• 대한화학회지
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• 제25권4호
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• pp.275-282
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• 1981

試藥겔 粒子를 채운 마이크로分析컬럼을 사용하여 水溶液중의 ppm레벨 이하의 크롬(VI)이온의 簡易分析法을 開發하였다. 115∼150 mesh의 XAD-2 樹脂를 실온에서 10분동안 에탄올에 膨潤시킨 다음, 유리관(안지름 1.5 mm, 길이 65 mm)에 채워 넣고 $2.0{\times}10^{-3}M$ diphenylcarbazide(DPC)-에탄올용액 1ml를 20분 동안에 흘려 분석컬럼을 만든다. 이 컬럼에 크롬(VI)이온을 포함한 황산산성의 試料水(pH 1) 0.5 ml를 40분 동안에 흘리면 컬럼의 위 끝으로부터 DPC겔의 흰색은 赤紫色으로 변색된다. 着色帶의 길이는 컬럼을 통과한 試料水중의 크롬(VI)濃度에 比例하므로 일정량의 試料水를 흘린 다음, 着色帶의 길이를 측정하여 미리 작성한 檢量線으로부터 크롬(VI)이온의 濃度를 구할 수 있다. 이 법으로 0.1∼0.8 ppm의 크롬(VI)이온을 ${\pm}5{\sim}{\pm}15{\%}$의 相對誤差로 정량할 수 있다. 본법은 妨害이온의 영향이 적기 때문에 가리움劑로 EDTA를 써서 크롬(VI)이온 (0.6 ppm)의 100배량의 철(III)이온과 50배 양의 구리(II)이온을 음폐시킬 수 있으며, 工場廢水중의 크롬(VI)이온의 分析에 應用하여 만족한 결과를 얻었다.

• 한국토양비료학회지
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• 제44권5호
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• pp.727-733
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• 2011

A new Korean standard for the determination of Cr(VI) in soils has been officially published as ES 07408.1 in 2009. This analytical method is based on the hot alkaline digestion and colorimetric detection prescribed by U.S. EPA method 3060A and 7196A. The hot alkaline digestion accomplished using 0.28 M $Na_2CO_3$ and 0.5 M NaOH solution (pH 13.4) at $90{\sim}95^{\circ}C$ determines total Cr(VI) in soils extracting all forms of Cr(VI), including water-soluble, adsorbed, precipitated, and mineral-bound chromates. This aggressive alkaline digestion, however, proved to be problematic for certain soils which contain large amounts of soluble humic substances or active manganese oxides. Cr(III) could be oxidized to Cr(VI) by manganese oxides during the strong alkaline extraction, resulting in overestimation (positive error) of Cr(VI). In contrast, Cr(VI) reduction by dissolved humic matter or Fe(II) could occur during the neutralization and acidic colorimetric detection procedure, resulting in underestimation (negative error) of Cr(VI). Futhermore, dissolved humic matter hampered the colorimetric detection of Cr(VI) using UV/Vis spectrophotometer due to the strong coloration of the filtrate, resulting in overestimation (positive error) of Cr(VI). Without understanding the mechanisms of Cr(VI) and Cr(III) transformation during the analysis it could be difficult to operate the experiment in laboratory and to evaluate the Cr(VI) results. For this reason, in this paper we described the theoretical principles and limitations of Cr(VI) analysis and provided useful guidelines for laboratory work and Cr(VI) data analysis.

• BMB Reports
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• 제40권1호
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• pp.100-106
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• 2007

The wound-inducible lipoxygenase obtained from maize is one of the nontraditional lipoxygenases that possess dual positional specificity. In this paper, we provide our results on the determination and comparison of the kinetic constants of the maize lipoxygenase, with or without detergents in the steady state, and characterization of the dependence of the kinetic lag phase or initial burst, on pH, substrate, and detergent in the pre-steady state of the lipoxygenase reaction. The oxidation of linoleic acid showed a typical lag phase in the pre-steady state of the lipoxygenase reaction at pH 7.5 in the presence of 0.25% Tween-20 detergent. The reciprocal correlation between the induction period and the enzyme level indicated that this lag phenomenon was attributable to the slow oxidative activation of Fe (II) to Fe (III) at the active site of the enzyme as observed in other lipoxygenase reactions. Contrary to the lagging phenomenon observed at pH 7.5 in the presence of Tween-20, a unique initial burst was observed at pH 6.2 in the absence of detergents. To our knowledge, the initial burst in the oxidation of linoleic acid at pH 6.2 is the first observation in the lipoxygenase reaction. Kinetic constants (Km and kcat values) were largely dependent on the presence of detergent. An inverse correlation of the initial burst period with enzyme levels and interpretations on kinetic constants suggested that the observed initial burst in the oxidation of linoleic acid could be due to the availability of free fatty acids as substrates for binding with the lipoxygenase enzyme.