Microwave-Assisted Acid Digestion: Evaluation of Reaction Vessel Design and Performance

Abstract

Nowadays, microwave-assisted procedures using closed vessels with thermal, chemical, and mechanical resistance are the state-of-the-art for efficient digestion of samples. Safety issues related to sample reactivity should be considered and analytical throughput is also a critical parameter. The choice of a specific vessel for a target application is not trivial and simple experiments are presented here for rice flour and bovine liver samples to illustrate effects of vessel design on digestion performance. Despite using the same heating program, the residual carbon contents varied from 22 to 67% to bovine liver digests and from 7 to 96% to rice flour digests. Quantitative recoveries were obtained for most analytes. Low recoveries were observed mainly for Ca and Fe. Analytical performance is related to different sizes, shapes and the gradient of temperature for each model of digestion vessel. It was demonstrated that taller vessels improved regeneration of nitric acid.

Metodologias analíticas alternativas para a avaliação de autenticidade de alimentos explorando análises hiperespectrais e fotometria por imagens digitais

“…O procedimento de preparo de amostra utilizado, envolvendo decomposição ácida assistida por micro-ondas em sistema fechado é considerado o estado da arte entre os procedimentos disponíveis visando à determinação elementar (KORN et al, 2008;GARITTA et al, 2021) As concentrações de minerais determinadas neste estudo foram superiores aos valores reportados na literatura para canela e cássia (AL-NUMAIR et al, 2007;RIBEIRO-SANTOS et al, 2017), inclusive em relação às reportadas nas tabelas nutricionais (ANSE/CIQUAL, 2020; TBCA, 2021; USDA, 2020), conforme demonstrado na Tabela 7.6.…”