glass column. Stationary phase: Apiezone grease N (10%) and Chromosorb W HF (149–177 μM). Column temperature: 180°C for the analysis of 2,5-dichloro-3-nitrothiophene; 110°C for the analysis of 2,5-dichlorothiophene. Detector temperature: 240°C. Vaporization chamber temperature: 240°C. Detector precision: FPD, 10*8. Carrier gas flow rate: N2 at 40 ml/min. Hydrogen pressure at the detector: 6.864*104 Pa to 7.845*104 Pa. B: Analysis steps: 1. Preparation of standard solutions for the calibration curve – Stock solution: 2,5-dichlorothiophene is accurately weighed and dissolved in methanol, then the solution is brought to a volume of 100 ml in a volumetric flask. Subsequently, 10 ml of this solution is taken and further diluted to 100 ml using methanol. Content of the working curve: Each 1 ml or 3 ml of the original solution is made up to 100 ml with methanol solution. The concentration of this solution is 1 μg and 3 μg of 2,5-dichlorothiophene per 1 ml. By adding exactly 5 μl of this solution, the working curve for 2,5-dichlorothiophene is obtained. 2. Preparation of the sample solution: Weigh out 1.5 ml of the dissolved ONCB sample with precision, and dissolve it in 10 ml of methanol solution. 3. Determination of the 2,5-DCNT content in the ONCB sample: An exact volume of 5 μl of the sample solution is analyzed using gas chromatography; the area of the 2,5-DCNT peak obtained through integration is then entered into the calibration curve for 2,5-dichlorothiophene, thereby determining the value of A. The content of 2,5-DCNT in sample ONCB is calculated using the following formula: X={A/（S*0.4）}*198/153. Where: X = the content of 2,5-DCNT in sample ONCB (ppm); A = the value of 2,5-dichlorothiophene obtained from the calibration curve (ug/ml); S = the weight of sample ONCB (g)