ISSUE FOCUS FEED & ADDITIVE MAGAZINE April 2023 33 If the sample is free of mycotoxins, or below the level of detection, a line will not appear. Quantification of mycotoxin levels is possible with a specialized reader or even through a smartphone app. Similar to LFDs, ELISA tests rely on the interaction between specific antibodies and mycotoxins that are present in a sample. The main difference with ELISA is that instead of using an antibody-coated test strip, ELISA technology uses antibody-coated microwells and a secondary antibody conjugate solution that is linked to an enzyme, which creates a detectable signal using substrate that remains when any unbound material is removed. The colour change that results from the reaction between the substrate and the enzyme can be measured using a spectrophotometer or microplate reader. Proportionally, the intensity of the signal created is inverse to the levels of mycotoxins present, i.e., the darker the colour, the less mycotoxin that is in the sample. Comparing the signal intensity that is generated against a set of known standards allows for the determination of the concentration of mycotoxin that is present in the sample. NEAR INFRARED SPECTROMETRY A mycotoxin detection method that does not fall neatly into either the rapid test or lab-based category, but has been receiving greater attention in recent years, is near infrared spectrometry (NIR). It works by revealing the interaction between electromagnetic radiation and chemical bonds in a given sample. Available as both handheld or desktop devices, similar to LFDs or ELISA methods, NIR offers a quick and inexpensive way to screen samples for mycotoxins. This system does, however, have a number of limiting factors, including large standard errors, lack of sensitivity and the inability to meet the demands of regulatory compliance in a testing program. This inability to accurately quantify mycotoxin concentrations means NIR remains an initial screening method that will highlight if a sample contains high or low toxin concentrations, with further testing required to accurately inform what mycotoxin control solutions should be implemented. LAB-BASED METHODS Of the lab-based methods that are available, high performance liquid chromatography (HPLC) and liquid chromatography tandem mass spectrometry (LCMS/MS) are two of the most recognized options. HPLC is based on the separation of mycotoxins in a sample using a high-pressure liquid chromatography column that contains a solid absorbent material. This stationary adsorbent material interacts with the mycotoxins in the sample, leading to their separation based on physical and chemical properties. Once separated, the mycotoxins are passed through a column at high pressure via a detector. As it passes through, the levels of mycotoxins is determined by comparing the signal that is given off against a set of known standards. LCMS/MS involves a combination of using the separation techniques that HPLC delivers with the powerful analytical properties of mass spectrometry. Once the sample extract has been separated based on its chemical and physical properties, the compounds are then sent to the mass spectrometer. The first mass analyser acts as a filter and only allows compounds of a certain mass through. For examPROS AND CONS OF RAPID TEST METHODS Pros • Quick generation of results, less than 25 minutes • Relatively inexpensive compared to labbased reference methods • Allow for on-site testing • Do not require trained lab technicians Cons • Only detects up to six main mycotoxins, individually • Not suitable for finished feeds or total mixed rations (TMRs) • Less sensitive than more advanced laboratory methods • Some providers still use chemical solvents
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