Recai İnam

A direct method for the determination of selenium and lead in cow's milk by differential pulse stripping voltammetry

The selenium and lead contents in milk samples from Turkey were determined using a hanging mercury drop electrode ( HMDE ) and differential pulse cathodic stripping voltammetry ( DPCSV ) and differential pulse anodic stripping voltammetry ( DPASV ), respectively. In this method, the milk samples were digested in HNO3 : HClO4 ( 1:1 ) mixture by a wet digestion procedure. The DPCSV of milk samples in 0.1 M HCl solution showed a peak for selenium at −0.56 V , and DPASV for lead showed a peak at -0.35 V. A deposition potential of -0.2 V for selenium, and −0.5 V for lead were suitable. The standard addition method was used to determine selenium and lead in the sample. The linear domain range was 75–1.2 μg/l for selenium with a correlation coefficient of 0.9981 and 185–8.7 μg/l for lead with a correlation coefficient of 0.9945. The proposed method provides a simple and suitable procedure for the determination of trace amounts of selenium and lead. In this method, there is no need for sophisticated instruments and tedious separation procedure. Selenium and lead contents of milk samples from three distinct regions of Turkey were obtained between 21.5–69.4 and 22.1–59.2 μg/l (n=4–5), with the relative standard deviations of 10.3–10.7 and 6.8–9.9% , respectively.

Simultaneous determination of selenium and lead in whole blood samples by differential pulse polarography.

The polarographic reduction of lead in the presence of selenite gives rise to an additional peak corresponding to the reduction of lead (Pb) on adsorbed selenium (Se) on mercury at -0.33 V. The selenium and lead content can be determined using this peak by the addition of a known amount of one of these ions first and then the second ion. The linear domain range of lead is 5.0x10(-7)-2.0x10(-5) M and for selenium 5.0x10(-7)-1.0x10(-5) M. Using this method 4.90x10(-7) M Se(IV) and 1.47x10(-6) M Pb(II) in a synthetic sample could be determined with a relative error of +2.0% and 1.8%, respectively (n=4). A recovery test after acid digestion for a synthetic sample was 97% for selenium and 96.5% for lead. The method was applied to 1 ml of digested blood, and 328+/-23 mug l(-1) Se(IV) and 850+/-62 mug l(-1) Pb(II) could be determined with a 90% (n=5) confidence interval.

Determination of selenium in garlic by cathodic stripping voltammetry

Abstract The selenium content in a garlic sample was determined on hanging mercury drop electrode (HMDE) using cathodic stripping voltammetry (CSV). In this method the dried garlic sample was digested in HNO3:HClO4 (1:1) by wet-digestion procedure. The CSV voltammogram in 0.1 M HCl solution showed a peak for Se at −0.56 V. Effect of deposition potential, deposition time and sweep rate on this peak were tried to determine the optimum experimental conditions. A deposition potential of −0.2 V was applied for 120 s while stirring the solution by passing nitrogen and followed a potential scan of 50 mV/s in a negative direction. The standard addition method was used to determine selenium in the sample. The linear domain range of Se (IV) was 2.0×10−8–6.0×10−7 M with a correlation coefficient of 0.9985. This method was used for the first time for the determination of selenium in garlic sample without any separation procedure and preconcentration techniques such as ion exchange, solvent extraction or hydride generation. The amount of selenium determined in three different samples from three different regions were 370±26 (n=5), 485±35 (n=4) and 365±46 (n=4) ng/g (dry-weight) with relative standard deviations of 7.0, 7.2 and 12.6%, respectively.

Differential Pulse Polarographic Determination of Moxifloxacin Hydrochloride in Pharmaceuticals and Biological Fluids

Abstract A simple, fast, sensitive and fully validated differential pulse polarographic (DPP) method for the determination of trace amounts of moxifloxacin in pharmaceutics, serum and urine is reported. Moxifloxacin exhibited irreversible cathodic peak over the pH 5.00–11.00 in Britton–Robinson (B–R) buffer. At pH 10.00 (the analytical pH), a well‐defined peak at −1.61 V versus saturated calomel electrode was obtained. The current has been characterized as being diffusion‐controlled process. The diffusion current constant (id) was 1.48±0.12 and the current–concentration plot was rectilinear over the range from 5×10−7 to 1×10−4 M with correlation coefficient (n=10) of 0.995. The proposed method was applied to commercial tablets and average percentage recovery was in agreement with that obtained by spectrophotometric comparison method. The method was extended to the in vitro determination of moxifloxacin in spiked human serum and urine.

A direct method for the polarographic determination of herbicide triasulfuron and application to natural samples and agrochemical formulation.

Polarographic behavior of triasulfuron herbicide in a Britton-Robinson (B-R) buffer was investigated by differential pulse polarography (DPP) and cyclic voltammetry (CV). Optimum conditions for the analytical determination were found to be pH 3.0 at a reduction potential of -1031 mV. Experimental results indicate an excellent linear correlation between the peak current and the concentration in the range of 0.19-11.6 microg mL(-1) (0.47-28.9 microM) with a correlation coefficient of 0.993. The limit of detection (LOD) and limit of quantification (LOQ) were obtained as 0.06 and 0.19 microg mL(-1) (0.15 and 0.47 microM), respectively. The precision of the method is satisfactory at a very low level, and the relative standard deviation (RSD) is 2.37% (n=5). Satisfactory recoveries achieved with spiked soil and dam water samples were between 98.4-103.0% and 100.0-104.0% at concentration ranges of.5.0-25.0 microg g(-1) and 0.40-2.0 microg mL(-1) (12.4-62.2 and 1.0-5.0 microM), respectively, inferring that the established method can be applied to real sample analysis. The method was extended to the direct determination of triasulfuron in agrochemical herbicide formulation Lintur 70 WG and average content of 4.37+/-0.16 (n=5) % was in close agreement with the 4.10% quoted by the manufacturer. The influences of some other commonly used pesticides and inorganic salts on the determination of triasulfuron were also examined.

Polarographic determination of herbicide thifensulfuron methyl/application to agrochemical pesticide, soil, and fruit juice

A novel, sensitive, simple, fast, and fully validated differential pulse polarographic (DPP) method for the determination of trace amounts of thifensulfuron-methyl in pesticide formulation, soil, and orange juice is reported. This procedure was based on a highly sensitive peak formed due to the reduction of thifensulfuron-methyl on a dropping mercury electrode over the pH range 1.00–10.00 in Britton–Robinson buffer. The polarographic reduction exhibits only a single peak in the pH ranges pH ≥ 3.0 and pH ≤ 6.0 and pH = 10.0 located at potential values of −1.010, −1.350, and −1.610 V (vs. SCE), respectively. The single peak appeared as a maximum at pH 3.0 (−1.010 V) was well resolved and suitable to be investigated for analytical use. This peak showed quantitative increments with the additions of standard thifensulfuron-methyl solution under the optimal conditions, and the cathodic peak current was linearity proportional to the thifensulfuron-methyl concentration in the range of 2 × 10−7–5 × 10−5 M. The limit of detection (LOD) and limit of quantification (LOQ) were obtained as 1.05 × 10−7 and 3.50 × 10−7 M, respectively, according to the relation k  × SD/b (where k = 3 for LOD, k = 10 for LOQ, SD is the standard deviation of the blank, and b is the slope of the calibration curve). The proposed method was applied to pesticide formulation (Harmony® Extra), and the average percentage recovery was in agreement with that obtained by the spectrophotometric comparison method, 97.82 and 102.6%, respectively. The method was extended to determination of thifensulfuron-methy in spiked soil and orange juice, showing a good reproducibility and accuracy with a relative standard deviation of 4.55 and 1.40%, and relative errors of +2.80 and +1.90%, respectively.

Square Wave Adsorptive Stripping Voltammetric Determination of Cyromazine Insecticide with Multi-Walled Carbon Nanotube Paste Electrode

The electrochemical behavior of cyromazine (N-cyclopropyl-1,3,5-triazine-2,4,6 triamine) insecticide has been studied at newly prepared multi-wall carbon nanotubes paste electrodes using square wave stripping voltammetry. The cyromazine was accumulated at 0.0 mV [vs. Ag/AgCl (3 M NaCl)] and a well-defined anodic peak obtained at +1110 mV in 0.1 M H2SO4. The cyclic voltammetric measurements showed an irreversible nature of oxidation wave in the range of scan rates comprised between 500 and 4000 mV s−1. The calibration curve obtained from square wave stripping voltammetry was linear in the range 0.41 to 83.30 µg/mL with a detection limit of 0.12 µg/mL. The method was applied to the direct determination of cyromazine in natural water samples. Recoveries calculated for river and tap water samples spiked with 10.0 µg/mL level were 101.5 ± 1.9% and 100.6 ± 2.3% at 95% confidence level, respectively. The method was extended to the determination of cyromazine in agrochemical formulation Trigard® with a recovery of 100.49% and accuracy was in agreement with that obtained by HPLC comparison method. Influences of some interfering ions and pesticides were also investigated.

Electro-oxidation of herbicide halosulfuron methyl on glassy carbon electrode and applications

Halosulfuron methyl, a fast-acting herbicide and is absorbed into leaf tissue within 1-2 days and translocated through the vascular system, interrupting amino acid production within the plant, can be detected using glassy carbon electrode the technique of adsorptive stripping voltammetry. The adsorptive stripping voltammetric behavior of halosulfuron methyl was investigated in pH range 1.0-10.0. Halosulfuron methyl was irreversibly oxidized at a glassy carbon electrode. Electrochemical techniques including adsorptive stripping voltammetry and cyclic voltammetry were employed to study the oxidation mechanism. The experimental parameters such as the accumulation potential, accumulation time and frequency were optimized. The linear range, detection limit and quantification for halosulfuron methyl were evaluated by adsorptive stripping voltammetry. Under the optimized conditions, the peak current is linear to halosulfuron methyl concentration in the range 4.1-50.0 μg mL(-1). Limit of detection and limit of quantification were 1.23 and 4.10 μg mL(-1), respectively. The interference of inorganic species and other some pesticides on the voltammetric response have been studied. The applicability to spiked soil and natural water was described and the recoveries for the standards added are 103.8% and 108.2%, respectively. The method is successfully applied for the determination of halosulfuron methyl in commercial formulation.

Polarographic determination of uranyl adsorption onto poly(acrylamide-g-ethylenediaminetetraacetic acid) hydrogels in the presence of cadmium and lead

Abstract Poly(acrylamide-g-ethylenediaminetetraacetic acid) [P(AAm-g-EDTA)] hydrogels with various compositions were prepared from ternary mixtures of acrylamide, ethylenediaminetetraacetic acid and water by using 60 Co γ-rays. This study showed that P(AAm-g-EDTA) hydrogels adsorb heavy metal ions such as UO 2 2+ in the presence of Pb 2+ and Cd 2+ selectively at certain pH’s. The external stimuli of pH, temperature and ionic strength play an important role on the adsorption behavior. Since a very sensitive electro-analytical technique, differential pulse polarography (DPP) was used for determination of UO 2 2+ adsorbed onto hydrogels (0.1–3.2 mg/g dry gel) from 5.0 mg/l aqueous solution without interfering Pb 2+ and Cd 2+ at certain pH’s. These hydrogels can be used directly as UO 2 2+ selective adsorbent for water and environmental pollutants without any pre-concentration techniques.

POLAROGRAPHIC DETERMINATION OF URANYL ION ADSORPTION ON POLY-(2-HYDROXYETHYL METHACRYLATE/ITACONIC ACID) HYDROGELS

Copolymeric hydrogel adsorbents containing hydrophilic groups both providing swelling in water and chelating with uranyl ions were prepared by using γ-rays and their adsorptive ability for recovering uranium from aqueous media was investigated. Uranyl adsorption capacities of the hydrogels were determined by polarographic techniques to be 4.9–6.0 (mg UO2 +2/g dry gel) at pH 3.87 and 4.2–5.6 (mg UO2 +2/g dry gel) at pH 5.4 from 15 ppm uranyl nitrate solution, depending on the mole content of IA in the hydrogel. The adsorption studies show that the temperature and the ionic strength of the solution influence uranyl ion adsorption by P(HEMA/IA) hydrogels.