S. Jayarama Reddy

Estimation of heavy metals in drinking water and development of heavy metal pollution index

Four heavy metals (Copper, Cadmium, Lead and Zinc) are monitored in drinking water at twelve important residential areas using DPASV Technique. The results indicate the water to free of heavy metal pollution. The data monitored have been used to compute Heavy metal pollution index (HPI) using weighted arithmetic mean method and the proposed Pollution Index (HPI) seems to be applicable in the assesement of overall water quality with respect to heavy metal pollution.

Voltammetric behavior of Cefixime and Cefpodoxime Proxetil and determination in pharmaceutical formulations and urine

Electrochemical reduction behavior of cephalosporins, Cefixime (CF) and Cefpodoxime Proxetil (CP) have been studied by using different voltammetric techniques in Britton-Robinson buffer system. Two well defined cathodic waves are observed for both the compounds in the entire pH range. Number of electrons transferred in the reduction process was calculated and the reduction mechanism is proposed. The results indicate that the process of both the compounds is irreversible and diffusion-controlled. The peak currents for CF and CP are found to be linear over the range of concentration 6.0 x 10(-8) to 1.2 x 10(-5) mol l(-1) and 8.8 x 10(-8) to 1.1 x 10(-5) mol l(-1), respectively. The lower detection limits are found to be 4.6 x 10(-8) and 8.52 x 10(-8) mol l(-1) for the two compounds. A differential pulse voltammetric method has been developed for the determination of these drugs in pharmaceutical formulations and urine samples.

Elemental concentrations in medicinally important leafy materials

Concentrations of elements, especially of trace elements toxic as well as non-toxic in biological materials show a high degree of biological, seasonal and spatial variability. These factors should be taken care of while sampling. Samples, even though collected at a great distance of time and space, should be representative and quantitatively comparable which is important for biomonitoring. Reference Materials (RMs) from biological materials such as leaves acquire importance in Analytical Quality Assurance work. A knowledge of element concentrations in highly consumed leafy samples is of interest. A large number of medicinally important leafy samples (50) have been analysed for elemental concentrations such as Zn, Cu, Ni, Co, Pb, As, Se, K, Cr, Na, P, S, Fe, Ca Mg, Mn and Fe. The concentrations of macro nutrients such as Ca, P, Mg, K, Fe and S range from 9.62 to 4174, 1.00-8.630, 3.53-35.50, 12.04-56.28, 0.111-3.845 g/kg and 1.124-5.843 mg/kg, of micro nutrients such as Cr, Co, Cu, Mn, Na and Zn range from 0.360-8.630, 0.050-3.470, 17.60-57.30, 10.5-81.6, 1.47-27.10 and 10.06-145.6 mg/kg whereas those of trace metals such as Pb, Cd, Ni, As and Se range from 1.19-16.30, 0.0036-0.453, 1.23-19.60, 0.12-7.360 and 0.654-3.50 mg/kg respectively. Influence of sampling parameters such as season and spatial variations has been assessed and the results are interpreted. Spatial variation and seasonal variation are observed to be statistically significant for Cu, Zn and Mn. Preparation of Secondary Reference Materials (SRMs) from the samples analysed is explored. Nutritive values of the leaves and intercorrelation between the metals are also discussed.

Voltammetric behavior of some fluorinated quinolone antibacterial agents and their differential pulse voltammetric determination in drug formulations and urine samples using a β-cyclodextrin-modified carbon-paste electrode

A voltammetric determination of ofloxacin (OF), norfloxacin (NF), gatifloxacin (GF), and lomefloxacin (LF) at a β-cyclodextrin-modified carbon-paste electrode (CDMCPE) is described. A large increase in the peak currents was observed in cyclic voltammetry (CV) and differential pulse voltammetry (DPV) of OF, NF, GF, and LF at CDMCPE compared with a bare carbon-paste electrode (CPE). These increases in the peak currents were attributed to the complex formation of the quinone group of the drugs with β-cyclodextrin. CV studies indicate that the process is irreversible and adsorption-controlled. The experimental parameters which influence the peak current responses of OF, NF, GF, and LF were studied. The reduction peak currents of OF, NF, GF, and LF change linearly over the common concentration range from 3.2 × 10−8 to 2 × 10−5 M, with a common correlation coefficient and limit of detection of 0.9995 and 2.4 × 10−8 M, respectively, in pH 4.0 Britton-Robinson (BR) buffer at an accumulation time of 160 s. The interference of metal ions in the peak current response was also studied. The modified electrode exhibited good sensitivity and stability. The proposed method was applied to the determination of OF, NF, GF, and LF in both commercially available drugs and spiked human urine samples.

Differential Pulse Adsorptive Stripping Voltammetric Determination of Nifedipine and Nimodipine in Pharmaceutical Formulations, Urine, and Serum Samples by Using a Clay‐Modified Carbon‐Paste Electrode

Abstract A simple, rapid, and selective differential pulse adsorptive stripping voltammetric (DPAdSV) method has been developed for the determination of nifedipine and nimodipine based on reduction of an aromatic nitro group in the drugs at a bare carbon‐paste electrode (CPE) and a clay‐modified carbon‐paste electrode (CMCPE). Compared with a bare CPE, CMCPE gave the highest sensitivity in the present developed method. The analytical parameters that affect the electrode reaction process have been studied in terms of pH of the supporting electrolyte, accumulation time, accumulation potential, and composition of a modifier on the adsorptive stripping response by using differential pulse voltammetry. When CMCPE was used, the peak current vs. concentration relationship was found to be linear over the range 4.6 × 10−10–2 × 10−7 M and 5.4 × 10−10–4 × 10−7 M, with a limit of detection (LOD) 3.9 × 10−10 and 4.8 × 10−10 M, and correlation coefficient of 0.9996 and 0.9998 for nifedipine and nimodipine, respectively. The method was applied successfully for the direct determination of nifedipine and nimodipine in tablet dosage forms, urine, and serum samples.

Electrochemical reduction of tellurium(IV)

Abstract Direct current and differential pulse polarographic techniques have been employed in the present study to understand the nature and the mechanism of the electrochemical reduction behaviour of tellurium in various aqueous supporting electrolytes. The consecutive reduction, Te 4+ → Te 0 → Te 2− in acid and slightly alkaline medium; Te 4+ → Te 2− in strongly alkaline medium and formation of two types of elemental tellurium (electrochemically at the electrode and chemically in the bulk) are observed and discussed. The possibility of the simultaneous estimation of tellurium with zinc and cadmium in the form of the semiconductor materials has been examined. Adsorption complication of the metal ions observed, if any, are reported.

Electroorganic synthesis of 6-aminonicotinic acid from 2-amino-5-chloropyridine

Abstract A synthesis of 6-aminonicotinic acid by electrochemical hydrogenation of 5-chloro-2-nitropyridine and electrochemical carboxylation of 2-amino-5-chloropyridine at a cathode surface in the presence of sulphuric acid and carbon dioxide in a dimethylformamide (DMF) solution at an apparent current density of 10 mA/cm2 using an undivided cell with good yields is reported.

Electrochemical determination of sparfloxacin in pharmaceutical formulations and urine samples using a β-cyclodextrin modified carbon paste electrode

Abstract The electrochemical behavior of Sparfloxacin at β-cyclodextrin modified carbon paste electrode (CDMCPE) has been studied. Compared with bare carbon paste electrode (CPE), the β-cyclodextrin modified carbon paste electrode exhibited a marked enhancement of current response of Sparfloxacin. Cyclic voltammetric (CV) studies indicate that the process was irreversible and adsorption controlled. To obtain a good sensitivity, the instrumental and accumulation variables were studied using Differential Pulse Voltammetry (DPV). A linear calibration plot was obtained over the 0.043–60 μM range with a correlation coefficient of 0.999 in pH 3.0 Britton Robinson buffer with a detection limit of 0.04 μM by using DPV. The peaks from the techniques CV and DPV are attributed to the complex formation of quinone group of the drug with β-cyclodextrin. The repeatability and reproducibility of the methods were within 7.52, 7.68% RSD for peak currents and 0.52, 0.60% RSD for peak potentials using CDMCPE. Quantitative analysis was performed by the standard addition method for Sparfloxacin in both urine and available pharmaceutical formulations. A spectrophotometric method was used as a reference method to assess the accuracy. Results obtained through spectrophotometric method were comparable to those obtained by CDMCPE.

Distribution of Toxic Trace Metals Zn, Cd, Pb, and Cu in Tirupati Soils, India

The concentrations of toxic trace metals in the soil samples collected from Tirupati, India, have been determined using differential pulse anodic stripping voltammetry (DPASV). The total metal concentrations of the soils in the study area were in the following ranges: 19.5 to 23.6 mg of Zn, 0.032 to 0.036 mg of Cd, 15.8 to 18.9 mg of Pb, and 19.0 to 23.4 mg of Cu per kg soil. Analysis of standard reference material IAEA-SOIL-5 indicates good accuracy. Recoveries were nearly quantitative for all elements studied. Comparison of the average metal concentration levels with world averages indicates an elevated value for Pb. The applicability of this method was crosschecked with AAS and the results were in good agreement.

Differential Pulse Anodic Stripping Voltammetric Determination of Pb, Cd, Cu, and Zn in Air, Diet, and Blood Samples: Exposure Assessment

Abstract Concentrations of heavy metals such as Pb, Cd, Cu, and Zn have been determined by using differential pulse anodic stripping voltammetry (DPASV) in air particulates, diet, and childrens blood residing at different locations of Tirupati. The reliability of the procedure for estimation of Pb, Cd, Cu, and Zn in environmental and biological samples by DPASV technique was checked by analyzing various standard reference materials. The observed daily intake of Pb, Cd, Cu, and Zn by children varies from 0.1014 to 0.3264, 0.0204 to 0.0372, 0.1953 to 0.3310, and 76.1902 to 78.3720 µg day−1 through inhalation, and 17.53 to 20.91, 1.92 to 2.32, 954.92 to 1264.70, and 5750.14 to 6774.56 µg day−1 through dietary intake, respectively. Retention times of Pb, Cd, Cu, and Zn in childrens blood are estimated by using levels of these metals in air particulates and by duplicating diet and blood of children. The observed average retention times for Pb, Cd, Cu, and Zn are 17.32, 7.85, 2.12, and 1.92 days, respectively.