PubMed · 2895076
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J I Reppun. 1987. Sudden death.. https://pubmed.ncbi.nlm.nih.gov/2895076/
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Capillary isotachophoresis (ITP) with conductimetric detection has been used for separating and determining bopindolol (I) in commercial mass-produced pharmaceutical preparations. The optimised operational electrolyte system consisted of 5 mM potassium picolinate and 5 mM picolinic acid (leading electrolyte, LE; pH 5.37) and 10 mM formic acid as the terminating electrolyte (TE). The driving and detection currents were 50 microA (for 350 s) and 10 microA, respectively. The single analysis took about 12 min. Under such conditions the effective mobility of I was determined as 16.73 10(-9)m(2) V(-1) s(-1) (with tetraethylammonium as the mobility standard). The calibration graph relating the ITP zone length to the concentration of I was rectilinear (r=0.99990) in the range 10-100 mg l(-1). The relative standard deviation (R.S.D.) was 0.90% (n=6) when determining 50 mg l(-1) of I in pure test solution. Sample pre-treatment of the tablets involved ice-cooled extraction of I with methanol. The method was suitable for determining I in Sandonorm tablets with R.S.D. value 1.45% (n=6). According to the validation procedure based on the standard addition method the recovery was 97.3%.
Characterization of the racemic species, which can be a racemic compound, a racemic conglomerate, or a pseudoracemate (solid solution), is a prerequisite for the design of crystallization resolution processes. It is useful to determine the solid/liquid equilibrium solubility of the enantiomer mixtures for crystallization operation. For the beta-blocker drug propranolol hydrochloride, Gibbs free energy of formation of racemic compound and entropy of mixing of the (R)- and (S)- enantiomers in the liquid state for racemic conglomerate were calculated. The structural differences between (R, S)-propranolol hydrochloride and its (S)-enantiomer were further investigated by powder X-ray diffraction patterns, infrared spectra, and solid-state NMR spectra. The solubility and metastable zone width of (R, S)- propranolol hydrochloride in a mixed solvent of methanol and acetone were determined by cooling crystallization over the temperature range 3.5-42.5 degrees C. The ternary solubility diagram of (R)-, (S)-propranolol hydrochloride was constructed using the same mixed solvent. The diagram will be useful as a guide for choosing crystallization operation conditions to produce pure enantiomers.
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