Residues from biological materials after pressure decomposition with nitric acid

Würfels, M.; Jackwerth, E.; Stoeppler, M.

doi:10.1016/s0003-2670(00)80900-9

Cited by 67 publications

(22 citation statements)

References 12 publications

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“…There is a direct relation between NO 2 formation, concentrated nitric acid volume, and sample amount. As described by Würfels et al, 20 an increase in the RCC was observed for biological samples when decreasing the mass of sample and keeping constant the acid volume. This effect occurs because of the reduction in NO 2 formation due to the lower sample mass.…”

supporting

confidence: 61%

“…On the other hand, the increase of the sample size influenced negatively the residual acidity (-3.96) leading to lower acidity values. These effects are expected and according to Würfels et al 20 the increase of the sample size generated higher quantities of NO 2 , resulting in better digestions. There is a direct relation between NO 2 formation, concentrated nitric acid volume, and sample amount.…”

Section: Factorial Designmentioning

confidence: 78%

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Use of factorial design for optimization of microwave-assisted digestion of lubricating oil

Costa¹,

Ferreira²,

Nogueira³

et al. 2005

J. Braz. Chem. Soc.

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A eficiência dos procedimentos de digestão em fornos de microondas pode ser afetada por parâmetros experimentais críticos, como massa de amostra, volume da mistura ácida, potência de radiação aplicada e o tempo da digestão. Neste trabalho foi proposta a utilização de um planejamento fatorial completo para a otimização da digestão de amostras de óleo lubrificante em forno de microondas, com recipientes fechados. O teor de carbono residual e a acidez final das soluções foram determinados em todos os digeridos provenientes do forno de microondas, como resposta ao planejamento fatorial. Cálcio, Cu, Mg, P, S e Zn foram determinados nos digeridos ácidos e a exatidão foi checada utilizando-se um material de referência certificado, NIST SRM 1848-Lubricating Oil Additive Package. Os resultados encontrados para as amostras e para o material de referência certificado estão em concordância a um nível de confiança de 95%. Tempo de digestão, potência de radiação aplicada, massa de amostra e as interações entre essas variáveis foram significativas (P < 5%), aplicando-se a análise de variância (ANOVA).This work proposes the use of factorial design for optimization of microwave-assisted digestion of lubricating oil. The accuracy of digestion procedures is affected by critical experimental parameters, such as sample amount, concentrated acid volumes, microwave radiation applied power, and digestion time. The effects of these key variables on the microwave-assisted digestion efficiency were investigated. The residual carbon content and the acidity were determined in all digestates after microwave-assisted digestion as response of the factorial design. Calcium, Cu, Mg, P, S, and Zn were determined in oil digestates obtained by using two systems: a cavity-and a focused-oven. The accuracy was checked using one standard reference material, NIST SRM 1848 -Lubricating Oil Additive Package. All determined and certified values are in agreement at a 95% confidence level. The digestion time, microwave applied power, sample mass, and the interaction between these variables were significant according to P-values when the analysis of variance (ANOVA) was used.Keywords: factorial design, microwave-assisted digestion, lubricating oil, metals IntroductionThe proposal of a new analytical method requires the optimization of the experimental variables and its validation. The first one involves the selection of the values of the factors that have an influence on the analytical signal and lead to the best results for the analytical process. The optimization of the proposed method allows us to understand effects that are not explained in a traditional way, such as those in which the analytical response is a multimodal function of the independent variables or when the effects of the variables are not additive and there is interaction among them. 1 Sample preparation involves digestion or extraction of the analytes before the analysis, 2 so this step is time limiting, requiring up to 60% of the complete analysis time, and is responsible for up to 30% of ...

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supporting

confidence: 61%

Section: Factorial Designmentioning

confidence: 78%

Use of factorial design for optimization of microwave-assisted digestion of lubricating oil

Costa¹,

Ferreira²,

Nogueira³

et al. 2005

J. Braz. Chem. Soc.

View full text Add to dashboard Cite

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“…Furthermore, the effectiveness of the digestion can be related to the chemical structures of organic 25 certain groups of substances, such as long-chain alcohols, carbohydrates and long-chain fatty acids, are nearly completely decomposed by nitric acid under pressure.…”

Section: Resultsmentioning

confidence: 99%

Determination of Elemental Impurities in Acyclovir Ointment and Raw Materials Using Microwave Acid Digestion (MW-AD) and ICP-MS

Gonzalez¹,

Silva²,

Amaral³

et al. 2016

Journal of the Brazilian Chemical Society

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Inorganic elements present in pharmaceutical products were determined by inductively coupled plasma-mass spectrometer (ICP-MS), employing microwave acid digestion as a sample preparation method. , were determined in acyclovir ointment and its constituents. Elemental impurities in the pharmaceutical samples were determined using an inductively coupled plasma-universal cell technology-mass spectrometer (ICP-UCT-MS) operated in kinetic energy discrimination (KED) and standard mode. The accuracy of the method was assessed by means of addition and recovery experiments. Except for Cr, spiked recoveries of the elements added to the samples before microwave acid digestion (MW-AD) step were between 95.1 and 126%, and after MW-AD step ranged from 85.6 to 132%. Limits of detection (LOD) obtained by proposed method is in agreement to those required by the U.S. Pharmacopeia Convention (USP), showing that the ICP-MS technique is well suited for quantification of these elements. The LOD's (ng L -

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“…Selenium, mainly present as selenocysteine and selenomethionine amino acids in tissue samples, 16 may be difficult to recover with use of formic acid unless elevated temperatures are used 17,18 and thus recovery of Se is not satisfactory if undigested proteins are removed by filtration prior to analysis of unheated mixtures. The presence of a residue requiring filtration leads to the conclusion that even with the addition of the heating step, extraction, rather than solubilization, is achieved.…”

Section: Resultsmentioning

confidence: 99%

An Evaluation of the Use of Formic Acid for Extraction of Trace Elements from Brazil Nut and Babassu Coconut and Its Suitability for Multi-Element Determination by ICP-MS

Lopes¹,

Silva²,

Grinberg³

et al. 2016

Journal of the Brazilian Chemical Society

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Formic acid extractions of Brazil nut and babassu coconut samples were undertaken prior to determination of Al, As, Ba, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Sr, V and Zn in their meat and oil portions by inductively coupled plasma mass spectrometry (ICP-MS) in an effort to accomplish a first order fractionation of the trace elements between these two components. An optimized full factorial design was applied to establish the best conditions for extraction. Microwave-assisted nitric acid digestions of samples and fractions along with analysis of certified reference material TORT-2 established the efficiency of recovery of the trace elements as well as provided a verification of accuracy. The multiple responses were analyzed using a desirability function wherein the recovery of the trace elements by extraction was compared with the determination of the total content as determined by nitric acid digestion. Although most trace elements presented a recovery higher than 85% using a formic acid extraction, Al suffered consistently low results for all samples (40-50%). Except for Al and Cr, the majority of the trace elements were present in the defatted fraction of both samples, i.e., Al (50 and 10%), Cr (86 and 60%), Ni (30 and 10%) and Sr (8 and 20%) in Brazil nut and babassu coconut oil fractions, respectively.

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Residues from biological materials after pressure decomposition with nitric acid

Cited by 67 publications

References 12 publications

Use of factorial design for optimization of microwave-assisted digestion of lubricating oil

Use of factorial design for optimization of microwave-assisted digestion of lubricating oil

Determination of Elemental Impurities in Acyclovir Ointment and Raw Materials Using Microwave Acid Digestion (MW-AD) and ICP-MS

An Evaluation of the Use of Formic Acid for Extraction of Trace Elements from Brazil Nut and Babassu Coconut and Its Suitability for Multi-Element Determination by ICP-MS

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