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Um sistema de combustao iniciada por microondas foi acoplado a um espectrometro de absorcao atomica com atomizacao em tubo metalico aquecido com chama (FF) do tipo ar-acetileno para a determinacao de cadmio em sangue. Amostras de sangue liofilizado foram preparadas como comprimidos, posicionadas em um suporte de quartzo e introduzidas em uma câmara de vidro empregada para a etapa de combustao. A câmara foi acoplada ao tubo metalico usando tubos de politetrafluoroetileno e de quartzo. A ignicao foi iniciada por irradiacao microondas usando solucao de nitrato de amonio adicionada em papel previamente descontaminado. Oxigenio foi usado na etapa de combustao e para o transporte dos produtos gerados ate o tubo aquecido. Grafite em po de alta pureza foi misturada com as amostras antes do preparo dos comprimidos. O volume da solucao de NH 4 NO 3 , a vazao de oxigenio, a estequiometria da chama, o tipo de suporte e a quantidade de massa de amostra foram avaliados. A calibracao foi possivel usando solucao de referencia adicionada a comprimidos de grafite de alta pureza, nao sendo necessario o uso de material de referencia certificado (CRM). Foi possivel a combustao de ate 56 mg de amostra, permitindo a obtencao de limite de quantificacao de 0,018 µg g -1 e massa caracteristica de 50 pg de Cd. Os valores dos brancos foram baixos (absorbância integrada menor que 0,01 s). Os resultados foram considerados satisfatorios com respeito a exatidao (concordância com valores de CRMs entre 95 e 99%) e a precisao (coeficiente de variacao < 12%). Ate 15 determinacoes podem ser feitas por hora incluindo a etapa de pesagem. Microwave-induced combustion system was coupled to a metallic flame furnace (FF) atomic absorption spectrometer and applied for cadmium determination in blood. Lyophilized blood samples were prepared as pellets, positioned on a quartz holder and introduced into a glass chamber used for the combustion step. The glass chamber was coupled to the metallic flame furnace by using polytetrafluoroethylene and quartz tubes. Ignition was performed by microwave radiation using ammonium nitrate solution added to a small piece of previously cleaned paper. Oxygen was used to assist the sample combustion and also to transport combustion products up to the FF heated by an air/acetylene flame. High purity graphite powder was mixed with samples before pellets preparation. The volume of NH 4 NO 3 solution, oxygen flow-rate, flame stoichiometry, sample holder type and the sample mass range were evaluated. Calibration step was feasible using adsorbed reference solution in pelletized high purity graphite avoiding the use of certified reference material (CRM). Sample masses up to 56 mg could be used allowing quantification limit of 0.018 µg g -1 and characteristic mass of 50 pg Cd. Low values for blanks were obtained (integrated absorbance lower than 0.01 s) and results were considered satisfactory regarding to both accuracy (agreement with results using CRMs between 95 to 99%), and precision (relative standard deviation < 12%). Up to 15 determinations can be performed per hour including the weighing step.

Determination of Cd in blood by microwave-induced combustion coupled to flame furnace atomic absorption spectrometry