• Bulletin of the Korean Chemical Society
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• v.25 no.7
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• pp.1019-1024
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• 2004

The present paper is focused on simultaneous sorption concentration of gold (III) and silver (I) from thiocyanate solutions using high-selective anion exchanger AN-25 and subsequent separation of these ions at various concentrations of thiocarbamide (eluent). As a result, silver (I) ions are completely eluted from AN-25 and gold (III) ions remain in the resin phase and can be determined directly in the solid phase by diffuse reflection spectroscopy. It is proposed to use the sorption-spectroscopic method for Au(III) determination in aqueous solutions. The calibration curve is linear in the concentration range of 1-19 mg/L (sample volume is 10.0 mL) and the detection limit is 0.05 ${\mu}g/mL$. The presence of Cu(II), Co(II), Fe(II) do not hinder this determination. Au(III) was determined in industrial solutions.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.04a
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• pp.150-155
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• 1997

Rapid Prototyping(RP) is the technique which is used to make prototypes or functional parts directly using the 3-D solid data. Before building the prototype, several processes such as transfering 3D data from CAD system(STL) determination of build-direction, adding support structure and slicing are required. Among the above processes. determination of build-direction is the target of this study. The build direction is determined by many factors according to the objective of the user, like part accuracy, number of support structure, build time, amount of trapped volume, etc, But it is not easy to determine the build-direction because there are many factors and some factors have dependent properties with one another. So, in this study the part accuracy, the number of support structures and build time are considered as the main factor to determine the optimal build-direction. To determine the optimal build-direction for increasing part accuracy, sum of projected area which caused stairstepping effect was considered. The less the projected area is the better part accuracy is About the optimal build-direction to minimize the amount of support structure, sum of projected area of facets that require support structures was considered. About the build time, we considered the minimum height of part we intended. About the build time, we considered the minimun height of part we intended to make.

• Journal of Pharmaceutical Investigation
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• v.40 no.3
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• pp.193-200
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• 2010

The objective of this study was to investigate the effects of sample preparation, HPLC conditions and peak measurement methods upon determining progesterone content of poly-d,l-lactide-co-glycolide microspheres. A series of the microspheres with different formulations was first prepared. To determine their actual drug contents, the microspheres were dissolved in tetrahydrofuran and diluted with various amounts of methanol to precipitate the polymer. After removal of polymeric precipitates, the filtrates were subject to HPLC analysis under versatile experimental conditions. Interestingly, the composition of a sample solution (e.g., the ratio of methanol to tetrahydrofuran) affected the magnitudes of both peak fronting and peak broadening of progesterone. Its peak became broader and more asymmetrical at lower methanol:tetrahydrofuran ratios. Furthermore, its peak height was influenced by the proportion of tetrahydrofuran in a sample solution. Such problems encountered with tetrahydrofuran were exacerbated when a larger volume of the sample solution was injected onto an analytical column. Under our experimental conditions a peak area measurement provided more accurate and reliable determination of progesterone content in various microspheres than a peak height determination. Optimizing the composition of a sample solution, HPLC chromatographic conditions and peak analysis methods was a prerequisite to an accurate determination of progesterone encapsulated within microspheres.

• Preventive Nutrition and Food Science
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• v.4 no.1
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• pp.79-83
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• 1999

A potentiometric biosensor employing a CO3-2 ion-selective electrode(ISE) and malic enzyme immobilization in al flow injection analysis (FIA) system was constructed. Analytical parameters were optimized for L-malate determination . The CO3-2 -ISE-FIA system was composed of a pump, an injector, a malic enzyme (EC1.1.1.40) reactor, a CO3-2 ion-selective electrode, a pH/mV meter and a recorder. Cofactor NADP was also injected with substrate for theenzyme reaction into the system. Optimized analytical parameters for L-malate determination in the CO3-2 ISE-FIA system were as follows ; flow rate, 14.5ml/hr ; sample injection volume, 100ul; enzyme loading in the reactor, 20 units ; length of the enzyme reactor , 7 cm ; tubing length form the enzyme reactor to the detector as a geometric factor in FIA, 15 cm . The response time for measuring the entire L-malate concentration range (10-2 ~10-5 mol/L ; 4 injections )was <15minutes . In this CO3-2 -ISE-FIA system, the potential differences due to th eformation of CO3-2 by the reaction of malic enzyme on L-malate were correlated to L-malate concentration in the range of 10-2 ~10-5mol/L ; the detection limit was 10-5 mol/L. This potentionmetric CO3-2 ISE--FIA system was found to be useful for L-malate measurement.

• Journal of the Korean Society of Tobacco Science
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• v.22 no.1
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• pp.91-98
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• 2000

This study was carried out to evaluate the uncertainty in the analysis of menthol content from the mentholated cigarette. Menthol in the sample cigarette was extracted with methanol containing an anethole as an internal standard, and then analyzed by gas chromatography. As the sources of uncertainty associated with the analysis of menthol, were the following points tested, such as the weighing of sample, the preparation of extracting solution, the pipetting of extracting solution into the sample, the preparation of standard solution, the precision of GC injections for standard & sample solution, the GC response factor of standard solution, the reproducibility of menthol analysis, and the determination of water content in tobacco, etc. For calculating the uncertainties, type A of uncertainty was evaluated by the statistical analysis of a series of observation, and type B by the information based on supplier's catalogue and/or certificated of calibration. Sources of uncertainty were subsequently included and mathematically combined with the uncertainty arising from the assessment of accuracy to provide the overall uncertainty. It was shown that the main source of uncertainty came from the errors in the reproducibility of menthol and water determination, the purity of menthol reference material in the preparation of standard solution, and the precision of GC injections for sample solution. The errors in sample weighing and volume measurement contributed relatively little to the overall uncertainty. The expanded uncertainty in the mentholated cigarettes, Korean and American brand, at 0.95 level of statistical confidence was $\pm$0.06 and $\pm$0.07 mg/g for a menthol content of 1.89 and 2.32 mg/g, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.181-181
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• 2012

The microwave probe for measuring plasma density is widely used for its advantages: First, it is not affected by the reactive gas. Second, it can measure local plasma parameters such as plasma density, plasma potential and plasma temperature. Third, it is simple and robust. A cut-off probe is the one of the most promising microwave probe. Recently, Kim et al. reveals the physics of the cut-off probe but the effect of the sheath on the determination of the plasma density is not explained. In this presentation, for taking account of sheath effects on determination of plasma density from the cut-off peak, a simplified circuit modeling and an E/M simulation are conducted. The results show that occupation ratio of sheath volume between two tips of the cut-off probe and subsequence pressure condition mainly change position of the cut-off peak with respect to plasma frequency. Magnitude of relative voltage taken on the impedance of sheath and the impedance of bulk plasma can explain this effect. Furthermore, effects of gap size, tip radius, and tip length ware revealed based on above analysis.

• Bulletin of the Korean Chemical Society
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• v.16 no.7
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• pp.582-588
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• 1995

The preconcentration and determination of trace Cd(Ⅱ), Cu(Ⅱ), Pb(Ⅱ), Mn(Ⅱ) and Zn(Ⅱ) in water samples were studied by the precipitate flotation using La(OH)3 as a coprecipitant. The analytes were quantitatively coprecipitated by adding 3.0 mL of 0.1 M La(Ⅲ) solution in a 1,000 mL water sample and adjusting the pH to 9.5 with NaOH solution. After the addition of the 1:8 mixed surfactant solution of each 0.1% sodium oleate and sodium lauryl sulfate, the solution was stirred with a magnetic stirrer for 10 minutes. The precipitates were floated to the surface by bubbling with nitrogen gas and collected in a small sampling bottle. The precipitates were dissolved in nitric acid and then the solutions were diluted to 25.00 mL with a deionized water. The analytes were determined by flame atomic absorption spectrometry. This procedure was applied to the waste water analysis. This technique was simple, convenient and especially rapid for the analysis of a large volume of sample. And also, from the recoveries of better than 92% which were obtained from real samples, this method could be judged to be applicable to the preconcentration and quantitative determination of trace elements in water samples.

• Safety and Health at Work
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• v.12 no.2
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• pp.209-216
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• 2021

Background: The article presents the results of studies performed in order to develop a new method of airborne potassium bromate(V) determination at workplaces. Methods: The method is based on a collection of the inhalable fraction of potassium bromate(V) using the IOM Sampler, then extraction of bromates with deionized water and chromatographic analysis of the obtained solution. The analysis was performed using ion chromatography with conductometric detection. The tests were performed on a Dionex IonPac®AS22 analytic column (250 × 4 mm, 6 ㎛) with AG22 precolumn (50 × 4 mm 11 ㎛). Results: The method provides for potassium bromate(V) determination within the concentration range of 0.043 ÷ 0.88 mg/m³ for an air sample of 0.72 m³ in volume, i.e., 0.1-2 times the exposure limit value as proposed in Poland. The method was validated in accordance with PN-EN 482. The obtained validation data are as follows: measuring range: 3.1-63.4 ㎍/mL, limit of detection (LOD) = 0.018 ㎍/mL and limit of quantification (LOQ) = 0.053 ㎍/mL. The developed method has been tested in the work environment, on laboratory employees having contact with potassium bromate(V). Conclusion: The analytical method allowed the determination of the inhalable fraction of airborne potassium bromate(V) at workplaces and can be used to assess occupational exposure.

• Analytical Science and Technology
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• v.20 no.1
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• pp.55-60
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• 2007

A sensitive technique for the determination of trace Cu(II) in various samples after the column preconcentration by adsorbing its N-benzoylphenylhydroxylamine (BPHA) onto benzophenone was developed. Several experimental conditions such as the pH of the sample solution, the amount of chelating agent, the amount of benzophenone, and the flowrate of sample solution and so forth were optimized. The interfering effects of diverse concomitant ions were investigated. Fe(III) and $CN^-$ interfered with more seriously than any other ions. However, the interference by these ions could be overcome sufficiently by adjusting the added volume of 0.01M BPHA to 10 mL. The dynamic range, the correlation coefficient ($r^2$) and the detection limit obtained by this proposed technique were 5.0~120 ng/mL, 0.9974, and 2.1 ng/mL, respectively. For validating this proposed technique, the aqueous samples (stream water, reservoir water, and wastewater), the plastic sample and the diluted brass sample were used. Recovery yields of 93~102% were obtained. These measured data were not different from ICP-MS data at 95% confidence level. This method was also validated by the rice flour CRM (normal, fortified) samples. Based on the results from the experiment, it was found that this proposed technique could be applied to the determination of Cu(II) in various real samples.

• Archives of Pharmacal Research
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• v.16 no.1
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• pp.57-61
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• 1993

Based on the turbidimetric response of protein with 50% trichloroacetic acid (TCA), this study aims to introduce an assay method for protein in solution. The standard procedure consists of mixing equal volume of sample solution (standard or unknown) with 50%-TCA solution and measuring the absorbance at 450 nm after 20 min. The absorbances of the solutions were almost stable over 120 min at room temperature. This assy method is simple, reproducible, and tolerant to many interfering substances. It can detect less amount than $10\mu$g/ml of bovin serum albumin. The assay method has low protein-to-protein variability over wide range of molecular weight.