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

Abstract

Um sistema de combustão iniciada por microondas foi acoplado a um espectrômetro de absorção atômica com atomização em tubo metálico aquecido com chama (FF) do tipo ar-acetileno para a determinação de cádmio 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 combustão. A câmara foi acoplada ao tubo metálico usando tubos de politetrafluoroetileno e de quartzo. A ignição foi iniciada por irradiação microondas usando solução de nitrato de amônio adicionada em papel previamente descontaminado. Oxigênio foi usado na etapa de combustão e para o transporte dos produtos gerados até o tubo aquecido. Grafite em pó de alta pureza foi misturada com as amostras antes do preparo dos comprimidos. O volume da solução de NH 4 NO 3 , a vazão de oxigênio, a estequiometria da chama, o tipo de suporte e a quantidade de massa de amostra foram avaliados. A calibração foi possível usando solução de referência adicionada a comprimidos de grafite de alta pureza, não sendo necessário o uso de material de referência certificado (CRM). Foi possível a combustão de até 56 mg de amostra, permitindo a obtenção de limite de quantificação de 0,018 µg g -1 e massa característica de 50 pg de Cd. Os valores dos brancos foram baixos (absorbância integrada menor que 0,01 s). Os resultados foram considerados satisfatórios com respeito à exatidão (concordância com valores de CRMs entre 95 e 99%) e à precisão (coeficiente de variação < 12%). Até 15 determinações 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 de...

Method for Determining Regional Reference Values of Metal Content in Biological Substrates and Their Intake into the Body via Drinking Water

“…It can be used without reference samples. It has a high sensitivity, but is an expensive method, which limits its use for numerous determinations of the metal content in the biosubstrates [ 27 ].…”

“…The generally accepted method of the quantitative analysis of biosubstrates is atomic absorption spectrometry, as it is the most selective, reproducible, and relatively inexpensive method that allows the fast, high-quality, and sufficiently high sensitivity determination of trace element concentrations in various biosubstrates [ 27 , 29 ]. The flame atomizers allow the determination of Na, K, Rb, Cs, Ca, and Mg; for the determination of Pb, Zn, Cd, Cr, Cu, As, Se, Mn, Ni, Fe, etc., variants with nonflammable atomizers are usually used [ 30 ].…”

Microwave-Induced Combustion

“…This system was successfully applied for botanical (tea) [70] and biological (blood [71]) samples for further Cd and Pb determination and relatively low LODs were obtained. As mentioned before, the combustion device can be easily fitted to conventional atomic absorption spectrometers and the procedure was exactly the same for different kinds of samples, and up to 20 determinations can be performed in 1 h (excluding the grinding and pressing steps).…”

Microwave-Assisted Solid Sampling Analysis Coupled to Flame Furnace Atomic Absorption Spectrometry for Cd and Pb Determination in Food-Contact Polymers

“…Some studies have developed systems allowing solid sampling using FAAS (SS-FAAS) [15][16][17][18][19][20][21], which minimizes the sample preparation step and reduces the LOD values. One example of this approach is the combination of microwave-induced combustion (MIC) with flame furnace atomic absorption spectrometry (MIC-FF-AAS) [22,23]. In this study, the sample was combusted in a domestic microwave oven, and the analyte gases were directed to a flame furnace atomizer positioned over the flame.…”

“…In this study, the sample was combusted in a domestic microwave oven, and the analyte gases were directed to a flame furnace atomizer positioned over the flame. However, this system presented some reproducibility issues, and it was hard to couple it to the FAAS equipment [22,23].…”