• Applied Chemistry for Engineering
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• v.34 no.1
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• pp.45-50
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• 2023

Microfluidic preconcentration technologies, which collect or extract low-abundance analytes in a specific location, have been spotlighted in various applications such as medical and bio-engineering. Here, we conducted extensive studies on the variables to be considered when concentrating target samples based on electrophoresis in an electromembrane system utilizing an ion exchange membrane. Using negatively charged Alexa Fluor 488 and positively charged Rhodamine 6G as fluorescent dyes, we examined the effects of flow velocity of the main channel, channel electrolyte concentration, and applied voltage on sample preconcentration. As a result, it was found that the preconcentration of the target sample occurs much better when the flow velocity is slow and the concentration of the main channel containing the sample is high, given that the channel concentration ratio (main and buffer) is constant. In addition, based on the experimental data acquired in this study, the electrophoretic mobility values of Alexa Fluor 488 and Rhodamine 6G were experimentally calculated and compared.

• Bulletin of the Korean Chemical Society
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• v.23 no.5
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• pp.693-698
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• 2002

A method has been described for the determination of Cu(Ⅱ), Pb(Ⅱ), Ni(Ⅱ), Cd(Ⅱ), Mn(Ⅱ) and Fe(Ⅲ) by flame atomic absorption spectrometry (FAAS) after preconcentration on Amberlite XAD-16 resin, using hexamethyleneammonium-hexamethylenedithiocarbamate (HMA-HMDTC) as a chelating agent, and NH3/NH4Cl buffer solution (pH 9). Influences of various analytical parameters such as pH, concentration of nitric acid, amount of analytes, diverse ions and sample volume were investigated. The relative standard deviation (RSD) and the detection limit (LOD) were found in the range of 0.8-2.9% and 0.006-0.277 ㎍/mL,respectively. Recoveries obtained by the column method were quantitative ( >95%) at optimum conditions.The method was applied to the determination of some metal ions in seawater and wastewater samples. A high preconcentration factor (about 150 for seawater and 75 for wastewater samples) and simplicity are the main advantages of this suggested method.

• Bulletin of the Korean Chemical Society
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• v.23 no.4
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• pp.545-549
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• 2002

A simple and rapid technique for the separation and preconcentration of lead in water and biological samples has been devised. Preconcentrationis based on the depositionof analyte onto a column packed with dithizone immobilized on sodium dodecyl sulfate coated alumina at pH $\geq$ 3. The trapped lead is eluted with 5 mL of 4 M nitric acid and determined by flame atomic absorption spectroscopy. A sample of 1 L, results in a preconcentration factor of 200 and the precision at 20${\mu}g$ $L^{-1}$ is 1.3%(n=8). The procedure is applied to tap water, well water, river water, vegetable extract and milk samples, and accuracy is assessed through recovery experiments and by independent analysis by furnace atomic absorption.

• Bulletin of the Korean Chemical Society
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• v.24 no.5
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• pp.555-558
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• 2003

An enrichment/separation system for atomic absorption spectrometric determinations of Cu(Ⅱ), Fe(Ⅲ), Ni(Ⅱ) and Co(Ⅱ) has been established. The procedure is based on the adsorption of the analytes as calmagite chelates on Chromosorb-102. The effects of some parameters including pH, amount of ligand, salt matrix, flow rates of sample and eluent solutions were investigated. Under optimized conditions, the relative standard deviation of the combined method of sample treatment, preconcentration and determination with FAAS (N=5) is generally lower than 5%. The limit of detection (3σ) was between 6.0-112.9 ㎍/L. The results were used for preconcentration of analytes from some sodium and ammonium salt.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 1999.10a
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• pp.96-98
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• 1999

환경시료들은 매트릭스의 조성이 매우 복잡하여 공존하는 성분들이 목적성분의 검출에 영향을 미치므로 분리하는 조작이 필요하다. 환경 중에 존재하는 물질들은 동적인 평형상태를 유지하고 있기 때문에 시료를 채취하여 실험실로 운반하여 보관하는 동안에 분석 대상 물질이 용기에 흡착, 휘발 및 화학 반응의 진행 등으로 인하여 시료의 손실 및 변질을 초래 할 수 있다.(중략)

• Bulletin of the Korean Chemical Society
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• v.19 no.7
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• pp.766-770
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• 1998

On-line preconcentration by direct precipitation with hydroxide has been developed and applied for the analysis of Cd in Inductively Coupled Plasma Atomic Emission Spectrometry. Cadmium is continuously precipitated with hydroxide and dissolved by nitric acid in on-line mode. Currently, the enrichment factor is more than 90 times for 20.0 mL of sample and could be further increased very easily. For a large sample throughput, 1.0 mL of sample loop is used and the enrichment factor is 4.5 with the sampling speed of 15/hr. The method has been applied to the analysis of NIST reference sample and has yielded good results with the certified value.

• Journal of the Korean Ceramic Society
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• v.51 no.5
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• pp.472-476
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• 2014

In this work, a new method that utilizes L-cysteine salicylaldehyde Schiff-base modified macroporous polystyrene resin (PS-CSC) as an effective sorbent has been developed for preconcentration of trace cadmium and lead in environmental water samples. The effect of pH, the contact time, the elution conditions, the flow rate, the initial concentration of target metal ions, and the effects of interfering ions on the preconcentration of the analytes were investigated. The maximum adsorption capacity of PS-CSC under optimum conditions for cadmium and lead were found to be 6.03 - 18.17 mg/g and 12.58 - 36.13 mg/g when the initial concentration of metal ions between 5.0 - 90 mg/L. The limits of detection for cadmium and lead were 2.46 ng/L and $0.52{\mu}g/L$, with a preconcentration factor of 200. The developed method has been validated by analyzing certified reference material and successfully applied for the enrichment and determination of trace cadmium and lead from environmental water samples.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.4
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• pp.417-428
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• 1999

The measurement of VOSCs(volatile organic sulfur compounds) in the air is nowadays a very important environmental research field. It is, however, very difficult because the concentration of the VOSC in ambient air is usually very low and the high reactivity makes it difficult to keep in container without loss of recovery. In this study, sampling method with cryogenic preconcentration is evaluated for analysis of atmospheric VOSC such as $CH_3SH,\;CH_3CH_2SH,\;CH_3SCH_3,\;CS_2,\;CH_3SSCH_3,\;CH_3SCH_2SCHA_3,\;and\;C_2H_5SSC_2H_5$ analyzed by GC-MS or GC-FID. Repeatabilities of measurement accompanied with preconcentration for 3-successive runs were in the range of 0.2~1.0% as a relative standard deviation. Stabilities up to 13 days were measured in 6 L canister and 10 L tedlar bag filled with VOSCs in ppb level. Higher stability was observed in tedlar bag as compared to canister with glass coated inner walls, and thiol compounds show dramatic losses in canister within 2~3 days. It is found that recovery over 70% was obtained in a week for all tested VOSCs when the compounds from ambient air matrix were stored in tedlar bag. It is also found that the stabilities of VOSCs are depending on humidity and coexisting compounds in matrix gas due to sample adsorption onto inner surface and reactivity. The results indicate the possibility and limitations of VOSC analysis in ambient air using container sampling method with cryogenic preconcentration.

• Analytical Science and Technology
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• v.33 no.4
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• pp.186-196
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• 2020

A simple and rapid preconcentration method of actinide from seawater using Actinide resin was developed and tested with the seawater spiked with a known U and Th. The developed method of Actinide resin based on column chromatography is less time-consuming and requires less labor compared with a typical co-precipitation technique for preconcentration of actinides. U and Th, which are relatively weak-bonded with Actinide resin among actinides, were used to determine the optimum flow rate of seawater sample and evaluate the capacity of Actinide resin to concentrate actinides from seawater. A flow rate of 50 mL min^-1 was available with Actinide resin 2 mL (BV, bed volume). When 5 or 10 L of seawater containing U were loaded on Actinide resin (2 mL, BV) at 50 mL min^-1, the recovery of U was 93 % and 86 %, respectively. For extraction of actinides bound with Actinide resin, we compared three methods: solvent extraction, ashing-acid digestion, and ashing-microwave digestion. Ashing-microwave digestion method shows the best performance of which is the recovery of 100 % for U and 81 % for Th. For the preconcentration of actinides in 200 L of seawater, a typical coprecipitation method requires 2-3 days, but the developed method in this study is achieved the high recovery of actinides within 12 h.

• Journal of Korean Society on Water Environment
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• v.28 no.6
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• pp.843-850
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• 2012

Due to the fast response to algae bloom issue in drinking water treatment plant, very fast determination methodology for algal toxin is required. In this study, column switching technique based online preconcentration method was combined with high resolution full scan mass spectrometer to save sample preparation time and to obtain fast and accurate result. After parameter optimization of online preconcentration, 1mL filtered sample was directly injected to trap column with switching valve system. Next, target toxins are eluted by 98% acetonitrile and analysed with 150 - 1,100 amu scan range at 50,000 resolving power. Method detection limit (MDL) for microcystin-LR, the most toxic isomer, was 0.1 ng/mL and others such as microcystin-YR, microcystin-RR and nodularin were 0.08, 0.03 and 0.04 ng/mL, respectively. This is the best improved sensitivities with 1mL volume in the literature. Furthermore, due to the use of ultra pressure HPLC (UPLC), the whole method run was completed in 4 min. Real sample applications for 173 sample including 55 surface water and 118 treatment plant samples for raw and treated water could be done within 16 hours. In our calculation, this methodology is roughly 80% faster than the previous manual solid-phase extraction with LC-MS/MS method.