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

Abstract

Fluorescent whitening agents (FWAs) are large, conjugated, anionic substances added to paper and board during manufacture to impart “whiteness” and “brightness.” 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 standard 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 195 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 commercial “take-out” food packaging found concentrations of tetrasulfo-FWA ranging between 200 and 223 mg/kg with no interferences. This is similar to concentrations found in a previous study using liquid chromatography. ©1999 John Wiley & Sons, Inc. J Micro Sep 11: 259–262, 1999. Published 1999 John Wiley & Sons, Inc.