In-house validation method for quantification of amoxicillin in medicated feedingstuffs with the use of HPLC-DAD technique

IntroductionA high-performance liquid chromatographic–diode array detector (HPLC-DAD) method for the determination of amoxicillin in medicated feedingstuffs was developed and validated. The method was used to investigate the quality requirements of animal feedingstuffs (declared content of active substance and feed homogeneity).Material and MethodsTwo-gram samples were extracted by potassium phosphate buffer solution. Extracts were filtered and directly analysed by HPLC-DAD without further clean-up. Amoxicillin was separated by acetonitrile and 0.01M phosphate buffer (pH 5.0) on a Phenomenex Luna C18 column.ResultsThis method provided average recoveries of 76.1 to 81.6% with coefficients of variation (CV, %) for repeatability and reproducibility in the ranges of 3.7–7.2% and 5.3–7.6%, respectively. The limit of detection was 51.2 mg/kg and limit of quantification was 103.0 mg/kg.ConclusionThe method was successfully validated and proved to be efficient, precise, and useful for quantification of amoxicillin in medicated feedingstuffs.

Effect of combination of electrolyte and buffer on electrical production in fuel cell microbial system with Pseudomonas sp. in molasses substrate

MFC is a bio-electrochemical system driving an electric current by using high-energy bacteria and oxidants. This research aimed to investigate the effect of electrolyte and buffer on electrical production using Pseudomonas sp. In Molasses substrate. The method in this research was the double compartment that consist of anode and cathode chambers. Both were related by salt bridge. This study showed that the addition of a combination of KMnO4 electrolyte solution with sodium phosphate buffer solution obtained a maximum potential difference of 0.67 V. The result also revealed that the combination of KMnO4 electrolyte solution with Potassium Phosphate Buffer solution produced a 1.44 mA maximum current with power density of 660.82 mW/m2.

SECOND-ORDER DERIVATIVE UV SPECTROPHOTOMETRIC AND RP-HPLC METHODS FOR THE ANALYSIS OF VILDAGLIPTIN AND APPLICATION FOR DISSOLUTION STUDY

This study describes two analytical methods, by second-order derivative UV spectrophotometric by HPLC, for determination of vildagliptin, a drug used for treatment of type 2 Diabetes Mellitus that belongs to a therapeutic class called inhibitors of dipeptidyl peptidase 4. The methods were validated in accordance with ICH and USP requirements. Analyses by UV derivative method were performed at 220 nm, which was the zero crossing point of excipient solutions. HPLC was optimized and the analysis was carried out using a Zorbax Eclipse Plus RP-C8 column (150 mm × 4.6 mm, 5 μm), detection at 207 nm, and potassium phosphate buffer solution pH 7.0 : acetonitrile (85:15, v/v) as mobile phase. In dissolution test, the conditions used were 0.01 mol L-1 hydrochloric acid in 900 mL of dissolution medium, USP apparatus 2 (paddle) and 50 rpm stirring speed. Both methods were successfully applied for analysis of dissolution samples from marketed vildagliptin tablets.

Photoelectrochemical Properties of Surface-Modified ZnSe:Cu(In,Ga)Se2 Photocathodes for Efficient and Durable Overall Water Splitting

Overall water splitting using a photoelectrochemical (PEC) cell composed of a photocathode and photoanode connected in a series is an attractive method to produce hydrogen from water under sunlight. Because driving forces of two photoelectrodes are combined for the water splitting reaction, narrow-gap materials can be used to achieve high solar-to-hydrogen conversion efficiency (STH). However, the STHs obtained from a PEC cell without any external bias voltage reported so far have been less than 1%. This is because of insufficient onset potentials and photocurrent values of photoelectrodes. For the sake of overcoming the drawbacks, (ZnSe)0.85(CuIn0.7Ga0.3Se2)0.15 ((ZnSe)0.85(CIGS)0.15) thin film photocathodes have recently been developed and reported to show a high onset potential of 0.89 VRHE and long absorption edge of 850-900 nm.2 These properties are suitable for use in the PEC cell. (ZnSe)0.85(CIGS)0.15 thin films are prepared by co-evaporation onto Mo-coated soda-lime glass substrates. Subsequently, CdS, a binary of Mo/Ti and Pt are deposited onto the photocathode surface as a buffer layer, surface conductor and hydrogen evolution reaction (HER) catalyst, respectively.3 The surface-modified (ZnSe)0.85(CIGS)0.15 photocathodes show a relatively high photocurrent value of 12 mA cm-2 at 0 VRHE and sufficient stability in a span of hours at potentials of more negative than 0.5 VRHE under simulated sunlight in a neutral potassium phosphate buffer solution.4 However, at potentials more positive than 0.5 VRHE, the photocurrent value attributed to HER dramatically decreases by half in just one hour mainly due to self-oxidation of the surface sulfide layer, accompanying detachment of the Mo/Ti and Pt at the surface. The poor stability at the positive potentials has made it difficult to construct durable PEC cell using the photocathodes. In this work, effects of surface modifications onto PEC properties of (ZnSe)0.85(CIGS)0.15 photocathodes are investigated. For the sake of suppressing the surface corrosion, the CdS layer was passivated with In2S3, which was formed by using chemical bath deposition (CBD).5 Figure 1 shows the current-time curves of the surface-modified (ZnSe)0.85(CIGS)0.15 photocathodes at 0.6 VRHE under simulated sunlight. Without the CBD treatment, the photocurrent value decreased by 50% in one hour under light irradiation. On the other hand, the In2S3-modified photocathode showed relatively stable PEC HER and the decline of the photocurrent value in one hour was decreased to 25%. It is highly possible that the improvement of stability originates from low solubility of indium oxide or hydroxide generated by the self-oxidation process, while the cadmium oxide and hydroxide are relatively soluble, which can cause corrosion of the surface. Furthermore, effects of oxide-coating onto the stability of the (ZnSe)0.85(CIGS)0.15 photocathode during PEC hydrogen evolution have also been investigated. Among various kinds of coating processes, direct formation of the oxide layer by photoelectrodeposition without annealing the photocathode is an effective method without exerting a bad influence on the underlying sulfide and selenide materials. In the presentation, the details of preparation conditions and PEC properties will be discussed. References J. W. Ager, M. R. Shaner, K. A. Walczak, I. D. Sharp and S. Ardo, Energy Environ. Sci. 2015, 8, 2811–2824. H. Kaneko, T. Minegishi, M. Nakabayashi, N. Shibata, Y. Kuang, T. Yamada and K. Domen, Adv. Funct. Mater. 2016, 26, 4570–4577. H. Kumagai, T. Minegishi, N. Sato, T. Yamada, J. Kubota and K. Domen, J. Mater. Chem. A 2015, 3, 8300–8307. H. Kaneko, T. Minegishi, M. Nakabayashi, N. Shibata and K. Domen, Angew. Chemie Int. Ed. 2016, 55, 15329–15333. F. Jiang, Gunawan, T. Harada, Y. Kuang, T. Minegishi, K. Domen and S. Ikeda, J. Am. Chem. Soc. 2015, 137, 13691–13697. Figure 1

Direct Electron Transfer of Hemoglobin on Manganese III Oxide-Ag Nanofibers Modified Glassy Carbon Electrode

We investigated the electrochemical behavior of hemoglobin by glassy carbon electrode modified with Mn2O3-Ag nanofibers. The Mn2O3-Ag nanofibers were used as facilitator electron transfer between Hb and glassy-carbon-modified electrode. The Mn2O3-Ag nanofibers are studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The hemoglobin showed a quasireversible electrochemical redox behavior with a formal potential of −49 mV (versus Ag/AgCl) in 0.1 M potassium phosphate buffer solution at pH 7.0. The designed biosensor possesses good stability and reproducibility and achieves 95% of the steady-state current in less than five seconds.

High-Pressure Liquid Chromatographic Determination of Ascorbic Acid in Cooked Sausages

The purpose of this paper was to study and optimize both extraction and high-pressure liquid chromatography (HPLC)–UV detection procedures to develop a proper method for the determination of ascorbic acid content in cooked sausages. A simple and sensitive reversed-phase HPLC method for the NH2-bonded phase has been described for the determination of ascorbic acid content in cooked sausages. Various extracting agents were tested to solubilize the vitamin, with 5% (wt/vol) metaphosphoric acid giving the best results. Samples were chromatographed with UV detection at 248 nm on a 25-cm Spherisorb NH2 cartridge with a 0.4-cm inside diameter with a mixture of 0.02 M potassium phosphate buffer solution (pH 3.6) and acetonitrile (40:60, vol/vol) for the mobile phase. The method's precision within a day was 1.2%, and its precision between days was 3.8%. The detection limit was 1.6 mg/100 g. Recovery ranged from 91.4 to 96.2% for ascorbic acid added to meat samples. Twenty samples of six different products were analyzed in duplicate. For the samples analyzed, the mean value for ascorbic acid ranged between 21.555 and 24.899 mg/100 g of fresh weight.

Biomechanical and biochemical changes in lumbar vertebrae of rapidly growing rats

Although growth-related biochemical, morphological, and biomechanical properties of rat cortical bone have been investigated, similar properties of immature rat vertebral bone have not been well characterized. Information about these properties is necessary, however, for comparative analyses of rat vertebral bone adaptation. Thus a method was developed to characterize growth-related differences in immature rat vertebral bone. The centra of sixth lumbar vertebrae (L6) of 44-day-old and 54-day-old male Sprague-Dawley rats were compressed to 50% of their initial height at a 50%/s strain rate while immersed in a potassium phosphate buffer solution (pH 7.4, 37 degrees C). Structural and material properties for the 54-day-old group that were significantly greater than those for the 44-day-old group included load, stress, and energy at the proportional limit; initial maximum load and stress; and load and energy at 50% strain. The structural stiffness of L6, as well as its elastic modulus, was significantly greater in the older animals. The calcium concentrations and calcium-to-collagen ratios in 54-day-old vertebrae were significantly greater than in younger animals. These results indicated that the specimen preparation and testing protocol developed for rat vertebrae produced reliable biomechanical results, even with the relatively small size of rat vertebrae bodies, and that the quantity and quality of the matrix of immature rat vertebral bone changed significantly during this period of rapid growth. Our test protocol will be useful for investigating the responses of rat vertebral bone to exercise, disease, and spaceflight.

STUDIES ON THE AMOEBA-TO-FLAGELLATE TRANSFORMATION OF TETRAMITUS ROSTRATUS

The amoebae of Tetramitus rostratus growing with Escherichia coli were inoculated into a yeast peptone broth and a potassium phosphate buffer solution, and flagellate formation was studied. In both, the numbers of flagellates formed and their proportional incidence increased with the number of amoebae inoculated. In buffer the numbers of flagellates reached a peak at 10 hours, and in broth at 23 hours.Comparisons between the buffer and broth, using the same inoculum, indicated that population density is only one factor governing flagellate formation, since this transformation was greater in buffer for a given population.Replacement of E. coli with four other monoxenic associates indicated that bacterial flora makes little difference in buffer on flagellate transformation, as flagellates were formed with all four genera. A search for a "flagellating substance" produced in the medium or within the cells was not successful.