Study on the determination method of benzene series in solvent-based coatings

The benzene products in solvent-type coatings were measured by the top air-gas chromatography method, the standard curve method of peak area outer label was quantitatively analyzed with retention time, and the hydrogen flame ionization detector (FID) was used, 50 m × 0. 32 mm × 1. Sample separation is carried out by a small calibre quartz capillary column of 0 m, using a sein-in sample and a tail blowing device, indicating the party.introduction
0 introduction
interior decoration material solvent-based coating containing benzene, toluene, xylene and ethyl benzene and other harmful pollutants to people's health, people in a short period of time when inhaling high concentrations of toluene, xylene, can appear the central nervous system anaesthetic effect, light people have dizziness, headache, nausea, chest tightness, fatigue, consciousness fuzzy, serious can cause coma to respiratory, circulatory failure and death. If long-term exposure to a certain concentration of toluene, xylene will cause chronic poisoning, headache, insomnia, depression, memory loss and other neurodebilitated symptoms . Long-term inhalation of toluene and xylene can cause damage to the body's nervous system. Benzene compounds have been identified by the World Health Organization as strong carcinogens and their levels must be controlled to ensure people's health.
At present, the common analysis methods of benzene, toluene, xylene and ethyl benzene in solvent-based coatings of interior decoration materials have two methods: top air-gas chromatography and direct sample gas chromatography after dilution of ethyl acetate. Ethyl acetate diluted directly into the gas chromatography, due to the complex composition of solvent-based coatings, diluted with ethyl acetate to form emulsion, can not be directly into the capillary column for separation, and therefore can not be determined. In this paper, the top air-gas chromatography method will be about 0. Samples of 200 0 g are coated on a 70 mm × 20 mm quantitative filter strip in a weighed 60 mL top empty bottle, the cap is tightened, and 4 h is balanced in a thermostat at 40 degrees C, and an airtase needle is used to extract 0. 20 mL top air directly into the column for chromatography analysis, with retention time qualitative, with the peak area outside the standard curve for quantitative analysis. After experiments, this method has the advantages of simple operation, high sensitivity, good precision, good accuracy and undisturbed, and is suitable for the determination of benzene, toluene and xylene content in solvent-based coatings of interior decoration materials. The minimum detection limits for benzene, toluene, xylene and ethylbenzene were 0. 02 sg and 0. At 36 μg, the measurement range is 0. 3 mg to 1. 8 mg and 0. 2 mg to 5. 0 mg. The correlation coefficients for each standard curve are at 0. 999 or more.1 Experimental part
1. Principle 1
Apply the sample to a quantitative filter strip in a weighed top empty bottle, weigh it and place it in a thermostat at 40 degrees C, balance 4 h, and take 0. 20 mL top air enters the column for chromatography analysis to preserve time qualitative, peak area outside the standard curve method for quantitative analysis.
1. 2 Instruments and reagents
1. 2. 1
gas chromatography: GC 9560 gas chromatography (with FID detector, sifier, tail blowing device).
non-polar quartz capillary column (DB-1 U.S. import): 50 m × 0. 32 mm ×1. 0 sm, coated with dmethyl polysilioxane.
workstation Zhejiang University Zhida N2000 software.
microscope: 1 mL airtable needle. 10 sl microscope, etc.
bottle: 60 mL.
temperature box, high purity nitrogen (purity of 99. 999%) , hydrogen generator, air generator.
1. 2. 2 Reagents
benzene, toluene, xylene, inter-toluene, phthalates, ethyl benzene (single-part) standard solution (chromatography pure).
1. 3 Chromatography conditions
selow and tail blow, severity ratio 1: 15, program heating up, initial temperature of 50 degrees C, maintain 5 min, heating rate of 10 degrees C /min, termination temperature of 250 degrees C, maintain 1 min, gas carrier for high purity nitrogen (purity of 99. 999%), hydrogen for gas, air for gas, flow nitrogen 30 mL/min, hydrogen 30 mL/min, air 300 mL/min.
1. 4 The drawing of the standard
1) the drawing of the benzene standard curve is shown in Figure 1.
take 5 60 mL top empty bottle, the filter paper into the top empty bottle after sealing, with trace syringe to absorb the following content of the standard solution injected into the top empty bottle of filter paper, sealed and placed in a 40 degrees C thermostat to balance 4 h, with an airtight needle to take 0. 20 mL top air for gas chromatography analysis, with peak area as the ordinate, respectively, benzene, toluene, xylene mass of the cross-sectional coordinates to draw the standard curve. The benzene standard series is set out in Table 1.
2) The drawing of the standard curve of benzene is shown in Figure 2 to Figure 5. The standard series of benzenes is set out in Table 2.
1. 5 Sample preparation
the top empty bottle weighing (accurate to 0. 1 mg), will be about 0. Samples of 200 0 g are applied to the filter strip and weighed after tightening the cap (accurate to 0. 1 mg), the difference in weight twice is the sample mass. Place the sample in a temperature box at 40 degrees C to balance 4 h and take 0. 2 mL top air for gas chromatography analysis. The quality of the sample was found from the standard curve, and the mass fraction of benzene, toluene and xylene was calculated:
of which C1 was the mass fraction of benzene in the sample;
, C2 is the mass fraction of benzene in the sample, m2 is the quality of toluene in the sample under test, m3 is the quality of xylene in the sample under test, m4 is the mass of ethyl benzene in the sample under test, sg; w is the quality of the sample, g. 2 Basic Experiments
2. 1 Minimum detection limit
The minimum amount or minimum concentration of the substance to be tested can be detected from the sample within the confidence limit of a particular analytical method.
author used a concentration of 5. The benzene-top empty bottle (the first point of the benzene standard curve) of 0 μg /mL has a sample size of 0. 4 mL,0 . 04 mL,0. 02 mL, 0. 004 mL,0. 002 mL, when the sample size is 0. At 002 mL, it is not checked out and the sample size is 0. At 004 mL, the minimum check-out is 0. 02 sg, so the minimum detection of benzene in this method is 0. 02 sg. The author uses a concentration of 3. The top air intake in the toluene plus xylene plus ethyl benzene top empty bottle (point 1 on the standard curve) of 33 μg /mL, the intake was 0. 10 mL, 0. 05 mL,0. 03 mL,0 . 02 mL. When the sample is 0. Not checked out at 02 mL, the amount of sample is 0. At 03 mL, the minimum check-out is 0. 36 sg. Therefore, the minimum detection amount of toluene and xylene in this method is 0. 36 sg.
2. 2 Precision
the precision of the analysis method is the degree of duplication between the data obtained by repeated measurements of a sample by this method, which is a relevant measure of the quality of the analysis results. The author called aolic acid paint 0. 200 0 g 5 servings, the same steps are prepared. Take 0. each of the 5 top empty bottles. 20 mL for determination. The results are found in Table 3.
1) Benzene. X - 0. 00%, Sx s 0. 00%, RSD s 0. 00%。 Extreme R - Max - Min - 0. 00%。 2) Toluene, xylene, ethylbenzene. X - 0. 44%, Sx s 0. 046 99%, RSD sx ÷ X × 100% s 11. 3%。 Extreme R - Max - Min - 0. 51% - 0. 38% s 0. 13%。
2. 3 Accuracy
Accuracy is a comprehensive index that reflects the system error and random error of this method, which determines the reliability and accuracy of the analysis method, and is represented by absolute error or relative error.
evaluation method can be used to evaluate the accuracy of analytical methods and measurement system errors by measuring standard substances or by measuring recovery rate by standard substances.
, toluene and xylene, the author used the method of measuring standard substances and percentage recovery rate to evaluate the accuracy of the analysis and measurement system.
2 60 mL top empty bottles, put the filter paper into the top empty bottle seal, with a trace syringe to absorb 1. 37 μg pure benzene solution, coated on a filter strip inside the top empty bottle, benzene content of 1. 20 mg, after balancing 4 h in a temperature box at 40 degrees C, take the balanced benzene top air 0. 20 mL directly into the sample for chromatography analysis. Toluene 2. 884 sl, phthalates2. 840 sl, xylene 2. 893 sl, inter-toluene 2. 903 sl, ethyl benzene 2. 884 sl, content is 2. 50 mg, the amount of five solutions and 12. 5 mg, balanced 4 h in a 40 oC thermostat, with a balanced top air of 0. 15 mL sample (0. 20 mL), as measured in Table 4.
3 Conclusion
The determination of benzene, toluene and xylene in solvent-based coatings of interior decoration materials was determined by top air-gas chromatography, and after experiments, the sensitivity of the method was high, and the minimum detection of benzene was 0. The minimum detection limit for toluene and xylene is 0. 36 sg. The precision of the method is good, called alicic acid paint 0. At 20 g, the intake is 0. At 20 mL, the relative standard deviation of benzene is 0. 0%, the relative standard deviation of toluene, xylene and ethyl benzene was 11. 3%, with a very poor 0. 1%。 High accuracy, benzene content of 1. At 20 mg, the relative error is 9. 6%, with a percentage recovery rate of 109. 6%。 The content of toluene and xylene and ethylbenzene was 1. At 25 mg, the relative error is 9. 6%, with a percentage recovery rate of 109. 8%。