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OBJECTIVE: To improve the pretreatment method for the detection of lead, manganese and their inorganic compounds in workplace air samples by flame atomic absorption spectrometry. METHODS: In this method, 20.0 mL of 1.0-2.0 mol/L nitric acid solution was used as the digestion solution to digest the microporous membrane sample at 140-160 ℃ to a volume of 0.5-1.0 mL. Samples were cooled and fixed to 10 mL and detected by flame atomic absorption spectrometry method. RESULTS: The lead detection had a good linear relationship in the range of 0.10-3.00 mg/L. The correlation coefficient was 0.999 5, the detection limit and the lower limit of quantification were 0.03 and 0.10 mg/L respectively(calculated by 3 and 10 times of standard deviation respectively). The minimum detection concentration was 0.004 mg/m~3, and the minimum quantitative concentration was 0.010 mg/m~3(collected by 75 L air calculation). The manganese detection had a good linear relationship in the range of 0.05-3.00 mg/L mass concentration. The correlation coefficient was 0.999 8, the detection limit and the lower limit of quantification were 0.015 and 0.05 mg/L respectively(calculated by 3 and 10 times of standard deviation respectively), the minimum detection concentration was 0.002 mg/m~3, and the minimum quantitative concentration was 0.007 mg/m~3(based on collection 75 L air calculation). The recovery rate of standard addition was 97.8%-99.6%, and the relative standard deviation within and between run were 0.4%-2.0% and 0.4%-1.7% respectively. CONCLUSION: The method is simple, the reagent consumption is small, the digestion temperature is low, the precision and accuracy are high. This method is suitable for widespread use.
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ABSTRACT Portable X-ray fluorescence spectrometer (pXRF) has been recently adopted by the Soil Science community for uses in both field and laboratory, obtaining the total content of several chemical elements in a few seconds. Sulfuric acid digestion is an expensive and time-consuming laboratory analysis that provides contents of Fe2O3, Al2O3, SiO2, TiO2 and P2O5, important for soil studies. Due to few pXRF studies in tropical soils, this work aimed to compare contents of Fe2O3, Al2O3, SiO2, TiO2 and P2O5 obtained by pXRF with sulfuric acid digestion results, and to evaluate the effects of varying forms of preparing soil samples and scanning with pXRF on the resulting values in Brazilian soils. Soils were scanned in five conditions in-field (in situ) and in laboratory, evaluating varying sample preparation methods, particle sizes and soil moisture. Four pXRF scanning operational modes were tested. Linear regressions were adjusted between results of pXRF and sulfuric acid digestion. Equations were validated with an independent set of samples. Statistical analyses compared the methods of preparing the samples. Adequate linear models reached R2 of 0.99 and 0.89 for Fe2O3 and TiO2, respectively. Validation promoted R2 greater than 0.97 and RMSE and ME close to zero for both oxides. Statistical differences of pXRF results were found among the methods of preparing samples. pXRF spectrometer has great potential to obtain Fe2O3 and TiO2 content rapidly and economically with high correspondence with laboratory results of sulfuric acid digestion analysis. Varying methods of preparing the samples promote differences in the results of pXRF.
RESUMO O espectrômetro portátil de fluorescência de raios-X (pXRF) foi recentemente adotado pela Ciência do Solo, para uso em campo e laboratório, para obtenção do conteúdo total de vários elementos químicos em poucos segundos. A digestão com ácido sulfúrico é uma análise laboratorial cara e demorada que fornece teores de Fe2O3, Al2O3, SiO2, TiO2 e P2O5, importantes para estudos sobre solos. Devido aos poucos estudos sobre o pXRF em solos tropicais, este trabalho objetivou comparar os teores de Fe2O3, Al2O3, SiO2, TiO2 e P2O5 obtidos pelo pXRF com os resultados de digestão com ácido sulfúrico e avaliar os efeitos de diferentes formas de preparo de amostras de solo e leitura com o pXRF sobre seus resultados para solos brasileiros. Os solos foram submetidos a leituras com o pXRF em cinco condições, em campo (in situ) e em laboratório, avaliando variados métodos de preparo de amostras, tamanhos de partículas e umidade do solo. Quatro modos de operação do pXRF foram testados. Regressões lineares foram ajustadas entre os resultados do pXRF e digestão com ácido sulfúrico. As equações foram validadas com um conjunto independente de amostras. Análises estatísticas compararam os métodos de leitura de amostras. Modelos lineares adequados atingiram R2 de 0,99 e 0,89 para Fe2O3 e TiO2, respectivamente. A validação promoveu R2 maior que 0.97 e RMSE e ME próximos a zero para ambos os óxidos. Foram encontradas diferenças estatísticas dos resultados do pXRF entre os métodos de preparo de amostras. O pXRF possui um grande potencial para obter rápida e economicamente os teores de Fe2O3 e TiO2 com elevada correspondência com os resultados laboratoriais da análise da digestão com ácido sulfúrico. Métodos variáveis de preparo das amostras promovem diferenças nos resultados de pXRF.
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OBJECTIVES@#To detect diatom in the organs of drowners by enzyme combined with strong acid digestion method, and evaluate its application value.@*METHODS@#A total of 40 cases which have been identified as drowning in local region were collected. Samples of the lung, liver, kidney, and the water of the scene were also gathered from each case. Strong acid digestion method, enzyme combined with strong acid digestion method, and enzymic digestion method were respectively performed to detect the diatom in the samples. The comparative analysis was made on digestion time, digestive power and detection rate of diatom, etc.@*RESULTS@#Enzyme combined with strong acid digestion method was significantly better than enzymic digestion method on digestion time and digestive power; enzyme combined with strong acid digestion method were obviously superior to strong acid digestion method on the detection rate of diatom.@*CONCLUSIONS@#Enzyme combined with strong acid digestion method combines the advantages of strong acid digestion method and enzymic digestion method. It has the characters of operation safety with little pollution to environment, which is worthy of further popularization and practice.
Subject(s)
Humans , Diatoms/isolation & purification , Drowning , Forensic Pathology/methods , Kidney/metabolism , Liver/metabolism , Lung/metabolismABSTRACT
Objective T o detect diatom in the organs of drow ners by enzym e com bined w ith strong acid digestion m ethod, and evaluate its application value. Methods A total of 40 cases w hich have been identified as drow ning in local region w ere collected. Sam ples of the lung, liver, kidney, and the w ater of the scene w ere also gathered from each case. Strong acid digestion m ethod, enzym e com bined w ith strong acid digestion m ethod, and enzym ic digestion m ethod w ere respectively perform ed to detect the diatom in the sam ples. T he com parative analysis w as m ade on digestion tim e, digestive pow er and de-tection rate of diatom , etc. Results E nzym e com bined w ith strong acid digestion m ethod w as significant-ly better than enzym ic digestion m ethod on digestion tim e and digestive pow er;enzym e com bined w ith strong acid digestion m ethod w ere obviously superior to strong acid digestion m ethod on the detection rate of diatom . Conclusion E nzym e com bined w ith strong acid digestion m ethod com bines the advan-tages of strong acid digestion m ethod and enzym ic digestion m ethod. It has the characters of operation safety w ith little pollution to environm ent, w hich is w orthy of further popularization and practice.
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Objective To com pare and explore the application value of diatom nitric acid digestion method and plankton 16S rDNA PCR method for drow ning identification. Methods Forty drow ning cases from 2010 to 2011 were collected from Department of Forensic Medicine of Wenzhou Medical University. Sam ples including lung, kidney, liver and field water fromeach case were tested with diatom nitric acid digestion method and plankton 16S rDNAPCR method, respectively. The Diatom nitric acid digestion method and plankton 16S rDNAPCR method required 20 gand 2g of each organ,and 15 mL and 1.5 mL of field water, respectively. The inspection time and detection rate were com pared between the two methods. Results Diatom nitric acid digestion method m ainly detected two species of diatom s, Centriae and Pennatae, while plankton 16S rDNA PCR method am plified a length of 162 bp band. The average inspection time of each case of the Diatom nitric acid digestion method was (95.30±2.78) min less than (325.33±14.18)min of plankton 16S rDNA PCR method (P<0.05).The detection rates of two methods for field water and lung were both 100% . For liver and kidney, the detection rate of plankton 16S rDNA PCR method was both 80% , higher than 40% and 30% of diatom nitric acid digestion method (P<0.05), respectively. Conclusion The laboratory testing method needs to be appropriately selected according to the specific circum stances in the forensic appraisal of drow ning. Com pared with diatom nitric acid digestion method, plankton 16S rDNA PCR method has practice values with such advantages as less quantity of sam ples, huge inform ation and high specificity.
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A method for evaluating inorganic constituents in the grass by ICP OES is proposed. The samples were digested with nitric acid plus hydrogen peroxide in a microwave system. Seventeen samples were collected in the metropolitan area of Curitiba and Castro in the Paraná State, Brazil. The following elements were studied: Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, Sb, Se and Zn. The linear coefficients of the curves were higher than 0.999 and the precision, expressed as the relative standard deviation, which was below 10%, being considered adequate. The accuracy was validated by using the recovery test (recoveries from 80 to 107%) and by the analysis of botanical certified materials. For one sample, two other digestion procedures, using two different mixtures of nitric and hydrochloric acids, produced results in agreement with the adopted procedure. Eleven out of the twenty studied elements could be quantified in real samples. High concentrations of Ca, K, Mg and P, the essential elements for bovines and other animals, were found. The results were evaluated using the principal component analysis that gathered the samples in three groups, according to the areas where the plants were grown.
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The acid digestion method for extracting diatoms has been widely used to confirm death by drowning, but its reliability is still disputed because some diatoms can be destroyed during the extraction process due to treatment with strong acid and heat. There is a need to develop an efficient and reliable digestive method to overcome the limitation of the present analytical procedure. In this study, the reliability and efficacy of quantitative and qualitative diatom analysis from seawater by an enzymatic digestion method was evaluated. We confirmed the merit of the enzymatic method that used proteinase K instead of nitric acid in the conventional method. As a result, the enzymatic method showed a higher recovery ratio and better preservation of the diatom structure, which is essential for quantitative (diatom density) and qualitative (species) interpretation of diatom analysis. This result indicates that the enzymatic method can replace the conventional acid digestion method to confirm cases of death by drowning since it is more reliable and yields conclusive results.