Capillary column gas chromatography determines benzene and toluene in water-based epoxy coatings

Water-based epoxy coatings are made of water-based epoxy resin and compound modified polyamine resin and other auxiliary materials, in recent years, laws and regulations on environmental pollution restrictions have been issued, which involve the paint industry has V O C emission limits, because the traditional solvent-based coatings in the V O C not only cause pollution to the environment, but also to the human body is extremely harmful, the state strictly restricts V O C emissions. It is an economical and practical method to measure benzene and toluene in water-based epoxy coatings by capillary column gas chromatography, which is accurate, high recovery rate, good reproducible, high precision, and simple operation. It provides a theoretical basis for quality control in the production of the coating
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1 Experimental part
1.1 instruments, reagents
S p-6890 gas chromatography (pillar temperature: 180 degrees C; test chamber temperature: 170 degrees C; gas flow: 0.8mL/min).
gasification chamber temperature: 1 6 0
degrees C; E L204 electronic balance; K Q-300D E-type CNC ultrasonic cleaner;
internal targets: isodol (analytical pure); calibration compounds: benzene, toluene (chromatography purity);
discists: ethyl ethylene, methanol (chromatography purity), positive propylene alcohol (chromatography pure);
water-based epoxy coating samples.
1.2 Principle
After the sample is diluted, it is injected directly into the gas chromatography, after the chromatography is separated, the compounds under test are separated from each other, and the hydrogen flame ionization detector is used for detection, using the internal standard legal quantity.
1.3 Gas chromatography optimal parameters of the determination and optimization
(1) to absorb 1 l benzene, toluene standard solution, injected into the gas chromatography, under different experimental conditions, to show the peak of benzene, toluene, after comparative observation to determine the best experimental conditions.
(2) according to chromatography conditions, it should be optimized each time with a known calibration compound to optimize the sensitivity, stability and separation of the instrument.
1.4 Qualitative Analysis
The compound under test in the qualitative test sample: the sample taken about 2g is diluted with ethyl acetate, and the sample is injected into the chromatography by 1 s L to determine the presence of the compound under test.
1.5 Pre-treatment and determination of
(1) precision coating sample 2.0g (accurate to 0.1m g), placed in a 20m L top empty bottle, and added methanol and ethyl and ultrasonic processing to extract the paint sample benzene, toluene; Record the peak area of the object under test.
(2) Calibration
called 0.02g calibration compound benzene, toluene in the sample bottle, said to take the internal subject matter 0.02g in the same sample bottle, using ethyl acetate dilution mix, seal the sample bottle and shake well, and then in the same conditions as the test specimen for separation determination.
1.6 Recovery rate test
2 experimental results and discussion of the
2.1 gas chromatography best parameters of the determination of
column temperature of 170 degrees C, chromatography peak expansion and tailing, temperature is too low; The temperature is too high, the column temperature is 1 8 0 degrees C, the peak shape does not expand without tailings, the material is completely separated, so the column temperature is 180 degrees C is the best. The temperature of the gasification chamber is 1 7 0 degrees C, compared with other spectral maps, the number of chromatography peaks has changed, the reproduction difference is poor, the temperature is too high, the gasification chamber temperature is 140 degrees C, the peak type is irregular, the temperature is too low, the gasification chamber temperature is 160 degrees C, the chromatography of the temperature, the peak type is normal, the peak number remains the same, so the gasification chamber temperature is 160 degrees C is the best.
2.2 Relative correction factor test results
2.2.1 Benzene relative correction factor determination
respectively, the quality of benzene is 0 . 0 2 0 7 g, 0 . 0 2 1 8 g , 0 . 0 2 1 3 g , with a mass of 0.0219g, 0.0205g, 0.0217g, measured The peak area of benzene is 1 9 8 1 5 . 9 4 5,2 0 1 0 3 . 1 0 9,1 9 7 2 . The peak area of the object was 19811.637, 17892.699, 18947.140, and the relative correction factor of benzene was 0.945.
the relative correction factor of toluene
respectively, the mass of toluene is 0 . 0 2 0 6 g , 0 . 0 2 2 0 g , respectively . 0 . 0 2 1 7 g , the mass of the inner object is 0.0219g, 0.0205g, 0.0217g, and the peak area of the benzene is measured to be 1 1 8 8 0 4 . 4 7 8,1 9 2 7 9 . 0 3 7,1 8 9 8 5 . 2 1 0 , peak of the inner object The area was 19811.637, 17892.699, 18947.140, respectively, and the relative correction factor for toluene was 0.995.
2.3 mark-up recovery test results
sample benzene measurement value of 0.16g/k g, toluene measurement value of 0.28g/k g, benzene sample size is 0.0122 g, 0.0231g, 0.0326g, Toluene samples were added at 0.0106 g, 0.0210 g and 0.0311 g respectively, and the benzene measurement values were 1.37 g/k, 2.46 g/k g, 3.40 g/g, and toluene measurement values were 1.34g/k g, 2.37g/k g, 3.38g/k g, the standard recovery rate of benzene is 99.23% to 99.41%, and the standard recovery rate of toluene is 99.63% to 99.82%.
2.4 Test results
the mass of the samples taken was 2 . 0 0 8 1 g, 1.9989g, 2.0119g, and the mass of the internal targets was 0.0216g, respectively. 0.0207g, 0.0231g, the peak area of benzene is 2 6 7 4 . 9 8 1, 2 6 1 6 . 5 0 9, 2961.351 The peak area of toluene was 4511.419, 4330.195, 4876.178, and the peak area of the internal object was 16479.233, 15332.637, 19107.531, the average percentage content of benzene was 0. 1 66%, R S D was 0.62%, toluene was 0.292% and R S D was 0.42%.
3 Conclusion
Capillary column gas chromatography measures the content of benzene and toluene in water-based epoxy coatings, simple operation, precision and high accuracy, by consulting the G B/18581-2001 "current coating safety standards" of benzene and toluene content limits, this product meets the paint safety standards. The method meets the measurement requirements and is suitable for popularization.