scholarly journals Voltammetric Study of the Copper Pentacyanonitrosylferrate Adsorbed on the Silica Modified with a Poly(propylene)imine Hexadecylamine Dendrimer for Determination of Nitrite

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
D. R. do Carmo ◽  
S. Gabriel ◽  
D. R. Silvestrini ◽  
U. O. Bicalho ◽  
L. R. Cumba
Keyword(s):  
Silica Gel ◽  
Cyclic Voltammogram ◽  
X Ray ◽  
Redox Couples ◽  
Voltammetric Study ◽  
Graphite Paste Electrode ◽  
Modified Surface ◽  
Poly Propylene ◽  
Paste Electrode

Poly(propylene)imine hexadecylamine dendrimer (DAB-Am-16) was anchored on the surface of 3-chloropropylsilyl silica gel and subsequently interacted with copper nitroprusside. The composite was characterized by infrared (FTIR), energy dispersive X-ray (EDX), and cyclic voltammetry. The above techniques confirmed the successful anchoring of the dendrimer on the silica gel modified surface and its interaction with copper nitroprusside. The cyclic voltammogram of CuNPSD was found to exhibit two redox couples with (Eθ′)1= 0.30 V and (Eθ′)2= 0.78 V versus Ag/AgCl ( mol L−1;  mV s−1) attributed to the redox processes and , respectively. The CuNPSD-modified graphite paste electrode was found to show a linear response of to  mol L−1for nitrite determination with a detection limit (DL) of  mol L−1and an amperometric sensitivity of 25.0 mA/mol L−1. The CuNPSD-modified graphite paste electrode was found to show a good electrochemical stability and an excellent response to the electrocatalytic oxidation of sodium nitrite.

scholarly journals Direct Preparation and Characterization of Copper Pentacyanonitrosylferrate Nanoparticles

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
D. R. Do Carmo ◽  
M. M. Souza ◽  
U. O. Bicalho ◽  
V. S. Dos Santos ◽  
J. P. Souza ◽  
...  
Keyword(s):  
Charge Transfer Band ◽  
Cyclic Voltammogram ◽  
X Ray Diffraction ◽  
X Ray ◽  
Peak Broadening ◽  
Vis Spectroscopy ◽  
Intervalence Charge Transfer ◽  
Direct Preparation ◽  
Graphite Paste Electrode ◽  
Paste Electrode

The present work describes the preparation of nanoparticles of copper pentacyanonitrosyl complexes starting from the compound sodium nitroprusside. Copper pentacyanonitrosylferrate (NCuNP) nanoparticles were successfully synthesized by using deionized water and formamide as solvent. The material was characterized by Fourier-transforming infrared spectroscopy (FT-IR), X-ray diffraction (XRD), ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and cyclic voltammetry (CV). The results revealed that the electronic spectra of NCuNP exhibited a broad intervalence charge transfer band at 685 nm. An XRD peak broadening pattern of the NCuNP was verified, indicating a particle decrease when formamide is used. The particle size of NCuNP is estimated to be 80 nm. The cyclic voltammogram of the modified graphite paste electrode with NCuNP showed two redox pairs with formal potentialsEθ′=0.36 V andEθ′=0.78 V (ν=20 mV s−1; KCl 1.0 M), attributed to the redox processCuI/CuIIand [FeII(CN)5NO]/[FeIII(CN)5NO], respectively. The graphite paste electrode with NCuNP presents electrocatalytic response for Sulfite determination.

scholarly journals A Silsesquioxane Organically Modified with 4-Amino-5-(4-pyridyl)-4H-1,2,4-triazole-3-thiol: Thermal Behavior and Its Electrochemical Detection of Sulfhydryl Compounds

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
D. R. Do Carmo ◽  
D. R. Silvestrini ◽  
H. S. Barud ◽  
N. L. Dias Filho ◽  
U. O. Bicalho ◽  
...  
Keyword(s):  
Nitrogen Atmosphere ◽  
Redox Couple ◽  
Cyclic Voltammogram ◽  
Linear Region ◽  
Formal Potential ◽  
Organically Modified ◽  
Graphite Paste Electrode ◽  
Sulfhydryl Compounds ◽  
Paste Electrode

The octakis(3-chloropropyl)silsesquioxane (SS) was organofunctionalized with 4-amino-5-4(pyridyl)-4H-1,2,4-triazole-3-thiol. The product formed (SA) was undergo another reactions in two steps, first with copper and so hexacyanoferrate (III) to form CuHSA. The organofunctionalized silsesquioxane was characterized by the following techniques: scanning electron microscopy (SEM), Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) in solid state, and thermogravimetric analysis in air and nitrogen atmosphere. The composite CuHSA was incorporated into a graphite paste electrode and the electrochemical behavior studies were conducted with cyclic voltammetry. The cyclic voltammogram of the modified graphite paste electrode with CuHSA showed one redox couple with formal potentialEθ′=0.75 V versus Ag/AgCl(sat)(KCl 1.0 mol L−1;v= 20 mV s−1) attributed to the redox process Fe(II)(CN)6/Fe(III)(CN)6of the binuclear complex formed. The redox couple presents an electrocatalytic response of sulfhydryl compounds such as n-acetylcysteine and l-cysteine. For determination of n-acetylcysteine and l-cysteine the modified graphite paste electrode showed a linear region in the concentration range of 2 to 20 mmol L−1. The modified electrode was chemically and electrochemically stable and showed good reproducibility.

Determination of Uranium in Carbonate Solutions by Extraction onto a Chemically Modified Surface

1977 ◽  
Vol 21 ◽  
pp. 59-69
Author(s):  
Bruce B. Jablonski ◽  
Donald E. Leyden
Keyword(s):  
Lower Limit ◽  
Silica Gel ◽  
Limit Of Detection ◽  
X Ray ◽  
Chemically Modified ◽  
Carbonate Concentration ◽  
Carbonate Solutions ◽  
Modified Surface ◽  
Materials Used

Silica gel treated with a commercial silylation reagent (Dow-Corning Z-6020) has been found to extract uranium from carbonate solutions. The materials used are simple to prepare and once the uranium is extracted, x-ray fluorescence may be employed to determine the uranium directly on the solid. A dependence of the extraction upon carbonate concentration is observed. A lower limit of detection of 2.46 μg of 0.12 ppm uranium from a 20 ml sample is obtained.

scholarly journals Preparative-scale HPLC Resolution of Metallacyclic η3-Allyltricarbonyliron Complexes and Determination of the Absolute Configuration by X-Ray Crystal Structure Analysis

1999 ◽  
Vol 23 (9) ◽  
pp. 578-579
Author(s):  
Rainer Schobert ◽  
Hermann Pfab ◽  
Jutta Böhmer ◽  
Frank Hampel ◽  
Andreas Werner
Keyword(s):  
Crystal Structure ◽  
Silica Gel ◽  
Structure Analysis ◽  
Absolute Configuration ◽  
Crystal Structure Analysis ◽  
Preparative Scale ◽  
X Ray ◽  
The Absolute

Racemates of (η3-allyl)tricarbonyliron lactone complex Fe(CO)3{η1:η3-C(O)XCH2CHCMeCH2} 1a (X = O) and (η3-allyl)tricarbonyliron lactam complex 2a (X = NMe) are resolved on a preparative scale by HPLC on cellulose tris(3,5-dimethylphenyl)carbamate/silica gel RP-8 and the absolute configuration of (-)-2a is determined by X-ray crystal structure analysis.

Electrochemical Determination of Brilliant Blue and Tartrazine Based on an Ionic Liquid-Modified Expanded Graphite Paste Electrode

2015 ◽  
Vol 98 (3) ◽  
pp. 817-821 ◽  
Author(s):  
Wenchang Wang ◽  
Ye Chen ◽  
Jing Zhang ◽  
Xue Wang ◽  
Zhidong Chen
Keyword(s):  
Ionic Liquid ◽  
Simultaneous Determination ◽  
Soft Drink ◽  
Expanded Graphite ◽  
Brilliant Blue ◽  
Experimental Conditions ◽  
Graphite Composite ◽  
Graphite Paste Electrode ◽  
Paste Electrode

Abstract A sensitive electrochemical method was developed for the simultaneous determination of Brilliant Blue (BB) and tartrazine (Tz) using an ionic liquid-modified expanded graphite paste electrode (IL-EGPE). The IL-EGPE was prepared by mixing ionic liquid-expanded graphite composite (IL-EG) with solid paraffin. Compared with the EGPE, the IL-EGPE remarkably enhanced the electrocatalytic oxidation signals of BB and Tz. Under optimal experimental conditions, the designed IL-EGPE exhibited wide linear responses to BB and Tz ranging from 5.0 × 10–9 to 4.0 × 10–6 M and 1.0 × 10–8 to 1.0 × 10–6 M, respectively. The detection limits for BB and Tz were 2.0 × 10–9 M (1.6 ng/mL) and 3.3 × 10–9 M (1.8 ng/mL) at an S/N of 3, respectively. This electrode showed good reproducibility, stability, and reusability. The proposed method was successfully applied in the simultaneous determination of BB and Tz in a soft drink with satisfactory results.

scholarly journals A Sensitive and Low-cost Analytical Method for the Electrochemical Determination of Quercetin, Based on 1-Ethylpyridinium Bromide/Carbon Paste Composite Electrode

2015 ◽  
Vol 7 (2) ◽  
pp. 27 ◽  
Author(s):  
Francis Tchieno ◽  
Ignas Tonle ◽  
Evangeline Njanja ◽  
Emmanuel Ngameni
Keyword(s):  
Carbon Paste Electrode ◽  
Analytical Method ◽  
Composite Electrode ◽  
Low Cost ◽  
Reduction Peak ◽  
Cyclic Voltammogram ◽  
Current Response ◽  
Carbon Paste ◽  
Paste Electrode

We report a simple, sensitive and low-cost electrochemical procedure for the quantification of quercetin (QCT), a flavonoid and an antioxidant, based on 1-ethylpyridinium bromide modified carbon paste electrode. A 1-ethylpyridinium bromide/carbon paste composite electrode was used. The cyclic voltammogram of QCT showed two oxidation peaks at +0.575 V (vs Ag/AgCl/3M KCl) and +0.865 V (vs Ag/AgCl/3M KCl), and a reduction peak at +0.371 V (vs Ag/AgCl/3M KCl) in HCl/KCl solution at pH 1. Differential pulse voltammetry (DPV) analysis in HCl/KCl at pH 1 showed three well-defined oxidation peaks while a single peak was recorded in phosphate buffer at pH 3. The peak currents of QCT significantly increased at the 1-ethylpyridinium bromide modified electrode in comparison with those recorded at the bare carbon paste electrode. This allowed the use of adsorptive stripping voltammetry to develop a simple and sensitive electroanalytical method for the determination of QCT. Key experimental parameters such as pH of the supporting electrolyte, the preconcentration time, the electrolysis potential, electrode composition, QCT concentration and interferents were investigated. The current response was found to be directly proportional to the concentration of QCT in the range from 2.48 x 10-7 M to 7.43 x 10-6 M, leading to a detection limit of 4.48 x 10-8 M. The developed analytical method was successfully applied to the determination of QCT in human urine samples.

Electrochemical Sensing of Bisphenol A by a Didodecyldimethylammonium Bromide-Modified Expanded Graphite Paste Electrode

2016 ◽  
Vol 99 (4) ◽  
pp. 1066-1072 ◽  
Author(s):  
Jing Zhang ◽  
Sa Ma ◽  
Wenchang Wang ◽  
Zhidong Chen
Keyword(s):  
Aqueous Solution ◽  
Bisphenol A ◽  
Linear Response ◽  
Expanded Graphite ◽  
Electrochemical Sensing ◽  
Good Reproducibility ◽  
Didodecyldimethylammonium Bromide ◽  
Graphite Paste Electrode ◽  
Paste Electrode

Abstract An electrochemical and sensitive sensing of 2,2-bis(4-hydroxyphenyl) propane [bisphenol A (BPA)] was developed based on a didodecyldimethylammonium bromide-modified expanded graphite paste electrode (DDAB-EGPE). The DDAB-EGPE was prepared by suspending an EGPE in a DDAB aqueous solution, and allowing the DDAB to form a hydrophobic film on the expanded graphite surface. Compared with the EGPE, the DDAB-EGPE showed improved electrochemical response of BPA because of the preconcentration of BPA in DDAB via hydrophobic interaction. Due to the electrocatalytic activity of BPA, a sensor for BPA was constructed based on the DDAB-EGPE. The DDAB-EGPE exhibited a wide linear response to BPA ranging from 6.0 × 10−8 to 2.0 × 10−5 mol/L with a detection limit of 7.1 nmol/L at S/N = 3. The designed sensor showed good reproducibility and stability. The proposed sensor was successfully applied to the determination of BPA in three types of real plastic product samples. This sensor presented a simple, rapid, and sensitive platform for the determination of BPA and could become a versatile and powerful tool for food safety.

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