Studies On The Analytical Methods For The Fluorescent Whitening Agents In Food Packaging Papers

Fluorescent whitening agents (FWAs) are a kind of compounds to increase whiteness character. In the paper and packaging industries, almost 80%of FWAs used are 4,4’-diaminostilbene-2,2’-disulfonic acid-based fluorescent whitening agents (DSD-FWAs). As DSD-FWAs have potential toxicities, they were not allowed to be added in the food packaging materials according to the regulations of USA, Europe and China. The characters and analytical methods of DSD-FWAs in food packaging papers (Chapter 1) were reviewed. Some analytical methods, such as the fluoremetric method, HPLC-PDA method and HPLC-FLD method on DSD-FWAs in food packaging papers were developed. The proposed methods were rapid, accurate and repeatable.(1) Determination of FWAs in food packaging papers by fluoremetric method (Chapter 2)The excitation and emission wavelength spectrums of FWAs were scanned to confirm the optimal excitation and emission wavelength. The background fluorescence of experimental solvents and apparatus were inspected. Some steps were conducted to reduce the background fluorescence. Based on the above research, a rapid screening fluoremetric method on FWAs in food packaging papers was established. The method meets the requirement of analysis according to the method validation experiments.(2) Determination of 11 DSD-FWAs by HPLC-PDA (Chapter 3)(A) Chromatography:The optimizations on the key factors in the chromatography, such as the elution method, organic modifier, concentration of ion pair reagent and the pH value of mobile phase were conducted. The 11 DSD-FWAs were successfully separated in the proposed condition.(B) Sample preparation:The food packging papers were prepared by shredding and high-speed smashing. It was validated that the preparation method was fully representative.(C) Optimization of extraction:The extraction method, solvent, temperature, duration time and times were optimized, and some problems of low recoveries were solved.The established method was systematically validated by a single laboratory. All parameters meet the methodology index. Limit of detections of the method was 1.1～2.0 mg/kg. This method was more selective in comparison of the fluoremetric method.(3) Determination of 11 DSD-FWAs by HPLC-FLD (Chapter 4)An analytical method of 11 DSD-FWAs in food packaging papers by HPLC-FLD was developed. Comparing to HPLC-PDA method, this method was as accurate, precise and more sensitive. Limit of detection of the method was 0.12～0.24 mg/kg. The proposed method provides a reliable means for risk monitoring and assessment of DSD-FWAs in food packaging paper.(4) Stability research on DSD-FWAs (Chapter 5)It was found that DSD-FWAs would not be biodegraded. However, they were easily photodegraded. The researches conducted indicated that the illumination condition for DSD-FWAs should be lower than 20 Lux.