Spectrofluorimetric determination of certain adrenergic agonist drugs in their pure forms and pharmaceutical formulations: Content uniformity test application

A new, simple, sensitive and rapid spectrofluorimetric method has been developed for determination of certain adrenergic agonists such as isoxsuprine hydrochloride, ritodrine hydrochloride and etilefrine hydrochloride in their pure forms and pharmaceutical dosage forms. The method depends on micellar enhancement of the native fluorescence of investigated drugs by using 2% w /v sodium dodecyl sulfate (SDS) as an anionic surfactant. The enhanced fluorescence intensity of investigated drugs was measured at 305 nm after excitation at 278 nm. The interaction of studied drugs with SDS was studied, and the enhanced fluorescence intensity was exploited to develop an assay method for the determination of investigated drugs. The relative fluorescence intensity–concentration plots were rectilinear over the range 0.15–3.00 μg ml^?1, with low quantification limits of 0.132, 0.123 and 0.118 μg mL^?1 for isoxsuprine, ritodrine and etilefrine, respectively. The proposed method was successfully applied for determination of studied drugs in their pharmaceutical formulations. Moreover, the high sensitivity of the proposed method allows performing the content uniformity testing of the studied drugs in their tablets by using the official United States Pharmacopeia (USP) guidelines. Statistical comparisons of the results with those of the reported methods revealed excellent agreement and indicated no significant difference in accuracy and precision.     

Determination of enalapril maleate and atenolol in their pharmaceutical products and in biological fluids by flow‐injection chemiluminescence

A chemiluminescent method using flow injection (FI) was investigated for rapid and sensitive determination of enalapril maleate and atenolol, which are used in the treatment of hypertension. The method is based on the sensitizing effect of these drugs on the Ce(IV)–sulfite reaction. The different experimental parameters affecting the chemiluminescence (CL) intensity were carefully studied and incorporated into the procedure. The method permitted the determination of 0.01–3.0 µg mL^?1 of enalapril maleate in bulk form with correlation coefficient r = 0.99993, lower limit of detection (LOD) 0.0025 µg mL^?1 (S/N = 2) and lower limit of quantitation (LOQ) 0.01 µg mL^?1. The linearity range of atenolol in bulk form was 0.01–2.0 µg mL^?1 (r = 0.99989) with LOD of 0.0003 µg mL^?1 (S/N = 2) and LOQ of 0.01 µg mL^?1. In biological fluids the linearity range of enalapril maleate was 0.1–2.0 µg mL^?1 in both urine and serum, and for atenolol the linearity range was 0.1–1.0 µg mL^?1 in both urine and serum. The method was also applied to the determination of the drugs in their pharmaceutical preparations. Copyright © 2009 John Wiley & Sons, Ltd.     

Use of cloud-point preconcentration for spectrophotometric determination of trace amounts of antimony in biological and environmental samples

This work presents a cloud-point extraction process using the micelle-mediated extraction method for simultaneous preconcentration and determination of Sb(III) and Sb(V) species in biological and environmental samples as a prior preconcentration step to their spectrophotometric determination. The analytical system is based on the selective reaction between Sb(III) and 3-dichloro-6-(3-carboxy-2-hydroxy-1-naphthylazo)quinoxaline (DCHNAQ) in the presence of cetyltrimethylammonium bromide (CTAB) and potassium iodide at pH 4.5. Total Sb concentration was determined after reduction of Sb(V) to Sb(III) in the presence of potassium iodide and ascorbic acid. The optimal reaction conditions and extraction were studied, and the analytical characteristics of the method (e.g., limits of detection and quantification, linear range, preconcentration, improvement factors) were obtained. Linearity for Sb(III) was obeyed in the range of 0.2–20 ng ml⁻¹. The detection and quantification limits for the determination of Sb(III) were 0.055 and 0.185 ng ml⁻¹, respectively. The method has a lower detection limit and wider linear range, inexpensive instrument, and low cost, and is more sensitive compared with most other methods. The interference effect of some anions and cations was also studied. The method was applied to the determination of Sb(III) in the presence of Sb(V) and total antimony in blood plasma, urine, biological, and water samples.     

Ceriometry,a combined method for chemical oxygen demand and dissolved oxygen (with a discussion on the precision of the winkler technique)

A ceriometric method is described in which Ce³⁺ salts are used for the determination of dissolved oxygen and Ce⁴⁺ salts for the determination of the chemical oxygen demand. The interference of COD in the O₂ determination, a common feature of most Winkler determinations, is corrected. The standard deviation is typically about 1% of the mean, and bias (inaccuracy) is very small.The method is simple, quick and reliable.The precision and accuracy of the Winkler method is discussed and compared with that of the Cerium method.     

The interaction of amino acids with o-phthaldialdehyde: A kinetic study and spectrophotometric assay of the reaction product

A detailed study has been made of the kinetics of interaction between amino acids and esters of amino acids and o-phthaldialdehyde in the presence of mercaptoethanol. The reaction products have been characterized. A spectrophotometric method for quantitative analysis of all amino acids, except proline and hydroxyproline, has been developed. The possibility of determination of amino acid esters in mixtures containing free amino acids has been demonstrated. It is noted that determination of glycine and histidine with the help of o-phthaldialdehyde has certain specificities associated with faster, compared to other amino acids, degradation of their derivatives. Optimal conditions for quantitative analysis of amino acids in solutions of higher than 10^?5m concentration are recommended. The reproducibility of the determination was ±2%.     

Potassium permanganate–acridine yellow chemiluminescence system for the determination of fluvoxamine,isoniazid and ceftriaxone

Based on the oxidation of acridine yellow by permanganate in basic medium, a new chemiluminescence system was developed for the sensitive determination of some important drugs. The remarkable inhibiting effect of fluvoxamine, ceftriaxone and isoniazid on this reaction was applied to their detection. A possible mechanism was proposed for this system based on chemiluminescence emission wavelengths and experimental observations. Under optimum conditions, calibration graphs were obtained for 1 × 10^?9 to 1 × 10^?6 mol/L of fluvoxamine; 2 × 10^?8 to 8 × 10^?6 mol/L of ceftriaxone and 5 × 10^?8 to 4 × 10^?5 mol/L of isoniazid. This proposed method was satisfactorily used in the determination of these drugs in pharmaceutical samples and human urine and serum. Copyright © 2014 John Wiley & Sons, Ltd.     

Terbium‐sensitized fluorescence method for the determination of deferasirox in biological fluids and tablet formulation

A novel, rapid and sensitive spectroflurimetric method was developed and validated for the determination of deferasirox in urine, serum and tablet samples based on sensitization of terbium fluorescence. The excitation and emission wavelengths were 328 and 545 nm, respectively. The optimum conditions for the determination of deferasirox were investigated considering the effects of various parameters. The method was quantitatively evaluated in terms of linearity, recovery, reproducibility and limit of detection. Under the optimal conditions, the fluorescence intensities were linear with the concentration of deferasirox in the range of 5 × 10^?9 to 5×10^?6 mol L^?1, with a detection limit of 1.5 × 10^?9 mol L^?1 and a relative standard deviation of 1.1–2.3%. Linearity, reproducibility, recovery and limit of detection made the method suitable for determination of deferasirox in urine, serum and tablets samples. Copyright © 2010 John Wiley & Sons, Ltd.     

Stability‐indicating micelle‐enhanced spectrofluorimetric method for determination of loratadine and desloratadine in dosage forms

A highly sensitive and simple spectrofluorimetric method was developed for the determination of loratadine (LRT) and desloratadine (DSL) in their pharmaceutical formulations. The proposed method is based on investigation of the fluorescence spectral behaviour of LRT and DSL in a sodium dodecyl sulphate (SDS) micellar system. In aqueous solution of acetate buffer of pH 4.5, the fluorescence intensities of both LRT and DSL were greatly enhanced (240%) in the presence of SDS. The fluorescence intensity was measured at 438 nm after excitation at 290 nm for both drugs. The fluorescence–concentration plots were rectilinear over the range 0.05–2.0 µg/mL for both LRT and DSL, with lower detection limits of 5.13 × 10^?3 and 6.35 × 10^?3 µg/mL for LRT and DSL, respectively. The method was successfully applied to the analysis of the two drugs in their commercial tablets, capsules and syrups, and the results were in good agreement with those obtained with the official or comparison methods. The proposed method is specific for the determination of LRT in the presence of other co‐formulated drugs, such as pseudoephedrine. The application of the proposed method was extended to stability studies of LRT and DSL after exposure to different forced degradation conditions, such as acidic, alkaline and oxidative conditions, according to ICH guidelines. Copyright © 2011 John Wiley & Sons, Ltd.     

Determination of the naturally occurring monoacetyl derivatives of di- and polyamines

A method is described for the determination of pmol quantities of monoacetylputrescine, N¹-acetylspermidine, N⁸-acetylspermidine and related compounds. The method is based on the derivatization of these compounds with 5-dimethylaminonaphthalene-1-sulphonyl-chloride, followed by thin-layer chromatographic separation. Cleanup steps allow the application of the method to urine analyses. From the repeated determination of acetylated polyamines in the urine of healthy individuals it can be concluded that these conjugates are the major excretory form of di- and polyamines.The cleanup steps used in this procedure and the method described for the stabilization of 5-dimethylaminonaphthalene-1-sulphonyl derivatives on thin-layer plates are advantageous also for the analyses of total polyamines in urine hydrolysates, and in related applications of the dansylation method.     

A new spectrofluorimetric method for determination of trace amounts histamine in human urine and serum

A new spectrofluorimetric method was developed for the determination of trace amounts of histamine in human urine and serum samples. In NaAc–HAc buffer solution of pH 4.0, histamine can react with the acetylacetone–formaldehyde system to produce a fluorescent derivative which emits yellow‐green fluorescence at 476 nm, according to the Hantzsch reaction, and the enhanced fluorescence intensity is in proportion to the concentration of histamine. Optimum conditions for the determination of histamine were also investigated. The dynamic range and detection limit for the determination of histamine is 5.96 × 10^–8–1.50 × 10^–5 mol/L and 4.35 × 10^–8mol/L, respectively. This method is practical and can be successfully applied to determination of histamine in human urine and serum samples. A proposal of the reaction pathway is suggested. Copyright © 2009 John Wiley & Sons, Ltd.     

Chemiluminescent derivatization of adenyl compounds with glyoxal derivatives in the presence of heteropoly acids and its application to the simple and sensitive determination of DNA

A chemiluminescence (CL) determination of adenyl compounds is described. CL derivatization of adenyl compounds with methylglyoxal dimethyl acetal was performed in the presence of tungstosilicic acid and propan-2-ol. CL from adenyl compounds was produced by hydrogen peroxide and L -cysteine ethyl ester in DMF and water. The proposed method is highly sensitive and specific to compounds containing adenine. Adenine was determined in the range 1.0 × 10⁻³ −5.0 × 10⁻⁸ M with the detection limit of 3.0 × 10⁻⁸ M (150 fmol per assay). The method was applied to the determination of DNA and detection limits of a few nanograms of DNA achieved. © 1998 John Wiley & Sons, Ltd.     

Simultaneous determination of citalopram and tadalafil by the second derivative synchronous fluorescence method in biological fluids; application of Box–Behnken optimization design

This is the first study focusing solely on that determination of tadalafil in the presence of citalopram as an antidepressant drug. The determination in biological fluids of a co‐administered antidepressant drug and a sexual stimulation drug is a very critical and important step for psychotic and ischaemic heart disease patients, especially in cases of emergency and this requires therapeutic drug monitoring. A sensitive, efficient and rapid assay was selected satisfactorily and applied for simultaneous determination of citalopram and tadalafil either in their pure forms, in tablet dosage forms or in spiked human plasma. There was a large overlap for both drugs, forming the broad band found in conventional fluorescence spectra and their related synchronous fluorescence intensity. Therefore, the development of a highly sensitive second derivative synchronous fluorescence method was demonstrated that removed this overlap. The proposed method depended on measuring the amplitudes of the second derivative of synchronous fluorescence intensity at suitable wavelengths of 301 nm and 367 nm for citalopram and tadalafil at Δλ = 60 nm, respectively. Box–Behnken design as a response surface methodology was used to fit models and create an optimization process encompassing a set of factors and resulting in an optimum response value specifically designed for this method. Under optimum conditions, the linear dynamic ranges for citalopram and tadalafil estimation were 20–900 and 5–400 ng ml^?1 with detection limits of 5.40 and 1.43 ng ml^?1, respectively.     

Cloud point extraction-flame atomic absorption spectrometry for pre-concentration and determination of trace amounts of silver ions in water samples

A cloud point extraction (CPE) method was used as a pre-concentration strategy prior to the determination of trace levels of silver in water by flame atomic absorption spectrometry (FAAS) The pre-concentration is based on the clouding phenomena of non-ionic surfactant, triton X-114, with Ag (I)/diethyldithiocarbamate (DDTC) complexes in which the latter is soluble in a micellar phase composed by the former. When the temperature increases above its cloud point, the Ag (I)/DDTC complexes are extracted into the surfactant-rich phase. The factors affecting the extraction efficiency including pH of the aqueous solution, concentration of the DDTC, amount of the surfactant, incubation temperature and time were investigated and optimized. Under the optimal experimental conditions, no interference was observed for the determination of 100 ng·mL⁻¹ Ag⁺ in the presence of various cations below their maximum concentrations allowed in this method, for instance, 50 μg·mL⁻¹ for both Zn²⁺ and Cu²⁺, 80 μg·mL⁻¹ for Pb²⁺, 1000 μg·mL⁻¹ for Mn²⁺, and 100 μg·mL⁻¹ for both Cd²⁺ and Ni²⁺. The calibration curve was linear in the range of 1–500 ng·mL⁻¹ with a limit of detection (LOD) at 0.3 ng·mL⁻¹. The developed method was successfully applied for the determination of trace levels of silver in water samples such as river water and tap water.     

VORFFIP-Driven Dock: V-D2OCK,a Fast and Accurate Protein Docking Strategy

The experimental determination of the structure of protein complexes cannot keep pace with the generation of interactomic data, hence resulting in an ever-expanding gap. As the structural details of protein complexes are central to a full understanding of the function and dynamics of the cell machinery, alternative strategies are needed to circumvent the bottleneck in structure determination. Computational protein docking is a valid and valuable approach to model the structure of protein complexes. In this work, we describe a novel computational strategy to predict the structure of protein complexes based on data-driven docking: VORFFIP-driven dock (V-D²OCK). This new approach makes use of our newly described method to predict functional sites in protein structures, VORFFIP, to define the region to be sampled during docking and structural clustering to reduce the number of models to be examined by users. V-D²OCK has been benchmarked using a validated and diverse set of protein complexes and compared to a state-of-art docking method. The speed and accuracy compared to contemporary tools justifies the potential use of VD²OCK for high-throughput, genome-wide, protein docking. Finally, we have developed a web interface that allows users to browser and visualize V-D²OCK predictions from the convenience of their web-browsers.     

Utility of Hantzsch reaction for development of highly sensitive spectrofluorimetric method for determination of alfuzosin and terazosin in bulk,dosage forms and human plasma

A highly sensitive, cheap, simple and accurate spectrofluorimetric method has been developed and validated for the determination of alfuzosin hydrochloride and terazosin hydrochloride in their pharmaceutical dosage forms and in human plasma. The developed method is based on the reaction of the primary amine moiety in the studied drugs with acetylacetone and formaldehyde according to the Hantzsch reaction, producing yellow fluorescent products that can be measured spectrofluorimetrically at 480 nm after excitation at 415 nm. Different experimental parameters affecting the development and stability of the reaction products were carefully studied and optimized. The fluorescence–concentration plots of alfuzosin and terazosin were rectilinear over a concentration range of 70–900 ng ml^?1, with quantitation limits 27.1 and 32.2 ng ml^?1 for alfuzosin and terazosin, respectively. The proposed method was validated according to ICH guidelines and successfully applied to the analysis of the investigated drugs in dosage forms, content uniformity test and spiked human plasma with high accuracy.     

Validated spectrofluorimetric method for the determination of tamsulosin in spiked human urine,pure and pharmaceutical preparations

A novel, sensitive and selective spectrofluorimetric method was developed for the determination of tamsulosin in spiked human urine and pharmaceutical preparations. The proposed method is based on the reaction of tamsulosin with 1‐dimethylaminonaphthalene‐5‐sulfonyl chloride in carbonate buffer pH 10.5 to yield a highly fluorescent derivative. The described method was validated and the analytical parameters of linearity, limit of detection (LOD), limit of quantification (LOQ), accuracy, precision, recovery and robustness were evaluated. The proposed method showed a linear dependence of the fluorescence intensity on drug concentration over the range 1.22 × 10^‐7 to 7.35 × 10^‐6 M. LOD and LOQ were calculated as 1.07 × 10^‐7 and 3.23 × 10^‐7 M, respectively. The proposed method was successfully applied for the determination of tamsulosin in pharmaceutical preparations and the obtained results were in good agreement with those obtained using the reference method. Copyright © 2013 John Wiley & Sons, Ltd.     

Simultaneous determination of type A-& B-trichothecenes and zearalenone in cereals by High Performance Liquid Chromatography — Tandem Mass Spectrometry

A rapid quantitative method for the simultaneous determination of the majorFusarium mycotoxins nivalenol, deoxynivalenol, fusarenon-X, 3-acetyl-deoxynivalenol, 15-acetyl-deoxynivalenol, diacetoxyscirpenol, HT-2 toxin, T-2 toxin and zearalenone in maize and wheat was developed. Raw extracts (acetonitrile/water 84/16) are cleaned-up with MycoSep^® columns., Chromatographic separation and end determination is carried out by HPLC-APCI-MS/MS.HPLC run times of 10 minutes considerably increases sample throughput and make this method suitable for routine analysis. The use of a triple quadrupole mass spectrometer allows the selective detection of the mycotoxins and their quantification in the low μg/kg-range.     

A direct spectrophotometric method for the simultaneous determination of zinc and cobalt in metalloproteins using 4-(2-pyridylazo)resorcinol

An assay involving the direct and simultaneous determination of low micromolar concentrations (1-10 μM) of both zinc and cobalt ions suitable for metal content analyses of metalloproteins is described. The procedure exploits differences in the visible absorption spectra of the chromophoric chelator 4-(2-pyridylazo)resorcinol (PAR) resulting from its complexation to Zn²⁺ and/or Co²⁺ ions and is based on the fit of experimental spectra to a linear addition of Beer-Lambert law. The method eliminates the need for separating or masking one of the metal ions prior to their quantification and could prove to be particularly useful in studies on Co²⁺-substituted zinc proteins.     

Fluorescence probe enhanced spectrofluorimetric method for the determination of sparfloxacin in tablets and biological fluids

Yttrium‐sensitized fluorescence was used to develop a sensitive and simple spectrofluorimetric method for the determination of sparfloxacin. The method is based on the strong fluorescence of sparfloxacin after adding the fluorescence probe yttrium in buffer solution (pH = 8), and various factors influencing fluorescence were investigated. Under optimum conditions, the enhanced fluorescence intensity of the system showed a good linear relationship with the concentration of sparfloxacin over the range 8 × 10^?7 to 1.4 × 10^?5 mol L^?1 with a correlation coefficient of 0.9997. The detection limit (S/N = 3) was determined as 9.01 × 10^?8 mol L^?1. The mechanism of the sensitizing effect of probe was discussed. This method has been successfully applied for the determination of sparfloxacin in pharmaceuticals, human urine and serum samples; the result obtained was satisfactory. Copyright © 2010 John Wiley & Sons, Ltd.     

Chemiluminescent assays for choline and phospholipase-D using a flow injection system

A flow injection chemiluminescent method is described for the determination of choline. The method is based on the production of hydrogen peroxide from choline using on-line covalently bound immobilized choline oxidase column. The product is mixed downstream and detected via the cobalt catalyzed chemiluminescent oxidation of luminol. The detection limit is 1×10⁻⁷ mol/L, with rsd 1.8 to 2.8% in the range 2–10×10⁻⁵ mol/L. The sample throughput is 30 per hour. The method was applied to the determination of choline produced off-line from phosphatidylcholine using phospholipase-D isolated from cabbage. © 1997 John Wiley & Sons, Ltd.