[Determination of eleven fluorescent whitening agents in paper food packaging materials by UPLC-FLD/PDA with series double-detector]

Objective: To establish a new qualitative and quantitative ultraperformance liquid chromatography-fluorescence detector / photodiode array detector with series double-detector method for the determination of eleven fluorescent whitening agents in paper food packaging materials.

Methods: The sample was extracted with 40%acetonitrile water solution, separated by Waters ACQUITY UPLC BEH C_(18)column( 1. 7μm, 2. 1 mm × 100 mm) and eluted gradient. The excitation wavelength and emission wavelength of fluorescence detector( FLD) were 350 nm and 430 nm, and the wavelength of photodiode array detector( PDA) was 350 nm. The detectors were used in series to achieve qualitative and quantitative detection.

Results: In the substrates of paper cups, paper bowls, paper trays and paper boxes, those eleven fluorescent whitening agents were separated properly. For both detectors, in the linear range of 25- 1000 ng / m L, the correlation coefficient was greater than 0. 99, and the recoveries of spiked recoveries were between 82. 2%- 104. 1% with the RSD less than 10%( n = 6). The detection limits ofthose eleven fluorescent whitening agents were 0. 20- 0. 28 mg / kg for FLD and 1. 4- 2. 5mg / kg for PDA.

Conclusion: The eleven fluorescent whitening agents could be separated properly with complete separation, good shapes and high recovery rate. This method is easy to operate also. Thus it's an effective method to detect the fluorescent whitening agents in paper food packaging materials.