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61.
Two simple and sensitive spectrophotometric and fluorimetric methods for the determination of tranexamic acid in tablets are developed. The methods are based on condensation the primary amino group of tranexamic acid with acetyl acetone and formaldehyde producing a yellow coloured product, which is measured spectrophotometrically at 335 nm or fluorimetrically at 480 nm the colour was stable for at least 1 h. Beer's law was valid within a concentration rang of 0.05-2.0 microg ml-1 spectrophotometrically and 0.05-0.25 microg ml-1 fluorimetrically. All the variables were studied to optimize the reaction conditions. No interference was observed in the presence of common pharmaceutical excipints. The validity of both methods was tested by analyzing tranexamic acid in its pharmaceutical preparations. Good recoveries were obtained and the results were comparable with those obtained by standard method. 相似文献
62.
Huda Alghamdi Majidah Alsaeedi Dr. Alyah Buzid Prof. Jeremy D. Glennon Prof. John H. T. Luong 《Electroanalysis》2021,33(5):1137-1142
Benzalkonium chloride (BAK) is a mixture of alkyl benzyl dimethyl ammonium chlorides, which is used primarily as a biocide, surfactant, preservative, and antimicrobial agent in the pharmaceutical industry, in particular in ophthalmologic and nasal solutions. However, BAK may cause harmful consequences on the eye structures of the anterior segment. Control of BAK identity and content is necessary by applying a sensitive detection method. This study unravels the use of a glassy carbon (GC) electrode and a pristine boron-doped diamond electrode (BDD) for the detection of four BAK homologs in a non-aqueous medium using square wave voltammetry (SWV). The BDD provided more reproducibility of the oxidation potential than GC with a correlation coefficient of 0.999. The irreversible oxidation peak was very broad and deconvoluted into 3 peaks corresponding to C12, C14, and combined C16–C18 to reflect their concentration ratio in the mixture. The method was then extended to the detection of the C12 homolog in the ophthalmic formulations with a limit of detection (LOD) of 0.4 μg/mL. The estimated BAK levels in three ophthalmic formulations were in agreement with the specified values by the manufacturers. The results were validated by high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection, confirming the presence of a single homolog (C12) in the eye drops. 相似文献
63.
Hairul Hisham Hamzah Nur Hidayah Saleh Bhavik Anil Patel Mohd Muzamir Mahat Saiful Arifin Shafiee Turgut Snmez 《Molecules (Basel, Switzerland)》2021,26(1)
The development of low-cost electrode devices from conductive materials has recently attracted considerable attention as a sustainable means to replace the existing commercially available electrodes. In this study, two different electrode surfaces (surfaces 1 and 2, denoted as S1 and S2) were fabricated from chocolate wrapping aluminum foils. Energy dispersive X-Ray (EDX) and field emission scanning electron microscopy (FESEM) were used to investigate the elemental composition and surface morphology of the prepared electrodes. Meanwhile, cyclic voltammetry (CV), chronoamperometry, electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) were used to assess the electrical conductivities and the electrochemical activities of the prepared electrodes. It was found that the fabricated electrode strips, particularly the S1 electrode, showed good electrochemical responses and conductivity properties in phosphate buffer (PB) solutions. Interestingly, both of the electrodes can respond to the ruthenium hexamine (Ruhex) redox species. The fundamental results presented from this study indicate that this electrode material can be an inexpensive alternative for the electrode substrate. Overall, our findings indicate that electrodes made from chocolate wrapping materials have promise as electrochemical sensors and can be utilized in various applications. 相似文献
64.
65.
The effect of different chromatographic conditions, such as buffer concentration and type of organic modifier, on the retention behavior of nine tricyclic neuroleptics on three different RP-HPLC columns was investigated. Two recently developed columns, calixarene-bonded (CALTREX) AIII) and monolithic (Chromolith) Performance RP-18e) columns, were compared with a conventional RP-C18 HPLC column (LiChrospher). The results showed how the mobile phase conditions had different effects on the analyte retention on these three columns. For example, the elution order of some analytes and the initiation of separation of the geometric isomers of the three analytes--which have E/Z-isomers (cis/trans-isomers)--could be altered by changing the conditions and the column type. Under identical conditions, a calixarene-bonded phase was the best for this separation, a monolithic phase gave comparable results and the conventional RP-column was the least effective. Concerning the geometric isomers separation, the Chromolith Performance RP-18e was superior. 相似文献
66.
Habtu Zegeye Naseer Shahzad Mohammad A. Alghamdi 《Nonlinear Analysis: Theory, Methods & Applications》2011,74(18):7304-7311
Let C be a nonempty, closed and convex subset of a real Hilbert space H. Let Ti:C→C,i=1,2,…,N, be a finite family of Lipschitz pseudocontractive mappings. It is our purpose, in this paper, to prove strong convergence of Ishikawa’s method to a common fixed point of a finite family of Lipschitz pseudocontractive mappings provided that the interior of the common fixed points is nonempty. No compactness assumption is imposed either on T or on C. Moreover, computation of the closed convex set Cn for each n≥1 is not required. The results obtained in this paper improve on most of the results that have been proved for this class of nonlinear mappings. 相似文献
67.
In this study, a method for enantioseparation of terbutaline and salbutamol was established using Chirobiotic V column as a stationary phase. Polar ionic mode applying mobile phase containing ammonium nitrate in 100% ethanol, pH 5.1 was found to give the best separation. The salt concentration in the mobile phase and pH value were found to be the most important chromatographic factors affecting separation. Separation of enantiomers of these two basic analytes was complete in less than 10 min without applying ammonium trifluoroacetate (ATFA) or triethylamine (TEA) salts. 相似文献
68.
69.
The production of composite polyamide–polystyrene microcapsules by successive polycondensation and radical polymerization
is easily possible in a one-pot multi-step reaction. The first step is the emulsification of the template oil phase that contains
terephthaloylchloride, styrene monomer, if necessary a cyclohexane–chloroform mixture, and the oil-soluble radical initiator
in an aqueous poly(vinyl alcohol) solution. Then, the polyamide capsule formation (second step) is started by the addition
of an aqueous diamine solution at 25 °C. Subsequently, the radical polymerization (third step) is initiated by raising the
temperature. The morphology of the composite capsules depends strongly on the amount of styrene monomer in the oil mixture
and the nature of the initiator. Interestingly, the styrene conversion is much lower if water-soluble initiators are used. 相似文献
70.
Pridatchenko ML Perlova TY Ben Hamidane H Goloborodko AA Tarasova IA Gorshkov AV Evreinov VV Tsybin YO Gorshkov MV 《Analytical and bioanalytical chemistry》2012,402(8):2521-2529
The amino acid sequence determines the individual protein three-dimensional structure and its functioning in an organism.
Therefore, “reading” a protein sequence and determining its changes due to mutations or post-translational modifications is
one of the objectives of proteomic experiments. The commonly utilized approach is gradient high-performance liquid chromatography
(HPLC) in combination with tandem mass spectrometry. While serving as a way to simplify the protein mixture, the liquid chromatography
may be an additional analytical tool providing complementary information about the protein structure. Previous attempts to
develop “predictive” HPLC for large biomacromolecules were limited by empirically derived equations based purely on the adsorption
mechanisms of the retention and applicable to relatively small polypeptide molecules. A mechanism of the large biomacromolecule
retention in reversed-phase gradient HPLC was described recently in thermodynamics terms by the analytical model of liquid
chromatography at critical conditions (BioLCCC). In this work, we applied the BioLCCC model to predict retention of the intact
proteins as well as their large proteolytic peptides separated under different HPLC conditions. The specific aim of these
proof-of-principle studies was to demonstrate the feasibility of using “predictive” HPLC as a complementary tool to support
the analysis of identified intact proteins in top-down, middle-down, and/or targeted selected reaction monitoring (SRM)-based
proteomic experiments. 相似文献