Electrochemical determination of rate constants and product yields for the spontaneous dediazoniation ofp-nitrobenzenediazonium tetrafluoroborate in acidic aqueous solution

2000 ◽  
Vol 32 (7) ◽  
pp. 419-430 ◽  
Author(s):  
Ma Emma Romero-Nieto ◽  
Carlos Bravo-D�az ◽  
Beatriz Malvido-Hermelo ◽  
Elisa Gonz�lez-Romero
Keyword(s):  
Aqueous Solution ◽  
Rate Constants ◽  
Electrochemical Determination ◽  
Acidic Aqueous Solution ◽  
Product Yields

scholarly journals Linear sweep polarographic determination of nucleic acids using acridine orange as a bioprobe

2007 ◽  
Vol 72 (11) ◽  
pp. 1085-1094 ◽  
Author(s):  
Wei Sun ◽  
Na Zhao ◽  
Xianlong Yuan ◽  
Kui Jiao
Keyword(s):  
Aqueous Solution ◽  
Acridine Orange ◽  
Electrochemical Method ◽  
Electrochemical Determination ◽  
Determination Method ◽  
Linear Regression Equation ◽  
Peak Potential ◽  
Linear Sweep ◽  
Buffer Solution

The interaction of acridine orange (AO) with double-stranded (ds) DNA in aqueous solution was investigated by linear sweep polarography (LSP) on a dropping mercury working electrode (DME). In pH 2.5 Britton-Robinson (B-R) buffer solution, AO had a sensitive linear sweep polarographic reductive peak at -0.89 V (vs. SCE), which could be greatly inhibited by the addition of dsDNA, with a positive shift of the peak potential. Based on the decrease of the reductive peak current, a new quantitative electrochemical determination method for dsDNA was developed with a linear range of 2.0?20.0 mg l-1 and the linear regression equation: ?Ip" (nA) = 111.90 C (mg l-1)+125.32 (n = 9, ? = 0.997). The influences of commonly co-existing substances, such as metal ions, amino acid, etc., on the determination were also investigated. The method is sensitive, rapid and simple with good selectivity. The new proposed method was further applied to the detection of RNA and three synthetic samples containing dsDNA with satisfactory results. The binding number and the equilibrium constant between dsDNA and AO were calculated by an electrochemical method.

scholarly journals Changes in the Surface Area of Silica-supported 12-Molybdophosphoric Acid in Relation to the Degree of Loading and the Calcination Temperature

1994 ◽  
Vol 11 (2) ◽  
pp. 83-93 ◽  
Author(s):  
L.B. Khalil ◽  
W.E. Mourad ◽  
B.S. Girgis
Keyword(s):  
Aqueous Solution ◽  
Surface Area ◽  
Silica Gel ◽  
Heteropoly Acid ◽  
Surface Acidity ◽  
Molybdophosphoric Acid ◽  
Surface Species ◽  
Considerable Decrease ◽  
Acidic Aqueous Solution

A technical silica gel (Grace-113) was impregnated with 12-molybdophosphoric solution to attain loadings of 0.72–13.4 wt.%. The air-dried solids were then calcined for 3 h at 400, 600 and 800°C, respectively, followed by determination of their N2 adsorption isotherms. The silica gel was thermally stable and suffered about 15% loss in area at 800°C. The impregnated silicas showed considerable decrease in surface area as a function of their heteropoly acid content. Two processes are suggested as taking part in the modification of pore structure: (1) diffusion of the aqueous heteropoly acid solution and its subsequent deposition; and (2) dissolution of silica gel in the acidic aqueous solution followed by interaction with HPMo to form either molybdosilicate or P–Si exchange products. Correlation with the previously studied catalytic conversion of isopropanol indicated that the activity was independent of the surface area. Catalytic dehydration on the 600°C and 800°C products seems to be associated with silicate, molybdate or MoO3 surface species rather than being due to surface acidity or the extent of the surface area.

Electrochemical Determination of Neomycin and Norfloxacin at a Novel Polymer Nanocomposite Electrode in Aqueous Solution

2017 ◽  
Vol 50 (12) ◽  
pp. 1887-1896 ◽  
Author(s):  
Siyabulela Hamnca ◽  
Lisebo Phelane ◽  
Emmanuel Iwuoha ◽  
Priscilla Baker
Keyword(s):  
Aqueous Solution ◽  
Polymer Nanocomposite ◽  
Electrochemical Determination

Free-radical reductions of arenediazonium ions in aqueous solution. V. Pulse-radiolytic determination of rate constants for some para-substitutedbenzenediazonium ions

1981 ◽  
Vol 34 (7) ◽  
pp. 1433 ◽  
Author(s):  
JE Packer ◽  
J Monig ◽  
BC Dobson
Keyword(s):  
Aqueous Solution ◽  
Free Radical ◽  
Rate Constants ◽  
Substituent Effect ◽  
Reduction Potential ◽  
Radical Anions ◽  
Semiquinone Radical ◽  
Substituent Group

Some rate constants for the reduction of para-substituted benzenediazonium ions by the radicals eaq-, ·CH2OH, (CH3)2·COH and some semiquinone radical anions have been measured. The substituent group has no effect on the rates with eaq-, but as the reduction potential of the reducing radical becomes more positive, the substituent effect increases, electron-withdrawing groups enhancing the rates. No free halide is formed on reduction of p-BrC6H4N2+ or p-IC6H4N2+ by eaq- or ·CH2OH.

Determination of Rate Constants for Ozonation of Ofloxacin in Aqueous Solution

2013 ◽  
Vol 35 (3) ◽  
pp. 186-195 ◽  
Author(s):  
Gracia Márquez ◽  
Eva M. Rodríguez ◽  
Fernando J. Beltrán ◽  
Pedro M. Álvarez
Keyword(s):  
Aqueous Solution ◽  
Rate Constants

Spectrophotometric Determination of Cyclamate in Foods: NMKL Collaborative Study

1987 ◽  
Vol 70 (3) ◽  
pp. 588-590
Author(s):  
Anna-Maija K Sjoberg ◽  
Timo A Alanko
Keyword(s):  
Aqueous Solution ◽  
Ethyl Acetate ◽  
Spectrophotometric Determination ◽  
Spectrophotometric Method ◽  
Collaborative Study ◽  
Soft Drinks ◽  
Uv Absorption ◽  
Acidic Aqueous Solution ◽  
Coefficients Of Variation

Abstract A spectrophotometric method for the determination of cyclamate was collaboratively studied in 9 laboratories. Ethyl acetate is added to extract cyclamate from acidic aqueous solution into water, and the cyclamate is then quantitatively converted to /V,./V-dichlorocyclohexylamine by adding excess hypochlorite. A',A'-Dichlorocyclohexylamine is determined by measuring its UV absorption at 314 nm. Six samples, 3 soft drinks with cyclamate levels of 0.36-0.47 g/kg and 3 jams with levels of 1.23-1.50 g/kg, were included in the study. Average recoveries of cyclamate were 99.7% in the soft drinks and 103.8% in the jams. Reproducibility coefficients of variation were 6.7% for the soft drinks and 4.4% for the jams.

scholarly journals Spectrofluorometric Determination of Citalopram in Pharmaceutical Preparations and Spiked Human Plasma Using Organized Media

2006 ◽  
Vol 89 (5) ◽  
pp. 1288-1295 ◽  
Author(s):  
Dina T El-Sherbiny
Keyword(s):  
Aqueous Solution ◽  
Human Plasma ◽  
Fluorescence Intensity ◽  
Pharmaceutical Preparations ◽  
Citrate Buffer ◽  
Acidic Aqueous Solution ◽  
Sds Micelles ◽  
Spectrofluorometric Determination ◽  
Organized Media

Abstract The native fluorescence of citalopram (CIT) was (obtained in citrate buffer of pH 6.5 with and without β-cyclodextrin (β-CD) or sodium dodecyl sulfate (SDS) as fluorescence enhancers at 305 nm using 242 nm for excitation. Micellar systems of ionic and nonionic surfactants were investigated by measuring the fluorescence intensity of the analyte-surfactant system. In slightly acidic aqueous solution of pH 6.5, CIT was better incorporated in CDs and SDS micelles. The luminescence emission from CIT was found to be greatly enhanced by SDS micelles. The fluorescence intensity enhancements in CDs medium and in SDS as ionic surfactant relative to slightly acidic aqueous solution were 125 and 250%, respectively. Organized media-enhanced spectroflourometric methods were developed for the determination of CIT, in pure form as well as in pharmaceutical preparations. The fluorescence intensity-concentration plots were rectilinear over the ranges 0.06 to 0.64, 0.04 to 0.40, and 0.02 to 0.26 μg/mL with lower detection limits of 0.02, 0.01, and 0.007 μg/mL, either in citrate buffer only or in β-CD and SDS as organized media, respectively. Furthermore, the high sensitivity attained by using SDS as organized medium allowed in vitro spectrofluorometric determination of CIT in spiked human plasma. Interference from endogenous amino acids has been overcome by using the solid-phase extraction technique; the mean recovery (n = 5) was 100.1 ± 0.8%

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