Extractive Spectrophotometric Methods for Determination of Clarithromycin in Pharmaceutical Formulations Using Bromothymol Blue and Cresol Red

Two simple and sensitive extractive spectrophotometric methods have been described for the analysis of clarithromycin in pure form and in pharmaceutical formulations. The methods involved formation of yellow colored chloroform extractable ion‐association complexes of clarithromycin with bromothymol blue (BTB) and cresol red (CR) in buffered aqueous solution at pH 4. The extracted complexes showed maximum absorbance at 410 and 415 nm for BTB and CR, respectively. Beer's law is obeyed in the concentration ranges 0.1–20 μg mL^?1 and 2.0–20 μg mL^?1 of clarithromycin with molar absorptivity of 2.01 × 10⁴ and 4.378 × 10³ for BTB and CR, respectively. The composition ratio of the ion‐association complex was clarithromycin: BTB and CR = 1:1 as established by Job's method. The methods have been applied to the determination of drug in commercial formulations. The results of analysis were validated statistically and through recovery studies.     

Three Spectrophotometric Methods for the Determination of Oxomemazine Hydrochloride in Bulk and in Pharmaceutical Formulations Using Bromocresol Green,Congo Red,and Methyl Orange

Abstract

Three simple, sensitive, and highly accurate spectrophotometric methods have been developed for the determination of oxomemazine hydrochloride (OXO‐HCl) in bulk and in pharmaceutical formulations. These methods are based on the formation of yellow ion‐pair complexes between the examined drug and bromocresol green (BCG), congo red (CR), and methyl orange (MO) as reagents in universal buffer solution of pH 3.0, 5.5, and 3.5, respectively. The formed complexes were extracted with chloroform and measured at 413, 495, and 484 nm, respectively for the three systems. The best conditions of the reaction were studied and optimized. Beer's law was obeyed in the concentration ranges 2.0–18.0, 2.0–14.0, and 2.0–16.0 µg ml^?1 with molar absorptivity of 4.1×10⁴, 1.1×10⁴, and 3.5×10⁴ mol^?1cm^?1, for the BCG, CR, and MO methods, respectively. Sandell's sensitivity, correlation coefficient, detection, and quantification limits are also calculated. The proposed methods have been applied successfully for the analysis of the drug in pure and in its dosage forms. No interference was observed from common pharmaceutical excipients and additives. Statistical comparison of the results with those obtained by HPLC method shows excellent agreement and indicates no significant difference in accuracy and precision.     

Simple and Sensitive Extractive Spectrophotometeric Method for the Assay of Mebeverine Hydrochloride in Pure and Pharmaceutical Formulations

Simple, sensitive, rapid and cost effective extraction spectrophotometric methods are described for the assay of mebeverine hydrochloride (MBH) in bulk samples and pharmaceutical formulations. These two methods (Bromophenol blue and Erichrome Black‐T) are based on the formation of chloroform soluble ion‐pair complexes of MBH with Bromophenol blue (BPB) and with Erichrome Black‐T (EBT), to form yellow and pink colored chromogen in a Glycine‐HCl buffer of pH 2.4 (BPB) and in a KCl‐HCl buffer of pH 1.4 (EBT) with absorbance maximum at 416 nm and at 524 nm for BPB and EBT respectively. The calibration graph is found to linear over 0.2–20 μg/mL (BPB) and 0.2–20 μg/mL (EBT), with molar absorptivity values of 1.8295 × 10⁴ 1 moL^?1 cm^?1 and 1.5896 × 10⁴ 1 moL^?1 cm^?1, respectively. The LOD (Limit of Detection) were found to be 0.090 μg/mL and 0.084 μg/mL and LOQ (Limit of Quantification) were 0.2997 μg/mL and 0.2730 μg/mL for the BPB and EBT method, respectively. The results of analysis for the two methods have been validated statistically and by recovery studies. The results are compared with those obtained with reported method. The proposed methods are simple, sensitive, accurate and suitable for quality control applications.     

Determination of Ciprofloxacin in Human Plasma and Urine by Precolumn Derivatization High Performance Liquid Chromatography with Fluorescence Detection

A sensitive, simple and selective high‐performance liquid chromatographic (HPLC) method was developed for the determination of ciprofloxacin in biological fluids. The method is based on the reaction between the drug and 4‐chloro‐7‐nitrobenzofurazan (NBD‐Cl) in borate buffer of pH 9.0 to yield a highly fluorescent derivative that is measured at 535 nm after excitation at 464 nm. The calibration curves were linear over the concentration ranges of 25–3000 and 50–3000 ng·mL^?1 for plasma and urine, respectively. The mean recovery of ciprofloxacin from plasma and urine was 98.37% and 98.40%, respectively. The method was found to be sensitive, precise, accurate, and reproducible. All of the validation parameters were within the acceptance range.     

Study on Frequency Doubling Scattering and Second—Order Scattering Spectra of Heparin—Methylene Blue System

Binding of heparin with methylene blue(MB) in pH5.7 Britton-Robinson buffer can result in a significant enhancement of frequency doubling scattering (FDS) and second-order scattering (SOS).Their maximum scattering wavelengths(λmax) appear at 350nm for FDS and 700nm for SOS,respectively.The optimum conditions of the reaction,the influencing factors and the relationship between the two scattering intensities and the concentration of heparin have been investigated.The new methods for the determination of trace amounts of heparin bassed on the FDS and SOS methods have been developed,which exhibit high sensitivities.The detection limits of heparin are 4.36ng/mL for the FDS method and 3.55ng/mL for the SOS method,respectively.Both of the methods have fairly godd selectivity and ware applied to the determination of heparin in sodium heparinate injection samples with satisfactory results.Moreover,the relative mechamisms have also been discussed.     

Study on the Interaction between a Novel Ionic Liquid Probe and Anionic Surfactants Using Resonance Light Scattering Spectra and Its Analytical Application

The interaction between anionic surfactants (AS) and 1‐hexadecyl‐3‐methylimidazolium bromide [C₁₆mim]Br was studied by using resonance light scattering (RLS) technique, UV‐Vis spectrophotometry and fluorometric methods. In Britton Robinson (BR) buffer (pH 6.0), [C₁₆mim]Br reacted with AS to form supermolecular complex which resulted in enhancement in RLS intensity. Their maximum RLS wavelengths were all at 390 nm. Some important interacting experimental variables, such as the solution acidity, [C₁₆mim]Br concentration, salt effect and addition order of the reagents, were investigated and optimized. Under the optimum conditions, quantitative determination ranges were 0.001–7 μg·mL^?1 for dodecyl sodium sulfate (SDS), 0.001–6 μg·mL^?1 for sodium dodecylbenzene sulfonate (SDBS) and 0.005–7 μg·mL^?1 for sodium lauryl sulfonate (SLS), respectively, while the detection limits were 1.3 ng·mL^?1 for SDS, 1.0 ng·mL^?1 for SDBS and 5.1 ng·mL^?1 for SLS, respectively. Based on the ion‐association reaction, a highly sensitive, simple and rapid method has been established for the determination of AS.     

Boron‐chelating fluorescent probe (BOPB) in the red region combined with CE‐LIF for the detection of NO in mice liver

Precise measurement of nitric oxide (NO) is of great importance to understand the function of NO in liver and the mechanism of liver injury. 8‐(3’,4’‐Diamino phenyl)‐3,5‐(2‐hydroxyphenyl)‐dimethylene pyrrole (BOPB), a fluorescent probe in the red region (>600 nm) newly developed in our group, has good photostability and excitation/emission wavelength of 622/643 nm matching well with commercial 635 nm semiconductor laser of CE‐LIF detection. Therefore, BOPB was used in CE‐LIF for the determination of NO in mice liver. Both derivatization and separation conditions were optimized. Derivatization reaction of BOPB and NO was carried out in pH 7.4 PBS buffer at 35°C for 12 min and the separation of NO derivative of BOPB (BOPB‐T) was achieved within 7.0 min in pH 9.0 running buffer containing 15 mM H₃BO₃–NaOH and 15 mM SDS. Good linearity was found in the range of 1.0 × 10^?9–5.0 × 10^?7 M with the LOD of 0.02 nM. The proposed method was applied to the analysis of NO in real samples, and NO concentration was obviously increased in acute liver injury of mice. Compared to existing derivatization‐based CE‐LIF methods for NO, this method has lower LOD and less background interference owing to detection wavelength of BOPB in the red region.     

Voltammetric Detection of the DNA Interaction with Toluidine Blue

Binding reactions of toluidine blue (TB) with herring fish DNA in pH 6.0 Britton–Robinson (B–R) buffer solution have been investigated by cyclic voltammetry and linear‐sweep voltammetry at a glassy carbon electrode. TB has a couple of well‐defined redox peaks. The addition of DNA into the TB solution resulted in the decrease of the redox‐peak currents and the shift negatively of the anodic peak potential. The values of the electrochemical parameters such as the electron number of the electrochemical reaction, the electron transfer coefficient and the electrochemical reaction standard rate constant in the absence and presence of DNA, as well as the values of binding constant and binding ratio of DNA with TB were obtained. Almost unchanged values of the electrochemical parameters in the absence and presence of DNA show that nonelectroactive complexes were formed when TB interacted with DNA. DNA concentration can be determined by the decrease of the peak current of TB. The binding mode of TB with DNA was discussed.     

Rapid screening of beta‐adrenergic agents and related compounds in human urine for anti‐doping purpose using capillary electrophoresis with dynamic coating

This paper presents a capillary electrophoresis method, developed for the detection, in human urine, of beta‐adrenergic agents and phenolalkylamines. The electrophoretic separation is achieved in less than 10 min and is based on the use of CEofix kit, for the dynamic capillary coating. The effects of accelerator buffer pH and separation voltage were investigated. The optimum buffer pH was found to be 2.5 for beta2‐agonists and 6.2 for beta‐blockers and phenoalkylamines with a separation voltage of 15 kV. Urine samples spiked with the compounds here studied were treated according to the standard procedure (SPE and evaporation to dryness) and analyzed by CE interfaced with an UV diode‐array, set at 195 and 210 nm. The quantitative validation results, obtained analyzing samples at three different concentrations, show a good precision of peak areas that do not exceed 5% for intra‐day assays and 10% for inter‐day assays. Good linearity (r² > 0.995) was obtained within the 50–500 ng/mL concentration range. The qualitative validation data show a relative migration times (MTs) variation lower than 1%. The analytes were clearly distinguishable in urine, with LOD and LOQ in the range of 10–80 and 40–100 ng/mL, respectively.     

Electrochemical Study of Gliclazide and Its Complexation with β‐Cyclodextrin

The electrochemical oxidation of gliclazide has been investigated at glassy carbon electrode in phosphate buffer solutions over the pH range 2.7–11.8 using cyclic and differential pulse voltammetry (DPV). Gliclazide exhibited one anodic peak in the pH range of 2.7–6.3 and a second peak was produced above pH 6.3. The oxidation processes have been shown to be irreversible and diffusion controlled. The formation of an inclusion complex of gliclazide with β‐cyclodextrin (β‐CD) has been investigated by cyclic and differential pulse voltammetry. A phase solubility study with spectrophotometric detection has been also applied. The stability constant of the complex was determined to be 839 and 360 M^?1 using the differential pulse voltammetric method and the phase solubility method, respectively.     

Electroanalytical Characteristics of Amisulpride and Voltammetric Determination of the Drug in Pharmaceuticals and Biological Media

The electrochemical oxidation of antipsychotic drug amisulpride (AMS) has been studied in pH range 1.8–11.0 at a stationary glassy carbon electrode by cyclic, differential pulse and square‐wave voltammetry. Two oxidation processes were produced in different supporting electrolyte media. Both of the oxidation processes were irreversible and exhibited diffusion controlled. For analytical purposes, very resolved voltammetric peaks were obtained using differential pulse and square‐wave modes. The linear response was obtained in the range of 4×10^?6 to 6×10^?4 M for the first and second oxidation steps in Britton‐Robinson buffer at pH 7.0 and pH 3.0 (20% methanol v/v), respectively, using both techniques. These methods were used for the determination of AMS in tablets. The first oxidation process was chosen as indicative of the analysis of AMS in biological media. The methods were successfully applied to spiked human serum, urine and simulated gastric fluid samples.     

Stability‐indicating chromatographic methods for determination of flecainide acetate in the presence of its degradation products; isolation and identification of two of its impurities

In this work, two stability‐indicating chromatographic methods have been developed and validated for determination of flecainide acetate (an antiarrhythmic drug) in the presence of its degradation products (flecainide impurities; B and D). Flecainide acetate was subjected to a stress stability study including acid, alkali, oxidative, photolytic and thermal degradation. The suggested chromatographic methods included the use of thin layer chromatography (TLC‐densitometry) and high‐performance liquid chromatography (HPLC). The TLC method employed aluminum TLC plates precoated with silica gel G.F₂₅₄ as the stationary phase and methanol–ethyl acetate–33% ammonia (3:7:0.3, by volume) as the mobile phase. The chromatograms were scanned at 290 nm and visualized in daylight by the aid of iodine vapor. The developed HPLC method used a RP‐C₁₈ column with isocratic elution. Separation was achieved using a mobile phase composed of phosphate buffer pH 3.3–acetonitrile–triethylamine (53:47:0.03, by volume) at a flow rate of 1.0 mL/min and UV detection at 292 nm. Factors affecting the efficiency of HPLC method have been studied carefully to reach the optimum conditions for separation. The developed methods were validated according to the International Conference on Harmonization guidelines and were applied for bulk powder and dosage form. Copyright © 2016 John Wiley & Sons, Ltd.     

Second‐order Scattering and Frequency Doubling Scattering Spectra of Thallium(III)‐Methotrexate System and Its Analytical Application

In pH 4.9 Britton-Robinson buffer solution, methotrexate (MTX) reacted with thallium(III) to form a 3∶1 chelate. This resulted in great enhancement of second-order scattering (SOS) spectra and frequency doubling scattering (FDS) spectra and appearance of new SOS and FDS spectra. Their maximum wavelengths were located at 520 and 390 nm, respectively. The increments of scattering intensities (ΔI) were directly proportional to the concentrations of MTX in the ranges of 0.022—2.0 μg•mL－1 (SOS method) and 0.008—2.5 μg•mL－1 (FDS method). The methods exhibited high sensitivities. The detection limits for MTX were 7.4 ng•mL－1 (SOS method) and 2.3 ng•mL－1 (FDS method), respectively. The optimum conditions of the reaction, the influencing factors and the effects of coexisting substances were investigated. A highly sensitive, simple and fast method for the determination of MTX has been developed. The method can be applied satisfactorily to the determination of MTX in human serum samples. In this work, the charge distribution of MTX was calculated by a CNDO quantum chemistry method. In addition, the reaction mechanism was discussed.     

Analytical Application of Resonance Rayleigh Scattering,Frequency Doubling Scattering,and Second-Order Scattering Spectra for the Sodium Alginate-CTAB System

Three new methods for the determination of trace amounts of sodium alginate (SA) based on the reaction of SA with cetyltrimethylammonium bromide (CTAB) by resonance Rayleigh scattering (RRS), frequency doubling scattering (FDS), and second-order scattering (SOS) have been investigated. The SA can react with CTAB in a pH 10.0 Britton–Robinson buffer to form a new product, which can lead to a significant enhancement of RRS, FDS, and SOS intensities and appearance of new spectra. The maximum scattering wavelengths, λex/λem, appear at 351 nm/351 nm for RRS, 240 nm/480 nm for SOS, and 870 nm/435 nm for FDS, respectively. The increments of the scattering intensities (ΔI) are proportional to the concentration of SA in a certain range. The detection limits (3σ) for SA are 3.69 ng mL^?1 for the RRS method, 6.91 ng mL^?1 for the FDS method, and 7.45 ng mL^?1 for the SOS method under optimum conditions. The proposed methods were applied to the determination of SA in real samples with satisfactory results.     

Spectrofluorimetric Determination of Reduced Glutathione Using Organic Nanoparticle Probes

Introduction Reduced glutathione (GSH) is a very important tripeptide.1 GSH widely exists in living tissues. In ani-mal organization, the concentration of free glutathione is in the range 0.5—10.0 mmol/L. Usually over 99% of glutathione is present in the reduced form in all organ-isms.2 Intermediates of GSH biosynthesis such as cys-teine, g-glutamyl-cysteine (g-Glu-Cys) or cysteinyl-gly- cine (Cys-Gly) also occur in the cell but at much lower concentrations.3 GSH plays an important bio…     

Incorporation of Tetrazolium Blue (TB)/Gold Nanoparticles (GNPs) into Carbon Paste Electrode: Application as an Electrochemical Sensor for the Sensitive and Selective Determination of Sotalol in Micellar Medium

The electrochemical oxidation of Sotalol (SOT) based on Tetrazolium Blue (TB)/gold nanoparticles (GNPs)‐modified carbon paste electrodes (CPE) have been studied in the presence of sodium lauryl sulphate (SLS). Cyclic voltammetry (CV), differential pulse voltammetry (DPV), chronoamperometry and electrochemical impedance spectroscopy (EIS) techniques have all been utilized within this study. GNPs and TB have a synergetic effect‐giving rise to highly improved electrochemical responses and provide an advantageous platform for the basis of an electrochemical sensor with excellent performance. The experimental parameters, electrodeposition time, pH and scan rate have all been examined and optimized. The sensing of SOT via DPV is found to exhibit a wide linear dynamic range of 1.0×10⁻⁷–7.5×10⁻⁴ M in pH 2. LOD and LOQ were calculated and found to correspond to 2.5×10⁻⁸ M and 8.3×10⁻⁸ M, respectively. The suggested sensor has been used successfully for SOT determination in pharmaceutical samples and human urine as real samples. Satisfactory recoveries of analyte from these samples are demonstrated indicating that the suggested sensor is highly suitable for clinical analysis, quality control and a routine determination of SOT in pharmaceutical formulations.     

Fluorescent Complexes of Nucleic Acids/8-Hydroxyquinoline/Lanthanum(III) and the Fluorometry of Nucleic Acids

Abstract

The ternary fluorescent complexes of nucleic acids/8-hydroxyquinoline/ lanthanum (III) were studied. Nucleic acids in the study involve natured and thermally denatured calf thymus DNA, fish sperm DNA and yeast RNA. In the range of pH 8.0–8.4 (controlled by NH₃-NH₄Cl buffer) ternary fluorescent complexes are formed which emit at 485.0 nm for calf thymus DNA and at 480.0 nm for yeast RNA (when excited at 267.0 nm) and emits at 483.0 nm for fish sperm DNA when excited at 265.0 nm. Based on the fluorescence reactions sensitive fluorometric methods for nucleic acids were proposed. Using optimal conditions, the calibration curves were linear in the range of 0.4–3.6 μg˙ml^?1 for calf thymus DNA, 0.4–4.0 μg-ml^?1 for fish sperm DNA and 0.4–4.0 μg˙ml^?1 for yeast RNA, respectively. The limits of determination (3σ) were 0.076 μg˙ml^?1 for calf thymus DNA, 0.068 μg˙ml^?1 for fish sperm DNA and 0.329 μg˙ml^?1 for yeast RNA, respectively. Five synthetic samples were determined with satisfaction.

     

Cationic poly(amidoamine) dendrimers as additives for capillary electroseparation and detection of proteins

We examine the influence of cationic poly(amidoamine) (PAMAM) dendrimers on capillary electroseparation–UV analysis of proteins. PAMAMs adsorbing to the capillary surface suppressed the wall‐adsorption of proteins; meanwhile, PAMAMs added to the buffer exhibited selectivity toward proteins. Presence of 3×10^?4 g/mL PAMAM generation one (G 1.0) in 30 mM phosphate, at pH 2.6, rendered significant enhancement in separation efficiency; the merged peaks of myoglobin and trypsin inhibitor were separated. Moreover, the protein–dendrimer interactions changed the inherent UV absorbance profiles of proteins. UV–Vis study showed that the absorbance of cytochrome C and transferrin increased at the detection wavelength of 214 nm; their detection sensitivity enhanced by 2.44 and 2.01‐folds, respectively, with addition of 5×10^?4 g/mL PAMAM G 1.0.     

Primary Photoprocesses in a Fluoroquinolone Antibiotic Sarafloxacin†

The photophysical properties of the fluoroquinolone antibiotic sarafloxacin (SFX) were investigated in aqueous media. SFX in water, at pH 7.4, shows intense absorption with peaks at 272, 322 and 335 nm, (? = 36800 and 17000 dm³ mol^?1 cm^?1, respectively). Both the absorption and emission properties of SFX are pH‐dependent; pK_a values for the protonation equilibria of both the ground (5.8 and 9.1) and excited singlet states (5.7 and 9.0) of SFX were determined spectroscopically. SFX fluoresces weakly, the quantum yield for fluorescence emission being maximum (0.07) at pH 8. Laser flash photolysis and pulse radiolysis studies have been carried out in order to characterize the transient species of SFX in aqueous solution. Triplet–triplet absorption has a maximum at 610 nm with a molar absorption coefficient of 17,000 ± 1000 dm³ mol^?1 cm^?1. The quantum yield of triplet formation has been determined to be 0.35 ± 0.05. In the presence of oxygen, the triplet reacts to form excited singlet oxygen with quantum yield of 0.10. The initial triplet (³A*) was found to react with phosphate buffer to form triplet ³B* with lower energy and longer lifetime and having an absorption band centered at 700 nm. SFX triplet was also found to oxidize tryptophan to its radical with concomitant formation of the anion radical of SFX. Hence the photosensitivity of SFX could be initiated by the oxygen radicals and/or by SFX radicals acting as haptens.     

Spectrophotometric Determination of Dextromethorphan Hydrobromide and Ketamine Hydrochloride in Pure and Dosage Forms

Three simple, sensitive and accurate spectrophotometric methods have been developed for the determination of dextromethorphan hydrobromide (DEX) and ketamine hydrochloride (KET) in dosage forms. These methods are based on the formation of ion‐pair complexes with bromocresol green (BCG), bromocresol purple (BCP), and bromophenol blue (BPB) in acidic medium. The coloured ion‐pair products are measured at 419, 409 and 417 nm for DEX and at 417, 408 and 416 nm for KET using BCG, BCP and BPB, respectively. Beer's law was obeyed in the range of 2.0–22 μg mL^?1 for DEX and 2.0–16 μg mL^?1 for KET. The composition of the ion‐pair was established by continuous variation and molar ratio methods. The proposed methods were applied successfully for the determination of DEX and KET in dosage forms applying the standard addition technique and compared statistically with the official methods. The molar absorptivity, Sandell sensitivity, detection and quantification limits were also calculated.