Mycotoxins quantification in feed and raw materials is extremely challenging because they are found in very low concentrations

Mycotoxins are toxic secondary metabolites produced by fungal species which contaminate raw materials and feed. The prevalence of mycotoxins worldwide supposes an outstanding challenge that has a negative impact on both animal and human health. The obligation to comply with regulation limits requires developing highly effective analytical techniques to detect, identify and quantify these compounds in feed and raw materials. 

 Nowadays, high performance liquid chromatography (HPLC) is one of the most widely used techniques for mycotoxins detection due to high reliability and sensitivity, but there are also, and increasingly, rapid test kits in the market designed according to their purpose and application.  

Regardless the analytical method selected, a critical parameter for mycotoxins control is the huge heterogeneity of their distribution within the sample. For this reason, sampling becomes one of the most important steps to carry out for a reliable mycotoxins analysis. This is because mycotoxins are unevenly distributed in the product, making it even more difficult to achieve representative and reliable analyses. 

Mycotoxins analysis methods

A wide variety of analytical methods have been developed for mycotoxins analysis. These can be classified in two main groups: chromatographic methods and rapid test methods. 

-Chromatographic methods (HPLC-MS)

It is a fact that feed and raw materials usually have multiple contamination by several mycotoxins in low concentrations. Using chromatographic methods, specifically with HPLC-MS (high performance liquid chromatography with a mass spectrometry detector), the simultaneous identification and quantification of several mycotoxins is possible in complex samples with low concentration.

Once sampling has been done, the analytical procedure to detect mycotoxins in feed and/or raw materials require some previous pretreatment steps in order to analyze the samples: 

First, the sample must be prepared to the optimal conditions for assay. This step may involve freeze-drying, crushing, and sieving processes, among others. 

Once the sample is ready, the extraction step begins, followed by the purification stage. These steps consist of extracting the mycotoxins from the sample, through different processes and solvents (organic and aqueous), and subsequently purifying the sample, in such a way that the purest possible extract is obtained for the assay (Amelin et al., 2013 ). 

Usually these two stages of the analytical process tend to be the most complex.  Due to the complexity of the samples, a good optimization of the parameters involved is necessary in order to obtain a robust and precise analytical method. 

Finally, the sample is injected into the equipment with all parameters optimized. 

HPLC-MS analytical method is the most reliable and sensitive for the detection and quantification of mycotoxins in samples of feed and raw materials. Besides, these techniques are fully automated and are performed in highly specialized laboratories. Furthermore, although these methods provide complete and reliable results, they are quite expensive tests that require equipment and qualified personnel. 

Rapid test methods

This group of analytical techniques allow rapid analysis with little equipment. They are mainly based in immunodetection techniques, and they are usually very useful for screening in feed mills as they allow analyzing numerous samples. 

Among them, we can find the quantitative method ELISA (Enzyme-Linked ImmunoSorbent Assay). This method is based on the detection of an immobilized antigen on a solid phase through an antibody that, through an enzyme, produces a reaction whose product can be measured spectrophotometrically, for example. This technique is versatile, robust, and simple, and employs economical reagents. 

Another immuno testing technique is the lateral flow test (LFT) or immunochromatographic strip test for the quantitative detection of mycotoxins. This technique involves the addition of the sample extract to a buffer solution and the resulting solution is added to a lateral flow test strip. This strip is incubated for a short period of time and read using a travel reader device. 

Estos métodos son fáciles, baratos y los resultados se obtienen en un breve espacio de tiempo. Además, no se precisa de personal especializado para su uso. Aún así, estas técnicas necesitan de un análisis posterior mediante HPLC-MS para su confirmación ya que, según la matriz analizada los inmunoensayos pueden dar resultados poco precisos y/o no fiable (Kolossova et al., 2009).