HPTLC-Densitometry Screening and Mass Identification of Fluorescent Whitening Agents Contamination in Cereal Flour

Abstract

In recent years, there was increasing concerns on food safety issues associated with fluorescent whitening agents from package materials. Here, we reported the development of a facile and reliable method suitable for high-throughput quantification and identification of two common fluorescent whitening agents (FWA 184 and FWA 367) in cereal products (wheat and rice flour), platformed by high-performance thin-layer chromatography. First, the sample preparation and cleanup were rapidly accomplished via an optimized solid–liquid extraction. The extracts and reference standard were simultaneously separated on silica gel plates, using the mixture of toluene and ethyl acetate (10/0.3, v/v) as the mobile phase. Then, rapid quantification was performed with densitometry in fluorescent mode (365 </ 400 nm, mercury lamp), reaching limit of detection 18–21 μg/kg; meanwhile, good linearity (R2 = 0.9999) of quantification can be achieved within a broad range (100–2000 pg/band). With real cereal samples, the quantitative measurement was validated, showing good spike-recovery rates (88.0–108.4%). Furthermore, the conclusive identification of the targeted band was directly realized by in situ mass detection, providing compound-specific signals (m/z 363.09 and 431.18, for FWA 184 and FWA 369, respectively) as the fingerprint evidence. The proof-of-concept result of this work demonstrated that HPTLC as a versatile analytical platform can achieve an ideal balance among throughput, simplicity, and detectability, therefore, particularly suitable for screen-oriented food analysis.