Polarography

The derivative from sucrose was prepared by substituting hydroxyl groups with chlorine. Identification of the modified sucrose was performed using the following analysis: Thin Layer chromatography (TLC), high performance liquid chromatography (HPLC), H-NMR, mass spectroscopy (MS), Inferred 1 spectroscopy (IR), melting point, OH groups. Moreover, some physical properties including: melting point, viscosity, surface tension and solubility.

A new complex has been synthesized of Cu (II) complex with 6-thioguanine and phyico-chemical characterized by amperometry, polarography elemental analysis and FTIR spectroscopy. After Synthesis of metal complex, it was evaluated it for antibacterial and antifungal activities against various pathogenic microorganisms such as; Streptococcus aureus, Proteus. M., klebsiella pneumonia and Asperginus niger, Nigrosporan S.P. B16-F10 melanoma cell and C-57BL/6 mice has been used for anticancer screening of metal complex for in vitro and in vivo study. The result of pharmacological studies with M: L revealed that the complex is more potent as compared to the pure drug as regards to its anticancer activity.

The electroanalytical behaviour of ketoconazole in Britton Á/Robinson buffer is described. The reduction process on the hanging mercury drop electrode (HMDE) gives rise to one peak over (/1.6 V (vs. Ag/AgCl/sat.KCl), within the pH range studied (4.7 Á/9.6). The results showed that the reduction of ketoconazole is irreversible and the limiting current is adsorption controlled. The dependence of the peak current on the concentration was studied by means of different polarographic and voltammetric techniques. Using adsorptive stripping differential pulse voltammetry (AdS-DPV), the detection limit (DL) reached was 5.3 )/10 (11 mol l (1 . Two procedures, based on differential pulse polarography (DPP) and AdS-DPV in aqueous medium were developed for the determination of ketoconazole in a gel formulation and spiked urine samples, respectively. #

A new derivative UV spectroscopic method was developed for the analysis of omeprazole in borate buffer (pH 10.0; 0.1 M). Second derivative spectra were generated between 200 -400 nm at N= 9, Du=31.5. The linearity range for values obtained from second derivative spectra was 0.2 -40.0 mg ml − 1 . The developed method was applied to five different commercial preparations of hard gelatin capsules containing enteric coated granules. The relative standard deviations were found to be 2.24% (brand A), 1.87% (brand B), 2.80% (brand C), 4.55% (brand D) and 1.09% (brand E). The data were compared with ones obtained from the polarographic method given in the literature and no difference was found statistically. © 1997 Elsevier Science B.V.

Tolbutamide is an antidiabetic drug. Its potency may be increased by modifying the drug by way
of molecular modification. In the present study the drug has been modified by its complex
formation with potassium bicarbonate and other organic compounds. The drug organic
compound interaction has been studied using differential pulse polarography and direct current
polarography. In KCl as supporting electrolyte of pH 3.4±0.1, tolbutamide produced a well
defined peak at -1.02v and it’s modified forms at relatively higher negative. The change in peak
potential and lowering in peak hight. Drug organic compound complaxation has completed.

Uranium is a toxic material hence numerous body systems such as the kidney, brain, liver, and heart can be affected by uranium exposure. The main effect is kidney toxicity. Uranium is a naturally occurring element found in low levels in all rock, soil, and water. All uranium isotopes may also cause radiation hazards, thus without any doubt an analysis of such materials in the surrounding environment is very important. The presented review is a summarization of all electroanalytical techniques for the determination of uranium and its compounds in various matrices. Totally 43 different methods are found in our literature survey. Out of these three are polarographic, 25 potentiometry, five capillary electrophoresis and 28 voltametric methods are available in the literature. Interferences of different ions and applications in different matrices are also given for each method.

Chemometric stability indicating methods are presented for the determination of rabeprazole sodium in presence of its acid induced degradation products using spectrophotometry, differential pulse polarography and differential pulse anodic voltammetry at a glassy carbon electrode. The applied chemometric techniques are multivariate ones including classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS). A difference spectrophotometric (DeltaA) method has also been applied. To develop the multivariate calibrations, a training set was used, consisting of 20 mixture solutions of rabeprazole sodium and its degradation products. These mixtures show percentage degradation ranging from 0.5-65%, 0.5-95% and 0.6-75% for the spectrophotometric, polarographic and anodic voltammetric calibrations, respectively. The UV absorbances were recorded in 0.1 M NaOH within the wavelength range 220-340 nm at 2 nm intervals. The polarograms and anodic voltammogram...

A novel antioxidative assay based on direct current polarography has been developed. Quantification of antioxidative (AO) activity has been based on a decrease of hydrogen peroxide anodic current in the presence of antioxidants. An efficient experimental procedure, without any special pretreatment of analyzed samples, has been applied. Antioxidative activity of different kinds of commercial beers (dark, blond, and alcohol-free), some small-scale made special beers with medicinal herbs and mushroom extracts, extracts themselves, as well as individual phenolic components present in beer has been measured. In addition, changes of AO activity during the full-scale industrial process of beer production have been monitored. A strong correlation between results obtained and total phenolics content has been observed. The assay can be recommended for application in brewing industry, either to survey a process with the aim to optimize relevant technological factors or to analyze quality of final product.

A strategy for adaptive control and energetic optimization of aerobic fermentors was implemented, with both air flow and agitation speed as manipulated variables. This strategy is separable in its components: control, optimization, estimation. We optimized parameter’s estimation (from the usual KLa correlation) using sinusoidal excitation of air flow and agitation speed. We have implemented parameter’s estimation trough recursive least squares algorithm with forgetting factor. We carried separate essays on control, optimization and estimation algorithms. We carried our essays using an original computational simulation environment, with noise and delay generating facilities for data sampling and filtering.

Our results show the convergence and robustness of the estimation algorithm used, improved with use of both forgetting factor and KLa dead-band facilities. Control algorithm used in our work compares favorably with PID using the integrated area criteria for deviation between oxygen molarity and critical molarity (set point). Optimization algorithm clearly reduces energetic consumption, respecting critical molarity. Integration of control, optimization and adaptive algorithms was implemented, but future work is needed for stability. Methods were defined and implemented for stability improvement. We have implemented data acquisition and computer manipulation of air flow and agitation speed for actual fermentors.

Hydrogen peroxide scavenging (HPS) activity of unfermented (green, yellow, and white), partially fermented (oolong), and completely fermented (black) tea (Camellia sinensis), maté(Ilex paraguariensis), and various herbal infusions, as well as individual compounds (flavan-3-ols, flavonols, cinnamic and benzoic acids, and methylxanthines), was assessed by recently developed direct current (DC) polarographic assay. Correlations of tea and herbal infusion HPS activity with total phenolic content determined using the Folin−Ciocalteu assay (FC-GAE) (0.81 and 0.93), ferric reducing/antioxidant power (FRAP) (0.97 and 0.92), 1,1-diphenyl-2-picrylhydrazyl (DPPH) (0.77 and 0.80), and 2,2′-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) scavenging (0.86 and 0.86) were statistically significant. Correlations between relative antioxidant capacity index (RACI), calculated by assigning all applied assays equal weight, and HPS (0.98), FRAP (0.97), ABTS (0.89), and DPPH (0.89) confirmed DC polarographic assay reliability when applied individually. Correlation analysis, ANOVA, and Levene and Tukey's HSD tests unequivocally confirmed this reliable, rapid, and low-cost assay validity, clearly demonstrating its advantages over spectrophotometric assays applied.

A highly sensitive and simple voltammetric method is proposed for the determination of N-nitrosoatenolol (NA) and N-nitrosopropranolol (NP) in simulated gastric juice. The method is based on measuring the differential-pulse polarographic peak produced by NA and NP in Britton-Robinson buffers of pH 3 and 4 for NA and NP, respectively. Both compounds yielded diffusion-controlled current with diffusion-current constants of 7.23 9 0.03 and 9.469 0.06 for NA and NP, respectively. The current-concentration plots were rectilinear over the range 0.16 -9.6 mg ml − 1 with minimum detectability (S/N= 2) of 0.015 mg ml − 1 (5× 10 − 8 M) for NA; for NP the range was 0.08 -8.0 mg ml − 1 with minimum detectability (S/N= 2) of 0.009 mg ml − 1 (3× 10 − 8 M). The proposed method was successfully applied to study the possible in vivo production of the nitroso-derivatives under the standard nitrosation reaction conditions recommended by WHO. The method is characterized by simplicity and higher sensitivity as compared with the reported HPLC method.

A highly sensitive polarographic method was developed for the determination of EDTA added as a preservative in certain pharmaceutical preparations. The method involved chelation with Eu(III) followed by polarographic measurement of the chelate formed. A well-defined cathodic wave was developed in Britton -Robinson buffers over the pH range 2-12. The wave was characterized as being quasi-reversible and diffusion controlled. The current -concentration relationship was found to be rectilinear over the ranges 8 -160 and 2 -120 mg ml − 1 , using DCt and DPP modes, respectively, with limit of detection of 0.1 mg ml − 1 using the DDP technique. The mechanism of the electrode reaction was verified. The proposed method was applied for the determination of EDTA in certain pharmaceutical dosage forms, and the results obtained were in agreement with those obtained by a reference method.

Electrochemical behaviour of pyrantel pamoate has been studied by using different voltammetric and polarographic techniques in Britton Robinson buffer system. Differential pulse polarographic and cyclic voltammetric methods have been developed for the determination of drug in pharmaceutical formulation. A well-defined cathodic wave and one anodic peak were observed for the pyrantel pamoate in the entire pH range. Number of electrons transferred in the reduction process was calculated and the reduction mechanism postulated. The results indicate that the electrode process is reversible and diffusion controlled. The proposed method has been validated. The peak current is found to be linear over the concentration range 4 × 10−4 to 2 × 10−2 mol L−1. The lower detection limit (LOD) and lower limit of quantitation (LOQ) is found to be 2.45 × 10−5 and 8 × 10−5 mol L−1.

A differential pulse polarographic assay was developed for determining flucytosine in tablets. The drug is extracted from the sample with water and hydrochloric acid and, after the pH is adjusted, an aliquot is added to the cell and the solution is polarographed at the dropping mercury electrode versus the saturated calomel electrode with 0.066 M Sørensen phosphate buffer (pH 5.6) as the supporting electrolyte. The polarographic peak height enables precise quantitative determination. The Ep value for flucytosine is −1.54 v versus the saturated calomel electrode. The mean recovery of the drug is 101.5% ±1.9 (SD). The method is simple, rapid, and precise.

Paracetamol is an analgesic drug. Its potency may be increased by
modifying the drug by way of molecular modification. In the present study the
drug has been modified by its complex formation with methanol and other
organic compounds. The drug organic compound interaction has been studied
using differential pulse polarography and direct current polarography. In
Britton Robinson buffer as supporting electrolyte of pH 7.2±0.1, paracetamol
produced a well defined peak at -1.18v and it’s modified forms at relatively
higher negative value. The change in peak potential and lowering in peak
height indicating drug organic compound complex formation

A spectrophotometric method for the indirect determination of captopril (CP) in pharmaceutical formulations is proposed. The proposed procedure is based on the oxidation of captopril by potassium dichromate and the determination excess oxidant on the basis of its reaction with diphenylcarbazide (DPC). Under the optimum conditions, a good linear relationship (r = 0.9997) was obtained in the range of 0.08-3.5 μg mL-1. The assay limits of detection and quantitation were 0.024 and 0.08 μg mL-1 , respectively. The results obtained for captopril determination in pharmaceuticals using the proposed method and those obtained with the US Pharmacopoeia method were in good agreement at the 95% confidence level.

A simple, fast and sensitive differential pulse polarographic method (DPP) for the determination of pymetrozine insecticide in pure form, agrochemical formulation, natural water and orange juice samples is proposed. The polarographic behavior of pymetrozine exhibited a double well-defined polarographic peaks at −580 and 950 mV (versus SCE), respectively. The peak potentials were strongly pH-dependent in that they shifted to more negative values with increasing pH. The polarographic reduction corresponding to the first peak at pH 2.0 (B-R buffer solution) showed quantitative increments with the additions of standard pymetrozine solution under the optimal conditions and the corresponding peak current was linearly proportional to pymetrozine concentration in the range of 4.97 × 10 −7 to 7.35 × 10 −5 mol L −1 . The limit of detection (LOD) and limit of quantification (LOQ) were obtained as 1.48 × 10 −7 and 4.93 × 10 −7 mol L −1 , respectively. The mean recoveries of the 5.0 × 10 −6 mol L −1 pymetrozine spiked to lake water and orange juice were (4.89 ± 0.23) × 10 −6 and (4.97 ± 0.19) × 10 −6 mol L −1 at 95% confidence level, respectively. The method was extended to the determination of pymetrozine in agrochemical insecticide formulation Plenum ® and accuracy was in agreement with that obtained by HPLC comparison method. Influences of some interfering ions and some other pesticides were also investigated. The mechanistic study was not pursued.

Antioxidant activity (AO) of commercial propolis extracts (PEs), available on Serbian market, was determined by direct current (DC) polarography. Polarographic anodic current of 5.0 mmol L À1 alkaline solution of H 2 O 2 was recorded at potentials of mercury dissolution. Decrease of the current was plotted against the volume of gradually added PEs. The volume of PE causing 20% current decrease was determined from the linear part of the plot. Antioxidant activity was expressed in H 2 O 2 equivalent (HPEq), representing the volume of PE that corresponds to 1.0 mmol L À1 H 2 O 2 decrease. Resulting HPEq ranged between 1.71 ± 0.11 and 8.00 ± 0.18 lL. Range of 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging activity was from 0.093 ± 0.004% to 0.346 ± 0.006%. Total phenolic content (TCP) of PE with superior AO activity was 5.31 ± 0.05%g GAE, while the extract with the lowest activity contained 1.45 ± 0.02%g GAE. Antioxidant activity, determined by polarographic method, was correlated with DPPH scavenging activity (R 2 = 0.991) and TCP (R 2 = 0.985). Validity of obtained results was further confirmed using ANOVA and post hoc Tukey HSD test.

A new borate ion selective electrode using solid salts of Ag3BO3, Ag2S and Cu2S has been developed. Detailed information is provided concerning the composition, working pH and conditioning of the electrode. An analytically useful potential change occurred from 1 × 10−6 to 1 × 10−1 M borate ion. The slope of the linear portion was 31 ± 2 mV/10-fold changes in borate concentration. The measurements were made at constant ionic strength (0.1 M NaNO3) and at room temperature. The effect of Cl−, Br−, NO3−, SO=4, H2PO4− anions and K+, Na+, Cu2+, Ag+, Ca2+ cations on borate response is evaluated and it was found that only Ag+ had a small interference effect. The lifetime of the electrode was more than two years, when used at least 4–5 times a day, and the response time was about 20–30 s. Borate content in waste water of borax factory, tap water of a town situated near to the borax factory and city tap water far from these mines were also determined. The validation was made with differential pulse polarography for the same water sample, and high consistency was obtained.

Nitroxoline has been reduced at the mercury electrode in buffered solutions (pH 2−11) in two irreversible cathodic steps. The first step was attributed to reduction of -NO 2 group to the hydroxylamine stage and the second one to reduction-saturation of the C=N double bond. DC-polarographic and various adsorptive stripping voltammetric methods were developed for determination of nitroxoline in bulk form. Limits of quantitation of 1.02 × 10 −6 , 3.05 × 10 −8 , 9.01 × 10 −9 , and 9.12 × 10 −10 M nitroxoline were achieved by means of the developed DC-polarography, differential-pulse-, linear-sweep-, and square-wave-adsorptive cathodic stripping voltammetric methods, respectively. All these electroanalytical methods were successfully applied for determination of nitroxoline in its Nibiol ® tablets. While only the developed adsorptive stripping voltammetry methods were successfully applied for determination of the drug in spiked human serum and for pharmacokinetic studies in real human plasma. The analysis was carried out without interference from common excipients and without the necessity for prior extraction or interaction with any reagent during the analysis.

Cancer of the prostate is an important and potentially fatal disease in humans, but its etiology is yet undefined.
Previous observations have shown that heavy metals play various roles in human health. The heavy metals zinc,
cadmium, lead, and copper (Zn, Cd, Cu, and Pb) are known to be associated with prostate cancer, but their
functions are unclear. This study examined and compared serum levels of these metals in prostate cancer patients
with those of a control group. In total, 72 subjects (36 controls and 36 prostate cancer patients) were included in
this study. Blood samples were collected from 36 newly-diagnosed prostate cancer patients and 36 healthy men who
were matched by age, sex, race, and smoking and drinking status. After samples were prepared, serum
concentrations of zinc, cadmium, lead, and copper were determined using polarography. Serum levels of cadmium
and copper were significantly higher in patients with prostate cancer than in controls (p<0.05). No significant
association was found between the serum levels of zinc and lead in prostate cancer patients compared with the
controls (p>0.05); however, the mean concentrations of zinc and lead were higher in patients. This study supports
the hypothesis that cadmium exposure increases prostate cancer risk. These findings can accelerate the diagnosis
and treatment of prostate cancer. No distinct association was found between serum levels of zinc and lead and
prostate cancer. More studies with larger sample sizes are needed to identify the role of heavy metals in prostate
cancer.

A new HPLC method with fluorescence detection using pyridinium hydrobromide perbromide as a post-column derivatising agent has been developed to determine aflatoxin M1 in milk and cheese. The detection limits were 1 ng/kg for milk and 5 ng/kg for cheese. The calibration curve was linear from 0.001 to 0.1 ng injected. The method includes a preliminary C18-SPE clean-up and the average recoveries of Aflatoxin M1 from milk and cheese, spiked at levels of 25-75 ng/kg and 100-300 ng/kg, respectively, were 90 and 76%; the precision (RSDr) ranged from 1.7 to 2.6% for milk and from 3.5 to 6.5% for cheese. The method is rapid, easily automatable and therefore useful for accurate and precise screening of aflatoxin M1 in milk and cheese.

In the present study, Fluorescence Resonance Energy Transfer (FRET) has been used to monitor the folding of a 31-mer cytosine rich DNA segment, from the promoter region of the human c-myc oncogene. Spectroscopic FRET data recorded along experiments carried out at different pH and ionic strength conditions were individual and simultaneously analyzed by Multivariate Curve Resolution (MCR) (1). The simultaneous analysis of several data matrices allowed the resolution of the system, removing most of the ambiguities related to factor analysis. From the results obtained, we report the evidence of the formation of a highly ordered structure (a quadruplex known as i-motif) in acidic and neutral pH values.

Total antioxidant (AO) activity of strong alcohol beverages such as wine and plum brandies, whiskeys, herbal and sweet fruit liqueurs have been assessed using a polarographic assay based on hydrogen peroxide scavenging (HPS). Rank of order of total AO activity, expressed as percentage of decrease of anodic oxidation current of hydrogen peroxide, was found analogous with total phenolic content estimated by Folin-Ciocalteau (FC) assay and radical scavenging capacity against the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH). Application of the assay for surveying of a quarter century long maturation of plum brandy in oak barrel was demonstrated. In addition, influence of different storage conditions on preservation of AO activity of some herbal liqueurs was surveyed. Wide area of application of this simple, fast, low cost and reliable assay in analysis and quality monitoring of various strong alcohol beverages was confirmed.

The electrochemical oxidation of sumatriptan on the surface of carbon paste electrode modified with multiwalled carbon nanotube and cobalt methyl-salophen complex is studied by using cyclic voltammetry and polarization studies. The results indicate that the drug is irreversibly oxidized in a one electron oxidation mechanism. It was found that the peak potential shifted negatively with increasing pH, confirms that H + participate in the oxidation process. The electrode is shown to be very effective for the detection of sumatriptan in the presence of other biological reductant compounds. The prepared modified electrode exhibits a very good resolution between the voltammetric peaks of sumatriptan, ascorbic acid and uric acid, which makes it suitable for the simultaneous detection of sumatriptan in the presence of these compounds in clinical and pharmaceutical preparations. It can be concluded that multi-walled carbon nanotube and Shiff base complex have synergic effect on electroacatalytic oxidation of sumatriptan. A linear range of 1-1000 μM and detection limit of 0.3 μM was obtained for sumatriptan from DPV measurements using this electrode in 0.1 M acetate buffered solution of pH 5.0. The electrode has been applied successfully for the determination of sumatriptan in synthetic serum and commercial tablets.

This paper describes the interaction of nickel (II) with ammonium piperidine-1-carbodithioate (APC) using Direct Current (DC) polarography (DCP) & differential pulse polarography (DPP) at the Dropping Mercury Electrode (DME) in NH 4 Cl-NH 4 OH buffer medium at pH 6.0. The polarograms shows a predominant peak for nickel (II)-APC at -1.30 V vs SCE, indicating the production of catalytic hydrogen wave (CHW) due to electrostatic interactions between APC and nickel (II). The interactions were characterized with UV-visible spectrophotometer, FT-IR and cyclic voltammetric techniques. The developed method was applied successfully to determine the nickel (II) levels in leafy vegetables and biological samples with acceptable recoveries.

This paper describes the interaction of nickel (II) with ammonium piperidine-1-carbodithioate (APC) using Direct Current (DC) polarography (DCP) & differential pulse polarography (DPP) at the Dropping Mercury Electrode (DME) in NH 4 Cl-NH 4 OH buffer medium at pH 6.0. The polarograms shows a predominant peak for nickel (II)-APC at -1.30 V vs SCE, indicating the production of catalytic hydrogen wave (CHW) due to electrostatic interactions between APC and nickel (II). The interactions were characterized with UV-visible spectrophotometer, FT-IR and cyclic voltammetric techniques. The developed method was applied successfully to determine the nickel (II) levels in leafy vegetables and biological samples with acceptable recoveries.

A new differential pulse polarographic (DPP) and catalytic adsorptive stripping voltammetric (CAdSV) methods for the determination of vanadium(V) have been developed. The CAdSV method is based on the adsorptive accumulation of the vanadium-chloroanilic acid (CAA) complex on the surface of a HMDE and the utilization of the catalytic reaction with BrO 3 − . The optimal CAdSV vanadium(V) response was obtained in (0.04 ÷ 0.2) M acetic buffer at pH 4.5-4.8 in the presence of (2.0 ÷ 4.0) × 10 −5 M CAA and (5.0 ÷ 10.0) × 10 −3 M KBrO 3 with an accumulation potential of (−0.10 ÷ −0.15) V and accumulation time of (80 ÷ 120) s. The sensitivity of the CAdSV was 42.7 nA nM −1 and the linearity range amounted from 2 × 10 −10 up to 5 × 10 −8 M for 100 s of accumulation. The R.S.D. was 4.5% at the 1.0 × 10 −9 V(V) level. The detection limits were found to be 2.8 × 10 −9 M for DP polarography and 9 × 10 −12 M for CAdSV with 100 s of accumulation. Possible interferences by Sb(III), Pb(II), Cu(II), Cd(II), Fe(III), Bi(III), Sn(II), Sn(IV), U(VI), Mo(VI) and surface active substances were evaluated. The results of the determination of V(V) in certified reference material water sample showed good reproducibility (R.S.D. = 3.4%) and reliability of the elaborated CAdSV method.

Reduction of the nitro group in l-alkyl-4-cyano-5-nitropyrazoles follows a pattern similar to that of 1alkyl-5-nitropyrazoles, involving the sequence H+, e, H+, e, 2e, 2H+. On the other hand, the sequence of proton and electron transfers in the reduction of the nitro group in l-alkyl-3-nitro-4-cyanopyrazoles differs from that in 1-alkyl-3-nitropyrazoles. Similarly, the reduction of 4-cyano-3( 5)-nitropyrazole differs from that of 3(5)-nitropyrazole, even when both of these reductions are affected by the dissociation of the NH group with pK, = 6.26 and 9.81, respectively. Similarly, the behavior of I-alkyl-4-carboxamido-5-nitropyrazoles resembles that of l-alkyl-5-nitropyrazoles, but that of l-alkyl-3-nitro-4carboxamidopyrazoles is different from that of 1-alkyl-3-nitropyrazoles. In l-alkyl-4-carboxamido-5hydroxylaminopyrazoles, the carboxamido group is reduced in a twoand four-electron process, but the low absolute value of the limiting current of wave i2 indicates the presence of competitive side reactions.

The electrohydro&menzatlon (EHD) of acrylomtnle (AN) on mercury from aqueous solutions was exarmned by a polarograpluc technique with posluve feedback for 1R compensauon as well as by differential-capacity measurements, w~th the aim of deterrmmng optimal experimental con&t~ons under which the formation of the hydrodlmer a&ponltnle (ADN) is decidedly favoured over that of the saturated monomer proplomtnle (PN). Several tetraalkylammonlum cations at low concentrations ( -10-3 M) and several supporting electrolytes were employed for tbas purpose. The best con&Uons for EHD were attained in aqueous solutions of 1.3 to 1.5 M Na + or Li + citrate contalmng 10 -3 M dode-cylethyl&methylammomum (DEDMA) bromade. Under these conditions a gradual increase In the AN bulk concentration from 10 -2 M to 0.2 M causes a progressive splitting of the single two-electron wave due to PN formation into two consecuUve one-electron waves, the first of wtuch is due to ADN formation Differential-capacity measurements ln&cate that such a progresslve passage from the formation of the saturated monomer to that of the hydrodlmer is accompamed by a gradual coadsorptlon of AN and DEDMA on the electrode surface, wluch demonstrates that the couphng reaction yielding ADN takes place m the adsorbed state.

The electrochemical characteristics of the herbicide metamitron have been studied in the pH range 1 to 9 by applying several polarographic techniques, namely DCP, TAST, and DPP, adsorptive stripping voltammetry, and cyclic voltammetry with HMDE. The reduction of this molecule evolves in four processes in pHs lower than 3, and in two steps between pH 3 and 9. All processes involve two electrons, are irreversible, and imply the reduction of the functions CN and N-NH2 that are present in the molecule. Also, an adsorption phenomenon was observed in several processes. The quantitative determination of metamitron can be carried out in an acetate medium (pH4.6), by applying DPP, with a detection limit of 50 μg/L and using adsorptive stripping voltammetry, reaching a detection limit of 0.5 μg/L. Assays of commercial samples are illustrated.

Measurements of heat dissipation, oxygen concentration and average vesicle size were correlated to study the effect of serum components on different types of liposome. The results indicate that the interaction between serum components and liposomes is exothermic and oxygen dependent, and leads to disruption of vesicles. The dependence of this effect on serum concentration, vesicle surface charge and type of liposome was also evaluated. Serum components did not produce any effect on conventional liposomes in the absence of oxygen. Moreover, in hypoxic conditions the serum-liposome interaction was delayed. Both results suggest that this interaction is an oxygen-dependent event. Finally, we confirmed that sterically stabilised liposomes remain unalterated in the presence of serum.

Clarithromycin is an antibacterial widely used for the treatment of a myriad of infections. Various methods including HPLC have been reported for its drug plasma concentration but they are more complex. In this study, we developed an electrochemical method for estimation of clarithromycin in blood using differential pulse polarography (DPP) after oral administration of pure clarithromycin suspension. The differential pulse polarography of clarithromycin showed peak with peak potential Ep is À1460 mV SCE at pH 6.5 AE 0.1. The developed electrochemical method was standardized and validated for the determination of clarithromycin in blood serum of albino rats. PK analysis included C max , T max , AUC 0-24 , elimination rate constant (K el ) and t 1/2 . C max were found to be 1.34 AE 0.16 mg/ml and 1.99 AE 0.22 mg/ml for plain clarithromycin and suspension formulation, respectively. Effects of ammonium tartarate concentration and pH were also studied as specificity parameters. Developed electrochemical method was found to be simple, accurate method for to estimate blood-clarithromycin profile and can also be used similarly for various dosage forms.

A novel vertically aligned carbon nanotube/graphene oxide (VACNT-GO) electrode is proposed, and its ability to determine atorvastatin calcium (ATOR) in pharmaceutical and biological samples by differential pulse adsorptive stripping voltammetry (DPAdSV) is evaluated. VACNT films were prepared on a Ti substrate by a microwave plasma chemical vapour deposition method and then treated with oxygen plasma to produce the VACNT-GO electrode. The oxygen plasma treatment exfoliates the carbon nanotube tips exposing graphene foils and inserting oxygen functional groups, effects in which improved the VACNT wettability (super-hydrophobic) crucial for its electrochemical application. The electrochemical behaviour of ATOR on the VACNT-GO electrode was studied by cyclic voltammetry, which showed it underwent an irreversible oxidation process at a potential of +1.08 V and pH cond 2.0 (0.2 mol L −1 buffer phosphate solution). By applying DPAdSV under optimized experimental conditions the analytical curve was found to be linear in the ATOR concentration range from 90 to 3.81 × 10 3 nmol L −1 with a limit of detection of 9.4 nmol L −1 . The proposed DPAdSV method was applied successfully in the determination of ATOR in pharmaceutical and biological samples, and the results were in close agreement with those obtained by a comparative spectrophotometric method at a confidence level of 95%.

Oxygen fluxes into and from root cells of Vitis rupestris (flooding sensitive), V. riparia (flooding tolerant) and V. vinifera (medium tolerance to flooding) were measured under different levels of O 2 availability using a recently developed polarographic O 2 -selective, vibrating-microelectrode system. The system enables fluxes to be measured with a spatial resolution of 2-3 lm and a temporal resolution of 10 s. No difference in root porosity was found among the genotypes when grown for 30 days in an aerated solution. Under normoxic conditions, O 2 influx was characterised by two distinct peaks, one in the division zone and the other in the elongation zone of the roots. This pattern was found in all three species studied, although the fluxes showed a different magnitude. The peak in the elongation zone coincided with maximum relative elemental growth rates. When the energetics of the cell was disturbed by cyanide, both growth and oxygen O 2 influxes ceased at the same time. Under hypoxic conditions, V. riparia plants showed a precise strategy directed toward the maintenance of enough O 2 for the respiratory needs of mitosis in the apical meristem of the roots. Thus, whereas in the division zone of V. rupestris and V. vinifera, at bulk O 2 concentrations of 0.094 mol m -3 , the O 2 influx was reduced by 70.5 and 38.5%, respectively, for V. riparia no variation in the O 2 influx was detected down to bulk O 2 concentrations of 0.078 mol m -3 . Moreover, in accordance with the different tolerances of the plants, the Vitis genotypes were found to differ in their radial O 2 loss from the adventitious roots when in an O 2 -free environment. The results are discussed in terms of possible mechanisms of response to anoxia in Vitis species with different tolerances to flooding. Keywords Anoxia AE Flooding AE Oxygen flux AE Oxygen-selective microelectrode AE Root AE Vitis (O 2 fluxes) Abbreviations DZ: division zone AE EZ: elongation zone AE MZ: mature zone AE REGR: relative elemental growth rate AE ROL: radial O 2 loss Planta (

The shape of scoliotic spines as measured from frontal radiographs (see Part I of this paper) is analysed with respect to interrelations between lateral deviation. lateral tilt and axial rotation of the vertebrae. These parameters are represented by sinusoidal functions of the longitudinal coordinate. The interrelations can, therefore, be expressed in terms of amplitude and phase relations. Two additional functions-'spinal tilt' and (local) curvature-are calculated from the first and second derivatives of lateral deviation. The method has been applied to three patient groups with different aetiology: 113 patients with idiopathic scoliosis (478 radiographs, partially follow-up examinations), 23 patients with scoliosis secondary to Wilms' tumour irradiation and 18 patients with scoliosis secondary to poliomyelitis. The amplitude and phase relations of all functions reveal a characteristic pattern which is apparently independent of the specific aetiology. The results show that the available biomechanic explanations ofcoupling of vertebral motions are questionable.

Isolated cytochrome-c oxidases from bovine heart and liver were reconstituted in liposomes with asolectin and the kinetics of cytochrome c oxidation were measured under various uncoupled conditions. With 40 m M KC1, 10 mM Hepes, pH 7.4, the liver enzyme showed a higher Vmax in the polarographic but a lower V,,, in the photometric assay. With 125 mM phosphate buffer at pH 6.0 both enzymes revealed identical kinetics. Reconstitution with pure phosphatidylcholine leads to a low activity, which is specifically stimulated for the heart enzyme by inclusion of 10% cardiolipin. Proteoliposomes of both enzymes prepared with asolectin have a high activity, which is unaffected by cardiolipin. Exchanging the intraliposomal buffer, Hepes, for phosphate causes an opposite change of the Vma, and a similar change of the K, for both enzymes suggesting a conformational change of the extraliposomal binding domain for cytochrome c through the membrane. Proteases change the kinetics of both enzymes, but to a different degree. The data indicate a complex and tissue-specific influence of nucleus-coded subunits on the catalytic activity of cytochrome-c-oxidase.