Determination of Vitamin B12 in Multivitamin Tablets by High Performance Liquid Chromatography

Abstract

Two procedures for separation and determination of vitamin B₁₂ in multivitamin tablets by reversed phase high performance liquid chromatography are proposed. Sample preparation is very simple: tablets are dissolved in distilled water, centrifuged and filtered. The sample solution is directly applied in the sample loop injector and chromatograms are obtained with gradient elution using water-methanol and water-acetonitrile as solvents. The peak of vitamin B₁₂ from samples of B-complex tablets is well separated with the two procedures. For multivitamin tablets, however, only the procedure with water and methanol as solvents was good for separation and quantification of vitamin B₁₂. Both procedures were verified by the standard addition method and also compared to a previously developed method using electrothermal atomic absorption spectrometry for vitamin B₁₂ determination.     

ACID DISSOCIATION BEHAVIOR OF 2, 3- AND 2, 3, 9,lO-METHYL- OR CYCLOHEXYL-SUBSTITUTED CYCLAMS,THEIR COMPLEXATION BEHAVIOR WITH COPPER@) AND THE AXIAL SOLVENT SPECTRUM OF THEIR COMPLEXESINTERACTION EFFECT ON THE LIGAND-FIELD

Abstract

Stability constants of Cu(Il)-complexes for 1, 4, 8, 11-tetra-azacyclotetradecane (cyclam) analogs with periphery substituted [14]aneN₄-ring, 2, 3-tetramethyl-, 2, 3, 9, 10-octamethyl-, 2, 3-cyclohexyl, and 2, 3, 9, 10-dicyclohexyl-cyclams have been determined at 25°C in aqueous solution. The UV-Vis absorption spectra of their complexes, ([Cu(L)] (C1O₄)₂), were measured in water and some typical organic solvents (methanol, acetone, propylene carbonate, formamide, N, N-dimethylformamide, and dimethylsulfoxide). A good linear relationship was found between the stability constant logK_CuL) and the difference between the wavenumber of maximum absorption in water and in the organic solvents (δλ_max ^?1 (W-S)). The value of logK_CuL at δλ_max ^?1(W-S) = 0 not only shows a linear relation to solvent parameters, donor number and dielectric constant, but also to the enthalpy of transfer of ClO₄ ^? from water to the organic solvents. The value is proposed as a new solvent parameter ‘Kλlue’ to be used as an index for solvent-effects on Cu(II)-complexes of cyclam analogs. The increasing order of the new parameter (log scale) is as follows; DMF(27.24)>DMSO(27.14)>FA(26.82)>MeOH(26.27)>PC(25.75)>AC(24.71). Another meaning of the new parameter is assumed from connection of the potentiometric data with spectrometric data. The solvent effects on stability and the UV-Vis spectra are assumed to be caused by perturbation of the D_{4 h} or axially-elongated ligand field through axial approach of solvent to the Cu(II)-complexes and by formation of a solvent-separated ion pair between a solvated Cu(lI)-complex cation and counter anion (ClO₄)     

Serum Injection of the HPLC Column for Carbamazepine Assay

Abstract

Serum was injected directly on an HPLC column packed with C₁, 6.5 μm particle size, 300 Å pore-packing material for carbamazepine determination. The use of a wide-pore column with low hydrophobicity eliminated excessive pressure buildup in the column from protein precipitation which is usually caused by the high concentration of organic solvents in the mobile phase. This simple approach can be utilized for the determination of other drugs and endogenous compounds in serum.     

Unusual structurally characterized pyridine carbinoxide copper(II) coordination compounds,isolated from organic solvents

The coordination behavior of pyridine carbinoxide [NC₅H₄(CH₂O)-2 or OPy] with copper in organic solvents was crystallographically determined. Initial attempts to generate the Cu(II) OPy derivatives from an alcoholysis exchange of Cu(OCH₃)₂, with H–OPy in toluene, led to the isolation of [Cu(µ_c-OPy)(O^cPy)]₂ (1, “c” indicates chelation). The square-based pyramidal geometries noted for each Cu center resulted from one O^cPy and two µ_c-OPy ligands, generating an unusual C_i symmetry. From the reaction of H–OPy and the Cu(I) species Cu(C₆H₂(CH₃)₃-2,4,6), mononuclear Cu(II) complex Cu(O^cPy)₂(H–OPy)₂ (2) was isolated. Compound 2 is unusual in that it adopts a square planar arrangement around the Cu metal center using two O^cPy ligands; however, the metal center also coordinates with two H–OPy molecules forming an octahedral geometry. Upon dissolution in water, both 1 and 2 react to form the previously reported Cu(O^cPy)₂ · 2H₂O (3). Attempts to add a Lewis base through dissolution of 1 in selected solvents (i.e., tetrahydrofuran, pyridine, 1-methylimidazole) led to [Cu(µ_c-OPy)(O^cPy)]₂ · H₂O (4), which possesses a C ₂ symmetry. The water was believed to be extracted from the “dry” solvents. A Cl derivative was also solved for the Cu(II)/Cu(I) species [Cu(OPy)₂]₂[CuCl(H–OPy)₂]₂ (5) from tetrahydrofuran dried over apparently contaminated sieves.     

Use of 3,5-Dinitrosalicylate Reagent for Glucose Determination in Mixed Solvents

Abstract

The reduction of 3,5-dinitrosalicylic acid to 3-amino-5-nitrosalicylic acid by glucose is the basis for a common method of glucose determination. We have demonstrated that the method can be used in mixed solvents consisting of water and any of several organic solvents. In some cases a calibration curve other than the curve for water alone must be used.     

The intensity change of IR OH bands by H-bonds

The integrated intensity change by H-bonds are measured for CH₃OH solved in different solvents of fundamental, 1. and 2. overtone OH stretching bands. A function A=f(ν) for the strong intensity change by H-bonds of the fundamental band is given, it shows a kink between pure van der Waals solvents and H-bond acceptors. - The contrary behavior of fundamental and 1. overtone bands for the T-dependence of pure CH₃OH and its LiClO₄-solutions could be canceled if the fundamental spectra are intensity corrected by A=f(ν). It is shown that the discussions between species and continuum models of water could become unique taking into account the function f(ν) and its kink, different for fundamental and overtone bands.     

Transparent,Electrically Conductive Composites Derived from Polypyrrole and Poly[Vinyl Chloride) by Vapor-Phase Polymerization: Effect of Environment on Polymerization and Reaction Mechanism

Abstract

Transparent, electrically conductive composite films were obtained by vapor-phase polymerization of pyrrole into a poly(vinyl chloride) (PVC) matrix containing FeCl₃. The effects of water and of organic solvents on the polymerization were investigated. It was found that the conductance of the films increases in the presence of both water vapor and of good solvents or swelling agents for PVC. The conductivity of the films rises with reaction time and so does the rate of increase with higher FeCl₃ concentration. The production of HCl was monitored by two methods, the precipitation of AgCl in an aqueous solution of silver nitrate and the increase in conductance of an aliquot of distilled water which had been placed into the reaction chamber. On the basis of our experimental results, we propose a reaction mechanism that explains the observed increase of conductance with time. A universal kinetic formula has been derived which relates the increase of electrical conductance to other parameters characterizing the boundary conditions of the polymerization.     

Enthalpies of alkyl sulfonates in water,heavy water,and water-alcohol mixtures and the interaction of water with methylene groups

The heats of solution of the sodium n-alkyl sulfonates from methyl to octyl have been measured at 25°C in water, D₂O, and three alcohol-rich mixtures with water, all at solute concentrations low enough so that solute-solute interaction is negligible. Methylene-group contributions to the enthalpies of transfer are readily identified. Collation with the results of earlier studies of enthalpies of transfer leads to the conclusion that methylene-group enthalpies of transfer can be identified as follows: 0.87 kcal-mole^–1 for transfers to the gas phase from water and –0.035 kcal-mole^–1 for transfers to D₂O from H₂O, independent of the solute type provided only that methylene-group contributions can be identified in the data. Compared to other solvents, water is about as lipophilic as dimethylsulfoxide or a mixture of 27 moles of water with 73 moles of methanol. However, the range of the interactions between different groups on a given solute molecule seems to be much greater in water than in any of the other solvents studied, making it more difficult to identify group contributions to solvation in water. Another example of the complexity of the solvation of alkyl groups in water is encountered when one compares the solvation enthalpy of hexane in various solvents with some of the above results.     

KOH/t-Butanol, eine wertvolle Alternative bei der Ma?analyse sehr schwacher S?uren

Zusammenfassung Ein neues Verfahren zur Bestimmung von Wasser in organischen Lösungsmitteln (auch in Spuren) wird beschrieben. Die Solvatochromie des Pyridiniumphenolbetains E _T30, die über eine einfach auszuführende UV-Absorptionsmessung bestimmt wird, ermöglicht zusammen mit einer zwei-Parameter-Gleichung eine exakte Wasserbestimmung in organischen Lösungsmitteln als Schnelltest und stellt damit eine Alternative zur Karl-Fischer-Titration dar.

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A new, uncomplicated procedure for the determination of small concentrations of water in organic solvents

Summary A new procedure for the determination of water (even in trace amounts) in organic solvents is described. The solvatochromism of the pyridiniumphenol betaine, E _T30, determined by a simple UV-absorption measurement, together with a two-parameter equation, permits an exact determination. The procedure is rapid and is, therefore, an alternative to the Karl-Fischer titration.

Herrn Prof. Dr. C. Rüchardt wird für die Unterstützung gedankt.     

Stabilities and Transfer Activity Coefficients from Water to Polar Nonaqueous Solvents of Benzo-15-Crown-5- and 15-Crown-5-Alkali Metal Ion Complexes

Stability constants (K_ML) of 1 : 1 benzo-15-crown-5 (B15C5) complexes with alkali metal ions were conductometrically measured in water at 25°C. Transfer activity coefficients of B15C5 and 15-crown-5 (15C5) from water to polar nonaqueous solvents were determined at 25°C. By using these data and the literature values, transfer activity coefficients of the B15C5 and 15C5 complexes with alkali metal ions from water to the polar nonaqueous solvents were calculated to study the solute-solvent interaction of the crown ether complexes. The stability of the B15C5 complex is lower in water than in any other nonaqueous solvent. The K_ML value for B15C5 is always smaller than the corresponding K ML value for 15C5. The interaction of the B15C5 or the 15C5 complex with the solvents depends on the alkali metal ion in the crown cavity. All the B15C5 and 15C5 complexes undergo hydrophobic hydration, which is particularly stronger for the B15C5 complexes with Na⁺ and K⁺. The unexpectedly lowest stability of the B15C5- or the 15C5-alkali metal ion complex in water among all the solvents is caused by the hydrogen bonding between ether oxygen atoms of uncomplexed B15C5 or 15C5 and water.     

Determimation of Cu and Fe in Hobium by Electrolytic Dissolution and Atomic Absorption Spectroscopy

Abstract

The method of electrolytic dissolution in organic solvents (saturated with NH₁Cl) followed by atomic absorption spectroscopy was applied to the determination of Fe and Cu impurities in niobium metal. It was found that a previously reported decrease in sensitivity could be attributed to precipitation of NH₄Cl on the walls of the feeding chamber of the spectrometer and could be avoided by diluting the solution before measurement.     

Design and preparation of a novel fluorescent naphthalimide derivative supramolecular self-assembly system and its bioimaging application

ABSTRACT

A novel fluorescent naphthalimide derivative gelator (N-18) was designed and characterised which could form a stable gel in 1,4-dioxane/H₂O (2/1, v/v), methyl sulfoxide (DMSO), ethanol/H₂O (4/1, v/v), acetone/H₂O (2/1, v/v) and methanol. The self-assembly process of molecule N-18 in the five solvents was carefully investigated by the field emission scanning electron microscope, UV-vis absorption spectra, fluorescence emission spectra, fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD) and water contact angle experiments. Different structures from microbelts to helical nanofibers were formed in the self-assembly process. Hydrogen bonding and π–π stacking interaction were the mainly driving forces for the formation of gel. At the same time, the hydrophobic surface with the contact angles of 133°–142° was observed on the xerogel films N-18 from the above five solvents. Interestingly, molecule N-18 could be applied in bioimaging in a living cell.     

具有聚集荧光增强性质的双(4-二乙氨基水杨醛)缩偶氮二甲酰肼二丁基锡的合成和晶体结构

在甲醇溶液中,卡巴肼、(4-二乙氨基)水杨醛和二乙酸二丁基锡"一锅法"反应,合成了一个新颖的基于双(4-二乙氨基水杨醛)缩偶氮二甲酰肼(L)的七配位有机锡配合物[Sn(L)(n-butyl)_2]n(T)。经元素分析、IR、(1H,119Sn,13C)NMR和X射线衍射晶体结构表征,T的晶体属单斜晶系C2/c空间群,中心锡周围由双(4-二乙氨基水杨醛)缩偶氮二甲酰肼的O,N配位原子占据赤道位置和2个丁基占据顶端位置形成畸变五角双锥构型。通过烯醇式氧原子的桥联配位作用,T向一维带状无限扩展产生"竹筏状"超分子结构。配合物T在二甲基甲酰胺、四氢呋喃、乙醇、甲醇和甲苯有机溶剂及其有机溶剂-水混合物中具有强荧光发射峰,当含水量的体积分数在0～10%(V/V)时具有良好的聚集荧光增强效应,含水量大于10%(V/V)时发生荧光淬灭。     

Determination of tarce water in non-polar organic solvents with a flow-injection system and tin tetrachloride or antimony pentachloride

Low levels of water (limit of detection 2-5 mg kg^1?)can be determined in a non-polar organic solvents such as benzene, 1,2-dichloroethane (DCE) and n-hexane by utilizing the reaction of water with SnCl₄ or SbCl₅. The reaction results of hydrolysis in halide and is accompanied by a decrease in optical absorption. With SnSl₄, the reaction is monitored near 300 nm and with SbCl₅ it is monitored at lower wavelengths (350-420). Niether reactons proceeds well in media containing only DCE and n-hexane. For this reason, the arrangemens involves a halide reagent dissolved in benzene which is merged with a benzene/n-hexane/DCE carrier stream into which samlpe is injected. A configuration in which only 2μl of a concentrated halide reagent solution is injected into the flowing sample stream is also shown to be viable for the determination of water in benzene. A membrane-permeation-based calibration method for preparing trace water standards is described.     

Solid-Phase Extraction and Capillary Gas Chromatographic Determination of Triazine Herbicides in Water

Abstract

A facile and efficient method is described for the determination of trace quantities of triazine herbicides, terbutryn, prometryn and ametryn in water. The procedure involved preconcentration of water samples by sorption on chromatographic grade silica gel particles with chemically modified surface, being covalently bonded with a nonofunctional C₈H₁₇ group. This was followed by solvent desorption with 2-propanol. The determinative step was achieved by capillary gas chromatography on Supelcowax-10 fused silica column using a nitrogen-phosphorus detector. The limit of detection was 0.1 μg-10 μgL^?1.     

Determination of Low-Molecular-Mass Aldehydes in Water Samples by Liquid Chromatography and Chemiluminescence Detection Using Continuous in situ Derivatization/Preconcentration with Dansylhydrazine

Abstract

A simple, expeditious, and sensitive method has been developed for the determination of low-molecular-mass aldehydes in water samples by liquid chromatography and peroxyoxalate–chemiluminescence detection. The method is based on continuous solid-phase extraction with in situ derivatization/preconcentration of the aldehydes using dansylhydrazine, which was first adsorbed on an RP–C₁₈ mini-column. For 10 mL of aqueous sample, the limits of detection (LOD) for C₁ to C₄ aldehydes were 20–30 ng L^?1, except for formaldehyde, which had an LOD of 400 ng L^?1. Application was illustrated by the determination of these aldehydes in water samples; the interday precision was always less than ca. 7%, and relative recoveries were more than 96%.     

Spectrophotometric Determination of Palladium(II) With 2, 2′-Dipyridylglyoxime

Abstract

A spectrophotometric method is described for the determination of palladium with 2,2′-dipyridylglyoxime. The effects due to pH, time, solvents, reagent concentration and diverse ions are reported. A new method of reagent synthesis is also described.     

New Rapid Assay for Nafcillin by Spectrofluorimetry in Pharmaceutical Dosage

Abstract

A method for the spectrofluorimetric determination of nafcillin is proposed (λ_ex = 226 nm, λ_em = 366 nm), for concentrations between 0.10 and 1.0 μg mL^?1. The method was performed in ethanol/water medium (30% V/V), at apparent pH 6.0 provided by adding of phosphate buffer solution with pH = 6.20.

The obtained values of detection and determination limits are 0.016 and 0.054 μg mL^?1, respectively.

The method was successfully applied to assay a commercial injection containing nafcillin sodium monohydrate.     

Derivatization of Xanthomegnin for Fluorometric Determination

Abstract

A derivatization procedure was developed for the fluorometric determination of purified xanthomegnin. A highly fluorescent product is formed by reaction of xanthomegnin with ammonia and hydrogen peroxide under defined conditions. The derivative is a light brown compound that can easily be dissolved in water or polar organic solvents. Its excitation and emission wavelengths in methanol are 340 and 445 nm, respectively. As little as 0.1 ng of xanthomegnin can be detected using high pressure liquid chromatography in a reverse phase system with fluorescence detection.