Document Detail


A critical evaluation of digestion procedures for coffee samples using diluted nitric acid in closed vessels for inductively coupled plasma optical emission spectrometry.
MedLine Citation:
PMID:  19362204     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The efficiency of diluted nitric acid solutions for digesting regular coffee samples was evaluated employing two closed vessel procedures: one was based on microwave-assisted heating and the other was based on conductive heating using pressurized Parr bomb. The efficiency of digestion was evaluated by determining residual carbon content (RCC) and residual acidity. The digestion was effective using both procedures, i.e. there were no solid residues after the decomposition reactions when using up to 3.5 mol L(-1) nitric acid solutions. It was demonstrated that the digestion procedures are critically dependent on reactions occurring in liquid and gas phase and that the formation of NO and its conversion to NO2 by O2 exerts a major effect in the oxidation of organic matter. These processes are more effective in closed vessels heated by microwave radiation due to the greater volume of these flasks and the temperature gradient that exists during the first step of the digestion process. The proposed model for the digestion processes in diluted nitric acid solution is corroborated by data about consumption of acid during the digestion and by measuring the pressure during the whole process.
Authors:
Jacira T Castro; Elisângela C Santos; Wagna P C Santos; Letícia M Costa; Mauro Korn; Joaquim A Nóbrega; Maria Graças A Korn
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Publication Detail:
Type:  Evaluation Studies; Journal Article; Research Support, Non-U.S. Gov't     Date:  2009-02-21
Journal Detail:
Title:  Talanta     Volume:  78     ISSN:  1873-3573     ISO Abbreviation:  Talanta     Publication Date:  2009 Jun 
Date Detail:
Created Date:  2009-04-13     Completed Date:  2009-07-30     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  2984816R     Medline TA:  Talanta     Country:  England    
Other Details:
Languages:  eng     Pagination:  1378-82     Citation Subset:  IM    
Affiliation:
Instituto de Quimica, Universidade Federal da Bahia, Campus Universitário de Ondina, Salvador, BA, Brazil.
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MeSH Terms
Descriptor/Qualifier:
Carbon / analysis
Coffee / chemistry*
Hot Temperature
Nitric Acid / chemistry*
Nitric Oxide / chemistry
Nitrogen Dioxide / chemistry
Oxygen / chemistry
Pressure
Spectrophotometry, Atomic / methods*
Chemical
Reg. No./Substance:
0/Coffee; 10102-43-9/Nitric Oxide; 10102-44-0/Nitrogen Dioxide; 7440-44-0/Carbon; 7697-37-2/Nitric Acid; 7782-44-7/Oxygen

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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