New analytical strategies based on mass spectrometry for food fraud and food safety

Abstract

[eng] The continuous increase in adulterations and contamination in food puts the integrity of food under continuous threat, which generates suspicion in the consumer. For these reasons, assuring the quality, authenticity, and safety of food for consumers and stakeholders is of great importance to the agri- food economy and human and animal health. To face fraudulent practices and food safety alerts, food control laboratories require fast, reliable, and simple analytical methods fulfilling the selectivity and sensitivity requirements and providing chemical structural information about the target compounds. This thesis is focused on the development of analytical strategies based on mass spectrometry to deal with two issues in the food analysis field, food fraud and safety. Regarding food fraud, in this thesis, analytical methods based on ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC‒MS/MS) for the determination of pigments and banned dyes in oils and spices have been developed. In addition, a UHPLC method coupled to high-resolution mass spectrometry (UHPLC‒HRMS) has been proposed to obtain pigment profiles for the characterization and authentication of these matrices regarding their geographical origin. For this purpose, both the chromatographic method (stationary phase and mobile phase) and the sample treatment (solid-phase and solvent extraction) have been optimized. The ionization behavior of analytes, as well as the product ions generated with different atmospheric pressure ionization (API) sources, such as electrospray (ESI), atmospheric pressure chemical ionization (APCI), and photoionization (APPI), have been studied. MS/MS studies allowed the assignment of the most characteristic and relevant product ions and the proposal of fragmentation pathways for each family of compounds using the complementary information obtained with both low- and high- resolution mass spectrometry. These studies also allowed the identification of common losses and/or fragment ions useful for the rapid detection of analytes in complex food samples, and the identification of unknown related compounds. The UHPLC‒MS/MS methods developed have provided good performance and enough sensitivity to determine the banned dyes in oils and spices. While UHPLC‒HRMS methods combined with chemometric methods have demonstrated the feasibility to detect fraudulent activities derived from the mixture of different qualities of olive oils and spices, as well as due to the doubtful geographical origin of the samples. Concerning food safety, the monitoring of contaminants requires not only methods that allow their unequivocal determination in the laboratory, but also on-site screening methods that reduce the number of samples to be analyzed by control laboratories. In this sense, a UHPLC‒MS/MS method has been developed for the determination of primary aromatic amines (PAAs) that migrate from food contact materials, as well as screening techniques based on ambient ionization mass spectrometry for the detection of growth promoters in food supplements. For the determination of PAAs, a pentafluorophenylpropyl column with superficially porous particles has been proposed, enabling the separation of 23 PAAs in a short analysis time and avoiding the use of ionic pair reagents in the mobile phase by using acidic additives. Furthermore, the ionization behavior of analytes in different API sources has been studied and the product ions generated by tandem spectrometry have been assigned to develop a reliable method. These studies demonstrated that APCI is the most suitable ionization source since it presents detection limits that meet with the legislation established by the European Union with the advantage of being less susceptible to matrix effects. On the other hand, two on-site screening methods have been proposed for the direct analysis of selective androgen receptor modulators (SARMs) and anabolic steroid esters. For this purpose, the laser diode thermal desorption-electrospray ionization (LDTD-ESI) and atmospheric solids analysis probe (ASAP) have been used. The configurations of the different devices (position and distances) have been evaluated and the operational parameters (composition and flow of solvent, temperature) have been optimized to obtain the highest ionization efficiency of analytes. Both methods have demonstrated the capability to identify suspect compounds in a short analysis time (<1 min) and their applicability for future on- site analysis of organic compounds.

[spa] El aumento continuado de adulteraciones y de contaminaciones hace que la integridad de los alimentos esté bajo una continua amenaza. Para hacer frente a estos problemas, los laboratorios de control alimentario necesitan disponer de métodos analíticos rápidos, fiables y sencillos que cumplan con los requerimientos de selectividad y sensibilidad y que proporcionen información estructural sobre los compuestos identificados. Así, esta tesis se centra en el desarrollo de estrategias analíticas basadas en la espectrometría de masas para hacer frente a dos problemáticas en el campo del análisis de alimentos, el fraude y la seguridad alimentaria. Para desarrollar todos estos métodos, se ha realizado un estudio exhaustivo del tratamiento de muestra y el comportamiento cromatográfico de las diferentes familias de compuestos, cuando esto era necesario, mediante la evaluación de diferentes fases estacionarias o la composición de la fase móvil, así como amplios estudios de ionización empleando fuentes a presión atmosférica convencionales y otras más novedosas con el fin de obtener iones característicos. Así mismos, se han realizado estudios de fragmentación que permitieran una detección inequívoca de los analitos de interés. En lo referido al fraude alimentario, los estudios realizados en esta tesis han permitido desarrollar métodos de análisis basados en la cromatografía de líquidos de ultra elevada eficacia acoplada a la espectrometría de masas en tándem (UHPLC‒MS/MS) para la determinación de pigmentos y colorantes prohibidos en aceites y especias. Además, se ha propuesto un método de UHPLC acoplado a la espectrometría de masas de alta resolución (UHPLC‒HRMS) para la obtención de perfiles de pigmentos que permita la caracterización y autenticación de estas matrices respecto a su denominación de origen. En lo que respecta a la seguridad alimentaria, se ha desarrollado un método de UHPLC‒MS/MS para la determinación de aminas aromáticas primarias que migran de materiales en contacto con los alimentos, así como técnicas de cribado basadas en “Ambient Ionization-Mass spectrometry” para la detección de promotores de crecimiento en suplementos alimentarios. Además, estas técnicas de cribado propuestas permiten el análisis in-situ de los alimentos, lo cual permitirá aligerar considerablemente la carga de trabajo de los laboratorios de control alimentario.