Determination of picomolar silver concentrations by differential pulse anodic stripping voltammetry at a carbon paste electrode modified with phenylthiourea- … (original) (raw)
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Electrochimica Acta, 2009
This study introduces the design of an anodic stripping voltammetric (ASV) method for the silver ion determination at a carbon paste electrode (CPE), chemically modified with phenylthiourea-nanoporous silica gel (Tu-SBA-15-CPE). The electroanalytical pro includes two steps: preconcentration of metal ions at an electrode surface, followed by quantification of the accumulated species by differential pulse anodic stripping voltammetric methods. Factors affecting the performance of the anodic stripping were investigated, including the modifier quantity in the paste, the electrolyte concentrations, the solution pH and the accumulation potential or time. The most sensitive and reliable electrode contained 10% Tu-SBA-15 and 90% carbon paste. The accumulation potential and time were set at, −200 mV and 300 s, respectively, and the scan rate at 50 mV s −1 in the scan range of −200 to 700 mV. The resulting electrode demonstrated a linear response over range of silver ion concentration of 8.0-80 pmol/L with detection limit (S/N = 3) of 5 pmol/L. The prepared electrodes were used for the silver determination in sea and tap water samples and very good recovery results were obtained. The accuracy was assessed through recovery experiments and independent analysis by graphite furnace atomic absorption spectrometry.
Monatshefte für Chemie - Chemical Monthly, 2010
A sensitive and selective procedure for the determination of silver(I) at p-isopropylcalix[6]arene modified carbon paste electrode has been developed. Silver(I) was accumulated in open-circuit design on the electrode surface via complex formation with the modifier at pH 9.00. After electrochemical reduction of silver(I), the anodic stripping wave of silver(0) appeared at ?0.04 V versus reference electrode on scanning the potential in the positive direction in 0.1 M H 2 SO 4 ? 2.0 9 10 -2 M KBr. The effects of various parameters such as preconcentration time, stripping medium, reduction potential, etc. were investigated. In the optimum condition, a linear calibration curve was obtained in the range of 5.0 9 10 -8 M to 2 9 10 -6 M with detection limit (3d) of 4.8 9 10 -8 M. Many coexisting metal ions had little effect on the determination of silver(I). Also, the proposed method was applied to the determination of silver(I) in X-ray photographic film samples. The results were in good agreement with those obtained by atomic absorption spectroscopy (AAS).
Journal of hazardous …, 2006
A new modified silica gel using 2,4,6-trimorpholino-1,3,5-triazin was used for separation, preconcentration and determination of silver ion in natural water by atomic absorption spectrometry (AAS). This new bonded silica gel was used as an effective sorbent for the solid-phase extraction ...
Advanced journal of chemistry. section A, 2019
A new ligand, 1,5-bis(para methoxyphenyl)-3-ethyl-1,4-pantaazadiene has been synthesized by reaction of the 4-methoxyaniline (panisidine) with ethylamine. The mixture was stirred in an ice bath for 30 min. The structure of the synthesized compound resulted from the IR and 1 HNMR and 13 CNMR. Afterwards, a carbon paste electrode modified with this new ligand was developed for the silver determination at nano molar level concentration. The electerochemical properties of this modified electrode was investigated by employing cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods in an acetate buffer solution (pH=4.8). The effect of pH, scan rate, percentage of modifier and buffer as supporting electrolyte on the electrode process were investigated. The oxidation peak of Ag + was observed at about 0.4-0.5 V. The resulting electrode demonstrated linear response across a 10-9 to 10-8 mol/L-1 of silver concentration range with a detection limit value of 1.61×10-10 mol/L-1 , on the basis of a signal to noise ratio of 3. Relative Standard deviation (RSD%) of the electrode performance was 2.41%. This MCPE, showed high sensitivity and selectivity to Ag + ions in aqueous samples.
Environmental Monitoring and Assessment, 2017
Amendment of a carbon paste electrode consisting of graphite and Nujol®, with a variety of organic and inorganic materials, allows direct adsorption of silver nanoparticles (AgNPs) from aqueous solution in either open or close circuit modes. The adsorbed AgNPs are detected by stripping voltammetry. Detection limits of less than 1 ppb Ag are achievable with a rotating disk system. More than one silver peak was apparent in many of the stripping voltammograms. The appearance of multiple peaks could be due to different species of silver formed upon stripping or variation in the state of aggregation or size of nanoparticles. With most of these packing materials, dissolved Ag + was also extracted from aqueous solution, but, with a packing material made with Fe(II,III) oxide nanoparticles, only AgNPs were extracted. Therefore, it is the best candidate for determination of metallic AgNPs in aqueous environmental samples without interference from Ag + .
Analytica Chimica Acta, 2002
A concentratkn technique urlng dmurkn of amher, and organic aclds across a hydrophoblc membrane was developed for the measurement of these compounds In seawater. Udng thls approach, the amlnes and organlc a c h are concentrated from seawater and also are separated from Inorganlc salts and most other dissolved organic compounds. Amlnes or organlc aclds In the concentrated sample are then quantnled by gas chromatography. Concentratlon factors up to 1000 can be achkved. Natural concentratlorn of amlnes and most organlc ackk of 10 nM can be measured In 500 mL of seawater. For acetlc acld, measurable leveb are hlgher (about 750 nM) because of the hlgher blanks. Lower detectlon llmlts can be achkved uslng a clrculatlon dMuslon method wlth larger volumes of water. Concentratlons of varlous amlnes and organic aclds obtalned urlng thb method are reported for coastal and estuarlne seawater, sedlment pore waters, and a freshwater lake.
Journal of Hazardous Materials, 2007
A very simple and ligand-less cloud point extraction (CPE) methodology for the preconcentration of ultra-trace amounts of silver as a prior step to its determination by electrothermal atomic absorption spectrometry (ETAAS) has been developed. The method is based on the extraction of silver at pH 9 by using non-ionic surfactant polyethyleneglycolmono-p-nonylphenylether (PONPE 7.5) without adding any chelating agent. Several important variables that affect the CPE efficiency and ETAAS signal were investigated and optimized. The preconcentration of 15 ml sample solution allowed us to achieve an enhancement factor of 60. The calibration graph using the preconcentration system was linear in the range of 5-100 ng l −1 with a correlation coefficient of 0.9991. The lower limit of detection (3s) obtained in the optimal conditions was 1.2 ng l −1. The relative standard deviation (R.S.D.) for eight replicate determinations at 30 ng l −1 Ag level was 4.2%. The proposed method was successfully applied to the ultra-trace determination of silver in water samples.
Annali di …, 2007
A simple and accurate spectrophotometric method for determination of trace amounts of silver ion in tap and wastewater solution and photographic solutions has been described. The spectrophotometric determination of silver ion using 2mercaptobenzoxazole (MBO) in the presence of Triton X-100 as nonionic surfactant has been carried out. The Beer's law is obeyed over the concentration range of 0.1-9.0 µg mL-1 of Ag + ion with the detection limits of 1.6 ng mL-1. The influence of type and amount of surfactant, pH, complexation time and amount of ligand on sensitivity of method were optimized. Finally the repeatability, accuracy and the effect of interfering ions on the determination of silver ion were evaluated. There is a good agreement between results of proposed method and atomic absorption spectrometry.
Given the increasing incorporation of silver nanoparticles as an antibacterial additive in washing machines and textiles, sensitive methods for accurate determination of Ag + ions in laundry relevant electrolytes (alkaline carbonate) are required. The most widely reported method, the silver ion selective electrode (ISE), lacked sensitivity and accuracy and was affected by the concentration of Na 2 CO 3 in solution. Differential pulse stripping voltammetry (DPSV) on glassy carbon electrodes (GCE) was therefore investigated as an alternative technique. Surface preparation of the GCE surface was essential and a suitable procedure was developed. A linear response was observed from 0 to 180 mg L -1 with a lower detection limit of 500 ng L -1 (5 nM). DPSV was shown to be significantly more sensitive and accurate in determining the Ag + activity than the silver ISE technique, particularly below 200 nM.