Fluorimetric determination of Ascorbic Acid in Vitamin C tablets using methylene blue

WOS: 000232679900007PubMed ID: 16204979In this study, a simple and sensitive fluorimetric method was described for the determination of Ascorbic Acid (AA). The procedure is based on the reaction between AA and Methylene Blue (MB). The fluorescence intensity of NIB was measured at excitation and emission of 664 and 682 nm, respectively. MB concentration was decreased as a function of decreasing fluorescence intensity due to forming colorless form of MB (Leuco-MB) in the reaction between AA and NIB. A linear relationship was obtained between the decreasing fluorescence intensity and the concentration of AA in the range of 3.0x10(-7)-6.0x10(-6) mol(.)l(-1). The detection limit was 2.5x10(-7) mol(.)l(-1). The proposed method was applied successfully for the determination of AA in Vitamin C tablets

AAS determination of cadmium in fruits and soils

WOS: 000175739900004The Cd concentration in fruit samples was determined by using slotted tube atom trap (STAT)enrichment-flame atomic absorption spectrometry (FAAS) and graphite furnace atomic absorption spectrometry (GF-AAS). To identify the Cd phases most responsible for fruit-available Cd, the soil samples near the fruit plants were also analyzed for Cd by using various digestion and selective extraction reagents. The relation between the fruit-Cd levels and the Cd concentrations in the soil extracts was studied. Total Cd concentrations found in the soils was in the range from 60 to 420 mug kg(-1); none of them exceeded 0.5 mg kg(-1) which is the limit level set for anthropogenic impact. It was observed that the Cd concentrations of the cherry, strawberry, apple, and grape samples correlates to the Cd concentrations of the HNO3-H2O2 digestion of soil, Organically bound Cd in soils was found to be less than in carbonate-bound Cd. While the Cd concentration of the EDTA extracts in some soil samples was 94% of total Cd, it was found to be only 35% in other soils. To assess the accuracy of the total procedure, the results of STAT-enrichment-FAAS and GF-AAS were compared and acceptable agreement was found. The detection limit, defined as three times the standard deviation of the blank, was 0.03 mug L-1

Manganese contents in fruits and soils in Elazig-Turkey region

WOS: 000222393600005Manganese concentrations in fruit samples were determined by using flame atomic absorption spectrometry (FAAS). To identify the Mn phases most responsible for fruit-available Mn, the soil samples near the fruit plants were also analyzed for Mn by using various digestion and selective extraction reagents. The relation between the fruit-Mn levels and the Mn concentrations in soil extracts was studied. Total Mn concentrations determined in the studied soils and fruits were found in the range of 330 to 1100 and 1.6 to 22 mg/kg, respectively. The negative interferences were observed from Ca, Mg and Al at the higher concentrations than the their concentrations at the measurement step. It was observed that the Mn concentrations of mulberry samples correlate to the manganese concentrations of the cold citric acid extracts of soils

Flow injection amperometric determination of ascorbic acid using a photoelectrochemical reaction after immobilization of methylene blue on muscovite

40th National Chemistry Congress -- SEP 04-07, 2001 -- ISTANBUL, TURKEYWOS: 000182782800004The photoelectrochemical determination of ascorbic acid (AA) was studied based on the photochemical reduction of methylene blue (MB) in 0.1 M phosphate buffer (pH 7.0). MB was used as a redox mediator for the modification of a carbon paste electrode (CPE) due to its facile reducible-oxidizible behaviour. Muscovite, which has a layered structure, was found to be a good and stable supporting material for the immobilization of MB by an ion exchange reaction. The dye is strongly retained and not easily leached from the matrix. MB was reduced to nearly quasi-reversible at the modified carbon paste electrode (MCPE). The oxidation peak potential of leuco-methylene blue (LMB) shifted from -100 mV to 50 mV in the presence of AA. For photo electrochemical amperometric studies, the operational potential was kept constant at +50 mV according to the oxidation of LMB, which was produced from the chemical reaction between AA and MB on the modified electrode surface. A laboratory-built flow cell system was constructed for the direct irradiation of the electrode surface with a 500-W halogen lamp. The optimum conditions for the flow injection (FI) amperometric determination of AA were 1.5 mL/min flow rate, 50 muL sample loop and 50 cm transmission tubing length and at a frequency of 60 samples per hour. AA could be determined in the concentration range 1.0x10(-6)-1.0x10(-4) M by using a photoelectrochemical FT method. The detection limit of this method was 1.0x10(-8) M. The relative standard deviation of five replicate injections of 6.0x10(-5) M AA was 2.0% in photoelectrochemical FI. The results obtained by the proposed procedure are in good agreement with those established using the triiodide procedure for the AA determination of pharmaceutical products

Photoelectrochemical investigation of methylene blue immobilised on zirconium phosphate modified carbon paste electrode in flow injection system

The adsorption of methylene blue (MB) onto zirconium phosphate (ZrP) was studied and the adsorption capacity value and isotherms were determined. The adsorption capacity of ZrP was increased after being exposed to gas phase n-butyl amine. The adsorbed MB on ZrP was used as a modifier material in carbon paste electrode (MCPE), which in turn was used in voltammetric investigations and flow injection (FI) amperometric determination of ascorbic acid (AA). A quasi-reversible electrode reaction of adsorbed MB was exhibited. A home made flow-through electrochemical cell with a suitable transparent window for irradiation of the electrode surface was constructed and used for amperometric FI studies. The photoamperometric-FI conditions were optimised as 1.5 mL min(-1) flow rate, a 25 cm transmission tubing length, a 100 mu L injection volume, and a constant applied potential of +100 mV versus SCE. The calibration curve for AA was linear over the concentration range from 1.0 x 10(-6) to 4.0 x 10(-5) M. The relative standard deviation of four replicate injections of 3.0 x 10(-5) M AA was 1.2 %. The results obtained for AA determination in pharmaceutical products are in good agreement with those obtained using the procedure involving the reaction between triiodide and AA. (c) 2005 Elsevier B.V. All rights reserved

Photophysical properties and electrochemistry of the N,N '-bis-n-butyl derivative of naphthalene diimide

WOS: 000224772700003The spectral-luminescent properties and electrochemistry of the N,N'-bis-n-butyl derivative of naphthalene diimide were studied. The main photophysical parameters (quantum yield, rate constants of fluorescence and of non-radiative deactivation and fluorescence lifetime) were determined. The LUMO value (-3.51 eV) was determined by cyclic voltammetry. The N,N'-bis-n-butyl derivative of naphthalene diimide (BBND) shows 2 reversible reduction steps (-1.19 V and -1.75 V vs. Ferrocene) in chloroform. Quenching the fluorescence emissions of aromatic donor molecules in acetonitrile revealed the electron acceptor ability of the studied naphthalene diimide derivative. It has been found that, in contrast to perylene diimide derivatives, which form 7-electron donoracceptor complexes with aromatic donor molecules of naphthalene, phenanthrene, pyrene and perylene, BBND does not form pi-electron-clonor acceptor complexes with aromatic donor molecules

Photophysical properties and electrochemistry of the N,N '-bis-n-butyl derivative of naphthalene diimide

The spectral-luminescent properties and electrochemistry of the N,N'-bis-n-butyl derivative of naphthalene diimide were studied. The main photophysical parameters (quantum yield, rate constants of fluorescence and of non-radiative deactivation and fluorescence lifetime) were determined