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KEYWORDSSimple and precise spectrofluorometric method has been developed and validated for the determination of linagliptin (LNG) in the range of 10-110 μg/mL. The results obtained were of good precision and statistically compared to the reference method using one-way analysis of variance (ANOVA). The method developed was satisfactorily applied to the analysis of the pharmaceutical formulation and proved to be specific and accurate for the quality control of linagliptin in its pharmaceutical dosage form. The development of spectrofluorometric method for the determination of LNG was of interest as no such methods have been reported.

KEYWORDSIn this work, the acidic degradation product of sitagliptin phosphate monohydrate (STG) was synthesized, separated and its structure was elucidated. Additionally, two reversed-phase liquid chromatographic (RP-LC) methods have been developed for the determination of STG. The first method comprised the determination of STG in binary mixture with sitagliptin acid degradation product (SDP) in laboratory prepared mixtures, in plasma and in dosage form. This method was based on isocratic elution using a mobile phase consisting of potassium dihydrogen phosphate buffer (pH =4.6) -acetonitrile (30:70, v:v) with fluorometric detection. The fluorometric detector was operated at 267 nm for excitation and 575 nm for emission. In the second method, the simultaneous determination of STG and metformin (MET) in the presence of SDP has been developed. In this method, the ternary mixture of STG, MET and SDP was separated using a mobile phase consisting of potassium dihydrogen phosphate buffer (pH = 4.6) -acetonitrile (15:85, v:v) with UV detection at 220 nm. Chromatographic separation in the two methods was achieved on a Symmetry ® Waters C18 column (150 mm × 4.6 mm, 5 μm). The optimized methods were validated and proved to be specific, robust and accurate for the quality control of the cited drugs in pharmaceutical preparations.

There are more than 100000 different species of fungi, many of which are beneficial to food and fermentation industries; however, hundreds are pathogenic to plants and a few hundreds have been shown to cause infection in humans. 1)Treatment of fungal infections is considerably more difficult than that of a bacterial infection as many fungal infections occur in poorly vascularised or avascular tissues. 2)Ketoconazole (KT), clotrimazole (CL), miconazole nitrate (MN) and econazole nitrate (EN) (Fig. 1) are imidazole derivatives which represent a large and emerging group of synthetic antifungal agents.Several methods for the determination of ketoconazole, clotrimazole, miconazole nitrate and econazole nitrate, have been described in the literature. They include volumetric, 3) spectrophotometric, [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] spectrofluorimetric methods, [19][20][21] capillary electrophoresis method, 22,23) thin layer chromatography, 24,25) gas chromatography 26,27) and high performance liquid chromatographic methods. [28][29][30][31][32][33][34][35][36][37][38][39][40] However, the imidazole antifungal derivatives are susceptible for the degradation due to the effect of temperature, oxygen, light and pH and the degraded products may be pharmacologically inactive. In addition, there are many antifungal pharmaceutical preparations containing some corticosteroid hormones and the pharmacopeial methods don't report any method for the determination of these drugs either in presence of their degradation products or in presence of corticosteroid hormones.In this study simple, rapid precise and selective densitometric and HPLC method for the determination of some antifungal drugs KT, CL, MN, and EN in pure form or in the presence of their degradation products were developed. The methods were successfully applied to determine these drugs in pharmaceutical dosage forms and in presence of some corticosteroid hormones. ExperimentalMaterials and Reagents Ketoconazole (KT) Sedico Pharmaceutical Co., 6 October City-Egypt. The purity of the sample was found to be 99.82Ϯ1.157 applying a non-aqueous titration pharmacopoeial method. 3)Clotrimazole (CL) Pharcopharmaceuticals, Alexandria-Egypt. The purity of the sample was found to be 99.87Ϯ1.856 applying a non-aqueous titration pharmacopoeial method. 3)Miconazole nitrate (MN) Minapharm-Egypt. The purity of the sample was found to be 99.776Ϯ1.695 applying a non-aqueous titration pharmacopoeial method. Control and Research; Cairo, Egypt. Received February 26, 2007; accepted September 30, 2007; The HPLC method determined mixtures of CL or EN with their degradation products which were separated and quantified on a Zorbax C8 column. Elution was carried out using methanol : phosphate buffer pH 2.5 (65 : 35 v/v) as a mobile phase at a flow rate of 1.5 ml/min and UV detection at 220 nm for CL. For EN, a mixture of methanol : water containing 0.06 ml triethylamine pH 10 (75 : 25 v/v) was used as a mobile phase at a flow rate of 1.5 ml/min and UV detection at 225 nm. ...

Two stability indicating chromatographic methods were proposed for the determination of almotriptan, eletriptan, and rizatriptan, in presence of their acid degradation products. The first method is a quantitative densitometric thin layer chromatography. The developing systems were; acetonitrile: methanol: dichloromethane: ammonia (10:6:3:1 v/v), ethyl acetate: methanol: ammonia (15:4:1 v/v), and methanol: acetonitrile: ammonia (9:4:1 v/v) for almotriptan, eletriptan and rizatriptan respectively. The TLC plates were scanned at 235 nm. Linear relationships were obtained over concentration ranges (5–50 μg/spot) for almotriptan and rizatriptan, and (5–60 μg/spot) for eletriptan. The second method based on the separation and determination of the studied drugs, using RP-HPLC technique. The separation was achieved on C18 Hypersil column, elution was carried out using phosphate buffer pH 3: methanol: acetonitrile (2: 1:1 v/v) at flow rate 2 mL/min and UV detection at 235 nm. Linear relationships were obtained over concentration ranges (10–200 μg/mL) for almotriptan and eletriptan, and (10–180 μg/mL) for rizatriptan. The chromatographic methods were successfully applied for the determination of each of the studied drugs in pure form, tablet form, and in laboratory prepared mixtures with their acid degradation products.