UV Spectrophotometric Techniques Research Articles

Ionic Strength Effect on the Stability of the V(V) + IDA Complex

In this research the interaction of dioxovanadium(V) with iminodiacetic acid has been considered at 25 °C and pH=1.00–2.50 in an ionic strength range of 0.1 to 1.0 mol⋅dm−3 of NaClO4 by UV spectrophotometric and potentiometric techniques. Only one species, VO2H2L+, was assumed on the basis of two stoichiometric models. The extended Debye-Huckel theory predicts the first order effects in simple electrolyte solutions. Interactions between the reacting species and the ionic medium are taken into account in the specific ion interaction model. Parabolic, specific ion interaction, and extended Debye-Huckel models have been compared and it has been shown that the parabolic model with two coefficients is satisfactory for this complexation reaction. The results have also been compared with the literature values.

Comparative Study of RP-HPLC and UV Spectrophotometric Techniques for the Simultaneous Determination of Amoxicillin and Cloxacillin in Capsules

Reversed-phase HPLC and UV spectrophotometric techniques using water as solvent have been developed and validated for the simultaneous determination of amoxicillin and cloxacillin in capsules. For both techniques, the linearity range of 60.073x2013;140.0 µg/mL was studied. The spectrophotometric data show that non-derivative techniques, such as absorbance ratio and compensation, and ratio spectra first-order derivative could be successfully used for the co-assay of amoxicillin and cloxacillin. Based on the statistical comparison of spectrophotometric and chromatographic data, the interchangeability between HPLC and UV spectrophotometric techniques has been suggested for the routine analysis.

Investigation on the Interaction of Newly Designed Anticancer Pd(II) Complexes with Different Aliphatic Tails and Human Serum Albumin

The pharmacokinetics and pharmacodynamics of any drug will depend, largely, on the interaction that it has with human serum albumin (HSA), the most abundant plasma protein. The interaction between newly synthesized Pd(II) complexes, 2,2'-bipyridin octyl dithiocarbamato Pd(II) nitrate (Octpd), 2,2'-bipyridin butyl dithiocarbamato Pd(II) nitrate (ButPd), 2,2'-bipyridin ethyl dithiocarbamato Pd(II) nitrate (EtPd), antitumor components, with human serum albumin, a carrier protein, were studied at different temperatures of 27 and 37 degrees C by fluorescence spectroscopy, far UV circular dichroism (CD), and spectrophotometric and differential scanning calorimetry (DSC) techniques. By the analysis of fluorescence intensity, it was observed that Pd(II) complexes have strong abilities to quench the intrinsic fluorescence of HSA through a dynamic quenching procedure. The binding parameters were evaluated by the fluorescence quenching method. The thermodynamic parameters, including DeltaH degrees , DeltaS degrees , and DeltaG degrees , were calculated by the fluorescence quenching method and indicated that hydrophobic forces play a major role in the interaction of Pd(II) complexes with HSA. Far-UV-CD results represented that Pd(II) complexes induced a decrease in content of the alpha helical structure of protein. The binding of newly designed drugs (Pd(II) complexes) on the blood carrier protein of HSA resulted in significant alterations on the structure and conformation of protein via decreasing stability of HSA by decreasing the T(m), a red shift in maximum fluorescence intensity, a decrease in content of the alpha-helical structure, and the increase of the nonpolar or accessible hydrophobic surface of HSA to solvent.

Comparative analysis of refolding of chemically denatured β-lactoglobulin types A and B using the dilution additive mode

The kinetic refolding of β-lactoglobulin (BLG), types A and B, by β-cyclodextrin, glucose and sorbitol has been investigated in aqueous solution using fluorescence, far UV-CD and UV-spectrophotometric techniques. A new Pd-complex has been used to denature the protein. CD and fluorescence studies indicated that when incubated with sugar, the denatured BLG is refolded into the native-like structure through the dilution additive mode resulting in a higher yield of active protein than without sugar. CD studies show that these sugars can induce a non-native α-helical structure in denatured BLG-A and -B, then aid in the refolding of the protein. Based on the present study, these sugars have a different effect on BLG-A than BLG-B because of their differences in protein thermal stability. BLG-A has a higher thermal stability than BLG-B due to differences in the amino acid sequences.

Complexation Models of N-(2-Carboxyethyl)chitosans with Copper(II) Ions

The copper(II) complex formation equilibria of N-(2-carboxyethyl)chitosans with three different degrees of substitution (DS = 0.42, 0.92, and 1.61) were studied in aqueous solution by pH-potentiometric and UV-spectrophotometric techniques. It was demonstrated that the complexation model of CE-chitosans depends on DS: the [Cu(Glc-NR(2))(2)] complexes are predominant for two lower substituted samples ("bridge model", log beta(12) = 10.06 and 11.6, respectively), whereas the increase of DS leads to formation mainly of the [Cu(Glc-NR(2))] complexes ("pendant model", log beta(11) = 6.41). As a model for copper complexation with a disubstituted residue of CE-chitosan, the complex of N-methyliminodipropionate [CuMidp(H(2)O)].(H(2)O) was synthesized and structurally characterized by XRD. The unit cell consists of two crystallographically nonequivalent Cu atoms having slightly distorted square pyramidal coordination; Midp constitutes the basal plane of the pyramid and acts as a tetradentate NO(3) chelate-bridging ligand by the formation of two six-membered chelate rings (average Cu-O 1.99 A, Cu-N 2.04 A) and a bridge via carbonyl O atom (average Cu-O 1.99 A), an apical position is occupied by a water molecule (average Cu-Ow 2.30 A).

Molecular structure factors in adsorptive removal of pyridinium cations, 1,4-pyrazine and 1-quinoline at high-area C-cloth electrodes for waste-water remediation

Adsorptive/electrosorptive removal of pyidinium (PyH +), N-methylpyridinium (PyMe +), 1,4-pyrazine (Prz) and PrzH +, and 1-quinoline (Qul) and QulH + from simulated waste-waters was investigated in 0.1 M H 2SO 4, 0.1 M KH 2PO 4+KOH (pH 7.0) buffer and 0.1 M KOH solutions using quasi-3-dimensional, high area C-cloth electrodes as interfaces. The adsorption/electrosorption, monitored kinetically by in situ UV spectrophotometric techniques, follows first-order kinetics. Rates of adsorption of the above N-heterocyclic solutes are enhanced by polarization of the C-electrodes, preferably by negative currents. Reversible electrosorption was observed in 0.1 M H 2SO 4 or in 0.1 M KH 2PO 4+KOH (pH 7.0) buffer solution for pyridinium cations (PyMe + and PyH +), leading to the possibility of easy and in situ regeneration of the surfaces of C-cloth electrodes in practical adsorptive removal applications. Negative, and alternate positive and negative polarization were found to have a strong and particular effect in promoting extents of adsorption for N-heterocyclic compounds such as PyMe +, Prz and Qul in buffer (pH 7) and KOH solutions, leading to complete removal in those cases.

Microbiological assay for determination of ofloxacin injection.

A simple, sensitive and specific agar diffusion bioassay for the antibacterial ofloxacin was developed using a strain of Micrococcus luteus ATCC 9341 as the test organism, ofloxacin at concentration ranging 12-27 microg ml(-1) could be measured in injection. A prospective validation of the method showed that method was linear (r=0.9994) and precise (CV=1.14). UV spectrophotometric and high performance liquid chromatographic techniques were chosen as a comparison methods for the determination of ofloxacin. The results obtained by three methods were statistically analyzed by analysis of variance (ANOVA) and the results obtained indicate that there is no significant difference among these methods.

Spectroscopic Studies on the Interaction of Aristololactam-β-d-Glucoside with DNA and RNA Double and Triple Helices: A Comparative Study

The interaction of aristololactam-beta-D-glucoside (ADG), a DNA intercalating alkaloid, with the DNA triplexes, poly(dT). poly(dA)xpoly(dT) and poly(dC).poly(dG)xpoly(dC+), and the RNA triplex poly(rU).poly(rA)xpoly(rU) was investigated by circular dichroic, UV melting profile, spectrophotometric, and spectrofluorimetric techniques. Comparative interaction with the corresponding Watson-Crick duplexes has also been examined under identical experimental conditions. Triplex formation has been confirmed from biphasic thermal melting profiles and analysis of temperature-dependent circular dichroic measurements. The binding of ADG to triplexes and duplexes is characterized by the typical hypochromic and bathochromic effects in the absorption spectrum, quenching of steady-state fluorescence intensity, a decrease in fluorescence quantum yield, an increase or decrease of thermal melting temperatures, and perturbation in the circular dichroic spectrum. Scatchard analysis indicates that ADG binds both to the triplexes and the duplexes in a noncooperative manner. Binding parameters obtained from spectrophotometric measurements are best fit by the neighbor exclusion model. The binding affinity of ADG to the DNA triplexes is substantially stronger than to the RNA triplex. Thermal melting study further indicates that ADG stabilizes the Hoogsteen base-paired third strand of the DNA triplexes whereas it destabilizes the same strand of RNA triplex but stabilizes its Watson-Crick strands. Comparative data reveal that ADG exhibits a stronger binding to the triple helical structures than to the respective double helical structures.

Protonation and Degradation Reactions ofs-Triazine Herbicides

Desethyl atrazine and desethyl terbutylazine, the degradation products of two commonly encountered pesticides, were investigated by UV spectrophotometric and electrochemical techniques. In a sufficiently acidic environment, both compounds undergo further redox degradation which involves the cleavage of the chlorine atom. The reaction is pH dependent and proceeds via the protonated forms of both compounds. Spectrophotometric data indicate that the pH required for this reaction is about one unit lower than that required for the degradation of the parent pesticides.

Improvement of Solubility and Dissolution of 19-Norprogesterone via Inclusion Complexation

In an effort to modify the solubility and dissolution rate of the contraceptive steroid, 19-norprogesterone in order to improve its bioavailability, the cyclodextrin complexation approach was chosen. In solution, the complex formation with β-cyclodextrin (β-CD), hydroxyethyl β-cyclodextrin (HE-β-CD) and hydroxypropyl β-cyclodextrin (HP-β-CD) was confirmed by using solubility, UV, IR and 1H-NMR spectrophotometric techniques. The phase solubility diagrams were categorized as AL-type. The complexing affinity of the CDs investigated were ranked as follows: β-CD > HP-β-CD > HE-β-CD. The complexation thermodynamic parameters were obtained from the temperature dependence of the dissociation constants. In the solid state, differential scanning calorimetery (DSC) and optical microscopy methods were utilized to characterize the complexes. Dissolution studies showed that such molecularly encapsulated forms offered a marked improvement in the dissolution rate compared to the parent drug.

Adsorption of CTAB at lignite-aqueous solution interface

The adsorption of a cationic surfactant (cetyltrimethylammonium bromide, CTAB) from aqueous solution onto the lignite was investigated. The samples used for the adsorption experiments were: fresh; demineralized; demineralized then oxidized. The oxidation process was conducted by dry method (in air at 150 and 200°C). The UV spectrophotometric techniques were used for the analysis of CTAB in solution. The adsorption isotherms were measured experimentally at 21 and 45°C, and it was found that the adsorption capacities of all samples increased with rising temperature, and the adsorption of CTAB decreased by demineralization and oxidation. The changes in the thermodynamic quantities, enthalpy and entropy, related adsorption process that occured in some steps were calculated. Isosteric heats of adsorption and the corresponding changes in entropy have found to be negative for all of the samples. From the abrupt difference between ΔH and ΔS for the demineralized sample and those of fresh sample, it was concluded that the orientation of CTAB molecules on the surface of the demineralized sample differs than that of fresh sample, and also that the adsorption of CTAB on the demineralized sample takes place with the hydrophobic interactions in addition to the electrostatic interactions, while in the case of fresh sample, the predominant mechanism of adsorption is through electrostatic interactions. Also, the lower values of ΔH for both demineralized and oxidized samples in comparison with the demineralized sample indicates that the oxidation process diminishes the contribution of the hydrophobic interactions to the adsorption of CTAB.

Determination of Theobromine, Theophylline, and Caffeine in Various Food Products Using Derivative UV-Spectrophotometric Techniques and High-Performance Liquid Chromatography

Abstract Accurate, sensitive and precise derivative ultraviolet Spectrophotometric and high-performance liquid chromatographic (HPLC) methods are described for the simultaneous determination of three natural methyl xanthines (theobromine, theophylline and caffeine) in various food products. The derivative UV-spectro-photometry, with zero crrosing technique of measurement was selected for determination of theobromine and theophylline. First-derivative procedure (D1) was adopted for theobromine determination in the presence of theophylline and caffeine; and second-derivative procedure (D2) was adopted for theophylline determination in the presence of theobromine and caffeine. Caffeine was determined by compensation method using the zero order spectrophotometry. The second method was based on HPLC on a reversed phase column, using a mobile phase of 0.01 M sodium acetate solution: acetonitrile (85:15%) at PH 4.0 with detection at 272 nm. Both methods show good linearity, precision and reproducibility. The developed methods proved to be applicable for the determination of methyl xanthines in various food products. The validity of the proposed methods were tested by analyzing laboratory-prepared mixtures containing the three components in various proportions and by analyzing several food products spiked with a known concentration of the three components.

Drug analyses in poisoned patients--the need to be specific.

Methods for the qualitative determination of drugs in blood and urine which have been used over the past 20 years have on several occasions given rise to incorrect interpretation due to their lack of specificity, which has resulted in falsely high values being reported for commonly requested drugs. Modern methods provide an opportunity to ensure specificity in the future but analysts must continue to be aware of the potential pitfalls. Examples of non-specificity in colorimetric, UV spectrophotometric, and immunological techniques are described and the clinical implications are demonstrated.

Adsorption of frothers at coal/water interfaces

The adsorption of phenol and three commonly used frothers, namely, terpineol, methylisobutylcarbinol (MIBC) and cresol, on coal surfaces has been studied through UV spectrophotometric and gas chromatographic techniques. The rate of attaining adsorption equilibrium of these alcohols onto coal is very slow, possibly due to pore diffusion. The adsorption isotherms are of typical Langmuir-type except for MIBC, where the adsorption density rises linearly with equilibrium concentration in solution in the range of concentration under study. Free energies of adsorption were calculated from the adsorption isotherms. The results indicate that adsorption occurs through hydrophobic interactions between the frother molecules and the coal surface. The effect of oxidation and pH on adsorption behavior was also studied. Oxidized coal is more hydrophilic and hence the adsorption of these nonionic surface-active agents is reduced after oxidation.

Isolation of two isomeric 2,6-nonadienals and two isomeric 4-heptenals from beef and mutton tallow.

AbstractBy the use of mainly chromatographic and UV spectrophotometric techniques, 4cis‐ and 4trans‐heptenal (with a “green” odor, characterized in high dilution as tallowy, creamy, butterscotch‐like) and 2trans,6cis‐ and 2trans,6trans‐nonadienal (with a “green”‐cucumber‐like and a tallowy odor) were isolated from reverted beef and mutton tallow.