Competitive lateral flow immunoassay for myco- or phycotoxin: the Test zone is formed by adsorbing a conjugate of the target compound (toxin); Control zone is formed by anti-species antibodies (white), reporters are specific (anti-toxin antibodies, black) and non-specific (grey) antibodies labelled with gold nanoparticles (GNP). Focalization of GNP-labelled antibodies determines a visible/detectable colour appearance on both the Test and Control lines, which can be related to analyte amount in a liquid sample.