The aim of this doctoral thesis is the study, development and validation of different immunochemical methods for determining chemical contaminants in produce and water, in a way that they may contribute to improving food quality and therefore to assure consumer safety. Spirotetramat is a highly efficient new-generation pesticide, marketed worldwide for use as insecticide in many agricultural crops. It has systemic properties, since short after absorption it translocates through both the xylem and the phloem, thanks to the fact that it is transformed by the plant into the much more polar spirotetramat-enol. Consequently, the residue definition for this insecticide in foods of plant origin with analytical purposes also includes said metabolite. On the other hand, anatoxin-a is a secondary alkaloid with acute neurotoxicity that can be found in fresh water. This toxin is produced by seven different genera of cyanobacteria, and has been detected in lakes and other water resources on all continents. The analysis of substances like spirotetramat and anatoxin-a is currently carried out by chromatographic methods like HPLC-MS. These techniques are highly sensitive and reliable; however, they require highly qualified personnel and expensive, non-portable equipment. Nowadays, the immunochemical methods, such as the ELISA (Enzyme-Linked ImmunoSorbent Assay) or the LFIA (Lateral Flow ImmunoAssay), constitute excellent complementary analytical options to instrumental strategies, since they are fast and inexpensive analytical methods, and are also very versatile so they can be adapted to particular analytical needs, such as screening assays for large numbers of samples or portable tests with visual reading of the results. The antibody affinity and specificity from a collection of spirotetramat and anatoxin-a immunoreagents was characterized in order to select conjugate/antibody pairs suitable for the development of competitive ELISA and LFIA tests. The assay conditions were optimized, and a study of the influence of different physicochemical factors over the analytical parameters of the selected immunoassays was carried out. Subsequently, the influence of the food matrix, particularly grape, grape juice and wine, as well as water from different sources, over the assay signal and sensitivity was evaluated. The different affinity of the available antibodies towards spirotetramat and spirotetramatenol led us to optimize the sample treatment procedure, so a hydrolysis step to transform spirotetramat into spirotetramat-enol in a controlled, rapid and quantitative way, was included. Thus, it was possible to provide results in the form of the sum of the concentration of both compounds in the sample, as required by current legislation. In addition, a procedure ~ 13 ~ using QuEChERS technology was developed to extract residues of this insecticide from grape samples, and polyvinylpolypyrrolidone was used to reduce interferences from wines and juices. In the case of waters, a simple filtration was applied to remove suspended particles. Mi...