The electrochemical oxidation of an antibacterial drug, gatifloxacin (GTF), at multi-walled carbon nanotube paste electrode was studied employing cyclic and differential pulse voltammetry methods. The effect of scan rate, pH, different electrolytes, pulse amplitude and accumulation time on electrochemical behavior of GTF were investigated. GTF shows a well-defined oxidation peak at +1.05 V in acetate buffer of pH 5.0±0.01. Under optimized conditions, the peak current is linear over the concentration range 2.13×10 -5 –1.7×10 -4 m with detection limit of 4.5×10 -9 m . The applicability of the proposed method is further extended to in vitro determination of the drug in biological fluids. Differential pulse voltammetry and UV-VIS absorption techniques were employed to probe the interaction between GTF and calf thymus DNA. The addition of ds-DNA to the analyte containing GTF results in a decrease of the peak current and a positive shift of the peak potential of GTF in differential pulse voltammetry analysis, indicating the dominance of the intercalating interaction. The spectroscopic data also confirm the interaction between GTF and ds-DNA. The combining constant (β) and combining number (m) of GTF-mDNA were also determined.
The theoretical titration curve of a weak acid with a strong base was considered. The limitation of the Henderson-Hasselbalch equation for the calculation of pH in the buffer region was discussed. One novel simple equation for the exact calculation of pH from the beginning of titration up to the equivalence point was derived. By using this equation with one implicit approximation (the dissociation of water), the calculation of pH values after each addition of titrant is possible. A novel equation provides the simple and exact calculation of pH in the range of buffer, and that can be done in a simple and logical way without complex handling of acid-base equilibrium with computer and spreadsheet software. The calculated titration curves for different concentrations of acetic acid and sodium hydroxide were shown.
A simple, sensitive, accurate and portable reverse flow injection (rFIA) spectrophotometric method is proposed for the on-line determination of trace phosphate in seawater. In acid conditions, phosphate reacts with ammonium molybdate to form molybdophosphoric acid, which forms a soluble complex compound with ethyl rhodamine B in the presence of polyvinyl alcohol. The absorbance of the complex compounds was measured by optical detector at 585 nm. Chemical factors and rFIA variables affecting the system were also discussed. Under the optimal conditions, the calibration graph for phosphate was linear over the concentration range from 2.0 to 200.0 μg/l with a correlation coefficient of 0.9995. The detection limit was 0.05 μg/l; the relative standard deviation was 0.61% for a solution containing 50 μg/l phosphate (n=15). The recovery of phosphate from three samples ranged from 96.4 to 98.4% of the added amount. The results obtained for phosphate by the proposed rFIA spectrophotometric method were in very close agreement with those using the conventional method.
Chemometric techniques are widely used for resolving overlapped spectra in different analysis type including simultaneous determination of active ingredients in pharmaceutical preparation. Processed data are used in some instances alternative to the raw data. Standardization, normalization, and mean centering are preferred data preprocessing methods in multivariate analysis techniques. In this study, derivative and ratio spectra derivative spectrophotometric methods are used in preprocessing for spectrophotometric data as an alternative to the other procedure in partial least squares technique (PLS-1) for resolving overlapped spectra of ternary mixtures of montelukast sodium, desloratadine, and levocetirizine dihydrochloride. Simultaneous determination and quantitation of these active ingredients from their bulk solutions and pharmaceutical preparations was achieved successfully by this developed and optimized partial least squares method. These results indicate that derivative and ratio spectra derivative spectrophotometric methods will be used as a new data preprocessing method in chemometric techniques from now on.
Despite the fact that mineral oils are commonly used in industry, they pose a serious health hazard for workers who are exposed to them due to their sensitizing and carcinogenic properties. Health protection in workers exposed to contact with these substances requires, in addition to collective means of protection, personal protective equipment such as gloves. This paper presents the current state of knowledge concerning permeation of oils and other water-insoluble or non-volatile substances through polymer membranes used in protective clothing and gloves, based on literature published worldwide. Various authors have presented critical assessment, methods of testing material resistance and measuring equipment used. The presented test methods for assessment of mineral oil permeation through the material of protective gloves have allowed the development of standards. We also present our own research in which we used solid collecting medium to investigate permeation of oils.
This paper describes a new, simple, precise, and accurate HPTLC method for simultaneous estimation of ethinyl estradiol and drospirenone as bulk drug and in tablet dosage forms. Chromatographic separation of the drugs was performed on aluminum plates precoated with silica gel 60 F 254 as the stationary phase and the solvent system consisted of toluene/methanol/ammonia (8:2:0.1) (v/v/v). Densitometric evaluation of the separated zones was performed at 280 nm. The two drugs were satisfactorily resolved with R f values of 0.29±0.02 and 0.42±0.02 for ethinyl estradiol and drospirenone, respectively. The accuracy and reliability of the method was assessed by evaluation of linearity (150–400 ng/spot for ethinyl estradiol and 30–80 ng/spot for drospirenone), precision (intraday RSD 0.84–1.01% and interday RSD 0.76–1.04% for ethinyl estradiol, and intraday RSD 0.76–1.32% and interday RSD 0.73–1.01% for drospirenone), accuracy (98.48±0.21% for ethinyl estradiol and 98.30±0.15% for drospirenone), and specificity, in accordance with International Conference on Harmonisation (ICH) guidelines.
In this paper, glassy carbon (GC) was modified through the electrochemical polymerization of chrysin (PolyChr/GC) on the surface in media where the electrode surface was aqueous and non-aqueous. Electrochemical polymerization was performed between +800 mV and +2600 mV in aqueous medium, and from +500 mV to +1800 mV in non-aqueous medium in 100 mV s -1 sweep rate with 30 cycles. Modified electrode surface characterization was done by cyclic voltammetry and electrochemical impedance spectroscopy. In the study, the interaction between the PolyChr/GC electrode surface and Cu(II), Zn(II), Cd(II), Pb(II), Co(II) and Ni(II) ions was investigated by using the square wave voltammetry technique. The PolyChr/GC electrode surface was found to be sensitive and selective towards Cu(II), Pb(II) and Cd(II) ions.
