Detection of alkaloids in foods with a multi-detector high-performance liquid chromatographic system

Abstract

A general screening method for alkaloid drugs in foods is described based on high-performance liquid chromatography with ultraviolet detection at three wavelengths, followed by fluorescence and electrochemical detectors in series. The chromatographic conditions include an ion-pairing reagent, which makes it possible to chromatograph acidic and basic drugs with one screen. Relative response ratios were determined from the peak areas of the alkaloids on the basis of all the detector signals. These ratios were used to create a “fingerprint” of the drugs and to predict the identity of an unknown component in a sample matrix. The fluorescence and electrochemical detectors allowed a detection limit for many of the alkaloids which would not be attainable with the ultraviolet detector alone. Typical detection limits with the electrochemical detector were 5–50 ng/ml and with the fluorescence detector 5–500 ng/ml, while the ultraviolet detector had detection limits of 1–20 μg/ml. The spiking concentrations in the relative response ratio experiments were approximately five times above the lowest detection limit. The extraction method investigated for orange juice yielded recoveries for most alkaloids of 80–100%. A stability study of ergot alkaloids in various food matrices demonstrated degradation, depending on the matrix, temperature, and duration of the experiment.