Study and Application on Polarographic Catalytic Wave of Human Serum Albumin in the Presence of Kio3

ABSTRACT

A polarographic catalytic wave of human serum albumin (HSA) in the presence of KIO³ was reported. In 0.1 M NaAc～HAc buffer (pH4.7) solution, a reduction wave of HSA with peak potential ?0.60 V (vs., Ag/AgCl) resulted from the reduction of five disulfide linkages to sulfhydryl group. In the presence of KIO³, HSA yielded a polarographic catalytic wave at the original potential due to reduction and regeneration of these disulfide linkages. The catalytic wave can be used to determine trace of HSA. In the 0.1 M HAc～NaAc (pH4.7±0.2) ～1×10^?3 M KIO³ solution, the peak current was linearly proportional to HSA concentration in the range of 1.5×10^?7～7.5×10^?7 M. The catalytic wave improved two orders of magnitude in sensitivity compared with corresponding reduction wave.     

Electrochemical studies of potassium ferrate(VI)

The electrochemical reduction of potassium ferrate(VI) in 6N-KOH occurs in three steps, at approximately +0.3, ?0.7, and ?1.4 V vs. Hg/HgO, 6N-KOH. The first reduction appears as a voltammetric wave on a platinum electrode and the second two are observed as polarographic waves with a dropping mercury electrode. Controlled potential coulometric, voltammetric, and chronopotentiometric studies indicate the reduction proceeds stepwise first to iron(III), then to iron(II) and finally to iron(0).     

Determination of trace thiocyanate by linear sweep polarography

In a thiocyanate solution containing iron (II), nitrite and ascorbic acid, a linear-sweep polarographic wave appears at ?0.42 V (vs. SCE). In anodic sweeps, the derivative peak current is directly proportional to the concentration of thiocyanate over the range 2×10^?8?1×10^?6 M; the detection limit is 1×10^?8 M. The procedure is used for the determination of trace thiocyanate (10^?3?10^?4 M) in saliva. The mechanism of the electrode process is discussed; the polarographic wave is ascribed to catalytic reduction of dissolved oxygen in the presence of an adsorbed ternary Fe/SCN/NO complex.     

A spectrophotometric and polarographic investigation of three new cyclohexene-substituted benzodiazepines

Three recently introduced benzodiazepine derivatives, tetrazepam (I), nortetrazepam (II) and menitrazepam (III) have been subjected to spectral and polarographic investigation. From the ultraviolet spectral data their pK(a)-values have been determined: 4.28 (I), 4.3 (II) and 3.5 (III). From the polarographic measurements it can be concluded that in I and II the 4,5 CN double bond is reduced with 2 electrons. For the first time for the benzodiazepine series it has been observed that in slightly alkaline solutions this process takes place in two separate 1-electron steps. In III, first the aromatic nitro group is reduced to a hydroxylamine group, then at more negative potentials the CN double bond is also reduced; its reduction wave mostly coalesces with that for the 6-electron reduction of the nitro group to an amino group. A differential pulse polarographic method is presented, for the determination of I, II, III at concentrations as low as 10(-7)M.     

Electrochemical reduction of S-oxides of diphenyl disulfide: Part II. Polarography in aqueous ethanol

In 50% ethanol the polarographic reduction of the S-oxides of diphenyl disulfide results in a fission of the sulfur-sulfur bond. Diphenyl disulfone is reduced by 2 electrons per molecle with benzenesulfinate ion as reduction product and gives rise to one polarographic wave. In the polarograms of phenyl benzenethiolsulfonate as well as phenyl benzenethiolsul-finate several waves appear due to the intermediate formation of a mercury compound, which is strongly adsorbed at the mercury electrode. Under polarographic and coulometric conditions the thiolsulfonate is reduced by 2 electrons in all with benzenesulfinate ion and thiophenol as reduction products. The total limiting current of the thiolsulfinate corresponds to a reduction by 4 electrons whereas 3 electrons per molecule are exchanged in coulometric experiments at a Hg-pool with thiophenol as the main reduction product.     

Acetylacetone as chelating reagent, extracting solvent, and electrolysis medium: Polarographic determination of uranium(VI) and iron(III)

The chelating reagent acetylacetone has been examined as a polarographic medium; a method for its purification has been developed and it is found that the specific conductance is 4.2 x 10(-8) mho/cm, the accessible potential ranges are from -0.16 to -2.26 V vs. Ag/0.1M AgClO(4) for the pure solvent and from -0.35 to -2.20 V in the solvent after extraction. In pure solvent ferric acetylacetonate exhibits one wave and the uranyl complex gives two waves. After extraction from aqueous solution at pH 6.8-7.0, both metal acetylacetonates are reduced more reversibly and at more positive potential than in the pure solvent. Calibration curves are linear in the range 10(-5) -10(-3)M metal ion in the extract. The direct polarographic determination of uranium and iron in acetylacetone after extraction of the chelate from aqueous solution has been developed.     

KIO3存在下溶菌酶的极谱催化波研究与应用

研究了溶菌酶(Lysozyme,LE)在KIO₃存在下的极谱催化波.在0.1mol/LHAc-NaAc(pH4.7±0.1)缓冲液中,LE有1个由Cys6～Cys127间双硫键还原产生的可逆波.其峰电位为-0.51V(vs.Ag/AgCl).当KIO₃存在时,在原电位处产生了LE的极谱催化波.该催化波是由于KIO₃及其中间价态衍生质点(包括自由基IO^-·,IO_{2^{-·)氧化LE还原产物巯基成双硫键所致.这是蛋白质极谱催化波的一种新类型.在0.1mol/LHAc-NaAc(pH4.7±0.1)-1×10-3mol/LKIO3支持电解质中,LE催化波的灵敏度比其还原波的高两个数量级,峰电流与LE浓度在2×10-7～1.0×10-6mol/L范围内有线性关系.100倍半胱氨酸和胱氨酸不干扰1.0×10-6mol/LLE的测定.}}     

Chelate adsorption for trace voltammetric measurements of iron(III)

Summary A very sensitive electrochemical stripping procedure for trace measurements of iron(III) is described. The chelate of iron with Solochrome Violet RS is adsorbed on the hanging mercury drop electrode, and the reduction current of the accumulated chelate is measured by voltammetry. The adsorption and redox behaviours are explored by cyclic voltammetry. The height of the chelate peak, which is about 0.28 V more negative than the peak of the free dye, is shown to be proportional to the iron concentration. Optimal experimental conditions include a preconcentration potential of –0.40 V, solution pH of 5.1 and a linear scan mode. The sharp chelate peak, associated with the effective interfacial accumulation, coupled with the flat baseline, facilitates measurements at the nanomolar and submicromolar concentration levels using short preconcentration times. The limit of detection after 1 min preconcentration is 0.04 gl^–1 (7 × 10^–10 M), and the relative standard deviation at the 10^–7 M level is 4.7%. The effects of possible interferences, due to coexisting metal ions or organic surfactants, are evaluated. The ability of measuring iron(III) in the presence of iron(II) is illustrated. Actual analyses of sea and tap waters are reported.

---

Chelat-Adsorption für voltammetrische Spurenanalyse von Eisen(III)

     

Polarographic determination of Ce(III) and Tm(III) using rare earth-DBF-chlorophosphonazo complex

The electrochemical behaviour of the DBF—chlorophosphonazo (DBF—CPA)—rare earth (RE) complex has been investigated in this paper. A highly sensitive polarographic adsorption wave was found in the RE(III)—DBF—CPA system and a new method for determination of trace total RE(III) has been established. The limit of detection was 1.8 × 10⁻⁸M. The results of determination of the total RE(III) content in Chinese standard reference materials of cast-iron and alloy steel were in good agreement with the certified values. The polarographic adsorptive waves of Ce(III) and Tm(III)—DBF—CPA overlap seriously. In order to improve the selectivity of determination, a non-linear regression model was employed to fit the peak height of the polarographic wave and the concentrations of Ce(III) and Tm(III). The predictive accuracy of this model for simulant mixtures was satisfied.     

Electroanalytical Study of the Reduction of Sb(III) in Tartrate Medium

Abstract

A systematic study on the reduction of Sb(III) on a mercury electrode in aqueous solution of tartrate ion has been carried out. The nature of the electrode reactions has shown to be a function of the acidity of the solution. Results from polarographic, coulometric and voltammetric experiments allow us to outline a model of electrode reaction according to which different Sb-tartrate complex ions can be reduced. Sensitivity and detection limits for the polarographic determination of Sb(III) in tartrate medium are given using several polarographic waves obtained at different pH. In this way, the selection of the basic medium is vindicated.     

Differential pulse polarographic behaviour of copper(II)-ethyleneglycol-bis-(2-aminoethylether)-tetraacetate and copper(II)-ethylenediaminetetraacetate chelates in the presence of Lanthanum(III)

Summary The substitution reduction waves of copper(II)-EGTA and copper(II)-EDTA chelates were investigated with differential pulse and tast polarographic methods. The reduction wave of copper(II)-EGTA chelate shifts to more positive potential in the presence of lanthanum(III) and a new differential pulse peak appears. The peak height increases linearly with increasing concentration of lanthanum(III) between 5 and 25 M. When the copper(II)-EDTA chelate is reduced in a supporting electrolyte containing no buffer solution, lanthanum(III) gives a substitution reduction peak, but in acetate buffer solution the lanthanum(III) peak disappears.

---

Differential-Puls-Polarographisches Verhalten des Kupfer(II)-Ethylenglykol-bis-(2-aminoethylether)-tetraacetat-Chelats und des Kupfer(II)-Ethylendiamintetraacetat-Chelats in Gegenwart von Lanthan(III)

Zusammenfassung Die Substitutionsreduktionswellen des Kupfer(II)-EGTE- und des Kupfer(II)-EDTE-Chelats wurden mit Hilfe der Differential-Puls- und der Tast-Polarographie untersucht. Die Reduktionswelle des Kupfer(II)-EGTE-Chelats verschiebt sich in Gegenwart von Lanthan(III) zu positiverem Potential und ein neuer Differential-Puls-Peak erscheint. Die Peakhöhe nimmt mit steigender Lanthanionkonzentration zwischen 5 und 25 M linear zu. Wenn Kupfer(II)-EDTE-Chelat im pufferfreien Leitelektrolyt reduziert wird, gibt Lanthan(III) einen Substitutionsreduktions-Peak, in Acetat-Pufferlösung jedoch verschwindet der Lanthan(III)-Peak.

     

Single-sweep polarography of the copper(II)-3-hydroxy-1-p-sulphonatophenyl-3-phenyltriazene complex and its analytical applications

A polarographic investigation of the copper-3-hydroxy-1-p-sulphonatophenyl-3-phenyltriazene (HSPT) complex in 0.05 M sodium tetraborate medium is described and a simple and sensitive single-sweep polarographic method for the determination of trace amounts of copper in biological samples is proposed. The complex was shown to be Cu(HSPT)2 with log beta' = 11.38. The polarographic wave is caused by the reduction of copper(II) in the adsorbed complex to copper amalgam on the surface of a mercury electrode. The current peak is directly proportional to the concentration of copper in the range 8.0 x 10(-9)-4.0 x 10(-6) M and the detection limit is 5.0 x 10(-9) M.     

Differential-pulse polarography of amino acids in acetaldehyde-borax medium

A differential-pulse polarographic method for the determination of amino acids is reported, based on the formation of Schiff's base compounds in borax buffer solution (pH 10.10) containing acetaldehyde. The compounds are reduced at a mercury electrode with peak potentials of about ?1.5 V (vs. SCE) and well defined polarographic waves are obtained which can be used to determine amino acids in borax medium. The differential-pulse polarographic method was found to be the most sensitive and suitable for the determination of amino acids in the concentration range 1 × 10^?6–8 × 10^?4 M (lysine) and 2.8 × 10^?6–1 × 10^?3 M (arginine). The polarographic characteristics of these waves were studied by differential-pulse polarographic and cyclic voltammetric methods. The waves are ascribed to the reduction of the imido group in the Schiff's base compounds. The procedure was applied to the determination of lysine and arginine in foodstuffs and the total proteins in serum samples.     

Trace adsorptive voltammetric determination of antimony in hair

A very sensitive electrochemical procedure for trace determination of antimony is described. The complex of antimony with p-dimethyl-aminophenyl-fluorone (p-DMPF) is adsorbed on a hanging mercury drop electrode (HMDE), and the reduction current of the accumulated complex is measured by voltammetry. In linear sweep voltammetry, the reduction potential of the complex is more positive than that of the free dye. The peak height of the complex is proportional to the concentration of antimony in the range of 4.0 x 10(-9) to 4.0 x 10(-7) M, the detection limit is 1.0 x 10(-9) M Sb(III) for a 5 min preconcentration time. The relative standard error for the determination of 8.0 x 10(-8) M Sb(III) is 2.9%.     

Polarography of metal-gallic complexes

The polarographic behavior of metal ions in perchlorate media containing gallic acid is described. Tungsten(VI) forms a complex with gallic acid which yields a single wave in these media, useful in the polarographic determination of tungsten. Evidence for complexation of chromium(III), copper(II), iron(III), molybdenum(VI), uranium(VI), vanadium(V), tungsten(VI), praseodymium(III), samarium(III), neodymium(III) and gadolinium(III) is obtained and the behavior of these metal ions is summarized.     

Polarographic reduction of 2,4,6-trinitrobenzene-1-sulphonic acid and some 2,4,6-trinitrophenyl-amino acid derivatives

The rapid d.c. polarography of 2,4,6-trinitrobenzene-1-sulphonic acid and its derivatives with serine (I), threonine (II), glycine (III) and histidine (IV) revealed a 3-wave reduction and a marked pH dependence of the reduction potential. The polarographic waves of the derivatives (2.5 × 10^?4 M) showed appreciable changes when sulphite ions were present, with the development of a new wave at more negative potential in ?0.01 M sulphite solutions at pH 7.0. The E_1/2 values of these waves in pH 7.0 supporting electrolyte were: (I) ?1000; (II) ?1007; (III) ?1021; (IV) ?949 mV (vs. Ag/AgCl, sat. KCl). These waves were used to determine the amino acids investigated (1–4 × 10^?4 M) in the presence of excess of 2,4,6-trinitrobenzene-1-sulphonic acid, with good precision (2%).     

Oscillopolarographic adsorptive wave determination of microamounts of orthophosphate

In the system HCl-Sb(III)-ammonium molybdate-acetone-butanone, PO(3-)(4), Sb(III) and Mo(VI) form a ternary heteropoly acid, which can be adsorbed on a dropping mercury electrode and reduced to a heteropoly blue. The electrochemical reaction produces a sensitive polarographic wave with peak potential of -0.42 V vs. SCE. The limit of determination of phosphate is 6 x 10(-8)M. The coefficients of variance are 10 and 3% for 0.1 and 1muM phosphate, respectively.     

Polarographic studies of iron complexes as potential contrast as agents in magnetic resonance imaging

Iron(III) complexes of polyaminocarboxylic acids of potential use as contrast agents in magnetic resonance imaging wre investigated by differential pulse polarography. The complexes with diethylenetrinitrilopentaacetic acid, trans-1,2-cyclohexylenedinitrilotetraacetic acid and triethylenetetranitrilohexaacetic acid (TTHA) wre found to decompose slowly at pH 7.2. With TTHA, a mixture of 1:1 and 2:1 complexes was obtained, and the transformation between the two complexes was slow. Ethylenediimonobis[(2-hydroxyphenyl)acetic acid] (EHPG) was found to be the most suitable ligand. The complex formation is kinetically slow, and a special procedure for the preparation of the complex is required; the complex is then stable for one week at pH 7.2. The polarographic measuremeents are preferably made at pH 9.2, where a well-defined reduction peak is obtained. The complex is stable for 2 days at pH 9.2. At pH values below 9, a double peak is obtained, except for low concentrations of the complex. Both Fe(III)EHPG and Fe(II)EHPG adsorb at the mercury electrode. The polarographic determination can be done in the presence of 10% of urine or serum without interference. The detection limit is in the low μM range.     

稀土元素的电分析化学研究 IX:铽-8-羟基喹啉——-高氯酸钠的极谱配合附波

In this paper the polarographic behavior of terbium-oxine(Ox)- sodium perchlorate system has been studied. In the solution of NaClO4, Ox has a well defined single-sweep polarographic wave P1. After the addition of Tb3+ a new wave P2 appears at more negative potential. A linear calibration curve of the decrease of P1 is obtained in Tb3+ concentration range from 1.0X10-6M to 1.0X10-5M under the optimun conditions of pH4.0-4.5, 0.1M NaClO4-8X10-5M Ox. The wave height of P2 increases linearly with Tb3+ concentration from 3.0X10-6M to 3.0X10-5M in 0.1M NaClO4-2.0X10-4M Ox. It has been shown by applying a number of polarographic techniques that the wave is an adsorptive complex wave. We proposed the reduction processes of the complex and determined the dissocation constants of Ox.     

Differential pulse polarographic determination of traces of iron in solar-grade silicon

Iron is determined, after volatilization of the matrix as hexafluorosilicic acid, by means of the polarographic iron(III) wave in a 0.1 M triethanolamine—0.1 M potassium bromate—0.5 M sodium hydroxide medium. Differential pulse polarography provides a detection limit of about 0.15 μg g^-1 with a precision of 1–2% and linear calibration graphs up to 0.5 μg Fe(III) ml^-1.