Sensitive extractive spectrophotometric methods for the determination of trazodone hydrochloride in pharmaceutical formulations.
(9/23)
Two simple, rapid and sensitive extractive spectrophotometric methods have been developed for the assay of trazodone hydrochloride (TRH) in pure and pharmaceutical formulations. These methods are based on the formation of chloroform soluble ion-association complexes of TRH with bromothymol blue (BTB) and with bromocresol purple (BCP) in KCl-HCl buffer of pH 2.0 (for BTB) and in NaOAc-AcOH buffer of pH of 3.6 (for BCP) with absorption maximum at 423 nm and at 408 nm for BTB and BCP, respectively. Reaction conditions were optimized to obtain the maximum color intensity. The absorbance was found to increase linearly with increase in concentration of TRH, which was corroborated by the calculated correlation coefficient values (0.9996, 0.9945). The systems obeyed Beer's law in the range of 0.2-14.5 and 0.2-14.1 microg/ml for BTB and BCP, respectively. Various analytical parameters have been evaluated and the results have been validated by statistical data. No interference was observed from common excipients present in pharmaceutical formulations. The proposed methods are simple, accurate and suitable for quality control applications. (+info)
Protein error of pH indicators in the presence of detergents.
(10/23)
The characteristics of color development due to a protein error in the dye-binding method in the presence of a non-ionic detergent has been investigated by the calculations based on the chemical equilibrium of a protein error. The calculation results were compared with those obtained using three pH indicators (Bromophenol Blue, Bromocresol Green and Bromocresol Purple) and three non-ionic detergents in the pH region from 1 to 13. In the experiments, the color development increased with the lower concentrations of the detergents, but decreased at higher concentrations. The pH where the color development reached a maximum value shifted to a higher pH as the detergent was added. These experimental results were reproduced by the calculation when the molar absorptivity of the dye-protein complex was assumed to increase due to adding the detergent. Such agreement between the experimental and the calculated results indicates that the characteristics of the color development in the dye-binding method in the presence of a non-ionic detergent can be analyzed by calculations based on the chemical equilibrium of a protein error. (+info)
Applications of a microplate reader in yeast physiology research.
(11/23)
Microplate readers have been useful assistants of researchers for several decades. This work is focused on the applications of a simple absorbance microplate reader in yeast physiology research, and its advantages and limitations in comparison with alternative methods are discussed. The two main procedures involved are measuring growth curves and monitoring the pH changes of medium using two different pH indicators. We suggest mathematical formulas for converting absorbance data into pH values. With a microplate reader as many as 96 samples can be simultaneously analyzed, while medium consumption is minimized to 100 microL per sample. The results can be observed in 24-48 h (for growth curves) or in 1-3 h (for pH changes) with minimal hands-on time required. (+info)
Influence of pH for the determination of serum albumin by a dye-binding method in the presence of a detergent.
(12/23)
In the dye-binding method, the absorbance increase caused by a protein error of a pH indicator is observed only in a restricted pH range. However, this pH range in the presence of a detergent has not yet been examined. Thus, the author investigated the pH (pH(UL)) where the absorbance increase becomes zero by a calculation based on the chemical equilibrium of a protein error of a pH indicator, and by experiments using four sulfonephthalein dyes. The pH(UL) value changed only with the detergent concentration, but did not change at all due to the dye, buffer solution or protein concentrations. Although the pH(UL) value was different according to the kind of dye used, it correlated well with the pK(D) values (dissociation constant) of BPB, BCG, BCP and BTB. The characteristics of pH(UL) in the reactions of the four dyes indicated good agreement with that obtained by a calculation. (+info)
The impact of the assay for measuring albumin on corrected ('adjusted') calcium concentrations.
(13/23)
Rapid sodium chloride tolerance test for presumptive identification of enterococci.
(14/23)
A rapid test is described which distinguishes enterococci from other group D streptococci in 8 to 24 h by use of a medium containing brain heart infusion agar, NaCl, dextrose, and bromocresol purple. (+info)
Bromcresol purple dye-binding methods underestimate albumin that is carrying covalently bound bilirubin.
(15/23)
We used automated and manual versions of two commonly used dye-binding methods for albumin to quantify albumin that had been modified by covalent addition of bilirubin. Dye-binding methods based on reaction with bromcresol purple underestimated the modified albumin by as much as 29%. Dye-binding methods based on reaction with bromcresol green were unaffected by the presence of covalently attached bilirubin. Neither method was affected by the presence of noncovalently bound bilirubin. (+info)
Dimer formation of bromocresol purple anions on the phosphorylated intermediate of sarcoplasmic reticulum.
(16/23)
The mechanism of spectral shift and absorption intensity change of the divalent bromocresol purple (BCP) anion was further investigated and it was characterized as a spectrophotometric membrane probe. At high concentrations (1-40 mM), the absorption intensity of th BCP anion at 590 nm (monomer band) decreased markedly with increase of the dye concentration, while another absorption band appeared at 554 nm. Analysis of the change of absorption intensity showed that the mared decrease resulted from dimer formation of BCP (polymer formation at concentrations higher than 20 mM). Wavelengths of maximum absorption (lambdamax) of the BCP anion were determined in various solvents and comparison of these lambdamax's with lambdamax of the BCP anion bound to SR showed that the hydrophobicity of the area of BCP anion binding to SR corresponded to a refractive index of 1.429. While the BCP anion bound to SR showed a monomer spectrum, a dimer band appeared for the BCP anion bound to SR-Pi (phosphorylated protein) with a marked decrease in the absorption intensity at the monomer band, indicating that two polar groups, binding sites for the BCP anions, closely approached each other in the SR-Pi configuration. (+info)