• Analytical Science and Technology
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• v.16 no.6
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• pp.509-512
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• 2003

Pretreatment method for the determination of total arsenic in seafood sample was studied. NIST SRM 1566a oyster tissue ($14.0{\pm}1.2mg\;As/kg$) as a standard arsenic compound in order to establish the decomposition method. We confirmed that the best way for pretreatment of seafoods to analyze total arsenic content precisely was $HNO_3-H_2SO_4-HCIO_4$ method by comparison of two methods which are dry ashing and wet ashing methods.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.23 no.4
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• pp.333-340
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• 2013

Objectives: This study was designed to establish an accurate analytical method for asbestos in a biological sample for determining occupational asbestos-related diseases and relief of the health effects of environmental asbestos. Methods: Biological samples were obtained from lungs of rats following intratracheal instillation of asbestos(Chrysotile, anthophyllite) and were prepared according to digestion method(Wet digestion, high temperature ashing, low temperature ashing). The samples were then analyzed for asbestos fibers using a transmission electron microscope equipped with an energy dispersive X-ray spectrometer. Results: Low temperature plasma ashing removed more of the organic components and reduced fiber loss compared to the wet digestion method, making specimens so prepared more suitable for transmission electron microsocpy. Conclusions: The low temperature ashing technique is the most accurate method for analyzing asbestos in biological samples.

• Korean Journal of Environmental Agriculture
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• v.14 no.3
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• pp.338-344
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• 1995

The wet ash method has been used as an official standard procedure for the analysis of Cd in brown rice in Korea, but this method involves several disadvantages. Thus, four analytical methods were compared in this experiment in order to find a more efficient method for the Cd analysis in brown rice. Evaluation was made based on both the Cd recovery percentages from the Cd-spiked samples and the relationships between Cd contents obtained by the official procedure and other methods. Results showed that ashing 50g brown rice at $600^{\circ}C$(dry ash method) recovered nearly 80% of the spiked Cd. This recovery percentage was a little lower than that of the wet ash method(87%) but higher than those of other methods. The dry ash method had the lowest standard deviations and revealed the highest correlation coefficient($r=0.98^{\ast\ast}$) in Cd contents with the standard wet ash method. These results demonstrated that the dry ash method, ashing 50g brown rice at $600^{\circ}C$, would be as efficient as the wet ash method and could be employed as a recommended procedure for the Cd analysis of brown rice.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.4
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• pp.325-331
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• 2007

In this study, the inter-metal dielectric material of FSG was changed by low-k material in $0.13{\mu}m$ foundry-compatible technology (FCT) device process based on fluorinated silicate glass (FSG). Black diamond (BD) was used as a low-k material with a dielectric constant of 2.95 for optimization and yield-improvement of the low-k based device process. For yield-improvement in low-k based device process, some problems such as photoresist (PR) poisoning, damage of low-k in etch/ash/cleaning process, and chemical mechanical planarization (CMP) delamination must be solved. The PR poisoning was not observed in BD based device. The pressure in CMP process decreased to 2.8 psi to remove the CMP delamination for Cu-CMP and USG-CMP. $H_2O$ ashing process was selected instead of $O_2$ ashing process due to the lowest condition of low-k damage. NE14 cleaning after ashing process lot the removal of organic residues in vias and trenches was employed for wet process instead of dilute HF (DHF) process. The similar-state of SRAM yield was obtained in Cu/low-k process compared with the conventional $0.13{\mu}m$ FCT device by the optimization of these process conditions.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.11
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• pp.902-909
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• 1991

A reproducible selective dry etch process of GaAs/AlGaAs Heterostructures for High Electron Mobility Transistor(HEMT) Device fabrication is developed. Using RIE mode with $CCl_{2}F_{2}$ as the basic process gas, the observed etch selectivity of GaAs layer with respect to GaAs/$Al_{0.3}Ga_{0.7}$As is about 610:1. Severe polymer deposition problem, parialy generated from the use of $CCl_{2}F_{2}$ gas only, has been significantly reduced by adding a small amount of He gas or by $O_{2}$ plasma ashing after etch process. In order to obtain an optimized etch process for HEMT device fabrication, we com pared the properties of the wet etched Schottky contact with those of the dry etched one, and set dry etch condition to approach the characteristics of Schottky diode on wet etched surface. By applying the optimized etch process, the fabricated HEMT devices have the maximum transconductance $g_{mext}$ of 224 mS/mm, and have relatively uniform distribution across the 2inch wafer in the value of 200$\pm$20mS/mm.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.1 no.2
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• pp.238-245
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• 1991

This study was analysis of ${\alpha}$-quartz in the 37 worker's lung died of coal workers' pneumoconiosis(CWP) and in the 9 normal's lung by Fourier transform infrared spectrophotometer. The results were as follows : 1. The dried lung weight percents in wet lung weight were 24.4%, 25.4%, coal workers' pneumoconiosis and normal lungs, respectively. Ash weight percents in dried lung weight were 7.7%, 5.0%, coal workers' pneumoconiosis and normal lungs, respectively. 2. The presision (as of coefficient of variation) for the ${\alpha}$-quartz determination were 2.6% in standard quartz (ranged from 9.9 to $198.0{\mu}g$) and 3.7% in ashed lung samples. 3. The characterstic ${\alpha}$-quartz absorption spectra in lungs of CWP were only shawn by LTA ashing. 4. Geometric mean of ${\alpha}$-quartz concentration in CWP lung was 173mg/100g dried lung. 5. The concentrations of ${\alpha}$-quartz in Korean CWP lungs were similar to those of foreign coal miner's lungs.

• 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.

• Korean Chemical Engineering Research
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• v.43 no.1
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• pp.27-32
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• 2005

We propose an effective and environmentally friendly dry stripping method using a supercritical carbon dioxide ($SCCO_2$) system modified by a single and multiple cosolvents to remove ion-implanted photoresist and residue from a wafer surface at three different temperatures (97, 148, $200^{\circ}C$) and pressures (200, 300, 400 bar). After high dose of ion implantation the photoresist was not easily removed by using pure $SCCO_2$, but swollen. The $SCCO_2$ system modified by single cosolvents and multiple cosolvents mixed with aprotic solvents could not effectively remove the heavy organics, but swell them. However, the $SCCO_2$ system modified with multiple cosolvent (5%, v/v) composed of DMSO and DIW showed high removal efficiency for ion-implanted photoresists at $97^{\circ}C$ and 200 bar for 30 min (about 80%). In this study it has been shown that the dry stripping method using $SCCO_2$ system modified with multiple cosolvents could replace either plasma ashing or acid and solvent wet bench method and dramatically reduce accompanied chemical usage and disposal.

• Analytical Science and Technology
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• v.11 no.1
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• pp.29-35
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• 1998

This study was performed to assess the levels of the Cr and Co in fisheries caught from the some areas of west coast in Korea. The samples were 26 kinds of fishes, 19 kindly of Mollusca and 3 kinds of Crustacea. They were ashed with 5 ml $HNO_3$ and then wet-decomposed with 10 ml of a mixture of $HNO_3:H_2SO_4:HClO_4$ (10:1:4). After ashing of samples, the amounts of Cr and Co in the samples were determined by ICP-AES analysis. The moisture content of molluscans was significantly higher than that of crustaceans (p<0.05), but there was no significant difference among fisheries in the Cr content. And the Co content of crustaceans was significantly higher than that of fishes and molluscans (p<0.001). There was no significance between contents of Cr and Co in fisheries. The Cr content of Arkshell was 422.00 ppm, which was the most amount compared with those of the other samples. And the Co in Myong-Ge was 3.78 ppm, which was the most amount. Areliscus honaleus (Cr:2.76 ppm, Co:0.97 ppm), Solen (Cr:6.56 ppm, Co:1.59 ppm) and dried barley shrimp (Cr:1.06 ppm, Co:0.90 ppm) contained great amount of Cr and Co.

• Korean Journal of Food Science and Technology
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• v.43 no.5
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• pp.525-531
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• 2011

This study was conducted to examine the contents of lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg) in meat and meat products in Korea. The contents of Pb, Cd, As, and Hg in 466 samples of beef, pork, chicken, duck, ham, and sausage were measured using inductively coupled plasma mass spectrometry or a mercury analyzer. Wet ashing and microwave method were compared, and the recovery and reproducibility of the microwave method were better than those of wet ashing for meat and meat products. The recovery of the microwave method was 98.1% for Pb, 104.6% for Cd, and 103.4% for As, respectively. The best result was obtained through digestion using an acid mixture ($HNO_3$/$H_2O_2$, 6:2). Hg content was measured using a mercury analyzer. As a result, the contents of Hg and Cd in samples were lower than those of Pb and As. The average contents of Pb were 0.009 mg/kg in beef, 0.010 mg/kg in pork, 0.006 mg/kg in chicken, 0.007 mg/kg in duck, 0.005 mg/kg in ham, and 0.009 mg/kg in sausage. The average Cd contents were 0.0004 mg/kg in beef, 0.0004 mg/kg in pork, 0.0005 mg/kg in chicken, 0.0012 mg/kg in duck, 0.0015 mg/kg in ham, and 0.0019 mg/kg in sausage. The average As contents were 0.016 mg/kg in beef, 0.004 mg/kg in pork, 0.021 mg/kg in chicken, 0.010 mg/kg in duck, 0.014 mg/kg in ham, and 0.018 mg/kg in sausage. The average Hg contents were 0.713 ${\mu}g/kg$ in beef, 0.902 ${\mu}g/kg$ in pork, 0.710 ${\mu}g/kg$ in chicken, 0.796 ${\mu}g/kg$ in duck, 1.141 ${\mu}g/kg$ in ham, and 1.052 ${\mu}g/kg$ in sausage. Based on the results of the National Health and Nutrition Survey 2005, the levels of dietary exposure to heavy metal contaminants in meat and meat products were compared with the provisional tolerable weekly intake(PTWI) established by the Joint FAO/WHO Expert Committee on Food Additives. The average dietary exposure of the general population from meat and meat products was 0.03-0.2% of PTWI for Pb, Cd, As, and Hg, which indicates a safe level for public health at present.