Buffer-Free High Performance Liquid Chromatography Method for the Determination of Theophylline in Pharmaceutical Dosage Forms

Purpose: To develop and validate a simple, economical and reproducible high performance liquid chromatographic (HPLC) method for the  determination of theophylline in pharmaceutical dosage forms.Method: Caffeine was used as the internal standard and reversed phase C-18 column was used to elute the drug and standard. The mobile phase was prepared by mixing water:acetonitrile:methanol at the ratio of 90:03:07 and the pH set at 4.6. Flow rate and ultraviolet (UV) detector were set at 1.0 mLmin-1 and 271 nm, respectively. The method was validated for linearity, recovery, accuracy, precision, specificity, and also for inter-day stability under laboratory conditions.Results: Retention time was 5.5 min. The limits of detection and  quantification were 12.5 ngmL-1 and 100 ngmL-1, respectively. Recovery accuracy (%) for different concentrations ranged from 100.05 to 102.43; regression coefficient (R2) of 0.994; precision RSD < 2.0, and negligible interference from common excipients.Conclusion: The method is simple, rapid, highly specific and suitable for the determination of theophylline. Absence of buffer and use of small quantity of organic solvents increase the life span of the column and reduce the cost of routine analysis of theophylline in industry.Keywords : Buffer-free, High performance liquid chromatography, Theophylline, Dosage form

Binary Ce(III) and Li(I) triflate salt composition for solid polymer electrolytes

This study describes the results of the characterization of solid polymer electrolytes using chitosan matrix plasticized with glycerol and doped with cerium and lithium triflates binary salt composition. The electrolytes were prepared by solvent casting method and characterized by thermal analysis (thermogravimetric analysis - TGA and differential scanning calorimetry - DSC), impedance measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and electron paramagnetic resonance (EPR). Samples are thermally stable up to 128-153ºC and most of them are amorphous. In some cases, the appearance of crystalline peaks is due to the diffraction of salt domains, which makes the samples less conductive. The room temperature conductivity maximum of 10-6 S cm-1 at 30ºC was obtained for the samples with the same total salts mass of 0.15 g (ChitCeTrif0.05LiTrif0.10 and ChitCeTrif0.10LiTrif0.05). Finally, the EPR analysis suggests that the local coordination environment of the paramagnetic Ce3+ is not the same in different samples. In summary, beside the modest conductivity values of these samples, they are still adequate for some electrochemical applications.We are grateful to the Fundação para a Ciência e Tecnologia and FEDER (Ref. UID/QUI/00686/2013 and UID/QUI/0686/2016) and program POCH/FSE for a grant SFRH/BD/97232/2013 (R. Alves) for financial support of this work. The authors are grateful to Mr. Marcos de Oliveira, Jr. for technical assistance. The financial support of the Brazilian agencies Capes and The Brazilian National Council for Scientific and Technological Development (CNPq) are gratefully acknowledged. Research was partially financed by the CeRTEV, Center for Research, Technology and Education in Vitreous Materials, FAPESP 2013/07793-6. M. M. Silva and A. Pawlicka acknowledges The Brazilian National Council for Scientific and Technological Development (CNPq) for grants provided by this institution (PVE grant 406617/2013-9 and PQ grant 305029/2013- 4).info:eu-repo/semantics/publishedVersio