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Simple, accurate, sensitive and validated UV spectrophotometric and chemometric methods were developed for the determination of imidapril hydrochloride (IMD) in the presence of both its alkaline (AKN) and oxidative (OXI) degradation products and in its pharmaceutical formulation. Method A is the fourth derivative spectra (D4) which allows the determination of IMD in the presence of both AKN and OXD, in pure form and in tablets by measuring the peak amplitude at 243.0 nm. Methods B, C and D, manipulating ratio spectra, were also developed. Method B is the double divisor–ratio difference spectrophotometric one (DD–RD) by computing the difference between the amplitudes of IMD ratio spectra at 232 and 256.3 nm. Method C is the double divisor-first derivative of ratio spectra method (DD–DR1) at 243.2 nm, while method D is the mean centering of ratio spectra (MCR) at 288.0 nm. Methods A, B, C and D could successfully determine IMD in a concentration range of 4.0–32.0 µg/mL. Methods E and F are principal component regression (PCR) and partial least-squares (PLS), respectively, for the simultaneous determination of IMD in the presence of both AKN and OXI, in pure form and in its tablets. The developed methods have the advantage of simultaneous determination of the cited components without any pre-treatment. The accuracy, precision and linearity ranges of the developed methods were determined. The results obtained were statistically compared with those of a reported HPLC method, and there was no significant difference between the proposed methods and the reported method regarding both accuracy and precision.

Loxoprofen sodium (LOX) is a recently developed novel propionic acid derivative. Owing to its instability under both hydrolytic and oxidative conditions, the development of simple, rapid and sensitive methods for its determination in the presence of its possible forced degradation products becomes essential. Two simple chromatographic methods, high-performance thin layer chromatography (HPTLC) and high-performance liquid chromatography (HPLC), were developed associated with ultraviolet (UV) detection. In HPTLC-densitometric method, the separation of LOX from its degradation products was achieved using silica gel F254 plates and toluene:acetone:acetic acid (1.8:1.0:0.1, v/v/v) as the developing system followed by densitometric scanning at 220 nm. In the HPLC-UV method, the separation was performed using isocratic elution system with acetonitrile: 0.15% triethylamine (pH 2.2) (50:50, v/v) on C18 analytical column. The flow rate was optimized at 1.0 mL·min-1 and UV detection was achieved at 220 nm. Validation was performed in accordance with the International Conference on Harmonization guidelines and the method was perfectly applied for determination of LOX in its pharmaceutical preparation. The results obtained were statistically compared to those obtained after application of the official HPLC method, where no significant difference was found incompliance with precision and accuracy. Identification and characterization of the possible hydrolytic degradation product under alkaline conditions and that produced during oxidative degradation using hydrogen peroxide were structurally elucidated using infrared and mass spectrometry analyses.

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UDC 535.243 and M. M. Abd El-Kawy a Linezolid (LIN) is considered the fi rst available oxazolidinone antibacterial agent. It is susceptible to hydrolysis and oxidation. Five simple, accurate, sensitive and validated UV spectrophotometric methods were developed for LIN determination in the presence of its alkaline (ALK) and oxidative (OXD) degradation products in bulk powder and pharmaceutical formulation. Method A is a second derivative one (D 2 ) in which LIN is determined at 240.9 nm. Method B is a pH-induced differential derivative one where LIN is determined using the fourth derivative (D 4 ) of the difference spectra (ΔA) at 285.3 nm. Methods C, D, and E are manipulating ratio spectra, where C is the double divisor-ratio difference spectrophotometric one (DD-RD) in which LIN was determined by calculating the amplitude difference at 243.7 and 267.6 nm of the ratio spectra. Method D is the double divisor-fi rst derivative of ratio spectra (DD-DD 1 ) in which LIN was determined at 270.2 nm. Method E is a mean centering of ratio spectra one (MCR) in which LIN was determined at 318.0 nm. The developed methods have been validated according to ICH guidelines. The results were statistically compared to that of a reported HPLC method and there was no signifi cant difference regarding both accuracy and precision.Introduction. Linezolid (LIN) or (S)-N-[[3-[3-fl uoro-4-(4-moropholinyl) phenyl]-2-oxo-5-oxazolidinyl] methyl] acetamide is considered the fi rst available oxazolidinone antibacterial agent. This is a new class of antimicrobials with good activity against Gram-positive bacteria. It possesses a unique mechanism of bacterial protein synthesis inhibition [1]. LIN shows strong activity against Gram-positive pathogens and is currently the only antibacterial agent that can be administered orally as well as intravenously with strong activity against methicillin-resistant Staphylococcus aureus. It may be particularly useful as an alternative to vancomycin in patients with renal function impairment, poor or no intravenous access, absence of glycopeptide tolerance, and those requiring outpatient therapy [2].A search of the literature reveals some LC methods for quantitation of LIN in tablets and in biological fl uids [3][4][5][6][7][8][9][10][11][12]. A chiral LC method has also been reported [13]. LIN was determined in the presence of its alkaline-induced degradation products using TLC densitometry, and D 1 and DD 1 methods [14]. Capillary zone electrophoresis was also applied for determination of LIN [15,16]. Its electrochemical characterization was also described [17]. The ICH guidelines [18] describe various stress conditions through which the stability of the active pharmaceutical ingredient (API) could be assessed. So, separation, identifi cation, quantifi cation, and characterization of the most probable and possible degradation products help in the improvement of the quality of API and its formulation.Most of the reported methods are based on chromatographic techniques requiring relatively high cost and long ana...