Mycotoxins are toxic metabolic by-products of fungi which can dangerously contaminate a wide variety of human foods and animal feeds, including edible nuts, oilseeds, cereal grains, and forages and products derived from them. Among the most significant are aflatoxins, a group of closely-related mycotoxins produced by the fungi Aspergillus flavus and A. parasiticus. Not all isolates of the fungus produce aflatoxins; thus, the mere presence of A. flavus or A. parasiticus does not mean that aflatoxins will be present in the substrate. Accordingly direct determination of mycotoxin level is an important aspect of quality control in foods and feeds.
Such measurements have conventionally been carried out by the use of high performance liquid chromatography (HPLC). However in those cases where HPLC equipment is not available or appropriate, determination by thin layer chromatography (TLC) is also possible. Commercial scanners are available for mycotoxin determination after TLC separation, using mercury lamps with an emission wavelength of 366 nm as a light source to stimulate fluorescence, which is detected and quantified by photo-multipliers.
For quantitative testing there are also radioimmunoassay techniques and immunochemically-based techniques such as enzyme-linked immunosorbent assay (ELISA) methods.
Qualitative detection of mycotoxins can be carried out using small chromatographic columns (traditionally called ‘minicolumns’). Various minicolumn methods have been adopted as official tests of the AOAC International (Association of Official Analytical Communities). The major uses of minicolumn tests for aflatoxin are as “go” or “no go” field tests to accept or reject for example a truckload of peanuts or corn, and as central laboratory screening tests to avoid the need to quantitatively test samples that do not contain a detectable amount of aflatoxin.
In our copending patent application PCT/GB2006/050115 we describe apparatus for the detection or determination of a target comprising a target compound, a derivatised target compound or target compound-stimulated moiety, said apparatus comprising: means for mounting a sample cartridge, which sample cartridge comprises a packing or coating capable of immobilising or isolating the target in a layer or band, an excitation unit for emitting radiation that excites fluorescent radiation, a detection unit that is sensitive to said fluorescent radiation, and means for relatively moving the mounting means and the detection unit whereby the fluorescent radiation from the target may be sensed.
Whilst the apparatus described in patent application PCT/GB2006/050115 is extremely useful, it only detects a single target compound or target compound-stimulated moiety at a time. Whist one tries to have only a single target compound, in practice there are often more than one target compounds present and it would be useful to be able to identify and quantify the plurality of target compounds.
It would be even more useful to be able to be able to detect one or more than one target compound or derivatised target compound at a time and one or more than one target compound at a time which does not produce fluorescent radiation.
Not all target compounds of interest fluoresce and it would be useful to identify such target compounds.