Effect of chlorambucil on potato subnormal germination and quality
A external standard method for determination of illegal additives in gasoline by gas chromatography was developed，and methylal and N－methyl aniline were rapidly analyzed． results showed that，the calibration curves of illegal additives had the good linear relationship in the range of 0 ～ 4% ( V/V) .The recoveries ranged from 98． 0% ～ 106． 0% ．
Key words:
gas chromatography; gasoline; methylal; N -methyl aniline.
With the development of society and economy, automobiles have become an important means of transportation in people’s daily life. With the increase in the number of automobiles year by year, the demand for gasoline for automobiles is also increasing, which brings huge business opportunities to the petroleum industry. It also comes with heavy pressure. Due to the limitation of domestic refining technology, the oil products produced by regular refineries are in short supply. Under the background of high raw material prices and the drive to maximize profits, some unscrupulous merchants use N-methylaniline, methylal and other low-cost products.
The use of expensive and potentially harmful chemical raw materials for oil blending has flooded the market with a large number of blended oil products, resulting in many gasoline quality problems. The antiknock effect of N-methylaniline is good, which can widen the ignition limit range of the mixture, improve the ignition success rate, and effectively improve the gasoline octane number. Add (volume fraction) 0 to gasoline. 5% to 5% of this type of antiknock agent, according to the gasoline
The original properties and composition, the properties of the solvent (such as polar or non-polar) can improve the octane number of the research method 1. 7 to 15 units. However, because the blended gasoline containing N-methylaniline is unstable and prone to colloid, it will cause damage to the vehicle in use, so in fact, there is a big problem in the performance of this type of gasoline. In addition, N-methylaniline is one of the highly toxic compounds listed by the health department. After invading the human body, it will cause tissue hypoxia and cause damage to the central nervous system, kidneys and liver. Methylal is a volatile organic solvent. It does not contribute to the octane number after adding gasoline, but because of its strong solvent, it has a certain cleaning effect. At present, methylal is widely used in the market to blend gasoline due to its low price and stable and readily available sources, thereby reducing the cost of oil products. Unconventional additives such as N-methylaniline and methylal are added to motor gasoline, but they are sold as “qualified gasoline”, which has great quality and safety risks. The biggest hidden danger of gasoline product quality and safety risk. Therefore, in my country’s vehicle gasoline standard GB 17930-2013 “Vehicle Gasoline”, it is clearly stipulated that compounds such as N-methylaniline and methylal should not be artificially added, but so far there is no formula for N-methyl aniline in vehicle gasoline. – Standard for the detection method of methylaniline and methylal. In this paper, an external standard method is established for the rapid detection of N-methylaniline and methylal in motor gasoline. The results show that the method is simple and reliable, with good repeatability and high accuracy, and can be used for the quality assessment of conventional motor gasoline. Routine testing and risk control.
1.Experimental part
1. 1 Instruments and reagents
Shimadzu Corporation 2010 plus gas chromatograph, hydrogen flame ionization detector. The purity of N-methylaniline and methylal are higher than 98%; there is no N-methylaniline and methylal motor gasoline.
1. 2 Sample preparation
1.3 Gas chromatography conditions
Capillary chromatography was carried out in rtx-wax (30m × 0.25mm × 0.25μm), injection volume 0.6μL, split ratio 200:1, injection port temperature 250°C, oven initial temperature 35°C, maintained for 5min, at 20°C/min The temperature was raised to 230 °C, maintained for 10 min, the detector temperature was 250 °C, and the carrier gas flow rate was 10 mL/min.
2 Results and discussion
2. 1 Qualitative screening
Because gasoline itself is a complex mixture composed of alkanes, aromatics, olefins and oxygenates, and there are many kinds of compounds, when illegal additives are detected by gas chromatography, they are easily interfered by other components. However, methylal and N-methylaniline are not common components in motor gasoline. In order to reduce the workload, the retention time of the blank sample and the standard sample added with methylal and N-methylaniline alone were used for comparison. Qualitative screening can rapidly identify both substances (see Figure 1).
2. 2 Standard curve drawing
Prepare 0%, 0.0% with methyl acetal and N-methylaniline standard solution. 5%, 1. 0%, 2. 0%, 4. 0% standard solution. Plot the standard curve with volume fraction (V/V) and peak area, and obtain the linear regression equation: Methylal: y = ax + b a = 9. 531496e – 006 b = 0, correlation coefficient R = 0. 9997; N-methylaniline: y = ax + b a = 3． 205404e – 006 b = 0, the correlation coefficient R = 0. 9990. Methylal and N-methylaniline showed a good linear relationship in the range of 0% to 4%.
2. 3 Determination of the detection limit of the method
The octane number of methylal is low, only 83-84. Because of its low price, there is a big price difference with the gasoline on the market. Oil suppliers often use it as a blending component of gasoline, which is the same as N-methyl. It is used in combination with aniline to reduce the cost of blending oil products. At the same time, in view of the complex composition of gasoline and the variety of changes, the volume fraction of additives is generally not less than 1%, so that it is profitable for illegal oil blenders, but for liquid oil samples such as gas stations, unconventional additions The residual amount of the material will be relatively low. Therefore, the detection limit of this method is artificially set as the volume fraction 0. 01%, in this way, it can not only ensure that gasoline with unconventional additives is not missed, but also try to avoid misjudgment caused by the complexity of gasoline composition.
2. 4 Recovery and precision of the method
The mixed standard solutions of different concentrations were added to the gasoline samples, and the determination was carried out according to this experimental method. From Tables 1 and 2, it can be seen that the recovery of methylal is 98. 0% to 103． 3%, the recovery rate of N-methylaniline was 100. 7% to 106. 0%.
Table1 Experimental results of repeatability and recovery rate about the methylal
serial number | Methylal spiked amount(V / V) / % | measured value(V / V) / % | Recovery rate/ % |
1 | 0．5 | 0．49 | 98．0 |
2 | 1．5 | 1．55 | 103．3 |
3 | 2．5 | 2．53 | 101．2 |
4 | 3．0 | 3．08 | 102．7 |
Table2 Experimental results of repeatability and recovery rate about the N－methyl Aniline
serial number | N-methylaniline spiked amount (V/V) / % Measured value (V / V) / % | Recovery rate/ % | |
1 | 0．5 | 0．53 | 106．0 |
2 | 1．5 | 1．51 | 100．7 |
3 | 2．5 | 2．54 | 101．6 |
4 | 3．0 | 3．06 | 102．0 |
3 Conclusion
The methylal and N-methylaniline in gasoline were completely separated from other gasoline components by capillary chromatography, and the external standard method was used for quantitative analysis. The method is simple and fast, and the quantitative results are accurate and reliable. The detection of the illegal additives methylal and N-methylaniline provides technical support and has a good application prospect.