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1.
A facile, rapid and ultra‐sensitive method for the determination of vitamin B12 (cyanocobalamin) at the sub‐nanomolar concentration range by using low‐cost, disposable graphite screen‐printed electrodes is described. The method is based on the cathodic preconcentration of square planar vitamin B12s, as occurred due to the electro reduction of Co(III) center in vitamin B12a to Co(I), at ?1.3 V versus Ag/AgCl/3 M KCl for 40 s. Then, an anodic square wave scan was applied and the height of the peak appeared at ca. ?0.73 V versus Ag/AgCl/3 M KCl, due to the oxidation of Co(I) to Co(II) in the adsorbed molecule, was related to the concentration of the vitamin B12 in the sample. EDTA was found to serve as a key‐component of the electrolyte by eliminating the background signal caused by metal cations impurities contained in the electrolyte (0.1 M phosphate buffer in 0.1 M KCl, pH 3). It also blocks trace metals contained in real samples, thus eliminating their interference effect. The method was optimized to various working parameters and under the selected conditions the calibration curve was linear over the range 1×10?10–8×10?9 mol L?1 vitamin B12 (R2=0.994), while the limit of detection for a signal‐to‐noise ratio of 3 (7×10?11 mol L?1 vitamin B12) is the lowest value of any reported in the literature for the electrochemical determination of vitamin B12. The sensors were successfully applied to the determination of vitamin B12 in pharmaceutical products.  相似文献   

2.
Estimation of vitamin B12 in blood is very important to determine in decifiency and diagnosis of anemic patients. Vitamin B12 in blood can be estimated by spectrochemical, enzymatic, radioisotopic and microbiological methods. In the present study vitamin B12 was determined in 48 normal subjects of Rawalpindi/Islamabad by radiometric microbiological assay (RMA) technique using a very rapid, sensitive and automated instrument Bactec 460. In this procedure14C-glucose media and microorganismsLactobacillus leichmannii were used. The sensitivity of the method for vitamin B12 is 1 pg/ml and the vitamin B12 found in normal subjects was in the range of 105–535 pg/ml with a median value of 246±6 pg/ml.  相似文献   

3.
The cyclic voltammetric response of electrodes modified with catalytically reactive blocks is simulated using finite difference methods. The responses of three different models using various block geometries are studied. The results are used to determine kinetic parameters of coupled liquid|liquid interfacial reactions. First, we examine the liquid–liquid reaction between aqueous vitamin B12S and pure trans-dibromocyclohexane (DBCH) microdroplets immobilized on a basal plane pyrolytic graphite (bppg) surface, immersed in an aqueous solution of vitamin B12. Second, cyclic voltammetry on electrodes modified with microdroplets of DBCH diluted in dodecane is employed to determine the apparent bimolecular interfacial rate constant for the initial step in the DBCH(oil)/B12S(aq) reaction. The results are compared with a previous SECM/ITIES study of a similar reaction.  相似文献   

4.
Vitamin B1‐selective electrodes with PVC membrane were developed that contain ion associates of vitamin B1 with an inorganic anion, BiI4?, and an organic anion, brilliant yellow, as electrode‐active substances. The linearity ranges of the electrode function are 1.0×10?5–1.0×10?2 and 1.0×10?4–1.0×10?2 M, the electrode function slopes are 33.0±1.0 and 33.1±1.1 mV decade?1, the detection limits are 5.5×10?6 and 8.3×10?5 M for BiI4? and brilliant yellow respectively. The working range of pH is 5–12. The efficiency of the use of electrodes for the vitamin B1 content control in multivitamin pharmaceutical preparations was shown by direct potentiometry and potentiometric titration methods.  相似文献   

5.
A method to determine vitamin B12 by measuring the chemiluminescence (CL) intensities using a flow injection (FI) system has been proposed. It is based on the catalytic effect of cobalt(II) in vitamin B12 on the CL reaction between luminol and hydrogen peroxide in a basic medium. The increment of the CL intensity is proportional to the concentration of vitamin B12 in the range 8.68–86.9 ng/mL (r 2 = 0.9984) with a detection limit (3σ) of 0.89 ng/mL. The CL response is obtained in 10 s at a flow rate of 3.0 mL/min with a relative standard deviation (RSD) of less than 2.5% (n = 6). The method has been successfully applied to the determination of vitamin B12 in pharmaceutical injections. The text was submitted by the authors in English.  相似文献   

6.
In this article, we describe a dipstick based immunochemiluminescence (immuno-CL) biosensor for the detection of vitamin B12 in energy drinks. The method is a direct competitive type format involving the immobilization of vitamin B12 antibody on nitrocellulose membrane (NC) followed by treatment with vitamin B12 and vitamin B12–alkaline phosphatase conjugate to facilitate the competitive binding. The dipstick was further treated with substrate disodium 2-chloro-5-(4-methoxyspiro {1,2-dioxetane-3,2¢-(5¢-chloro)tricyclo[3.3.1.13,7]decan}-4-yl)-1-phenyl phosphate (CDP-Star) to generate chemiluminescence (CL). The number of photons generated was inversely proportional to the vitamin B12 concentration. After systematic optimization, the limit of detection was 1 ng mL−1. The coefficient of variation was below 0.2% for both intra- and inter-assay precision. Vitamin B12 was extracted from energy drinks with recovery ranged from 90 to 99.4%. Two different energy drinks samples were analyzed, and a good correlation was observed when the data were compared with a reference enzyme linked immuno sorbent assay (ELISA) method. The developed method is suitable for an accurate, sensitive, and high-throughput screening of vitamin B12 in energy drinks samples. The dipstick technique based on immuno-CL is suitable for the detection of several analyte in food and environmental samples.  相似文献   

7.
A rapid and simple preconcentration step applying packed-fiber solid-phase extraction columns has been investigated to vitamin B_(12).The extraction performance of the new method was investigated preliminarily on vitamin functional drink.The analysis used a reversed-phase C_(18) column,with a photo-diode array detector at 220 nm.The samples were preconcentrated with packed-fiber solid-phase extraction columns.Good linearity was observed in vitamin functional drink.The repeatability of extraction performa...  相似文献   

8.
The Interaction between vitamin B12 (VB12) and fish sperm DNA was investigated in physiological buffer (pH 7.4) using the methylene blue (MB) dye as a spectral probe by spetcrophotometery, viscosity measurements and cyclic voltammetry. The apparent binding constant of vitamin B12 with DNA was found to be 3.2×105 mol−1·L. The voltammetric behavior of vitamin B12 has been investigated at glassy carbon electrode using cyclic voltammetry. Thermodynamic parameters including ΔH0, ΔS0 and ΔG0 for the interaction between VB12 and DNA have determined as −2.3×104, 27.54 and −3.1×104J·mol−1·K−1 respectively. One indication of DNA binding mode with VB12 was the change in viscosity when a small molecule associates with DNA. The diffusion coefficients of VB12 in the absence (D0)f and presence of DNA (D0)b was calculated as 5.04×10−6 and 1.13×10−6 cm2·s−1 respectively. The results indicated that vitamin B12 can bind to DNA and the major binding mode was intercalative binding.  相似文献   

9.
Cyanocobalamin (B12) is a photosensitive vitamin, and its photodegradation to hydroxocobalamin (B12b) in liposomes has been investigated. The values of apparent first-order rate constants (kobs) for the photodegradation of B12 in liposomes (nine preparations) are in the range of (0.52-2.24) × 10–3 min–1, compared to 3.21 × 10–3 min–1 for B12 in aqueous solution (pH 5.0). The entrapment efficiency of B12 in liposomes is 26.4-38.8%. The values of kobs show a linear relation with phosphatidylcholine (PC) content in liposomes, indicating the influence of PC in inhibiting the rate of photolysis of B12. The value of the bimolecular rate constant for photochemical interaction of B12 and PC is 0.32 M–1 min–1, indicating the stabilizing effect of PC on the photolysis of B12. The ratio of B12 stabilization in liposomal preparations is in the range 2-6 compared to that of the unentrapped vitamin The stabilization of B12 is mediated by a photoinduced charge-transfer B12-PC complex that leads to the reduction of B12 to B12r, which is then oxidized to B12b that has low susceptibility to photolysis. The extent of stabilization of B12 probably depends on the degree of interaction between the two compounds under the reaction conditions, indicated by the loss of B12 fluorescence.  相似文献   

10.
We studied biogas fermentation from alcohol waste fluid to evaluate the anaerobic digestion process and the production of vitamin B12 as a byproduct. Anaerobic digestion using acclimated methanogens was performed using the continuously stirred tank reactor (CSTR) and fixed-bed reactor packed with rock wool as carrier material at 55°C. We also studied the effects of metal ions added to the culture broth on methane and vitamin B12 formation. Vitamin B12 production was 2.92 mg/L in the broth of the fixed-bed reactor, twice that of the CSTR. The optimum concentrations of trace metal ions added to the culture liquid for methane and vitamin B12 production were 1.0 and 8 mL/L for the CSTR and fixed-bed reactor, respectively. Furthermore, an effective method for extracting and purifying vitamin B12 from digested fluid was developed.  相似文献   

11.
Metallopolyion films of cobalt corrin vitamin B12 hexacarboxylate and poly(l-lysine) [B12(COOH)6–PLL] covalently attached to carbon electrodes were used to cyclize n-bromoalkyl-2-cyclohexenones in microemulsions with good catalytic efficiency. Trans-1-decalone was obtained in up to 60% yields at reasonable current efficiency. Turnover rates were 30–85 fold greater for films compared to dissolved catalyst. There was no dependence of turnover rate on microemulsion composition, suggesting that cleavage of the alkyl-cobalt bond in the alkyl-CoIII intermediate is rate determining. 5-Endo-trig cyclization giving 4-hyndrindanone is disfavored by Baldwin's rules, but B12(COOH)6–PLL films in microemulsions still gave 24% yields at relatively high turnover numbers. It is possible that proton donors at film reaction sites protonate a carbanion intermediate to give competitive product 2-propyl-2-cyclohexen-1-one to decrease the yield of 4-hyndrindanone.  相似文献   

12.
A rapid and sensitive ultra-performance liquid chromatography–tandem mass spectrometry method with electrospray ionization (UPLC–ESI–MS/MS) for analysis of B-group vitamins in honey has been presented. Aim of this study is the characterization of different types of Turkish honeys according to B-group vitamins. Vitamins were determined in 17 different types of Turkish honey samples by UPLC–ESI–MS/MS. Heather honey samples were distinguished among the studied honeys with the richest vitamin content with 286.10?mg/kg, and it is followed by sunflower honey and thyme honey with the total vitamin contents of 206.01 and 163.27?mg/kg, respectively. The presence of vitamin B1 (thiamine), vitamin B2 (riboflavin), vitamin B3 (nicotinamide, B3N and nicotinic acid, B3H), vitamin B6 (pyridoxine), and vitamin B9 (folic acid) was detected in all the honey samples analyzed. Moreover, vitamin B5 (pantothenic acid) was observed in most of them. Vitamin B12 (cyanocobalamin) and vitamin B7 (biotine) were not detected in the studied honey samples. Turkish honey samples showed efficacious vitamin content for the consumers.  相似文献   

13.
The preparation and study of electrochemical properties of a graphite screen-printed electrode (SPE) modified with the GO/Fe3O4@SiO2 (GO is graphene oxide) nanocomposites are described. The morphologies of the GO/Fe3O4@SiO2 nanocomposites were examined by scanning electron microscopy. The electrochemical oxidation of vitamin B6 (pyridoxine) on SPE modified with the GO/Fe3O4@SiO2 nanocomposite was investigated by cyclic voltammetry, differential pulse voltammetry, and chronoamperometry. Under optimum conditions (pH 7.0), the vitamin B6 oxidation at the surface of the modified SPE occurs at a potential about 190 mV less positive than that at the unmodified SPE. A linear voltammetric response for vitamin B6 was obtained in the concentration range 1.0?10 6—9.0?10 4 mol L–1 with a detection limit of 5.2?10 7 mol L–1 using differential pulse voltammetry. The developed sensor was also successfully applied for determination of trace level of vitamin B6 in both the standard vitamin B6 sample and biological samples (urine).  相似文献   

14.
Replacing the central cobalt ion of vitamin B12 by other metals has been a long‐held aspiration within the B12‐field. Herein, we describe the synthesis from hydrogenobyric acid of zincobyric acid ( Znby ) and zincobalamin ( Znbl ), the Zn‐analogues of the natural cobalt‐corrins cobyric acid and vitamin B12, respectively. The solution structures of Znby and Znbl were studied by NMR‐spectroscopy. Single crystals of Znby were produced, providing the first X‐ray crystallographic structure of a zinc corrin. The structures of Znby and of computationally generated Znbl were found to resemble the corresponding CoII‐corrins, making such Zn‐corrins potentially useful for investigations of B12‐dependent processes. The singlet excited state of Znby had a short life‐time, limited by rapid intersystem crossing to the triplet state. Znby allowed the unprecedented observation of a corrin triplet (ET=190 kJ mol?1) and was found to be an excellent photo‐sensitizer for 1O2Δ=0.70).  相似文献   

15.
The electrocatalytic reactions of vitamin B12s with three vicinal dibromides (cis-1,2-dibromocyclohexane, trans-1,2-dibromocyclohexane and 1,2-dibromobutane) are investigated in homogeneous and heterogeneous media. In the latter, cyclic voltammetry with basal plane pyrolytic graphite electrodes modified with microdroplets of dodecane + dibromide is employed to obtain kinetic parameters for the liquid/liquid reaction. The homogeneous and interfacial reactions exhibit marked differences in reactivity and the contrasting behaviour of the two systems suggests the liquid/liquid interface has a major role in the B12s/RBr2 reaction, consistent with a polar solvent effect.  相似文献   

16.
The effects of irradiation doses, irradiation temperature and a combined treatment of irradiation and cooking on the vitamin B6 and B12 contents of grass prawns have been studied. Grass prawns were irradiated at refrigerated (4°C) or frozen (-20°C) temperatures with different doses. A domestic cooking procedure was followed after irradiation. The changes in vitamins B6 and B12 of both raw and cooked grass prawns were evaluated. Results showed no significant changes of vitamin B6 and B12 in grass prawns with a radiation dose up to 7 kGy at either 4°C or -20°C. Irradiation at 4°C caused more destruction of vitamin B12 but not vitamin B6 than did irradiation at -20°C in grass prawns. There was significant destruction of both vitamins B6 and B12 in unirradiated samples during cooking. The introduction of the irradiation process before cooking had no effect on either vitamin. These results indicate that the loss of vitamins B6 and B12 in the combined treatments was caused mainly by thermal destruction.  相似文献   

17.
The synthesis of cobyrinic acid derivatives by reduction of dehydrocobyrinates is largely unexplored. It is, however, a rational path to B12 analogues that lack specific substituents of the corrin moiety of natural B12 derivatives. The partial syntheses of four epimeric 7‐decarboxymethyl‐cobyrinates is described, which is achieved by reduction of Δ7‐dehydro‐7‐de[carboxymethyl]‐cobyrinate with zinc or with the ‘prebiotic’ reducing agent formic acid. A direct and remarkably efficient route was found to 7‐decarboxymethyl‐cobyrinates, which are cobyrinic acid derivatives in which the c‐side chain at ring B of vitamin B12 is missing. The structures of the hexamethyl‐7‐decarboxymethyl‐cobyrinates were characterized and the stereochemical and conformational properties at their newly saturated ring B were analyzed. The stereochemical outcome of the reduction was found to depend strongly on the reaction conditions. In 7‐decarboxymethyl‐cobyrinates, both peripheral carbon centres of ring B carry a hydrogen atom, and the characteristic quaternary carbon centre at C7 of the cobyrinic acid moiety of vitamin B12 is lacking. The still highly substituted 7‐decarboxymethyl‐cobyrinates are readily dehydrogenated in the presence of dioxygen, furnishing 7‐de[carboxymethyl]‐Δ7‐dehydro‐cobyrinate as the common, unsaturated oxidation product. The noted stability of vitamin B12 and of other CoIII‐cobyrinates in the presence of air is a consequence of their highly substituted corrin macrocycle, a finding of interest in the context of chemical rationalizations of the B12 structure.  相似文献   

18.
《Analytical letters》2012,45(16):2593-2605
A method was developed for the determination of vitamin B12 based on the enhancement of cobalt (II) on the chemiluminescence (CL) reaction between luminol and percarbonate (powerful source of hydrogen peroxide). The release of cobalt (II) from the vitamin B12 was reached by a simple and fast microwave digestion (20 s microwave digestion time and a mix of nitric acid and hydrogen peroxide). A charge coupled device (CCD) photodetector, directly connected to the cell, coupled with a simple continuous flow system was used to obtain the full spectral characteristics of cobalt (II) catalyzed luminol-percarbonate reaction.

The optima experimental conditions were established: 8.0 m mol L?1 luminol in a 0.075 mol L?1 carbonate buffer (pH 10.0) and 0.15 mol L?1 sodium percarbonate, in addition to others experimental parameters as 0.33 mL s?1 flow rate and 2 s integration time, were the experimental conditions which proportionate the optimum CL emission intensity. The emission data were best fitted with a second-order calibration graph over the cobalt (II) concentration range from 4.00 to 300 µ g L?1 (r2 = 0.9990), with a detection limit of 0.42 µ g L?1. The proposed method was successfully applied to the determination of vitamin B12 in pharmaceuticals.  相似文献   

19.
Aerosol matrix-assisted laser desorption ionization (MALDI) with a reflection time-of-flight mass spectrometer was used to study fragmentation of vitamin B12. Six MALDI matrices were used: 2,5-di-hydroxy benzoic acid (gentisic acid), 4-nitroaniline, 3,5-dimethoxy-4-hydroxy cinnamic acid (sinapic acid), 3,4-di-hydroxy cinnamic acid (caffeic acid), trans-4-hydroxy-3-methoxy cinnamic acid (ferulic acid), and α-cyano-4-hydroxy cinnamic acid (4-HCCA). Mass spectra were obtained with a 355-nm pulsed Nd:YAG laser at irradiances between 0. 1 and 5 GW/cm2 (between 3- and 150-mJ pulse energy). Loss of CN was a major product of prompt ion source fragmentation and the ratio of fragmented to intact analyte was found to be strongly dependent on matrix and weakly dependent on laser irradiance. Additionally, free cobalt ions and cobalt ions bound to small methanol clusters were observed in the mass spectra. The cobalt removal from the corrin ring of vitamin B12 results from direct photon absorption by vitamin B12, but is enhanced by the presence of matrix.  相似文献   

20.
In this work, a simple and rapid analytical procedure was applied for simultaneous determination of folic acid (vitamin B0), thiamin (vitamin B1), riboflavin (vitamin B2) and pyridoxal (vitamin B6) based on the absorbance data in the pH range 2.0‐12.0 at 25 °C using parallel factor analysis (PARAFAC). The effect of the pH as the most important factor on the sensitivity of the determination was studied. The spectral data were recorded in 400‐650 nm intervals and a 2‐12 pH range for all four vitamins. The calibration set was constructed in the concentration ranges of 4‐22, 1‐20, 6‐26, and 4‐20 μg mL?;1 for B6,B2,B1 and B0, respectively. The root mean squares errors of prediction for the prediction set, (RMSEP), are 0.65, 0.63, 1.13 and 0.34 for B0,B1,B2 and B6, respectively. The recovery percent for the validation set are in the range of 90.6 to 107.0%. The effect of the experimental conditions and diverse species were discussed. The optimum values of these factors were searched according to the relative standard deviation of the prediction set of mixtures solutions.  相似文献   

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