Linear Sweep Polarography Research Articles

The use of some heterocyclic azo dyes in polarographic analysis of metal ions

The method of linear sweep polarography was used to investigate the reduction of 4-(2-thiazolylazo)resorcinol (TAR) in the presence of Ga(III), Sc(III), In(III), Au(III), Co(II), Pd(II), Pt(IV), and Zr(IV) ions and the reduction of 4-(2-pyridylazo) resorcinol (PAR) in the presence of Au(III) and Pd(II) ions. The influence of pH, component concentration, sweep rate, on the reduction of azo dyes in the presence of metal ions was studied. Metrological and analytical characteristics of TAR-metal ions reduction were calculated. It has been established that Ga(III) and Sc(III) ions slightly affect (it was observed a potential shift in the cathodic region and a slight decrease of the reduction current) on the reduction of dye, and in the presence of Au(III), Pd(II), Zr(IV) ions the peak of the dye decreases at established pH range. In the presence of In(III), Pt(IV) ions the new cathode peaks are observed. It was found that the sensitivity of the determination is approximately the same for all investigated metals and LOQ is approximately 10 -6 M. Key words: polarography, azo dyes, 4-(2-thiazolylazo)resorcinol, 4-(2-pyridylazo)resorcinol, platinum, scandium, gallium, gold.

Overlapped peaks resolution for linear sweep polarography using Gaussian-like distribution

A resolution method based on Gaussian-like distribution for overlapped linear sweep polarographic peaks was proposed to simultaneously detect the polymetallic components, such as Zn(II) and Co(II), coexisting in the leaching solution of zinc hydrometallurgy. A Gaussian-like distribution was constructed as the sub-model of overlapped peaks by analyzing the characteristics of linear sweep polarographic curve. Then, the abscissas of each peak and trough were pinpointed through multi-resolution wavelet decomposition, the curve and its derivative curves were fitted by using nonlinear weighted least squares (NWLS). Finally, overlapped peaks were resolved into independent sub-peaks based on fitted reconstruction parameters. The experimental results show that the relative error of half-wave potential pinpointed by multi-resolution wavelet decomposition is less than 1% and the accuracy of Ip fitted by NWLS is higher than 96%. The proposed resolution method is effective for overlapped linear sweep polarographic peaks of Zn(II) and Co(II).

Linear sweep polarographic determination of nucleic acids using acridine orange as a bioprobe

The interaction of acridine orange (AO) with double-stranded (ds) DNA in aqueous solution was investigated by linear sweep polarography (LSP) on a dropping mercury working electrode (DME). In pH 2.5 Britton-Robinson (B-R) buffer solution, AO had a sensitive linear sweep polarographic reductive peak at -0.89 V (vs. SCE), which could be greatly inhibited by the addition of dsDNA, with a positive shift of the peak potential. Based on the decrease of the reductive peak current, a new quantitative electrochemical determination method for dsDNA was developed with a linear range of 2.0?20.0 mg l-1 and the linear regression equation: ?Ip" (nA) = 111.90 C (mg l-1)+125.32 (n = 9, ? = 0.997). The influences of commonly co-existing substances, such as metal ions, amino acid, etc., on the determination were also investigated. The method is sensitive, rapid and simple with good selectivity. The new proposed method was further applied to the detection of RNA and three synthetic samples containing dsDNA with satisfactory results. The binding number and the equilibrium constant between dsDNA and AO were calculated by an electrochemical method.

Electroreduction of dipyridamole at mercury-coated platinum microelectrode

The electroreduction of Dipyridamole (DIP) was studied in 0.10 mol L-1 phosphate buffer solution (pH 3.0) on a mercury coated platinum microelectrode (Hg-ME), employing cyclic, linear sweep voltammetry and polarography techniques. The similarity between Hg-ME voltammetric profile and the sigmoidal polarographic waves both with a diffusion limited current is showed. Experiments with a hanging mercury drop electrode (HMDE) were performed in parallel to confirm the results obtained with Hg-ME, which indicated that the reduction occurs in two irreversible steps involving two electrons and two protons each step. The limiting diffusion current, concerning the first step, allows estimating the diffusion coefficient for DIP as being equal to 2.04 x 10-5 cm2 s-1.

Rapid determination of telmisartan in pharmaceutical preparations and serum by linear sweep polarography

The polarographic behaviors of telmisartan (TE) are investigated in 0.8 mol/l NH 3·H 2O–NH 4Cl (pH=8.9) supporting electrolyte. The results demonstrated that the reduction peak is obtained at ca. −1.30 V, which corresponds to a catalytic hydrogen wave. Based on the catalytic hydrogen wave, a novel method has been developed for the determination of telmisartan by linear sweep polarography. Calibration curve is linear in the range 2.0×10 −7 to 3.0×10 −6 mol/l and the detection limit is 1.0×10 −7 mol/l. The proposed method is applied to the rapid determination of the telmisartan in capsule forms and biological sample without pre-separation.

Adsorption-parallel catalytic waves of cinnamic acid in hydrogen peroxide-tetra-n-butylammonium bromide-acetate system

The mechanism of the adsorption-parallel catalytic wave of cinnamic acid (C6H5-CH = CH-COOH) in acetate buffer (pH = 4.0)-H2O2-tetra-n-butylammonium bromide (Bu4N · Br) solution was studied by the linear-sweep polarography, cyclic voltammetry and digital simulation approach. Experimental results indicate that the reduction mechanism of cinnamic acid isECdimE’ process, in which the C = C double bond of cinnamic acid first undergoes 1e, 1H+ reduction to produce an intermediate free radical C6H5-CH-CH2-COOH(E), then the further reduction of the free radical in 1e, 1H+ addition (E’) occurs simultaneously with a dimerization reaction between two free radicals (Cdim). Bu4N· Br enhances the polarographic current of cinnamic acid and shifts the peak potential to positive direction. The enhancement action of Bu4N· Br is due to the adsorption of cinnamic acid induced by Bu4N+ species. In addition, H2O2 causes the parallel catalytic wave of cinnamic acid. The mechanism of the catalytic wave isEC’ process because H2O2 oxidizes the free radical of cinnamic acid to regenerate the original C =C bond(C’), preventing both the further reduction and the dimerization of the free radicals. The apparent rate constantkf of the oxidation reaction is 1.35×102 mol· L-1· s-1. A new class of catalytic waves for organic compounds, the adsorption-parallel catalytic waves upon the dual enhancement action of both the surfactant and oxidant, has been presented.

A New Polarographic Adsorptive Catalytic Wave for the Determination of Trace Tellurium in Smog Dust and Wheat Flour

Linear-sweep polarography of tellurium in sulfuric acid solution containing methylene blue produces a wave at −0.82 V (vs SCE). In a cathodic sweep, the derivative peak current is directly proportional to the concentration of tellurium over the range 4 × 10−9to 1 × 10−7g/ml, and the detection limit is 2 × 10−9g/ml. The polarographic wave is an adsorptive catalytic hydrogen wave. This method has been applied to the determination of trace amounts of tellurium in smog dust and wheat flour, with satisfactory results.

Polarographic immunoassay coupled with catalytic amplification of labeled copper ions

A new approach of polarographic immunoassay based on the catalytic amplification of the labeled metal ions and the polarographic detection of the catalytic product was developed. In this approach, the copper ions used as the catalyst for substrate conversion instead of natural enzyme were labeled to model antigen diphtheria toxoid (DT) through the bifunctional chelating reagent diethylenetriamine pentaacetic acid (DTPA). After heterogeneous competitive immunoreaction, the oxidation of substrate o-phenylenediamine (OPD) was catalyzed by the labeled copper ions to generate an electroactive product 2. 3-diaminophenazine (DAP); subsequently, the product DAP was detected with linear-sweep polarography. The proposed assay can determine the concentration in the range of 10–1000 ng/mL of DT, two orders of magnitude more sensitive than those based on the direct detection of the metal ion labels. The proposed immunoassay can be applied to detecting various proteins of interest.

Determination of hemoglobin in plasma and serum by linear-sweep polarography

A new method for the determination of hemoglobin (Hb) is described. It is based on the amplification of the Hb enzyme-catalyzed reaction between O-phenyldiamine (OPD) and H2O2 and polarographic measurement of the enzyme-generated product 2,2′-diaminoazobenzene (DAA). A linear calibration plot has been obtained within the range of 1∼20 μg/ml (r = 0.987) Hb. The assay is performed on the microtitre plate to avoid the influence of serum protein and to obtain good reproducibility. The method is practical, reliable and convenient, and has been applied to determine Hb in plasma and serum.

The nature of voltammetric waves of copper complexes with dimethylglyoxime in ammonia and borate buffer solutions

AbstractThe voltammetric and adsorptive characteristics of the Cu‐DMG complexes in a wide range of Cu concentration (from 5 × 10−8 M to 1 × 10−3 M) have been investigated in ammonia and borate buffer. Evaluation of the electrode process included the examination of the effect of Cu, DMG, buffers, ethanol and Triton X100 concentration, buffer capacity and ionic strength, pH and instrumental parameters. The adsorption phenomena were observed by direct current, linear scan, pulse and alternating current polarography and voltammetry. At high Cu concentration the additional effects such as spikes on the pulse and linear scan voltammetric curves as well as maxima and erratic behavior on the direct current polarograms were observed. From the voltammetric and the potentiostatic transient studies it has been found that these effects are caused by the nucleation and condensation processes. From the bulk electrolysis and microelectrolysis results it follows that the Cu‐DMG complex is reduced with participation of two electrons and no proof has been found that in the presence of a Cu‐DMG complex a catalytic hydrogen wave is formed. The adsorptive properties of the Cu‐DMG complex can be utilized for sensitive determination of Cu traces (from 1 × 10−7 M to ca. 1 × 10−5M Cu) or for simultaneous determination of Cu, Ni and Co by differential pulse polarography or linear fast sweep polarography.

Adsorptive complex catalytic polarographic determination of germanium in soils and vegetables

The very sensitive adsorptive complex catalytic wave of Ge(IV)-catechol-NaBrO 3 with acetic acid—sodium acetate as supporting electrolyte in linear-sweep polarography has been successfully applied to the determination of germanium in vegetables and soils. The optimum experimental conditions are: 0.07 M acetic acid—sodium acetate buffer of pH 4.6, 1.5 × 10 −3 M catechol and 0.1 M NaBrO 3. The detection limit of Ge(IV) is 1.0 × 10 −9 M and the linear range is 1.0 × 10 −9 −7.0 × 10 −6 M. Different acid digestion procedures were compared, and a HNO 3-HClO 4-HF digestion method for the soil sample and a HNO 3-HClO 4-H 2SO 4 digestion method for the vegetable sample were adopted. The experiments show that the polarographic wave behaves as an adsorptive complex wave and also as a parallel catalytic wave.

Polarographic Investigation and Determination of Bilirubin

A rapid and sensitive Polarographic method for the determination of bilirubin is described. In a solution containing 0.03 M NaOH, 1.0×10-3 M Na2SO3 and 2.0×10-4 M EDTA, bilirubin can cause a Polarographic wave at about -0.26 V (vs. SCE) when potential sweeps from —0.65 V to —0.1 V. The peak current varies linearly with bilirubin concentration over a range of 8.0×108 M to 6.0×10-6 M as determined by derivative linear sweep polarography. A low detection limit of 5×10-8 M is obtained. The method has been developed for the determination of bilirubin in serum and medicine. In this research, the characteristics of the Polarographie wave have been investigated, and it has been confirmed to be an adsorptive wave. The electrochemical mechanism is discussed, the wave is ascribed to the oxidation of mercury.

Direct Determination of Hemolysin Activity in Antiserum by Linear–Sweep Polarography

Abstract A novel method for direct determination of hemolysin activity in antiserum by linear–sweep polarography(LSP) was developed in this paper. This method is based on a reduction wave of active hemolysin in phosphate buffer solution. The peak height of hemolysin is linear proportional to its activity in the range of 6×10−6 unit/mL to 2×10−3 unit/mL. Deactivated hemolysin, other proteins and chemicals present in biological fluids do not interfere in the assay. This method is very rapid, simple, highly specific and sensitive.

Indirect determination of bilirubin by linear sweep polarography

A polarographic method for the determination of bilirubin is described: In hydroquinone-sodium phosphate buffer (pH 11.2) medium, bilirubin can be rapidly oxidized to a green product, which causes a sensitive polarographic wave at −0.83 V (vs. SCE); the peak current of the wave is linear with the bilirubin concentration over a range of 3×10−7 to 5×10−6 mol/l. It has also been found to be more stable than that produced by bilirubin; in general, it can remain unchanged for about 1 h at room temperature and exposure to air. This overcomes the instability of bilirubin for its direct assay to a certain extent. If a small amount of EDTA is added to the solution, the stability of the wave can be further improved. In addition, the characteristics of the wave have been investigated and it has been confirmed to be an adsorptive catalytic wave. The chemical reaction mechanism is discussed and the green product is confirmed to be biliverdin.

Polarographic behaviour of antiepilepsirine and its application

A sensitive adsorptive wave of antiepilepsirine was obtained in 0.2 M H 2SO 4 by using linear-sweep polarography. The peak potential is −0.98 V vs. SCE. The peak height is proportional to the concentration of antiepilepsirine over the range 5.0 × 10 −8–1.0 × 10 −6 M. The method was applied to the determination of antiepilepsirine. The wave is believed to result from irreversible adsorption through studies of its electrochemical behaviour and reaction mechanism.

Determination of progesterone based on the enhancement effect of surfactants in linear sweep polarography

A rapid and sensitive linear sweep polarographic method for the determination of progesterone is described. In basic media (0.01 M borax, pH 9), progesterone can be reduced at a dropping mercury electrode and the peak current increases greatly when low concentrations of cationic surfactants such as cetyltrimethylammonium bromide (CTAB) are added to the sample solution. Because of synergistic adsorption of progesterone and CTAB on the electrode surface, the polarographic wave exhibits a sensitivity that is 40 times greater than that in the absence of CTAB. A low detection limit of 2 × 10 −8 M is obtained. A linear relationship between peak current and concentration of progesterone holds in the range 8 × 10 −6−4 × 10 −8 M. The electrochemical behaviour of progesterone was investigated, and an adsorptive reduction wave was confirmed. The method was developed for the assay of progesterone in pharmaceutical preparations and in the blood of pregnant women.

STUDIES ON THE POLAROGRAPHIC BEHAVIOUR OF INDIUM-PAN COMPLEX

In the 0.05mol/L HAc- NaAc supporting electrolyte(pH5.7), a sensitive adsorptive complex wave of In(III) and PAN complex has been obtained by using linear sweep polarography. The peak potential Ep is -0.65V(vs. SCE) and the peak current Ip is directly proportional to the concentration of In(III) from 5.0×10-8.-2.0×8-6smol/L. The limit of detection is 1.0•10-8mo1/L. The composition of the complex has been ascertained to be 1:2. The electrode reaction mechanism for the complex was studied by using linear sweep and cyclic voltammetry, Npp etc.

Single Sweep Polarographic Determination of Trace Nitrite in Ferrous and Ascorbic Acid Medium

The (FeNO)2+ complex can be formed in a solution that contains ferrous ion (ammonium ferrous sulfate), nitrite (sodium nitrite) and ascorbic acid. With a dropping mercury electrode, this complex has a catalytic wave at -0.58V which can be used for the determination of trace nitrite in the range of 1×10-7 to 4×10-4M with the detection limit of 5×10-8M. The function of ascorbic acid is to reduce NO2- to NO quantitatively for complete formation of the electroactive complex. The mechanism of the electrode process has been studied by linear sweep polarography, direct current polarography, cyclic voltammetry and spectrophotometry.

Linear sweep polarographic studies of trace gold in an N‐allyl‐N′‐(sodium‐p‐phenylsulphonate)thiourea medium

AbstractUsing linear sweep polarography (LSP) in an acidic solution (pH 2.8) containing Au(III) ions and N‐allyl‐N′‐(sodium‐p‐phenylsufonate)thiourea (NTu), the product of the reaction between Au(III) and NTu (NDF) is reducible at the mercury electrode with two waves at about −0.40 and −0.95 V [versus the saturated calomel electrode (SCE)]. In the presence of excess chloride, the potential of the first wave shifts positively to −0.35 V. This forms the basis of a highly selective and sensitive method for gold. The linear range for gold is from 1 × 10−7 to 3 × 10−M, and the detection limit is 5 × 10−8 M (9 ppb). This method has been used for the determination of gold in ore samples, and the results agree well with values obtained by accepted procedures. Various electrochemical techniques were used to study the mechanism of the redox process. The reaction mainly involves the formation of C,C′‐di‐N‐allyl‐N′‐ (sodium‐p‐phenysulfonate)dithiodiformamidine (NDF). Unlike some explanations reported in the literature about the reduction of formamidine derivatives (containing an SS bond) on an Hg electuode, the electrode process for the first wave (−0.40 V) is ascribed to the reduction of the HgS film, which is caused by the reaction of Hg with adsorbed NDF. In the presence of excess Cl‐ ions, the mixed precipitation film of HgS·xHg2Cl2 may be formed on the electrode surface and make the first wave shift to −0.35 V. The second wave (−0.95 V) is caused by the irreversible reduction of NDF.

Determination of trace nitrite by catalytic polarography in ferrous iron thiocyanate medium

This paper concludes that (FeSCNNO) + is formed in a solution that contains ferrous iron (ammonium ferrous sulfate), thiocyanate (sodium thiocyanate), nitrite (sodium nitrite) and sodium perchlorate (supporting electrolyte). With a Dropping Mercury Electrode (DME), this ternary complex has three reduction waves at −0.5, −0.8 and −1.0 V vs. SCE, respectively. In the presence of oxygen, a catalytic wave related to the first reduction (−0.5 V) is used for the determination of trace nitrite in the concentration range of 3×10 −8 to 1 × 10 −6 M. The detection limit is 1 × 10 −8 M (0.46 ppb NO 2 −). The mechanism of the electrode process has been studied by linear sweep polarography (LSP), dc polarography, cyclic voltammetry, and controlled potential coulometry. The reduction process is proposed to be: ▪ 4B + O 2 + 4H + → 4A + 2H 2O with (FeSCNNO) + ad formed in the following steps: 3NO 2 − + 2H + → 2NO + NO − 3 + H 2O Fe 2+ + SCN − + NO → (FESCNNO) + (FeSCNNO) + ⇆ (FeSCNNO) + ad