Determination of fluorescent whitening agents in paper and board packagingmaterials by capillary electrophoresis

Fluorescent whitening agents (FWAs) are large, conjugated, anionic substanc es added to paper and board during manufacture to impart "whiteness" and "b rightness." A method has been developed to determine disulfo-, tetrasulfo-, and hexasulfo-FWAs in paper and board using capillary electrophoresis (CE) . Fluorescent whitening agents are extracted from paper samples using a sta ndard hot-water extraction. The extracts are analyzed by free-flow CE using ammonium acetate (100 mM, pH 9.0) as the run buffer. Fluorescent whitening agents are detected by through-column ultraviolet (UV) scanning between 19 5 and 365 nm. Limits of detection (mg/kg paper) ranged between 2 and 12 mg/ kg with recoveries between 84 and 92%. Analysis of three samples of commerc ial "take-out" food packaging found concentrations of tetrasulfo-FWA rangin g between 200 and 223 mg/kg with no interferences. This is similar to conce ntrations found in a previous study using liquid chromatography. (C) 1999 J ohn Wiley & Sons, Inc.