• Journal of Korean Society of Environmental Engineers
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• v.33 no.1
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• pp.32-38
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• 2011

In this study, the correlations of concentrations in sediment heavy metals between two pretreatment methods, total digestion and aqua regia digestion, have been investigated. Total 43 samples had been collected from streams and lakes in Yeongsan and Seomjin watersheds. They were decomposed in two pretreatment methods and five metal components (Cd, Cr, Ni, Pb, Zn) were analyzed. Overall average concentrations of heavy metals were Zn>Cr>Pb>Ni>Cd in the order. The concentrations of aqua regia digestion were 35.0% (Cd), 53.8% (Cr), 66.2% (Ni), 64.4% (Pb) and 76.4% (Zn) of the concentrations of total digestion and heavy metal concentrations of total digestion were higher. Heavy metal concentrations in sediments from lakes were higher than those from streams. The correlation equations between the concentrations of total digestion and aqua regia digestion were obtained. The concentrations of Zn and Ni, which showed strong linear correlations, increased in aqua regia digestion as the concentration in total digestion increased. The linear correlation coefficients between two digestion methods for most analyzed metals were above the average correlation. However, these results can be applied with limitations due to heterogeneity of sediments.

• Analytical Science and Technology
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• v.16 no.3
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• pp.212-217
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• 2003

The memory effect of silver and aqua regia in the vessel by their permeation was studied during the microwave digestion of samples under the operating conditions of high temperature and pressure. The extent of permeation in vessels with the solution containing silver 5 mg has been shown to be $0.97{\mu}g/mL$ for the digestion of $HNO_3$ solution and $0.47{\mu}g/mL$ for the digestion of oil sample under condition of MDS 180T program ($180^{\circ}C$, 220 psi).

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.6-8
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• 2005

The forest soils of 92 sites in Korea were analyzed to survey heavy metal background levels using aqua regia digestion method and 0.1N HCl extraction method. From these results, the average natural contents of heavy metals were Cd 0.287, Cu 15.26, Pb 18.43, Cr 25.36, Zn 54.27, Ni 17.68mg/kg for aqua regia method, and Cd 0.040, Cu 0.48, Pb 3.06, Cr 0.09, Zn 1.54, Ni 0.27mg/kg for 0.1N HCl extraction method. The range of correlation coefficients between heavy metal contents obtained from two methods(aqua regia and 0.1N HCl) was significant as $0.24{\sim}0.88$, and the correlation coefficients were decreased in order of Cd, Pb, Cu, Ni, Cr, Zn.

• Journal of the Mineralogical Society of Korea
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• v.26 no.1
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• pp.45-54
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• 2013

In order to dissolve Au, Ag, and other valuable metals from gold ore concentrate, raw gold concentrate was pre-treated by roasting and salt-roasting at $750^{\circ}C$. The roasted concentrate was treated with aqua regia digestion to dissolve the valuable metals and higher amount of Au, Ag, and valuable metals were extracted from the roasted concentrates than from the raw concentrate. Higher amount of these metals were also extracted from the salt-roasted concentrate than from the roasted concentrate. The results of the gold dissolution experiments showed that the gold dissolution was most efficient when particle size, roasting temperature, and the percentage of added salt in salt roasting were about $181{\sim}127{\mu}m$, $750^{\circ}C$, and was 20.0%, respectively. The XRD analysis suggests that quartz and pyrite were not destroyed even through roasting at $750^{\circ}C$ and decomposition with aqua regia. However, through salt roasting, pyrite was completely decomposed, whereas quartz could not be destroyed through salt-roasting at $750^{\circ}C$ and aqua regia digestion. Accordingly, it was expected that the gold contained in quartz can not be dissolved through salt-roasting and treatment with aqua regia.

• Korean Journal of Food Science and Technology
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• v.15 no.3
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• pp.225-230
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• 1983

Aqua-regia method is reported for simultaneous determination of potassium, sodium, calcium, magnesium, zinc, manganese, copper and iron in high-fat fish tissue. Samples are digested with conc nitric and conc hydrochloric acid in a volumetric flask. After digestion, aqua-regia extracts of samples are analyzed by direct flame atomic absorption spectrophotometry. The aqua-regia method is compared with dry ashing method and $H_{2}SO_{4}-HNO_{3}$ method. For quantiative determination of calcium, magnesium and zinc, the aqua-regia method and dry ashing method are superior to $H_{2}SO_{4}-HNO_{3}$ method. In case of the other elements-potassium, sodium, manganese, copper and iron-the three methods gave the similar results. Because samples can be processed by aqua-regia method easily, rapidily, cheaply and safely, aqua-regia method is suitable for the routine preparation of a large number of samples simultaneously.

• Journal of Soil and Groundwater Environment
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• v.15 no.5
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• pp.8-15
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• 2010

The purpose of this research is to check the validation of an auto-analysis method combined with aqua regia digestion apparatus for improvement of water distillation method used as a fluorine test of soil. Fluorine contents of CaO used in the pretreatment course of water distillation method were 120 mg/kg ~ 5,064 mg/kg at the blank test, which was exceeded up to maximum 12.5 times of the soil standard, so it was estimated due to a effect of fluorine existing as impurities of CaO. The recovery test of the same samples indicated that water distillation method and auto-analysis method were 134.5mg/kg and 161.7mg/kg respectively, the recovery ratio of the latter was 16.8% higher than the formal. The validation test of two methods satisfied the standard, but auto analysis method was excellent more than distillation method. Also, auto analysis method could save a analysis time up to maximum 4.7 times by comparison with water distillation method.

• Journal of Soil and Groundwater Environment
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• v.23 no.1
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• pp.25-29
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• 2018

The effect of soil grinding on total As and Pb concentrations determined by aqua regia method was examined. Among six field-collected, air-dried soil samples tested, soils A, B, C, and E were directly sieved through a $150-{\mu}m$ sieve without grinding and showed 2.18 to 3.03 times higher total As concentrations and 2.62 to 3.45 times higher total Pb concentrations than those of the soil samples prepared to allow all soil particles to pass through the $150-{\mu}m$ sieve by grinding. The reason can be ascribed to the fact that those soils contain fine particles (i.e., < $150{\mu}m$ in diameter) only 4.6 to 6.8% of the total soil weights. On the other hand, for D and F soils, fine particles smaller than $150{\mu}m$ accounted for 57 and 46%, respectively, so that the effect of grinding on As and Pb concentrations were relatively low (As: 1.15 and 1.23 times, Pb: 1.36 and 1.49 times, respectively). The result demonstrates that grinding prior to $150-{\mu}m$ sieving is necessary to ensure the homogeneity of soil samples and hence to obtain more accurate heavy metal concentrations in soils. This is especially true for soil samples with less fine soil particles and/or microaggregates (i.e., below $150{\mu}m$).

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.6
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• pp.464-472
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• 2014

The Codex Committee of Contaminants in Food (CCCF) has been discussing a new standard for arsenic (As) in rice since 2010 and a code of practice for the prevention and reduction of As contamination in rice since 2013. Therefore, our current studies focus on setting a maximum level of As in rice and paddy soil by considering bioavailability in the remediation of As contaminated soils. This study aimed to select an appropriate single chemical extractant for evaluating the mobility of As in paddy soil and the bioavailability of As to rice. Nine different extractants, such as deionized water, 0.01 M $Ca(NO_3)_2$, 0.1 M HCl, 0.2 M $C_6H_8O_7$, 0.43 M $HNO_3$, 0.43 M $CH_3COOH$, 0.5 M $KH_2PO_4$, 1 M HCl, and 1 M $NH_4NO_3$ were used in this study. Total As content in soil was also determined after aqua regia digestion. The As extractability of the was in the order of: Aqua regia > 1 M HCl > 0.5 M $KH_2PO_4$ > 0.43 M $HNO_3$ > 0.2 M $C_6H_8O_7$ > 0.1 M HCl > 0.43 M $CH_3COOH$ > deionized water > 1 M $NH_4NO_3$ > 0.01 M $Ca(NO_3)_2$. Correlation between soil extractants and As content in rice was in the order of : deionized water > 0.01 M $Ca(NO_3)_2$ > 0.43 M $CH_3COOH$ > 0.1 M HCl > 0.5 M $KH_2PO_4$ > 1 M $NH_4NO_3$ > 0.2 M $C_6H_8O_7$ > 0.43 M $HNO_3$ > 1M HCl > Aqua regia. BCF (bioconcentration factor) according to extractants was in the order of : 0.01M $Ca(NO_3)_2$ > 1 M $NH_4NO_3$ > deionized water > 0.43 M $CH_3COOH$ > 0.1 M HCl > 0.43 M $HNO_3$ > 0.2 M $C_6H_8O_7$ > 0.5 M $KH_2PO_4$ > 1 M HCl > Aqua regia. Therefore, 0.01 M $Ca(NO_3)_2$ ($r=0.78^{**}$) was proven to have the greatest potential for predicting As bioavailability in soil with higher correlation between As in rice and the extractant.

• Applied Chemistry for Engineering
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• v.10 no.4
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• pp.568-575
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• 1999

Two different digestion procedures for the simultaneous determination of major and platinum-group element(PGE) in spent automobile catalysts containing PGE and silicates by inductively coupled plasma atomic emission spectrometry(ICP-AES) are compared. Combinations of mixed aids using HF, $HNO_3$, HCl, $HClO_4$, $H_2O_2$, and $H_3BO_3$ are utilized for the hot plate dissolution method and the closed-vessel microwave digestion method, The latter method has been shown to be relatively superior in terms of recovery, analysis time, and amount of aqua regia (3 parts HCl + part $HNO_3$ required to dissolve PGE in comparison with conventional open vessel hot-plate dissolution. The best results were drawn from the following conditions: In closed Teflon PFA vessels under microwave heating with temperature/pressure regulation, a 0.25 g portion of sample was digested in 2 mL of HF, 2 mL of $HNO_3$ and 6mL of HCl under the pressure of 200 psi(13.79 bar) at $180^{\circ}C$ for 1hr, followed by a second digestion stage with 16 mL of 5%(w/v) boric acid under the pressure of 20 psi(1.38 bar) at $100^{\circ}C$ for 10 min. After the microwave heating, the sample was post-treated with 10 mL of aqua regia twice by hot-plate heating. This condition gives the PGE recovery within 85~110% and the relative standard deviations within 2%. The method developed can therefore be regarded as an alternative method for routine analysis of spent automobile catalysts.

• Analytical Science and Technology
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• v.23 no.6
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• pp.511-517
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• 2010

Dissolution procedure of vanadium pentoxide, which is widely used as a catalyst for production of sulfuric acid or an oxide reaction of the numerous organic compounds, was investigated. Reagent of vanadium pentoxide was completely dissolved in aqua regia-$H_2O_2$-HF solution, but plate type of vanadium pentoxide sample was not clearly dissolved with mixed acids. Thus, in order to establish the dissolution procedure for plate type of vanadium pentoxide, the solubility of vanadium pentoxide was investigated through comparison of acid treatment-fusion and microwave digestion methods. The optimized acid for dissolution of vanadium compound was found to be mixing acids of aqua regia, $H_2O_2$ and HF. Acid-fusion and microwave digestion methods have a similar property in the solubility of vanadium compound, but the latter was more quick and convenient procedure. The content of vanadium pentoxide was found to be $97.9{\pm}0.9%$ using an inductively coupled plasma atomic emission spectrometer after dissolution of a sample with the microwave digestion system.