[en] In this Final Degree Project, two analytical methods were developed for the determination of lead in the microalga Isochrysis galbana and in nests of velutine or asian wasps, respectively. Both procedures are based on the preparation of slurries from the pulverized samples and their subsequent analysis using ultrasonic stirring coupled with electrothermal atomic absorption spectrometry (US-ETAAS). For each type of matrix, a previous treatment was applied to adapt them to the analysis. The microalgae were subjected to a washing step in order to eliminate the saline content of the culivation medium. The wasp nests were pulverized in the presence of liquid nitrogen to favor the crushing of the plant fibers of the material to obtain a fine powder. In addition, for this type of samples a subsequent calcination stage was necessary in order to eliminate the organic matter and to concentrate the content of the analyte. The slurries were prepared directly in the autosampler cup (1 mL) and the optimal content of HNO3 and Triton® X-100 was studied to obtain homogeneous and stable suspensions. The measurement conditions by ETAAS were studied, and in the case of microalgae it was necessary to use palladium as a chemical modifier. Each established method presents good analytical characteristics and an adequate sensitivity for the determination of Pb in the studied samples. The precision achieved was satisfactory, within the acceptance criteria (DER < 10 %), and the accuracy was acceptable, with recoveries between 116.6 % and 75.2 % for a plant material with certified and indicative lead content, respectively.

[gl] Neste Traballo de Fin de Grao desenvolvéronse sendos métodos analíticos para a determinación do chumbo na microalga Isochrysis galbana e en niños de avespas velutinas ou asiáticas, respectivamente. Ambos procedementos baséanse na preparación de suspensións das mostras pulverizadas e a súa análise posterior mediante axitación por ultrasóns xunto coa espectrometría de absorción atómica de atomización electrotérmica (US-ETAAS). Para cada tipo de matriz, aplicouse un tratamento previo para adaptalas á análise. As microalgas foron sometidas a un proceso de lavado para eliminar o contido salino do medio de cultivo. Os niños de avespa pulverizáronse en presenza de nitróxeno líquido para favorecer a trituración das fibras vexetais de dito material e obter un po fino. Ademais, para este tipo de mostras foi necesaria unha etapa de calcinación posterior para eliminar a materia orgánica e concentrar o contido de analito. As suspensións preparáronse directamente no cubilete do automuestrador (1 ml) e estudouse o contido óptimo de HNO3 e Tritón® X-100 para obter suspensións homoxéneas e estables. Estudáronse as condicións da medición por ETAAS e no caso das microalgas foi necesario empregar o paladio como modificador químico. Cada método establecido presenta boas características analíticas e unha sensibilidade adecuada para a determinación de Pb nas mostras estudadas. A precisión acadada foi satisfactoria, dentro dos criterios de aceptación (DER < 10 %), e a exactitude aceptable, con recuperacións entre o 116,6 % e o 75,2 % para un material vexetal con contido en plomo certificado e indicativo, respectivamente.