Showing papers in "Journal of The Korean Chemical Society in 1991"

Determination of Hg (II) Ion at a Chemically Modified Carbon Paste Electrode Containing L-Sparteine

Abstract: A mercury ion-sensitive carbon-paste electrode (CPE) was constructed with l-sparteine. Mercury (II) ion was chemically deposited by the complexation with l-sparteine onto the CPE. The surface of CPEs was characterized by cyclic voltammetry and anodic stripping voltammetry in an acetate buffer solution, separately. Exposure of CPEs to acid solution could regenerate surface and reuse it for deposition. In 5 deposition/measurement/regeneration cycle, the response was reproducible and in licnear up to M with linear sweep voltammetry. In case of using the differential pulse technique, we have obtained the linear response up to M with relative standard deviation of %. The detection limit was M for 20 minutes of the deposition. We have investigated the interference effect of various metal ions, which are expected to form the complex with ligand. Silver (I) ion of these has interfered with the analysis of Hg (II) ions. However, pretreatment of the silver (I) ion with potassium chloride led to no interference on the analysis of mercury ions in aqueous solution.

Nonstoichiometry and Characteristics of the Perovskite $Y_{1-x}A_xFeO_{3-y}$ (A = Ca, Sr) Systems

Abstract: Nonstoichiometric solid solutions of (A = Ca, Sr) systems with perovskite structure were prepared for x = 0.00, 0.25, 0.50, 0.75 and 1.00 at 1200 under atmospheric pressure, respectively. Crystallographic structures of the solid solutions of all compositions have been determined by the analysis of X-ray diffraction patterns. Reduced lattice volume of the system was decreased with increasing x value and that of the system was increased with increasing the x value. The mole ratios of to , , values in the solid solutions have been determined by Mohr salt's method of analysis and then the mixed valency was identified by Mossbauer spectroscopic analysis at 298 K. The y values were calculated from the x and , and then nonstoichiometric chemical formulas were fixed. The conduction mechanism could be explained by hopping model of the conduction electrons between the mixed valence states.

Synthesis of New Inhibitors on NADH-Ubiquinone Oxidoreductase

Abstract: Kun Hoe Chung', Kwang Yun Cho, Nobutaka Takahashi* ',and Shigeo Yoshida** Organic Div. I, Korea Research Institute of Chemical Technology, Daejeon 305-606, Korea. ^Department of Agricultural Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113, Japan **Chemical Regulation of Biomechanisms Lab., The Institute of Chemical and Physical Research, Wako-shi, Saitama 351-01, Japan (Received January 22, 1991)

Theoretical Studies on the Cationic Polymerization Mechanism of Oxetanes(II)

Abstract: The cationic polymerization of energetic substituted oxetanes which have pendant energetic group such as azido and nitrato are investigated theoretically, using semiempirical HF/3-21G, MINDO/3, MNDO and AM1 method. The stereo- and electronic structure of binary molecular complex composed of energetic substituted oxetane and boron trifluoride can be explain by molecular orbital theory. The reactivity of propagation in the copolymerization of oxetanes can be presented by the positive charge on carbon(C2) atom of oxetane and energy level of the lowest unoccupied molecular orbital(LUMO) of propagating species of oxetanes. The reactivity ratios for copolymerization of oxetanes are a random copolymer-zation which is agree with MO calculated and experimental results. The relative equlibrium concentration of cyclic oxonium and open carbenium ions is found to be a major determinant of mechanism, owing to the rapid equilibrium of these cation forms and the expectation based on calculation that in the prepolymer propagation step, SN1 mechanism will be at least as fast as that for SN2 mechanism.

A Study on the Simultaneous Analysis of Regulated Pesticides Residues from Rice and Soy Bean

Abstract: The simultaneous determination method which simply determined regulated pesticides was investigated. Sample was extracted with acetone-methanol and partitioned with methylene chloride after addition of saturated NaCl solution. Entract was purified by Bio-Beads S-X3 column using cyclohexane-methylene chloride (1 : 1) as eluate. The determination of pesticides was performed by BP-1 capillary column gas chromatography using ECD and NPD. The average recoveries of pesticides in rice and soy fbean were over 83% and 81%, respectively. It was possible to detect pesticides in rice up to 0.002 ppm by and up to 0.05 ppm by carbaryl and in soy bean up to 0.01 ppm by -BHC and up to 0.3 ppm by carbaryl.

Nonstoichiometry and Magnetic Property of the $Nd_{-x}Sr_{x}CoO_{3-y}$ System

Abstract: A series of samples in the system (x = 0.00, 0.25, 0.50, 0.75 and 1.00) have been produced by heating the reactants at 1200C under atmospheric pressure. The solid solutions were analysed by X-ray diffraction spectra, thermal analysis, and SEM micrographs. X-ray powder diffraction assigns the compositions of x = 0.00, 0.25, 0.50 and 0.75 to the cubic system and the composition of x = 1.00 to the orthorhombic system. The reduced lattice volume is increased with increasing x values in the system. The mole ratio of or values are determined by the Iodometric titration method and are maximum at the composition of x = 0.50. The magnetic measurement shows that a ferromagnetism is appeared in the compositions of x = 0.00, 0.25, 0.50 and 0.75 and then an antiferromagnetism in the composition of x = 1.00. The measurement of the electrical conductivity shows that the semiconductivity is appeared in the composition of x = 0.00, 0.25 and 1.00 and the metallic conductivity in the composition of x = 0.50 and 0.75. The magnetic and electrical properties of the samples are discussed with the nonstoichiometric

Macrotri-and Macrotera-cyclic Ni (II) and Cu (II) Complexes. Synthesis of the Complexes and the Square Planar-Octahedral Equilibrium of the Ni (II) Complexes

Abstract: Template condensation reactions of formaldehyde with appropriate tetramines and diamines in the presence of N(II) or Cu(II) ion produce square planar complexes of hexaaza macrotricyclic and macrotetracyclic ligands (M = Ni(II) or Cu(II); L = 4-methyl-1,3,6,8,11,14-hexaazatricyclo[12,2,1,]octadecane(C), 1,3,10,12,15,18-hexaazatetracyclo[16,2,1,docosane(D) 4-methyl-1,3,6,8,12,15-hexaazatricyclo[13,3,1,]eicosane(F), or 1,3,10,12,16,19-hexaazatetracyclo[l7,3,1,tetracosane(G). These complexes contain two 1,3-diazacyclopentane or 1,3-diazacyclohexane rings in the six-membered chelate rings. The complexes of C and F contain one methyl group and those of D and G one cyclohexane ring in the five-membered chelate ring. Synthesis and characterization of the Ni(II) and Cu(II) complexes are presented. The effects of the ligand structure on the equilibrium in aqueous solutions are described.

The Reactivity and Regiochemical Effect of Nitrosonium Species in the Nitrosation of N-Methyl-N'-Substituted Phenylureas

Abstract: The regioselectivity in the nitrosation of seven N-methyl-N'-substituted phenylureas (; G = H, p-CH, m-CH, m-CHO, p-F, m-F, m-Br) was examined using NaNO and 4 different acids (diluted HCl, HCOOH, CHCOOH, CFCOOH). In all cases, the two regioisomeric products, N-nitroso-N-methyl-N'-substituted phenylureas (A) and N'-nitroso-N-methyl-N'-substituted phenylureas (B) were observed to be formed as major products and product ratios were determined by the integration of their methyl peaks in H-NMR. Electron donating substitutent(G) on phenyl of the ureas generally led to increase the ratio of B to A. The data have revealed that the relative sensitivity of the nitrosonium species (HONO, HCOONO, CHCOONO, CFCOONO) toward the change of electron density on nitrogen with phenyl substitutents are 1.00 : 0.93 : 0.78 : > ∼ 0.7.

Stability Constants of Nitrogen-Oxygen Donor Macrocyclic Ligand-Metal Ion Complexes in Aqueous Solutions

Abstract: The protonation and the metal ion complexation of 15 to 18 membered diaza crown ether such as 1,12-diaza-3, 4 : 9, 10-dibenzo-5, 8-dioxacyclopentadecane(NtnOenH), 1,13-diaza-3,4 : 10,11-dibenzo-hydroxy-5,9-dioxacyclohexadecane(NtnOtnH), 1,13-diaza-3,4 : 10,11-dibenzo-15-hydroxy-5,9-dioxacyclohexadecane(Ntn(OH)OtnH), 1,15-diaza-3,4 : 12,13-dibenzo-5,8,11-trioxacycloheptadecane (NenOdienH) and 1,15-diaza-3,4 : 12,13-dibenzo-5,8,11-trioxacyclooctadecane(NtnOdienH) were studlied by potentiometry and NMR spectroscopy. The protonation constants were used to predict basicity of crown ethers. The sequence of the basicity was NenOdienH . Changes on the basicity were explained in terms of the effects of substituents and the degree of twistness of the macrocyclic ring. The sequence of the complex stabilities were Co(II) H and C-NMR studies for heavy post-transition metal complexes indicated that the nitrogen atom has greater affinity on metal ions than oxygen atom and the planarity of the rings was losed by the complexation with metal ions.

Selective Oxidation of 2,6-di-tert-butylphenol by Oxygen Adducted Pentadentate Schiff Base Cobalt (II) Activated Catalysts and Electrochemical Properties of Cobalt (II) Catalysts in Aprotic Solvents

Abstract: Activated oxidation catalysts are generated by the treatment of pentadentate Schiff base cobalt(Ⅱ) complexes with the oxygen saturated DMF solution. Oxidation of 2,6-di-tert-butylphenol by homogeneous oxidation catalysts of superoxo type pentadentate schiff base cobalt(Ⅲ) complexes yields 2,6-di-tert-butylbenzoquinone(BQ) as a major product. And /Co mole ratio of homogeneous oxidative catalysts such as [Co(Ⅲ)(sal-DET)] and [Co(Ⅲ)(sal-DPT)]by PVT method of the oxygen absorption in DMSO and pyridine solution was 1:1, 1:1.52 in DMF solution and -peroxo type cobalt(Ⅲ) complexes formed at solid state. The redox reaction processes of superoxo type cobalt(Ⅲ) complexes as homogeneous oxidation catalysts were investigated by cyclic voltammetry and DPP method at a glassy carbon electrode. As a result of electrochemical measurements the reduction processes of oxygen adducted superoxo type cobalt(Ⅲ) complexes occurred to four steps including prewave of -in 0.1M TEAP-DMSO and 0.1 M TEAP-Pyridine as supporting electrolyte solution.

Chemical Equilibrium between Metalloporphyrins (MTPP and M(o-Cl)TPP) and Basic Ligands(L). (M = $Zn^{2+],\;Cu^{2+},\;Ni^{2+}$: TPP = tetraphenylporphyrin, (o-Cl)TPP = tetrakis (ortho-chlorophenyl)porphyrin: L = imidazole, pyridine, 1-methylimidazole, 2,6-lutidine)

Abstract: The axial ligations of nitrogenous bases (pyridine, imidazole, 1-methylimidazole and 2,6-lutidine) to Zn(II)-, Cu(II)-, and Ni(II)-tetrakis(o-chlorophenyl)porphyrin(o-ClTPP), and -tetraphenylporphyrin (TPP) were investigated in organic solvents and at 0.01M of ionic strength. The equilibrium constants for the ligation reactions of methalloporphyrins were determined using spectrophotometric method at 15∼35. In case of M(II)-TPP the equilibrium constants K were considerably larger than those of M(II)-(o-Cl)TPP, depending on steric effect of the porphyrin. The linear relationships between logK of the axial ligation and of nitrogenous base were shown in M(II)-TPP, but not in M(II)-(o-Cl)TPP. The stabilities of MTPP(L) were controlled by the reation enthalpy and entropy, while those of M(o-Cl)TPP almost by the reaction entropy. The coordinating power of solvent to the methalloporphyrin were also studied in , DMF and DMSO. From those results the solvent effects on the equilibrium constants were discussed.

A Study on Complex Formation of Heavy Metal Ions with N,N'-Oxalybis(salicylaldehyde hydrazone)

Abstract: The complexation of N,N'-oxalylbis(salicylaldehyde hydrazone) (OBSH) with Zn (II), Cd (II), and Pb(II) ions was studied by polarographic method in DMSO solution. The order of stability constants was Cd(II)

Kinetic Studies on the Nucleophilic Addition of Thiourea to ${\beta}$-Nitrostyrene Derivatives

Abstract: The rate constants for the nucleophilic addition reactions of thiourea to -nitrostyrene derivatives(p-H, p-Cl, p-CH, p-OCH, p-NO) were determined by UV spectrophotometer and rate equations which can be applied over a wide pH ranges were obtained. On the basis of substituent effect, general base catalysis and rate equations, a reaction mechanism was proposed and revealed quantitively. Above pH 9.00, sulfide anion adds to the double bond(Michael type addition) and between pH 7.00 and 9.00, the neutral molecules and its anions add to the double bond competitively. Below pH 7.00, the addition reaction to double bond is initiated by the addition of neutral thiourea molecule.

Solubilization and Photosensitizing Properties of Some Anthracene Derivatives in Aqueous Micellar Solutions

Abstract: The chemical evidence for involvement of singlet oxygen during photoirradiation for 2-ethylanthracene [2-EA] and 9-phenylanthracene [9-PA] was based on the rapid decomposition of 1,3-diphenylisobenzofuran [DPBF] in methanol-water mixture and aqueous CTAB, and SDS micellar solutions. The average microenvironmental polarities of 2-EA and 9-PA were estimated by UV spectroscopic characteristics sensitive to the polarity of solvent. When 2-EA and 9-PA were solubilized in aqueous CTAB, SDS and Brij 35 solutions, their average microenvironmental polarities were polar, and their microenvironmental polarity parameter showed little dependence on the ionic properties of the micelles. The average microenvironmental polarity of 2-EA was similar to the polarity of 40% (w/w) aqueous ethanol, and that of 9-PA was similar to the polarity between 30 and 40% (w/w) aqueous ethanol. It was found that the greater part of these species might be distributed at the surface of micelles when they were solubilized in aqueous micellar solutions. The methanol-water mixture solution appeared to have characteristics more favorable for photooxidation reaction than aqueous micellar solutions.

A Study on Complex Formation of Cd (II) Ion with Hydrazide Schiff

Abstract: The complexation of hydrazide schiff base ligands such as N,N'-oxalylbis(salicylaldehyde hydrazone), N,N'-malonylbis(salicylaldehyde hydrazone), and N,N'-succinylbis(salicylaldehyde hydrazone) with Cd(II) ion was studied by polarographic method in DMSO solution. The order of stability constants was OBSH H and S of the complexation were distributed on the complex stabilities.

Syntheses of Metalloporphyrins and Polymer-bonded Metalloporphyrin and Their Catalytic Effects on Benzoquinone Photoreduction

Abstract: pyrrole과 benzaldehyde 및 그 유도체로부터 meso-tetraphenylporphyrin(TPP)과 그 유도체 다섯가지를 합성한 후 이를 Co(II), Cu(II), Zn(II)의 염화물과 반응시켜 각각의 metalloporphyrin 착화합물을 만들고, 이 중 meso-tetra(p-aminophenyl)porphyrin(TNPP)을 다공성 polystyrene 수지와 반응시킨 후 여기에 Cu(II)의 염화물을 작용시켜 고분자결합 metalloporphyrin 착화합물 : Cu(Res-NH-TPP- $NH_2$ )을 만들었다. 합성한 porthyrin 화합물들은 가시광선, 적외선 및 전자스핀공명 스펙트럼으로 확인하였고, 금속함량은 원자흡광 분광광도법으로 측정하였다. 합성한 porphyrin 화합물을 benzoquinone 광환원반응에 촉매로 이용한 결과, 일반적으로 유리 porphyrin보다 metalloporphyrin이, metalloporphyrin 중에는 Cu-TNPP의 촉매효과가 높았으며, 이에 고분자를 결합시키는 경우 효과가 더욱 향상됨을 알 수 있었다. 【Six free base porphyrins were synthesized by reacting pyrrole with benzaldehyde or its derivatives and then reacted with metal chlorides to prepare corresponding metal complexes. In addition, polymer-bonded porphyrins were synthesized by treating chloromethylated styrene-divinyl benzene (1%) copolymer beads with meso-tetra (p-aminophenyl)porphyrin (TNPP) solution and then treated with cupric chloride to obtain Cu(Res-NH-TPP- $NH_2$ ). The porphyrin compounds were characterized by visible, inffrared and electron spin resonance spectral analyses. The metal contents of metalloporphyrins were determined by atomic adsorption spectrophotometry. The synthesized porphyrin compounds were subsequently examined for their catalytic strength and found the activity to increase in the following order: free base porphyrins; metalloporphyrins; polymer-bonded metalloporphyrin. Among metalloporphyrins, Cu-TNPP showed the greatest catalytic power.】

Adsorptive Stripping Voltammetry of the Indium-8-Hydroxyquinoline Complex

Abstract: A sensitive stripping voltammetric study of the complex of indium with 8-hydroxyquinoline at a hanging mercury drop electrode was investigated in 0.1M acetate buffer solution. The effects of various analytical conditions on the reduction peak current of the adsorbed complex were discussed. Optimal analytical conditions were found to be the ligand concentration of M, solution pH 4.75, scan rate of 10 mV/s, deposition potential of -0.450V, a deposition time of 90 second. Interferences by other trace metals and Triton X-100 were also discussed. Detection limit was 0.2 ppb of indium after 90 sec. Deposition time, and the relative standard deviation(n = 10) at 4 ppb was 3.2%.

Electrochemical Behaviors of N'-phenyl-N-(2-chloroethyl)-N-nitrosourea Analogous and Synthesis of N-aminourea

Abstract: N'-phenyl-N-(2-chloroethyl)-N-aminourea has been prepared from N'-phenyl-N-(2-chloroethyl)-N-nitrosourea by means of the electrochemical reduction with the mercury pool electrolytic cell. In order to find out the optimum condition of the reaction, the voltammetric behaviors for N'-aryl-N-(2-chloroethyl)-N-nitrosourea derivatives have been investigated by the cyclic voltammetry and polarography. The peak potentials was shifted to the negative direction as the pH value of the solution decrease. The substituent effects of phenyl ring on the peak potential were not observed in this case. (5:3) EtOH/4 N-HCl mixed solution was employed for the electrolysis. The applied potential was -0.7 V vs. Ag/AgCl/4 N-HCl electrode. The number of electrons participated to the reduction process was 4, respectively. The product was identified by FT-IR, NMR, mass and/or elemental analysis data.

푸리에 변환을 이용한 전기화학적 임피던스 측정 시스템 제작

Abstract: 푸리에 변환을 이용하여 100kHz의 주파수 범위까지 사용할 수 있는 전기화학적 임피던스 측정시스템을 제작하였다. 이 시스템은 신호 발생기, 특수하게 고안된 정전위기, 고속 자료수집 장치, 시스템 제어기 및 컴퓨터 인터페이스로 구성되었다. 우리가 제작한 시스템은 lock-in amplifier를 사용하는 상품과 성능이 비슷하였다. 측정에 소요되는 최소 시간은 사용된 최적 주파수의 한 주기에 해당하므로 상당히 짧아졌다. 이 시스템을 사용하면 부식 초기와 같이 시간에 따라 변하는 전기화학적 계면현상을 임피던스 측정법으로 연구할 수 있으리라 전망된다. 【Electrochemical impedance measurement system using Fourier transform was constructed in the range of the frequencies up to 100 kHz. This system consists of pseudo-random noise generator, specially designed potentiostat, fast data acquisition system, system controller, and computer interface. The performance of the constructed system was found to be almost same as the commercially available system using lock-in amplifier. Measuring time was significantly reduced because the minimum time for the measurement depended on one cycle of the lowest frequency used. It would be possible to study time-varying electrochemical impedance systems such as the initial stages of corrosion processes using this system.】

명반 및 수산화 알루미늄을 이용한 ${\alpha}$ -Al $_2$ O $_3$ 의 합성 (I) 규산 알루미늄광으로부터 순수한 ${\alpha}$ -Al $_2$ O $_3$ 추출을 위한 용해도 모델 계산 및 실험적 검증

Abstract: 천연규산 알루미늄광인 힐로이사이트 광물로부터 고순도 ${\alpha}-Al_2O_3$ 를 합성하기 위해 황산용액을 사용한 습식합성법을 이용하였다. 추출된 황산 알루미늄 용액내에 존재하는 각종 불순물을 제거하기 위해 각 금속이온의 수산화물과 탄산화물의 형성을 고려, pH에 따른 용해도곡선을 도시하였다. 이를 기초로 ${\alpha}-Al_2O_3$ 의 전구물질인 순수한 암모니움 명반은 pH = 1.5∼2.5에서, 수산화 알루미늄은 pH = 6∼8에서 각각 합성하였으며, 이로부터 얻어진 ${\alpha}-Al_2O_3$ 의 순도는99.7 ${\%}$ 와 99.0 ${\%}$ 였다. 여기서 불순물에 대한 정제효과는 암모니움 명반으로부터 합성된 경우(Na = 0.047 ${\%}$ , Si = 0.092 ${\%}$ )가 수산화 알루미늄으로부터 합성된 경우Na = 0.29 ${\%}$ , Si = 0.12 ${\%}$ )보다 매우 높은 결과를 보였다. 【High-purity alumina powder was prepared by extracting the natural alumino-silicate mineral (halloysite) in H $_2$ SO $_4$ solution. For the selective precipitation of alum and aluminum hydroxide, the solubility diagram was prior calculated by also considering the formation of hydroxides and carbonates for all the metal ions in an aqueous solution, which allow us to control the contamination of impurities envolved in the natural minerals. Ammonium aluminum sulfate (alum) and alumium hydroxide could be successfully prepared at pH = 1.5∼2.5 and pH = 6∼8, respectively according to our solubility diagrams. The purity of alum-and hydroxide-derived ${\alpha}-Al_2O_3$ was determined to be 99.7 ${\%}$ and 99.0 ${\%}$ , respectively, which indicates the former route would be more desirable for the large scale application. It is also worthy to note that the impurities like Na and Si were strongly reduced in the former (Na = 0.05 ${\%}$ , Si = 0.09 ${\%}$ ) compared to the latter (Na = 0.29 ${\%}$ , Si = 0.12 ${\%}$ ).】

Alum and Hydroxide Routes to ${\alpha}-Al_2O_3$ (II) Ultra-Fine Alumina by Thermal Decomposition

Abstract: In order to synthesize high-purity alpha alumina fine powder, the aluminum hydroxide and ammonium aluminum sulfate(alum) precursor were prepared from natural alumino-silicate(halloysite). The thermal decomposition mechenism for both precursors was elucidated by DTA/TG, XRD and IR analysis. The microstructure, specific surface area and purity of were characterized by SEM, and BET analysis. The particle size of was determined to be = 0.1∼0.5 m. However, the specific surface area for the alum derived (89.0 m/g) was extremely higher than that for the aluminum hydroxide derived one(7.3 m/g).

Simultaneous Analysis of Stimulants and Narcotic Analgesics by Capillary Column Gas Chromatography with Nitrogen Phosphorus Detector

Abstract: 질소를 함유한 흥분제와 마약성 진통제 18종류의 약물들을 gas chromatography-nitrogen phosphorus detector(GC-NPD)를 사용하여 human urine으로부터 동시에 신속하게 분석할 수 있는 최적조건을 찾기 위하여 pH 변화와 추출용매 변화에 따른 회수율을 조사하였다. pH 8.5에서 에테르를 추출용매로 사용하였을 때 가장 적은 방해영향과 가장 좋은 회수율을 나타냈다. NPD에 대한 각 약물들의 상대 감응인자를 구하였고, 이 상대감응인자는 약물이 가지고 있는 질소원자의 갯수가 증가할수록 작은 값을 나타냈다. 생체시료 중의 약물들을 신속하게 검정하기 위하여 내부표준물질인 diphenylamine에 대한 relative retention time(RRT)을 작성하였다. 상대머무름 시간은 0.1% 이하의 정밀도를 나타냈다. 【A systematic analysis of 18 stimulants and narcotic analgesics containing nitrogen atom (s) in human urine by gas chromatography with nitrogen phosphorus detector (GC-NPD), is described. The urinary extract with diethyl ether at pH 8.5 showed good recoveries of the drugs and less interference peaks on GC chromatogram. Retention data were standardized by the calculation of relative retention times using diphenylamine as the internal standard. The relative standard deviations of retention times were less than 0.1% for the within-run analyses. The response factor (RRF) of a drug relative to the internal standard was calculated. RRF decreased with increasing number of nitrogen atoms. This technique can be adapted to various analytical toxicology problems.】

Adsorptive Stripping Voltammetry of Indium-Morin Complex

Abstract: A sensitive adsorptive stripping voltammetric study was investigated on the complex of indium with morin at a hanging mercury drop electrode in 0.1 M acetate buffer (pH 3.20) solution. The adsorption phenomena were observed by differential-pulse voltammetry. The effects of various analytical conditions were discussed on the reduction peak current of the adsorbed complex on the surface of HMDE. Interferences by other trace metals and surfactant were also discussed. Detection limit was 2.6 nM of indium after 90 second deposition time, and the relative standard deviation (n = 7) at 4TEX>${\mu}g$/l indium was 2.0%.

Lipids Constituents of the Korean Marine Sponges

Abstract: Various sterols and uncommon fatty acids have been isolated from the three species of Korean marine sponges. Odd-numbered pentadecanoic, heptadecanoic methyl ester and branched 12-methyltetradecanoic, 14-methylpentadecanoic, 15-methylhexadecanoic and 14-methylhexadecanoic methyl ester were isolated along with common tetradecanoic and hexadecanoic methyl ester from Heteropiidae sponge Vosmaeropsis japonica Hozawa collected from Sohuksan island of the Korea sea. Futher elution with more polar solvent gave 5-cholestan-3-ol along with minor amount of ergost-25-ene-3,5,6-triol. On the other hand, marine sponge Hymeniacidon sinapium collected from Yesu Dolsan island of the Korea sea was shown to contain 5-cholestan-3-ol, along with minor amount of cholesterol, palmitic, palmitoleic, oleic, stearic, linolenic, and arachidonic acid ethyl ester. Unknown marin sponge collected from the same region was shown to contain large amount of tetradecanoic tetradecyl and hexadecyl ester and cholesteryl acetic and fatty acid ester.