In this work, a sensitive electrochemical platform for determination of cadmium was obtained using graphene-Nafion modified bismuth film glassy carbon electrode by differentialpulseanodicstrippingvoltammetry (DPASV) analysis. The performances of the graphene-modified sensor were systemically studied. It demonstrated that the graphene-modified sensor exhibited superior analytical performance for cadmium over a linear range from 1 μg L -1
organisms does not depend only on the total metal concentration in the solution. The concentration of free metal ion, in most cases, is a key factor in predicting the bioavailability of heavy metal. In this paper the results of the chemical speciation of Pb in the water of Modrac Lake are presented. Modrac lake is an artificial lake formed for the purposes of providing drinking water and water for industry. The water of the lake is extremely vulnerable, because it is the main recipient of wastewater from the nearby coal mine as well as municipal wastewater. Samples were analysed using differentialpulseanodicstrippingvoltammetry (DPASV). The samples were taken from four typical areas of lake through the four seasons. The samples from the depth of 2.5 m, and from each location two samples were taken. Complexing capacity and stability constant were calculated.
an ammonium solution), then it was transferred to a flack (25 mL) and supplemented with water. This final solution was used for the determination of thallium in the studied pharmaceutical preparations using flow injection analysis differentialpulseanodicstrippingvoltammetry (FIA-DPASV). The pre-concentration of Tl was carried out at a potential of –900 mV vs. SCE over 900–3600 seconds depending on the Tl concen- tration. Voltammograms were recorded after medium exchange on pure 0.05 M EDTA (Figure 3). The results were evaluated on the basis of several additions of an internal standard (typically 3 additions). The detection limit of the method (calculated on a 3SD basis) was 50 pg L -1 (0.25 pM).
The present study reported on the development of a sensitive DPASV method for the detection of heavy metal ions using glassy carbon electrode by in-situ addition of N,N’-bis[2-hydroxyacetophenone]ethylenediamine (OAcPh-en). The functional groups of OAcPh-en are expected to make effective coordination with heavy metal ions to enable a new simple and precise strippingvoltammetry technique for the ultra-trace determination of Cd(II), Cu(II), Pb(II) and Zn(II) in aqueous solution.
In this work, an ionic imprinted hybrid material organically modified with 3-(2-imidazolin-1- yl)propyltriethoxysilane with copper(II) as template was prepared and structurally characterized, using elemental analysis, X-ray powder diffraction (XRD), thermogravimetric analysis, infrared spectroscopy and solid state 13 C and 29 Si nuclear magnetic resonance (NMR). Experiments with cyclic voltammetry and differentialpulseanodicstrippingvoltammetry (DPASV) showed that the electrode prepared was stable over 100 cycles, with high reproducibility. Copper(II) ions could be quantified in water/Brazilian sugar cane spirit (cachaça). Calibration curve for detection was obtained from 5.98 – 201.42 g L -1 of copper(II) concentration, with a correlation coefficient of R 2 = 0.995; n = 12. The detection limit obtained was (LOD) as 0.74 g L -1 and the limit of quantification (LOQ) was of 2.48 g L -1
mL of distilled and deionized water. Then, the solution was purged with pure nitrogen for 10 minutes. The background voltammogram was obtained using the following run conditions for differentialpulseanodicstrippingvoltammetry (DPASV): Mode: Stripping; initial potential: 1250 mV; final potential: 500 mV; gain (1-20): 10; deposition time: 120s; quite time delay: 30s.
Cyclic voltammetry, linear sweep anodicstrippingvoltammetry (LSASV) and differentialpulseanodicstrippingvoltammetry (DPASV) were performed with a Pstat10 potentiostat interfaced to a PC for data acquisition via the General Purpose Electrochemical System Software Package (GPES) version 3.4 (Autolab, Windsor Scientific Limited, Slough Berkshire UK). The cell used for the voltammetric measure ments was obtained from Metrohm (Switzerland); a small magnetic stirrer bar was placed in the bottom of the cell for stirring in the pre-concentration step of DPASV. This was rotated at a fixed constant rate by a rotary stirrer (Mini MR Stirrer, Whatman, Maidstone, Kent, UK). All measurements were made using the PDE was the working with a saturated calomel reference (Russell, UK) electrode and a graphite rod counter electrode.
The speciation of arsenic in groundwater samples using Square Wave AnodicStrippingVoltammetry (SWASV), DifferentialPulseAnodicStrippingVoltammetry (DPASV) and Normal PulseAnodicStrippingVoltammetry (NPASV) are described. Good resolution of the species, arsenic (III) and arsenic (V) is achieved using SWASV. The reliability of the methods was checked by analyzing the total arsenic content of the samples by Hydride Generation Atomic Absorptioion Spectrophotometer and by analyzing prepared controlled laboratory standard solution. Since this technique is comparatively cheaper than other available techniques it could be a better analytical technique for arsenic speciation from water. In this study, the assessment of inorganic arsenic species in ground water of Kalkini (Madaripur) and Hajigonj (Chandpur) is reported. It shows that arsenic content in water in different locations is irregular. Most of the locations contain higher level of As(III) than As(V). The highest concentration of arsenic is found in Anayetnagor (554.46 ± 0.07 g/L) of Kalkini and Raichar (562 ± 0.50 g/L) of Hajigonj. However, the level of total arsenic and As(III) of most of the villages of the study areas are more than the WHO guideline value (50 g/L). Therefore a proper monitoring process should be evolved along with the development of methods to keep the water free from arsenic.
Bismuth (Bi) nano-needle, nano-rod, nano-sheet, and nano-flower were synthesized using a facile one- step solvothermal method by adjusting the volume of ethylenediamine (EDA). The prepared Bi nano- particles were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis and their formation mechanism was discussed. Bi nano-particle modified carbon paste electrode (CPE) combined with differentialpulseanodicstrippingvoltammetry (DPASV) was developed for the determination of Cd (II). It was shown that Bi nano-flower modified electrode displayed the highest detection sensitivity on account of its particular three-dimensional structures. The stripping peak currents of Cd (II) at “bulk” and “drop coating” Bi nano-flower modified CPEs were compared with those of Bi film modified CPEs using “in-situ” and “out-situ” plating methods. The optimized detection conditions were 5% Bi nano-flower bulk modified CPE at pH 4.4, deposition potential of -1.2 V (vs. AgCl/Ag) and deposition time of 200 s. The linear range, sensitivity and detection limit were0.05 - 1 M, 27.5 A/M, and 2.4 nM , respectively. The proposed Bi nano-flower bulk modified CPE was conveniently usable in the trace Cd (II) analysis for environmental water samples with the recovery rang of 91.1%-105.6%.
For electrochemical detection of metals, differentialpulsevoltammetry (DPV) and differentialpulseanodicstrippingvoltammetry (DPASV) were employed. Measurements were carried out with an Autolab analyser in connection with VA-Stand 663, 800 Dosino and 846 Dosing Interface (Metrohm, Switzerland) in standard electrochemical cell with three electrodes. Hanging mercury drop electrode (HMDE) was used as a working electrode, Ag/AgCl/3 M KCl electrode served as reference electrode and glassy carbon electrode was auxiliary. All measurements were performed in the presence of the acetate buffer (0.2 M, pH 5.0) at 25 °C. The analysed samples were deoxygenated prior to measurements by purging with argon (99.999%). GPES 4.9 software was employed for data processing. The parameters of DPV were as it follows: initial potential 0.15 V; end potential -1.3 V; deposition potential 0.15 V; duration 240 s; equilibration time 5 s; modulation time 0.06 s; time interval 0.2 s; potential step 0.002 V; modulation amplitude 0.025 V. The parameters of DPASV were as it follows: initial potential -1.3 V; end potential 0.15 V; deposition potential -1.3 V; duration 240 s; equilibration time 5 s; modulation time 0.06 s; time interval 0.2 s; potential step 0.002 V; modulation amplitude 0.025 V. Other experimental details are indicated in the following papers [90-95].
Concern over the harmful effect of toxic metals in the environment warrants the need of continuous improvement for their determination. Conventional methods such as inductively coupled plasma-mass spectrometry (ICP-MS) and atomic absorption spectrophotometry (AAS) for the determination of metal ions in aqueous solution have several drawbacks such as time consuming manipulation steps, need for sophisticated instruments and high maintenance costs. Alternative methods such as electrochemical technique have been suggested, particularly offering advantages in terms of speed of analysis, low cost, easy operation and ability to directly determine metal ion in complex aqueous samples. In the present study, acetophenone-benzaldehyde ethylenediamine compounds, N,N’-bis(2-hydroxyacetophenone)ethylenediamine, bis(4- hydroxybenzaldehyde)ethylenediamine, bis (benzylidene)ethylenediamine and N,N’-bis(2- hydroxy-4-methoxyacetophenone)ethylenediamine were synthesized and applied to modify carbon based electrodes for the determination of metal ions using electrochemical techniques. The ligands were used in-situ to enhance the detection of cadmium (Cd(II)) and copper (Cu(II)) ions using differentialpulseanodicstrippingvoltammetry (DPASV). Under the optimized conditions the proposed in-situ DPASV method for Cd(II) and Cu(II) provides good limits of detection (LOD) and limit of quantification (LOQ) in the range of 0.1 - 1.0 µg L −1 and 1.30 - 4.53 µg L -1 respectively. The relative recoveries obtained for Cd(II) and Cu(II) in tap water and sea water samples were in the range of 82 - 118%. A composite carbon paste electrode modified with bis(benzylidene)ethylenediamine was successfully fabricated for the determination of Cd(II) using square wave anodicstripping voltammetric technique. The response surface methodological approach employing the Box-Behnken design was utilized to optimize the experimental conditions for the detection of Cd(II). Under optimized conditions, a linear response over a wide range of Cd(II) concentrations (1–500 µg L −1 ) with low LOD (0.4 µg L -1 ) and LOQ (1.4 µg L -1 ) were observed. The electrode employed in this styudy exhibited exceptional recovery results over a wide range of Cd(II) concentrations in the sea and tap water samples. A modified electrode consisting of multi-walled carbon nanotubes (MWCNT), 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF 6 ),
In this work, a gold microelectrode was employed to detect Cu 2+ by differentialpulseanodicstrippingvoltammetry (DPASV) in environmental water samples. Due to the excellent properties of microelectrode, low detection limit and wide linear range can be obtained. Additionally, experimental parameters, including the pH value of the supporting electrolyte, the accumulation potential and the accumulation time have been investigated in detail. The practical application of gold microelectrode has been carried out for determination of Cu 2+ in tap water, lake water and commercial drinking water samples.
The voltammetric behavior of ciprofloxacin was investigated using cyclic voltammetry and differential-pulseanodicstrippingvoltammetry at bare glassy carbon (GC) electrodes and DNA- modified glassy carbon (DNA-GC) electrodes. For both types of electrodes, only one anodic irreversible wave was observed. A comparison between the current responses for the ciprofloxacin at the modified DNA-GC and unmodified GC electrodes, it was showed that the DNA- modified electrode exhibits a significant enhancement of the voltammetric current response with a better peak shape. Also, the interaction of ciprofloxacin with DNA was studied by using cyclic voltammetry technique at (DNA-GC) electrodes, which showed a weak interaction with a binding constant (K) = 2.89 x 10 5 M -1 . A linear relationship between the peak current and ciprofloxacin concentrations was observed in the range 1.0–10.0 µM, with a slope a detection limit of 0.117 µM, with r = 0.998, and 1.0 µM.
Preparation of Pre-PGEs. Pre-PGEs were prepared by two different pretreatment methods: cyclic voltam- metric technique and chronoamperometric technique. In the first technique, the cyclic voltammograms were applied at various potential ranges [(–1.0 V → +2.0 V); (–0.3 V → +2.0 V), (+0.5 V → +2.0 V); (+1.0 V → +2.0 V) or (+1.5 V → +2.0 V)] with a scan rate of 50 mV/s for 5 scans. In the second method, the sur- face of PGE was pre-treated by applying a potential of +1.45 V for 60 s in the supporting electrolyte (0.1 M phosphate buffer solution containing 0.1 M KCl, pH 7.0). After the pretreatment, the Pre-PGEs were used for the determination of TA using anodicstrippingdifferentialpulsevoltammetry (ASDPV) (potential range 0–0.8 V; potential step 25 mV; potential pulse: 25 mV; pulse time 0.05 s; scan rate 50 mV/s). The ef- fects of pH, accumulation potential and accumulation time were optimised. All of the PGE electrodes were treated directly before each measurement.
The Tl + quantification precision was evaluated applying two approaches: 1) increasing the Pb 2+ excess keeping the Tl + concentration constant and 2) increasing the Tl + concentration keeping the Pb 2+ excess constant. For this purpose: 1) ASDAPV curves of 100 ppb Tl + were registered at increasing Pb 2+ concentration up to 600 ppb in 0.1 mol L -1 supporting electrolyte (see Fig. 3). The Tl + cathodic peak keeps its height intact up to 6-fold excess of Pb 2+ The further Pb 2+ concentration increase causes a progressive Tl + cathodic peak overlapping, decreasing the precision of its quantification. For comparison a complete overlapping of the Tl + peak occurs even at Tl + to Pb 2+ concentration ratio as low as 1 to 1, applying in stripping mode the most common voltammetric technique, the DifferentialPulseVoltammetry, as shown in Fig. 1.
Unfortunately, the interfering species concentrations are usually higher than that of In 3+ which makes its precise voltammetric quantification problematic because of the peaks overlapping. For example, by the application of the first order technique DifferentialPulseVoltammetry (DPV) peak overlapping occurs even at Cd 2+ concentration less than that of In 3+ (see the text below). Instrumental, mathematical and chemical approaches have been developed till now to solve the interference problem. The instrumental approach was directed mainly to the scan rate and the mercury film thickness optimization [1, 20, 34]. The chemical approach includes species extraction, complexation or inhibition requiring complicated sample pretreatment performed by trained personnel degrading the results precision and cost efficiency [18, 22, 35]. The mathematical approach applying digital methods for curve treatment is easy, but peak heights altering occurs causing quantification precision degradation . Unfortunately, none of the mentioned approaches resulted in complete solution of the problem to yield precise quantification of In 3+ traces in presence of higher concentrations of interfering species.
A variety of well-known and accurate analytical techniques are capable of measuring the arsenic concentrations in water samples, as Atomic Absorption Spectroscopy (AAS), Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), Gas Chromatography (GC), High Performance Liquid Chromatography (HPLC) or Capillary Electrophoresis (CE), for instance [9-10]. These methods are expensive and laboratory-based demanding well trained technicians to conduct the measurements; thus, are not suitable for field detection [2, 10]. Therefore, there is an increasing need to develop portable devices which gives reliable measurements for the detection of arsenic at low cost. Currently, the development of electrochemical methods for arsenic detection is and active research area due to the sensitivity, portability and short time required to perform the measurements . Electroanalytical methods such as strippingvoltammetry, potentiometry and differential-pulse polarography have been reported for determination of very low concentrations of arsenic in natural waters samples [4, 11-13]. Electroanalytical techniques provide a low cost, rapid and portable option for routine in-field monitoring of large numbers of samples. According to their sensitivity, anodicstrippingvoltammetry (ASV) has been established as the most important technique for the determination of trace amounts of arsenic. ASV comprises the preconcentration of As (0) produced from reduction of As (III) and deposited on the electrode surface followed by anodicstripping of As (0) . In order to improve this analytical procedure several working electrode have been used as Au, Pt, Ag, Hg, boron doped-diamond (BDD) or nano-particle and carbon nano-tube modified electrodes which reports limits of detection from 0.0026 to 170 μ g L -1 [11, 13].
The quantitative range of the proposed NPG sensor for the analysis of As 3+ was studied with the optimized parameters above. As presented in figure 8, the stripping peak current was increased with the increasing concentration of As 3+ , and a good linearity was obtained in the concentration range from 0.001 to 4 μg/mL. A detection limit (LOD) of 0.001 μg/mL was obtained (S/N=3). The linear equations is y=14.4797x+0.3081. The linear correlation coefficient is 0.9992.