title: Effect of simultaneous cooling on microwave-assisted wet digestion of biological samples with diluted nitric acid and O2 pressure.
abstract: The present work evaluates the influence of vessel cooling simultaneously to microwave-assisted digestion performed in a closed system with diluted HNO3 under O2 pressure. The effect of outside air flow-rates (60-190 m(3) h(-1)) used for cooling of digestion vessels was evaluated. An improvement in digestion efficiency caused by the reduction of HNO3 partial pressure was observed when using higher air flow-rate (190 m(3) h(-1)), decreasing the residual carbon content for whole milk powder from 21.7 to 9.3% (lowest and highest air flow-rate, respectively). The use of high air flow-rate outside the digestion vessel resulted in a higher temperature gradient between liquid and gas phases inside the digestion vessel and improved the efficiency of sample digestion. Since a more pronounced temperature gradient was obtained, it contributed for increasing the condensation rate and thus allowed a reduction in the HNO3 partial pressure of the digestion vessel, which improved the regeneration of HNO3. An air flow-rate of 190 m(3) h(-1) was selected for digestion of animal fat, bovine liver, ground soybean, non fat milk powder, oregano leaves, potato starch and whole milk powder samples, and a standard reference material of apple leaves (NIST 1515), bovine liver (NIST 1577) and whole milk powder (NIST 8435) for further metals determination by inductively coupled plasma atomic emission spectroscopy (ICP-OES). Results were in agreement with certified values and no interferences caused by matrix effects during the determination step were observed.
authors.affiliation: Departamento de Química, Universidade Federal de Santa Maria, Santa Maria, Rio Grande do Sul 97105-900, Brazil.
authors.forename: Cezar A
authors.initials: CA
authors.lastname: Bizzi
authors.affiliation: Departamento de Química, Universidade Federal de São Carlos, São Carlos, São Paulo 13565-905, Brazil.
authors.forename: Joaquim A
authors.initials: JA
authors.lastname: Nóbrega
authors.affiliation: Departamento de Tecnologia e Ciência dos Alimentos, Universidade Federal de Santa Maria, Santa Maria, Rio Grande do Sul 97105-900, Brazil.
authors.forename: Juliano S
authors.initials: JS
authors.lastname: Barin
authors.affiliation: Departamento de Química, Universidade Federal de Santa Maria, Santa Maria, Rio Grande do Sul 97105-900, Brazil.
authors.forename: Jussiane S S
authors.initials: JS
authors.lastname: Oliveira
authors.affiliation: Departamento de Química, Universidade Federal de Santa Maria, Santa Maria, Rio Grande do Sul 97105-900, Brazil.
authors.forename: Lucas
authors.initials: L
authors.lastname: Schmidt
authors.affiliation: Departamento de Química, Universidade Federal de Santa Maria, Santa Maria, Rio Grande do Sul 97105-900, Brazil.
authors.forename: Paola A
authors.initials: PA
authors.lastname: Mello
authors.affiliation: Departamento de Química, Universidade Federal de Santa Maria, Santa Maria, Rio Grande do Sul 97105-900, Brazil. Electronic address: ericommf@gmail.br.
authors.forename: Erico M M
authors.initials: EM
authors.lastname: Flores
mesh_terms: D000273:Adipose Tissue; D000818:Animals; D002417:Cattle; D002623:Chemistry Techniques, Analytical / Q000379:methods*; D003611:Dairy Products; D005504:Food Analysis; D008099:Liver; D027845:Malus; D008872:Microwaves; D017942:Nitric Acid / Q000737:chemistry*; D031341:Origanum; D010100:Oxygen / Q000737:chemistry*; D018515:Plant Leaves; D011198:Solanum tuberosum; D013025:Glycine max; D013213:Starch; D013696:Temperature
chemical_list: D017942:Nitric Acid; D013213:Starch; D010100:Oxygen
keywords: Digestion efficiency; Microwave-assisted digestion; Mild conditions; Pressurized vessel; Simultaneous cooling; Wet ashing