Fading Reaction Research Articles

Fading Spectrophotometric Method for the Determination of Polyvinylpyrrolidone with Eosin Y

Abstract In weak acid medium, eosin Y (EY) has a strong absorption band in the visible light region, and the maximum absorption wavelength (λmax) is at 517 nm. There is no light absorption for polyvinylpyrrolidone (PVP) in 250–700 nm. When EY was reacted with PVP to form a binding product, a fading reaction of EY appeared and the maximum fading wavelength was still located at 517 nm. At the same time, a smaller absorption peak was observed at 545 nm. The extent of the fading (ΔA) is directly proportional to the concentration of PVP in the range of 0.40–3.20 mg· L−1. The fading reaction has high sensitivity. The molar absorptivity (ε) is 6.4×106 L·mol−1·cm−1 and the detection limit for PVP is 0.12 mg·L−1. The influencing factors for the reaction have been studied, and the results show that the selectivity is good. Based on this fact, a new fading spectrophotometric method for the determination of PVP with EY has been developed, which is simple and rapid, and it can be applied to the quantitative determination of PVP in beer samples.

Study on the absorption and fluorescence and resonance Rayleigh scattering spectra of Cu (II)-fluoroquinolone chelates with erythrosine and their applications

In pH 4.2–5.0 Britton-Robinson buffer solution medium, fluoroquinolone antibiotics (FLQs), such as ciprofloxacin (CIP), norfloxacin (NOR), ofloxacin (OF), levofloxacin (LEV), lomefloxacin (LOM), and sparfloxacin (SPA), react with Cu (II) to form chelate cations, which further bind with erythrosine to form the ion association complexes. They can result in the changes of the absorption spectra. Simultaneously, erythrosine fades obviously and the maximum fading wavelength is located at 526 nm. The fading reactions have high sensitivities. Thus, new spectrophotometries of determination for these drugs are developed. The ion-association reactions result in the quenching of fluorescence, which also have high sensitivities. The detection limits for six antibiotics are in the range of 7.1–12.2 μg·L−1. Furthermore, the reactions can result in the enhancement of resonance Rayleigh scattering (RRS). The maximum scattering peaks of six ion-association complexes are located at 566 nm, and there are two small RRS peaks at 333 nm and 287 nm. The detection limits for fluoroquinolone antibiotics are in the range of 1.70–3.10 μg·L−1 for RRS method. Among the above three methods, the RRS method has the highest sensitivity. In this work, we investigated the spectral characteristics of the absorption, fluorescence and RRS, the optimum conditions of the reactions, and the properties of the analytical chemistry. In addition, the mechanism of reactions were discussed by density function theory (DFT) and AM1 methods.

A Highly Sensitive Spectrophotometric Assay of Bleomycins Based on the Fading Reaction of Some Halofluorescein Dyes

AbstractIn weak acidic medium, anticancer antibiotics bleomycin A5 (BLMA5) and bleomycin A2 (BLMA2) can react with halofluorescein dyes such as erythrosin (Ery), eosin Y (EY), eosin B (EB) and rose bengal (RB) by virtue of electrostatic attraction and hydrophobic force to form the ion‐association complexes, which can result in the fading reactions of four halofluorescein dyes. The maximum fading wavelengths of these four dyes were located at 527 nm for Ery, 515 nm for EY, 517 nm for EB and 546 nm for RB, respectively. The decrements of absorbance ((A) were directly proportional to the concentrations of bleomycin in a certain range. A new method for the determination of bleomycins anticancer drugs based on fading reactions of halofluorescein dyes has been developed. The method was not only highly sensitive but also simple and rapid. The molar absorptivities (ε) ranged from 1.5×105 to 7.5×105 L·mol−1·cm−1. It was applied to determination of the bleomycins in human serum, urine and rabbit serum samples. In this work, the spectral properties and the optimum reaction conditions were investigated. The structure of ion‐association complexes and the reaction mechanism were discussed.

Photophysical properties and photochemical rearrangement of single crystal salicylideneaniline in solution

Salicylideneaniline originally crystallized from a solution has lemon yellow color. Irradiation with near ultraviolet causes the color change from yellow to red. The red state changes spontaneously back to yellow in 2 ms. This change is accelerated by visible light. Kinetic data are reported in the temperature range between 10 and 60 °C, for the dark fading reactions of the colored isomers formed by the near ultraviolet irradiation. Observed the decay kinetics was first order reactions. Activation energies and entropies of activation are reported for ethanol. The observation of T–T absorption and emission were complicated due to the colored isomer formation during the optical pumping.

Kinetic cosolvent effects on the alkaline fading of crystal violet in the presence of sodium dodecyl sulfate micelles

The alkaline fading reaction of crystal violet (CV) in anionic micelles of sodium dodecyl sulfate (SDS) in the presence of various amounts of cosolvents, ethanol, propanol, ethylene glycol and propylene glycol, was studied under pseudo-first-order conditions. The reaction was monitored spectrophotometrically by measuring the decrease in the absorbance of CV at 590 nm. The results indicated that SDS micelles exhibited an inhibiting effect on this reaction and this can be reasonably accounted for in terms of electrostatic interactions. Presence of cosolvents reduced the inhibitory effect of SDS micelles, i.e. increased the reaction rate. Effectiveness of cosolvent as accelerators of SDS inhibited reaction is in the following order: propanol > ethanol > propylene glycol > ethylene glycol.

염기성 용액에서 마젠타 아조메틴 색소의 퇴색 반응속도와 메커니즘

A magenta azomethine dye(D) was synthesized from the reaction of 3-methyl-1-phenyl-2-pyrazoline-5-one with N,N-diethyl-1,4-phenylenediamine. The magenta azomethine dye was identified on the basis of elemental analysis, , infrared, and GC/MS studies. The magenta azomethine dye was decomposed in a basic solution. Rate constants of the fading reaction of magenta azomethine dye in ethanol-water solvent were measured spectrophoto­metrically at 540 nm. Reaction rate was increased with the increase of in the region of . The reaction was governed by the following rate law. -d[D]/dt = A possible mechanism consistent with the empirical rate law has been proposed.

Study of Kinetics of Bromophenol Blue Fading in Alcohol-Water Binary Mixtures by SESMORTAC Model

Solvent effects on the kinetics of bromophenol blue fading have been investigated within a temperature range in binary mixtures of methanol, ethanol, 1-propanol, ethylene glycol and 1,2-propanediol with water of varying solvent compositions up to 40% by weight of organic solvent component. Correlation of logk with reciprocal of the dielectric constant was linear. Finally a mechanism was proposed for the bromophenol blue fading upon SESMORTAC (study of effect of solvent mixture on the one-step reaction rates using the transition state theory and cage effect) model, by means of this model, the fundamental rate constants of the fading reaction in these solvent systems were calculated.

Study of Kinetics of Bromophenol Blue Fading in the Presence of SDS, DTAB and Triton X-100 by Classical Model

In this paper, kinetics of reaction between Bromophenol blue (BPB) and OH − , called fading, has been studied through a spectrophotometric method in the presence of nonionic Triton X-100 (TX-100), anionic sodium dodecyl sulfate (SDS) and cationic dodecyl trimethyla mmonium bromide (DTAB) surfactants. The influence of changes in the surfactant concentration on the observed rate constant was investigated. The results are treated quantitatively by pseudophase ion-exchange (PPIE) model and a new simple model called “classical model”. The binding constants of BPB molecules to the micelles and free molecules of surfactants, their stoichiometric ratios and thermodynamic parameters of binding have been evaluated. It was found that SDS has nearly no effect on the fading rate up to 10 mM, whereas TX-100 and DTAB interact with BPB which reduce the reaction rate. By the use of fading reaction of BPB, the binding constants of SDS molecules to TX-100 micelles and their Langmuir and Freundlich adsorption isotherms were obtained and when mixtures of DTAB and TX-100 were used, no interaction was observed between these two surfactants.

04/00551 Spectrophotometric determination of trace chromium in fly ash: Xia, C. et al. Guangpuxue Yu Guangpu Fenxi, 2003, 23, (1), 205–206. (In Chinese)

In HNO3 medium the fading reaction of arsenazo III oxidated with Cr2O7(2-) was used as to determine trace Cr in fly ash containing Cr. The results show that the fading reaction has high sensitivity in the medium of 3.2 mol.L-1 nitric acid, the molar absorptivity of 3.9 x 10(6) L.mol-1.cm-1 at 520 nm, and Beer's law is obeyed for Cr (VI) in the range of 0.0-40.0 micrograms.L-1. Contents of Cr in fly ash were determined with satisfactory results.

Deuterium isotope effect on the solid-state thermal isomerization of photo-coloured cis-keto species of N-salicylideneaniline.

Deuterium isotope kinetic effect in the solid state was observed by using thermal fading reaction of photo-coloured species derived from N-salicylideneaniline deuterohydroxyl derivative; thus, the existence of a cis-keto form in the photo-coloured Schiff base crystals was suggested experimentally along with 6-methyl-substitution effect on the stability of the photoproduct.

Micellar Catalysis of Composite Reactions—The Effect of SDS Micelles and Premicelles on the Alkaline Fading of Crystal Violet and Malachite Green

ABSTRACT The effect of SDS micelles and premicelles on the reversible alkaline fading reactions of crystal violet and malachite green were studied. Micellar and premicellar catalysis models for 1-1 type reversible reactions were proposed. The rate constants of forward and backward reactions and equilibrium constants of these reversible alkaline fading reactions in SDS micellar solutions were obtained from a micellar catalytic model. Under the premicellar condition the average number of SDS molecules per substrate molecule with n surfactant molecules was obtained from a premicellar catalytic model. The results indicated that both SDS micelles and premicelles exhibited an inhibiting effect on the forward reaction, while they exhibited an accelerating effect on the backward reaction. These results can reasonably be accounted for in terms of electrostatic interactions.

Spectrophotometric determination of vitamin B 1 in a pharmaceutical formulation using triphenylmethane acid dyes

A highly sensitive colour reaction has been developed, based on the fact that vitamin B 1 reacted with a triphenylmethane acid dye such as thymol blue, bromothymol blue, bromophenol blue, bromocresol green, phenol red or cresol red to form an ion-association complex in a weak-base aqueous solution in the presence of some solubilization agents e.g. polyvinyl alcohol, emulgent OP, Triton X-100 or Tween-20. The wavelengths of maximum absorbance of the six ion-association complexes were between 420 and 450 nm, and fading reaction appeared at the longer wavelength and the maximum fading wavelengths were between 550 and 620 nm. The reactions had highly sensitivities and their apparent molar absorptivities of the colour reactions were (0.82–1.65)×10 5 l mol −1 cm −1 and those of fading reactions were (1.26–3.92)×10 5 l mol −1 cm −1 depending on the different dye systems. The composition ratio of the ion-association complex was vitamin B 1:dye=1:1 as established by Job's and equilibrium shift methods. The method had good selectivity and could be applied to direct spectrophotometric determination of vitamin B 1 in aqueous phase without using organic solvent extraction. Therefore, the method was simple and rapid. The colour reaction mechanism was discussed with the quantum chemistry method.

Decarboxylation and alkaline colour fading reactions in presence of humic substances

Humic substances (HSs) can substantially influence velocity of reactions in the environment as shown on example of decarboxylation and alkaline colour (e.g., malachite green and crystal violet) fading reactions. In colour fading and decarboxylation reactions of 6-nitrobenzisoxazole-3-carboxylic acid HS act as inhibitors, but additions of surfactants change the pattern of reaction. The inhibitory activity of HSs much depends on their origin. The velocity of studied reactions depends also on pH, temperature and concentration of HS used. Possible micellar catalysis mechanism has been suggested.

Photochromic coatings including silver halide microcrystals via sol–gel process

Photochromic coatings including silver halide microcrystals were formed on a glass substrate via the sol–gel process. 3-Glycidoxypropyltrimethoxysilane and methyltrimethoxysilane were used as starting materials of the ormosil matrices. The 3-chloropropyltrimethoxysilane and bromophenyltrimethoxysilane were added as halogen sources and silver colloidal dispersions were introduced into the precursor solution. The precursor solution was applied using a spin-coating process on a silica buffer layer which prevents Ag + migration into the glass substrate. The coated glass became transparent and photosensitive after Ag(Cl 1− x Br x ) microcrystals were precipitated in the coatings above 300°C. However, fading reaction did not proceed at room temperature. It was found that the deposition of a sensitizing layer including cuprous ions on the photosensitive layer was very effective in promoting fading reaction at room temperature. The cuprous ions in the sensitizing layer penetrated and diffused into the photosensitive layer during coating and firing. The cuprous ion located near or in the Ag(Cl 1− x Br x ) microcrystals acted as an effective sensitizer.

Photochromism of Guest N-Salicylideneaniline in the Rooms of Host Bile Acid Derivatives

Definite clathrate crystals of deoxycholic acid and its amide and alcohol derivatives as host molecules with N-salicylideneaniline as a guest molecule were prepared to investigate their photochromic properties. The photocoloration study was done by irradiating the crystal powder with 365 nm light; the thermal fading reaction of the photocolored species was followed by reflectance spectrophotometry at 303 K. From the sharp difference in the first-order rate constants of the thermal bleaching of the photochromes, it was found that the thermal unimolecular motion of photo-colored species was strongly influenced by the neighboring environments in the crystal state.

フィルム式簡易積算日射計による群落内光環境計測法の検討

A film-solarimeter was examined for field use. It integrates the solar radiation from the light transmittance of the film coated azo dyes. Relations between the film transmittance and the exposed solar energy were studied to make calibration curves under the field condition. At the same time, the variance of fading reaction of each film was investigated before and after the exposure. In order to evaluate field application, film-solarimeters were deployed to measure the amount of solar radiation inside the canopy of deciduous broad-leaved forest through three seasons. Several characteristics, merits and limits are found. If choose the appropriate time ranges and the possible happenings will be understood, the film-solarimeter must be an effectual and easy method to measure the amount of solar radiation in the experimental field.

Structure Reactivity Correlations of Azo Reactive Dyes Based on H-acid: I. NMR Chemical Shift Values, p Ka Values, Dyestuff Aggregation and Dyeing Behaviour

In this series of papers we report on structure reactivity correlations with respect to the degradation of dyestuffs. For this purpose a series of monoazo vinylsulphone/monochlorotriazine reactive dyes, based on H-acid with systematically varied substituents, was investigated in aqueous solution as well as on cellulosic substrates. In the first part we discuss the selected dyes, their synthesis, characterization, dyeing behaviour and some features which are pertinent to an understanding of the fading reactions, namely, the pKa values of the dyes and their aggregation behaviour.

Structure reactivity correlations of azo reactive dyes based on H-acid: II. Dye degradation by hypochlorite

In this paper we report on substituent effects on the degradation of azo reactive dyes based on H-acid by hypochlorite in aqueous solution and on cellulosic substrates. Based on the pH dependence of the fading reaction, we establish a new perception which says that in the pH range above 5 only the dissociated form of the corresponding ortho-hydroxyazo dyes undergoes the degradation, and thus the dye's p Ka value becomes a decisive criterion for the fastness to hypochlorite. With this background at hand, we use an expanded version of the Hammett equation, including the dyes' p Ka values, to yield a linear free energy relationship. Also, the effect of dyestuff aggregation on the fading is investigated.

Simultaneous multiwavelength study of thereaction of phenolphthalein with sodium hydroxide

A photodiode array (PDA) spectrophotometer was used to study the fading reaction of phenolpthalein in dilute sodium hydroxide solution. The principal component analysis (PCA) method was employed to identify the number of light absorbing species in the kinetics system. The target factor analysis (TFA) procedure, coupled with the Broyden-Fletcher-Goldfard-Shanno (BFGS) optimization method, was applied to the observed data to deduce the rate constants and the concentration-time profile of the reaction. The internal referencing method was shown to be essential in improving the quality of data obtained by a single beam PDA spectrophotomer.

KINETICS OF THE LIGHT‐INDUCED COLOR FADING OF VACUUM‐PACKAGED TURKEY BOLOGNA1

ABSTRACTThe light‐induced color fading reaction for vacuum packaged turkey bologna was studied using tristimulus colorimetry. Significant (P < 0.001) time and temperature effects were found for redness (+a and a/b ratio) decrease and yellowness (+b) increase during 1.5 h of light exposure. Lightness (L) increase at the product's surface was affected by time (P < 0.001) but not temperature (P > 0.05). Alterations of the redness and yellowness components of the product's hue were found to fit first order reaction kinetics. When the Arrhenius relationship of the temperature dependency of rate constants was applied, activation energies (Ea's) of 7.4, 2.6 and 6.2 kcal/mole were obtained for +a decrease, +b increase and a/b ratio decrease, respectively. The kinetics data for turkey bologna confirm that light‐induced color fading at the product's surface is more dependent on the extent of yellowness increase than on redness decrease.