Assay Development for Aminoglycosides by HPLC with Direct UV Detection.

The absence of UV chromophores in the structure of most aminoglycosides impedes an easy and straightforward development of analytical methods. It was demonstrated that addition of borate to the mobile phase allowed direct detection of aminoglycosides at the lower end of the UV spectrum. Although the borate ion complexes preferably with compounds possessing vicinal diols, the aim of this study was to develop an assay for tobramycin that does not contain vicinal diols in its structure. Amikacin, an aminoglycoside with a broad spectrum, was added to the study for its high therapeutic importance. An assay for both has been developed and validated. This method was developed on an XBridge C18 column (4.6 mm x 250 mm; 5 µm) and the mobile phase consisting of methanol-disodium tetraborate decahydrate buffer (0.1 M; pH = 9.0)-water (20:20:60) supplemented with 1 g/L sodium octanesulfonate was run isocratically at a column temperature of 40°C. After validation according to International Conference on Harmonization guidelines, this method was tested on two commercially available pharmaceutical formulations, Amukin® and Tobrex®. The developed method was fast, accurate, easy to use and cheap as it did not require sophisticated equipment or tedious derivatization steps.

Dependence of the kinetic and thermodynamic parameters on hydrophilic-lipophilic character of alprazolam, clonazepam, diazepam, doxepin and haloperidol in alkaline environment.

Examination of the stability of clonazepam, diazepam, alprazolam, haloperidol, and doxepin in basic solutions was performed, together with an assessment of the kinetic (k, t0.1i t0.5) and thermodynamic (Ea, ΔH(++)i ΔS(++)) stability-indicating parameters, which were compared with the lipophilicity (logP) of the studied drugs. It was observed that the calculated values of Ea, ΔH(++) and ΔS(++) for the studied drugs increased from 41.04 kJ/mol to 125.50 kJ/mol, from 37.82 kJ/mol to 122.24 kJ/mol and from -167.09 J/Kmol to 53.02 J/Kmol, respectively, along with an increase of lipophilicity (logP) from 2.12 to 4.30 for the most hydrophilic alprazolam to the most lipophilic haloperidol. The degradation products were identified using UPLC/MS/MS method.