On-site determination of the migration amount of fluorescent whitening agents from paper to finger by fluorescence spectrophotometry

A fluorescence collecting unit was self-assembled in our lab. This unit in combination with a fluorescence spectrophotometer was applied to quantify fluorescent whitening agents (FWAs) in paper samples. The unit is small and portable, containing three light emitting diodes and a lens. The light emitting diodes were used as excitation light sources, and the emitted fluorescence entered the fluorescence spectrophotometer for signal detection after passing through the lens and a fiber. With high sensitivity, not only the total amount of FWAs in the paper samples could be determined but also the trace amount of FWAs migrated from paper to finger could also be obtained. The limit of detection was 0.12 mg m^-2. Thirty practical paper notebook samples were analyzed for their FWA content before and after finger touch. For the purpose of comparison, the European standard method was also applied to determine the migration of FWA in these paper notebook samples. The correlation of the analytical results obtained by the present method with those obtained by the well-established European standard method was satisfactory.