Indirect determination of aflatoxin B₁ in beer via a multi-commuted optical sensor.

This paper reports the determination of aflatoxin B₁ (AFB₁), one of the most carcinogenic substances known. A multi-commuted flow injection-solid phase spectroscopy (FI-SPS) system combined with photochemically induced fluorescence (PIF) was developed, for the first time, for its quantitative determination. A strongly fluorescent degradation product was obtained on-line by irradiation with ultraviolet light. The determination was carried out by measuring the fluorescence intensity of the photo-product at 353/424 (λ (ex)/λ (em)), once retained on C₁₈ silica-gel filling the flow-cell. A linear dynamic range of 0.09-12 µg l⁻¹, detection limit as sensitive as 29 ng l⁻¹ and a relative standard deviation (RSD) of 1.4% were obtained. The method proposed was satisfactorily applied to the determination of AFB₁ in different types of beer (normal and non-alcoholic). Hydrophobic compounds were eliminated from beer samples and AFB₁ was extracted with acetonitrile by solid-phase extraction on C₁₈ sorbent. Recoveries of the target compound from spiked beers were between 94 and 106%. The results obtained in the analysis of real samples are in good agreement with those provided by a reference chromatographic method.