• Journal of the Korean Chemical Society
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• v.52 no.1
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• pp.16-22
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• 2008

on-line system for preconcentration and separation of lead(II) is presented. The method is based on the complex formation of Pb(II) with adsorbed Methyl thymol blue on activated carbon. The conditions of preparing the solid phase reagent and of quantitative recovery of Pb(II) from diluted solutions, such as acidity of aqueous phase, solid phase capacity, and flow variables were studied as well as effect of potential interfering ions. After preconcentration step, the metal ions are eluted automatically by 5 ml of 0.5 M HNO3 solution and the lead ions content was determined by flame atomic absorption spectrometry. Under the optimum conditions, the lead ions in aqueous samples were separated and preconcentrated about 1000-fold by the column. The detection limit was 0.001 g mL-1. Lead has been determined in river and tap water samples, with recovery of 98 to 102%.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1564-1568
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• 2011

A solvent extraction separation, preconcentration and determination of thorium with a new crown, 2-ethyl-N-benzyl-4,7,10,13,16-pentaoxa-1-azacyclooctadecane (MACE), is described in the study. The amount of thorium in the aqueous phase and organic phase was determined by Inductively Coupled Plasma-Optical Emission Spectroscopy and Ultraviolet-Visible, respectively. Thorium loaded organic phase was quantitatively stripped in a stage by using 1.0 M $HNO_3$. Thorium was effectively extracted with MACE in the pH range of 6-7 to produce a 3:2 complex ratio in the chloroform. A highly sensitive and rapid spectrophotometric method was described for determination of trace amounts of thorium with MACE. The effective molar absorption coefficient at 281 nm is $1.98{\times}10^3\;mol^{-1}cm^{-1}$, and the system complies with Beer's law in the range from 0.464 to 2.32 ${\mu}gm\;L^{-1}$ of thorium. Thorium was also determined in standard and environmental samples.

• Analytical Science and Technology
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• v.12 no.4
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• pp.332-340
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• 1999

Homemade cryogenic preconcentration system is constructed to preconcentrate the VOCs in the ambient air collected in canister. Homemade preconcentrator equipped with GC-MS was used for analysis of air sample containing VOCs at ppb level identified in EPA TO-14 method. The system was evaluated for analytical performance by comparison with the results of adsorption tube method widely used in the past, and shows good agreement for concentrations of benzene, toluene, ethylbenzene, and xylenes.

• Bulletin of the Korean Chemical Society
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• v.25 no.8
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• pp.1125-1129
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• 2004

This work assesses the potential of natural Analcime Zeolite as an adsorbent for preconcentration of lead (II) traces. Lead is quantitatively retained on 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol by column method with Analcime in the pH range of 5-6.5 and 2 mL $min^{?1}$ flow rate. Lead was removed from the column with 10.0 mL of 4 M hydrochloric acid and was determined by anodic stripping differential pulse voltammetry. 0.5ppb detection limit was obtained and linear dynamic range was 3 to $1.2{\times}10^5$ ppb in final solution with correlation coefficient of 0.999 and relative standard deviation of ${\pm}$ 1.2% (for eight replicate determination of 2.5 ${\mu}g\;mL^{?1}$ of lead). Various parameters such as the effect of pH, flow rate, instrumental conditions and interferences of some ions on the determination of lead have been studied in detail for optimization of conditions. The method was successfully applied for determination of lead in various samples.

• Bulletin of the Korean Chemical Society
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• v.25 no.8
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• pp.1156-1160
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• 2004

The technique of an on-line preconcentration by the direct sulfide precipitation has been developed. Sn was homogeneously precipitated by sulfide, which was generated in situ from the hydrolysis of thioaceteamide. Precipitate was collected on a filter in the line and dissolved out instantaneously by KOH to be sent to an ICP. The enrichment factor was 4 with the sampling speed of 15/hr for 1.0 mL of sample. It was increased to more than 40 times when the sampling volume was increased to 10 mL with the sampling speed of 5/hr. $Sn^{2+}/Sn^{4+}$ could be separately determined with the on-line precipitation technique. The method was applied to the analysis of NIST SRM 1566 Oyster sample and yielded good agreement with the certified value.

• Bulletin of the Korean Chemical Society
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• v.30 no.7
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• pp.1516-1520
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• 2009

A sensitive technique for the determination of trace Co(II) in various samples after column preconcentration by adsorbing onto silica gel loaded with 1-nitroso-2-naphthol was developed. Several experimental conditions, such as pH of sample solution, the amount of silica gel loaded with 1-nitroso-2-naphthol, the flow rate for adsorption and so forth, were optimized. The interfering effects of diverse concomitant ions were investigated. Fe(III) interfered with more than any other ions, but the interference by Fe(III) was completely eliminated by adjusting the amount of silica gel loaded with 1-nitroso-2-naphthol to 0.30 g. The dynamic range, the correlation coefficient ($R^2$), and the detection limit obtained by the proposed technique were 3.0-140.0 ng m$L^{-1}$, 0.9942, and 1.81 ng m$L^{-1}$, respectively. For validating the technique, the aqueous samples (tap water, reservoir water, stream water, and wastewater) and the plastic samples were used as real samples. Recovery yields of 93.0-107.0% were obtained. These measured data were not different from ICP-MS data at the 95% confidence level by F test. Based on the results of the experiment, it has been found that the proposed technique can be applied to the determination of Co(II) in various real samples.

• 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.

• Analytical Science and Technology
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• v.14 no.5
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• pp.432-441
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• 2001

An automated on-line portable preconcentration-short column gas chromatograph was developed, which used preconcentrator using adsorption tube with Tenax-GR and Curie-point heating. The developed system operated with 3 steps of processing, preconcentration, thermal desorption, and analysis and cleaning, and could continued operating within 1~2 min cycle. The recoveries of preconcentrator for toluene was ranged between $94.7{\pm}6.6%$ and $103.8{\pm}3.1%$ with less than 7% of RSD. For benzene, toluene and xylene(BTX) standard gas test, IDL was 41, 49, $472ng/m^3$ benzene, toluene and o-xylene, respectively. The BTX mixture was analyzed within 30 sec with baseline separation by the system equipped with 4 m long capillary column. The deficiency of separation power caused by short column was solved by the control of sample injection volume and inlet/outlet pressure ratio. The automated portable preconcentration-short column gas chromatograph system was found to be useful for the continuous air monitoring of BTX at ppb levels in ambient air.

• Bulletin of the Korean Chemical Society
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• v.21 no.1
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• pp.121-124
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• 2000

• Bulletin of the Korean Chemical Society
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• v.19 no.7
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• pp.784-786
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• 1998