Two simple, specific, accurate, precise, sensitive and cost effective spectrophotometric methods have been developed and validated for quantification of linagliptin in pure form and pharmaceutical formulations. Method A is established on the computation of absorbance of purple coloured chromogen complex at 463 nm which is formed by the condensation reaction of the primary amine group of linagliptin with vanillin (Schiff base formation). Method B is established on computation of absorbance of orange coloured chromogen at 454 nm which is formed by the condensation reaction of the primary amino group of linagliptin with NQS (1, 2-naphtho quinine 4- sulphonic acid sodium salt) reagent. Two methods executed linearity in the concentration range of 2.5-20 mg/ml and 10-90 mg/ml for method A and B respectively. Linear relationship with good correlation coefficients of 0.998 and 0.995 were monitored between absorbance and corresponding concentrations of linagliptin in vanillin and NQS respectively. The limit of detection, limit of quantification, molar absorptivity, sandell’s sensitivity and ring born concentrationvalues were determined for the two spectrophotometric methods. The contemplated methods were validated statistically as per ICH guidelines. The reliability of both the methods is further ascertained by performing recovery tests by standard addition method. No significant interference was inspected from the excipients commonly used as pharmaceutical aids with the assay procedure. The contemplated methods were simple, sensitive, specific and can be successfully employed in routine analysis of linagliptin in pharmaceutical dosage forms.

Mometasone furoate is a synthetic glucocorticoid with anti-inflammatory and anti-allergic effects, used for the treatment of allergic rhinitis, asthma, and dermatoses. In this study, a spectrophotometric method, as a selective and sensitive method, was developed for the determination of mometasone furoate after DERIVATIZATION. For this purpose, mometasone was first reacted with sodium cyanide to prepare the drug derivatives. After that, the effects of different variables such as reaction solvent, concentration of the reagents, pH, and reaction time were studied. The final results showed that the determination method was linear in the range of 2-18 μg/ml. It seems that after 24 hours, the reaction was complete. The reaction product was characterized by NMR and FT-IR spectroscopy, and the accuracy and precision of the developed method were also studied. At last, the method was checked on Mometasone Ointment (0. 1%), and the results were compared with the results of the HPLC method as a standard method.

Separation of some biogenic amines via RP-HPLC using mixed micellar mobile phase was investigated. The compounds were derivatized before hand by dansyl chloride as a chromophoric reagent. Appropriate conditions for separation, were determined by studying factors such as temperature, type and percentage of organic modifier, concentration of surfactants (SDS and Brij-35) and the pH of the mobile phase. The number of theoretical plates (N), asymmetry factor (B/A) and selectivity factor (α) considered as criteria for finding the appropriate conditions for separation. Appropriate condition, were: 40˚C, 40 mM SDS, 0.5 mM Brij-35 and 10% 1-propanol at pH=5.

Fatty acids play important roles in biological systems and the newborns fatty acids requirements are covered only by the milk. It is of particular interest to qualify the content of the fatty acids in the milk. This study was performed to determine the levels of some fatty acids in the infant formulas and also to describe a method without DERIVATIZATION for the fatty acids analysis and applying it to the control of infant formulas. Free fatty acids were produced by adding isopropanol-KOH to milk fat extract and heating it to saponify and acidify by H2SO4. Free fatty acids were extracted and were quantified by capillary gas chromatography on a fused silica column (AT-1000) and flame ionization detector. The average experimental values of lauric, palmitic, stearic and linoleic fatty acids contents of twenty infant formulas were 6.47, 16.52, 2.11 and 14.56 g/100g, respectively. The obtained experimental values of lauric and linoleic fatty acids contents of twenty infant formulas were in good agreement with the values proposed by standards of codex alimentary.

In this study, a simple, rapid, and an economical method has been proposed for the extraction, preconcentration, and determination of parabens (methyl-, ethyl-, and propylparaben) in different samples based on DERIVATIZATION by acetic anhydride and preconcentration using air-assisted liquid–liquid microextraction in a single step. In this method, 1, 1, 2, 2-tetrachloroethane (extraction solvent) containing mL-level of acetic anhydride (DERIVATIZATION agent) is injected into aqueous sample containing parabens and picoline (catalyst). The mixture of aqueous and organic phases is withdrawn into a glass syringe and then injected into the test tube for several times till a turbid solution is obtained. After centrifuging, 1 mL of the sedimented phase is injected into gas chromatography-flame ionization detector. The effect of catalyst volume, DERIVATIZATION agent volume, extraction solvent type and volume, ionic strength of the solution, pH, and numbers of extraction on the extraction efficiency is investigated. Under the optimal conditions, the enrichment factors and enhancement factors for the parabens were obtained in the ranges of 310-353 and 2,484-5,298, respectively. Limits of detection were between 0.18 and 8.5 mg L-1. The method was found to be linear over the range of 10-10,000 mg L-1 with good coefficients of determination (R2 > 0.999). The obtained extraction recoveries ranged from 69 to 107 % and precision of the method, expressed as relative standard deviation (RSD %), was within the range of 4.0-13 %. The proposed method was successfully applied for determination of parabens in different samples such as cream, toothpaste, and mouthwash.

Electrochemical oxidation of levodopa (LD) as one of the most well-known neurotransmitters has been studied in the presence of some aniline derivatives. The electron transfer of LD is followed by two competitive reactions in the presence of these amines. The reactions are the Michael additions of side chain amine group of LD and/or aromatic amines to electrochemically generated o-quinone. There are two ECE mechanisms for both pathways and the competition between these inter and intramolecular reactions drastically depends on the pH of the medium. The pH dependence of reactions has been studied and the observed homogeneous rate constants of the reactions were estimated by digital simulation of cyclic voltammograms. The effect of aniline substituents was also studied with regard to their reactivities toward o-quinone of LD and the competitive reactions. Based on the obtained results, the products of intermolecular reactions are electroactive diphenylamine derivatives and their half-wave potentials depend on the nature of the aniline substituent.