Intermolecular and low-frequency intramolecular Raman scattering study of racemic ibuprofen.

We report the low-temperature Raman scattering study of racemic ibuprofen. Detailed analysis of the racemic ibuprofen crystal symmetry, related to the vibrational properties of the system, has been presented. The first principle calculations of a single ibuprofen molecule dynamical properties are compered with experimental data. Nineteen, out of 26 modes expected for the spectral region below 200cm(-1), have been observed.

High-performance liquid chromatographic assay of fleroxacin in human serum using fluorescence detection.

A HPLC method has been developed for the direct assay of fleroxacin in serum, without previous extraction. Serum samples, after the addition of sodium dodecylsulfate (0.5%), were injected directly into an LC Hisep column. The mobile phase consisted of acetonitrile, water and triethylamine in a per cent volume ratio 18:80:2. The pH of the mobile phase was adjusted to 6.50 with the addition of phosphoric acid. The drug was detected fluorometrically at lambda (ex )=280 nm and lambda (em )=450 nm . The linear concentration range of fleroxacin was between 0.01 and 2.0mg/l with a detection limit of 1ng/ml.

Study of solution equilibria between aluminum(III) ion and ofloxacin.

The complex formation equilibria between aluminium(III) ion and ofloxacin in 0.1 mol/l(-1) ionic medium at 298 K were studied by glass electrode pH-metric and UV spectrophotometric measurements. Within ofloxacin to aluminium mole ratio ranging from 2:1 to 25:1 and in pH interval from 2.5 to 10.5, the obtained experimental results were explained by the formation of the following complexes: AI(Hoflo) (log beta1,1,1 = 15.93 +/- 0.03), Al(oflo)2 (log beta1,2,0= 14.84 +/- 0.07), Al(oflo) (log beta1,1,0 = 10.20 +/- 0.04) as well as several other mixed and pure hydrolytic complexes. The structure and mechanism of the formation of the complexes and their possible implications on aluminum toxicity were discussed.

Spectrophotometric determination of oxytetracycline in pharmaceutical preparations using sodium molybdate as analytical reagent.

A spectrophotometric method is proposed for the determination of oxytetracycline in pharmaceutical preparations. The method is based on the measurement of the absorbance of the molybdate-oxytetracycline complex at 404 nm (pH 5.50; mu = 0.1 M; 20 degrees C). The composition of the complex (1:1) was determined by the application of the spectrophotometric methods of Job and Bent-French (pH 5.50; lambda = 390 nm; mu = 0.1 M). The relative stability constant (K' = 10(4.6) of the complex was obtained by the methods of Sommer and Nash (pH 5.50; lambda = 390 nm; mu = 0.1 M; 20 degrees C). The molar absorptivity of the complex was 9.5 x 10(3) l mol-1 cm-1. Beer's law was obeyed over the concentration range 2.48-34.78 micrograms ml-1. The relative standard deviation RSD (n = 10) was 0.27-0.39%. The method proposed can be applied to the assay of oxytetracycline in capsules. The detection limit of oxytetracycline is 2.5 micrograms ml-1.

Spectrophotometric determination of pefloxacin in pharmaceutical preparations.

It has been established that the antibiotic pefloxacin (Abaktal) methanesulphonate reacts with Fe(III) at pH 1.00-8.00 to form a water-soluble complex with maximum absorbance at 360 nm. The composition of the complex, determined spectrophotometrically by the application of Job's, molar-ratio and Bent-French's methods, was pefloxacin: Fe(III) = 1:1 (pH = 2.50; lambda = 360 nm; mu = 0.1 M). The relative stability constant, obtained by the methods of Sommer and Asmus was 10(5.02) (pH = 2.50; lambda = 360 nm; mu = 0.1 M). The molar absorptivity of the complex at 360 nm was found to be 4.8 x 10(3) l mol-1 cm-1. Beer's law was followed for pefloxacin concentrations of 2.15-85.88 micrograms ml-1. The lower sensitivity limit of the method was 2.15 micrograms ml-1. The relative standard deviation (n = 10) was 0.57-1.07%. The method can be applied to the rapid and simple determination of pefloxacin in aqueous solutions and tablets.