| Fluorescent whitening agent 4,4’-bis(2-methoxystyryl)-1,1’-biphenyl(CBS-127) and 2,5-Di(5-tert-butylbenzoxazol-2-yl)thiophene(OB)are widely used in paper and food contact materials, but long-term use of paper which added to fluorescent whitening agent will affect vision, the food packaging which touched directly will have serious consequences for human health. Therefore, it is very important to detect fluorescent whitening agents in paper and food contact materials accurately. High performance liquid chromatography is an important analytical technique in the fields of chemistry, medicine, industry, agriculture, commodity inspection, forensic and so on. It can detect fluorescent whitening agent OB and CBS-127 accurately and rapidly.In the first chapter, fluorescent whitening agent’s types, synthesis, physical and chemical properties, application and harm were introduced briefly. Furthermore, several methods of detection, extraction, purification, the background and significance of the research were summarized.In the second chapter, mounts of experiments were done to determine the excitation and emission wavelength of the two substances, which shows that the excitation wavelength of the fluorescence detector is 370 nm, and the emission wavelength is 404 nm. Optimization of the detection conditions was carried out from the aspects of the solvent, mobile phase composition, column temperature and flow rate. The optimized conditions for this detection are dichloromethane as the standard solvent, the mobile phase composition was Vmethanol: Vwater: Vacetonitrile=75:5:20, the column temperature was 30℃, the flow rate was 1.0 m L/min. Under the optimal experimental conditions, the linear relationship of the fluorescent whitening agent OB was Y=30.938X+1.3968, the correlation coefficient was 0.9996, Linear range is 0.01~1 mg/L, the detection limit is 0.001 mg/kg. The linear relationship of the fluorescent whitening agent CBS-127 was Y=62.271X+6.5898, the correlation coefficient was 0.9998, linear range is 0.01~1 mg/L, the detection limit is 0.004 mg/kg.In the third chapter, the extraction solvent, volume and ultrasonic time were optimized. The best optimum conditions was 30 m L dichloromethane as the extraction agent, extracted three times, ultrasoniced 30 min in 10 m L solvent every time. Comparing the purification effect of C18 and CN columns as stationary phase, CN column’s recovery rate was significantly higher than the C18 column. The conditions of detecting OB and CBS-127 in paper cup by CN SPE-HPLC was determined. The sample solution, leaching solution, elution reagent and the volume of elution reagent at the purification step in CN column were optimized. The hexane-dichloromethane(3:7) as sample solution, leaching with 80% methanol water, eluted with 6 m L ethanol and 6 m L dichloromethane.Differents paper cups were analyzed under the optimum experimental conditions,the results showed that the concentration of OB were 0.0268±0.28 μg/g、0.4608±0.10 μg/g 、 0.2124±0.06 μg/g and 0.4900±0.06 μg/g, average recovery rate were 84.84%~92.58%, only detected to CBS-127 in samples 1 and 4, the concentrations were 0.0384±0.12 μg/g and 0.0222±0.02 μg/g, average recovery rate were 79.21%~84.66%In the forth chapter, simultaneous determination of fluorescent whitening agent CBS-127 and OB by multi-walled carbon nanotubes solid phase extraction-High Performance Liquid Chromatography. Comparing the dispersed solid phase extraction and solid phase extraction in experiments, the kind of eluent in dispersive solid phase extraction was explored, the dosage of multi-walled carbon nanotube, type and volume of eluent in solid phase extraction were explored, however, both methods can not simultaneous detection of fluorescent whitening agent CBS-127 and OB effectively.Then, the fluorescent whitening agent CBS-127 and OB in food contact materials were detected by MWCNTs solid phase extraction-high performance liquid chromatography respectively. The composition of mobile phase, column temperature, extraction solvent, extraction volume and ultrasonic time, the dosage of multi walled carbon nanotube, sample solution and leaching solution, eluent and elution volume were optimized respectively.(1) The optimum experiment conditions of the CBS-127 as follows: the mobile phase is Vmethanol: Vwater(95:5), column temperature is 30℃, using dichloromethane 21 m L as the extraction solvent,extracted three times, 7 m L every time, fresh keeping film and disposable plastic gloves was ultrasounded 20 min every time, bread bags was ultrasounded 30 min, the dosage of multi walled carbon nanotubes was 40 mg, ethylacetate-dichloromethane(4:6) as sample solution, 70% methanol-water 2 m L as leaching solution, 5% ammonium-acetonitrile mixture solution 5 m L as eluent, average recovery rate was 90.65%~92.91%.The food contact materials(fresh keeping film, disposable plastic gloves and bread bags) were measured under the optimum experimental conditions. The results showed that the concentration of CBS-127 were 0.8742±0.04 μg/g, 0.4752±0.02 μg/g and 1.2084±0.08 μg/g respectively, the average recovery rate was 90.65±0.11%、92.91±0.23% and 91.22±0.16%.(2) The optimum experiment conditions of the OB as follows. the mobile phase was Vmethanol: Vwater was 85:15, the column temperature is 40 ℃, the hexane as extraction agent, extraction volume was 30 m L, extracted three times, extraction volume was 10 m L and ultrasonic time was 30 min every time. Dosage of multi wall carbon nanotubes was 20 mg, sample solution was 60% dichloromethane-hexane mixture solution, leaching solution was 90% methanol-water, eluent with 4 m L THF.Under the optimal experimental conditions OB in food contact materials(fresh keeping film, disposable plastic gloves, and plastic bags) were determined. Experimental results shows that the plastic wrap was not detected, the disposable plastic gloves’ s content was 59.9316±1.60 mg/g. The average content of plastic bags was 0.7551±0.8 mg/g by calculated, the average recovery rate in three materials were 90.74±0.15%、90.02±0.18% and 87.96±0.23%. |
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