Spectrofluorimetric determination of guanethidine sulphate,guanfacine hydrochloride,guanoclor sulphate and guanoxan sulphate in tablets and biological fluids,using benzoin

A sensitive and rapid Spectrofluorimetric method for the determination of guanethidine sulphate, guanfacine hydrochloride, guanoclor sulphate and guanoxan sulphate in tablets and spiked human serum and urine samples is described. The method is based on the reaction of monosubstituted guanidino compounds in an aqueous potassium hydroxide solution with benzoin, in the presence of -mercaptoethanol and sodium sulphite. Highly fluorescent derivatives were obtained, with excitation and emission maximum wavelengths around 325 and 430 nm, respectively. In optimal reaction conditions, the linearity ranges were 0.04–0.28 g/ml, with relative standard deviations less than 2%. The method has been successfully applied to the determination of these drugs in tablets. The results are highly correlated with the B.P. method. Chloroform (or for guanoxan dichloromethane) was used to extract the drugs from serum and urine at basic pH, followed by the proposed fluorimetric method. The limit of detection is 0.02 g/ml for the selected drugs.     

Spectrofluorimetric determination of proguanil in biological fluids

A spectrofluorimetric method for proguanil in biological fluids is described based on the reaction of proguanil with 9-fluorenecarboxylic acid chloride and measurement of the resulting s-triazine derivative. The limits of detection for proguanil in methanol, water, plasma, urine and saliva are 1.5, 5.1, 7.6, 4.2 and 11.9 ng ml^?1, respectively. Preliminary results for proguanil levels in plasma and saliva following a single 100-mg oral dose are reported.     

Simultaneous quantitative determination of amiloride hydrochloride and hydrochlorothiazide in tablets by high-performance liquid chromatography

Summary A procedure for the simultaneous quantitative determination of amiloride hydrochloride and hydrochlorothiazide by high-performance liquid chromatography is proposed. A reversed-phase LiChrosorb C8 stationary phase is used. The eluent consisted of an acetonitrile/0.1M phosphate buffer pH3 (15∶85) mixture, containing 50mM propylamine hydrochloride. In this system amiloride hydrochloride, a basic drug, eluted with a acceptable asymmetry factor (Asf=2.1). A simple extraction procedure with methanol is used. Relative standard deviations of 0.87% and 1.6% were obtained for amiloride hydrochloride and hydrochlorothiazide respectively. Chlorothiazide, a thiazide diuretic, is a suitable internal standard. Furthermore the method is also specific for other thiazide diuretics, potassium-sparing diuretics and loop diuretics and for the respective hydrolysis productes of both drugs. Analysis time is reduced to a minimum; the chromatographic separation is complete within 6 minutes.     

Spectrofluorimetric determination of fexofenadine hydrochloride in pharmaceutical preparation using silver nanoparticles

A novel sensitive fluorimetric method was investigated for the assay of fexofenadine hydrochloride (FEX) using silver nanoparticles (NPs) as a fluorescence probe. The NPs, which were prepared by chemical reduction of silver nitrate with sodium borohydride (reducing agent) in aqueous solution (without organic stabilizers) were water soluble, stable and had narrow emission band. The addition of drug to NPs solution caused considerable quenching of the emission band of silver NPs, which was likely due to the complexation of the drug to silver NPs. Under the optimum conditions, the quenched fluorescence (FL) intensity was linear with the concentration of FEX in the range of 1 × 10^?7 to 2.5 × 10^?5 mol L^?1 (0.9985) with a detection limit of 1.2 × 10^?8 mol L^?1. The quenching mechanism of the studied drug on the emission band of silver NPs was explained by Stern–Volmer law. The developed method was applied to FEX determination in a pharmaceutical formulation (allegra tablets) and biological fluids (human serum and urine).     

Potentiometric determination of antihistaminic diphenhydramine hydrochloride in pharmaceutical preparations and biological fluids using screen-printed electrode

The performance characteristic of sensitive screen-printed (SPE) and carbon paste (CPE) electrodes was investigated for the determination of diphenhydramine hydrochloride (DPH) drug in pure, pharmaceutical preparations and biological fluids. Different experimental conditions namely types of materials used to prepare the working electrode (plasticizer), titrant, pH, temperature and life time were studied. Under these conditions, the SPE shows the best performance than CPE with respect to total potential change and potential break at the end point. The SPE and CPE exhibit suitable response to DPH in a concentration range of 1.0.10^{− 2} to 1.0.10^{− 6} mol/L with a limit of detection 9.70.10^{− 7} and 9.80.10^{− 7} mol/L, respectively. The slope of the system was 55.2 ± 1.0 and 54.7 ± 1.0 mV/decade over pH range 3.0–8.0 and 3–7 for SPE and CPE, respectively. Selectivity coefficients for DPH relative to a numbers of potential interfering substances were investigated. The SPE and CPE show a fast response time of 10 and 16 s and were used over a period of 2 months with a good reproducibility. The sensors were applied successfully to determine DPH in pharmaceutical preparations and biological fluids. The results are compared with the official method.     

Spectrofluorimetric determination of levofloxacin in tablets, human urine and serum

A spectrofluorimetric method to determine levofloxacin is proposed and applied to determine the substance in tablets and spiked human urine and serum. The fluorimetric method allow the determination of 20–3000 ng ml⁻¹ of levofloxacin in aqueous solution containing acetic acid–sodium acetate buffer (pH 4) with λ_exc=292 and λ_em=494 nm, respectively. Micelle enhanced fluorescence improves the sensibility and allows levofloxacin direct measurement in spiked Human serum (5 μg ml⁻¹) and urine (420 μg ml⁻¹), in 8 mM sodium dodecyl sulphate solutions at pH 5.     

Spectrofluorimetric determination of moxifloxacin in tablets, human urine and serum

A spectrofluorimetric method to determine the antibiotic moxifloxacin is proposed and was applied to pharmaceuticals, human urine and serum. The fluorimetric method allows the determination of 30-300 ng mL-1 moxifloxacin in aqueous solution containing phosphoric acid-phosphate buffer (pH 8.3) with lambda exc = 287 nm and lambda em = 465 nm. Detection and quantification limits were 10 and 30 ng mL-1, respectively, with a relative standard deviation (n = 10) of 2%. This method was applied to the determination of moxifloxacin in three Spanish commercial pharmaceutical formulations. Another variant of the method in micellar medium allows the direct measurement of moxifloxacin in human serum and urine by standard additions. The enhanced fluorescence of moxifloxacin in 8 mM sodium dodecyl sulfate (SDS) solution at pH 4.0 (acetic acid-acetate buffer) for lambda exc = 294 nm and lambda em = 503 nm shows the same linear range as the aqueous method with a 25% lower slope (with detection and quantification limits of 15 and 60 ng mL-1, respectively, and a relative standard deviation of 1.3%), but permits the background fluorescence for urine and serum blanks to be minimized. Hence, sufficient sensitivity is reached to determine therapeutic concentrations of the drug in urine (average recovery 102 +/- 2%) and serum (average recovery 105 +/- 2%) samples.     

Selective potentiometric determination of zolpidem hemitartrate in tablets and biological fluids by using polymeric membrane electrodes

The construction and electrochemical response characteristics of 4 polymeric membrane sensors were investigated for potentiometric determination of zolpidem hemitartrate. The construction of the 4 sensors was based on the formation of ion-pair complexes between the drug cation and ionic sites in the ratio of 1:2, respectively. Two of the sensors were constructed by using ammonium reineckate or ammonium tungstate as the fixed ionic site in a polymeric matrix of polyvinyl chloride (PVC) (sensors 1 and 2). Linear responses over the concentration range of 10(-5)-10(-3)M, with cationic slopes of 30 and 30.7 mV per concentration decade, were obtained by using sensors 1 and 2, respectively. The third sensor was fabricated by using PVC carboxylate (PVC-COOH). The dissociated COOH groups in the PVC-COOH act as a mediator and/or ionic site. A linear response was obtained over the concentration range of 10(-5)-10(-2)M with a cationic slope of 29 mV per concentration decade. Sensor 4 was fabricated by using 2,6-didodecyl-beta-cyclodextrin as the ionophore, polyurethane (Tecoflex) as a polymeric matrix, and potassium tetraphenyl borate as the ionic site; it showed a linear response over the concentration range of 10(-7)-10(-2)M with a cationic slope of 28.9 mV per concentration decade. The direct potentiometric determination of zolpidem hemitartrate in pure forms by using the 4 proposed sensors gave average recoveries of 98.5+/-0.7, 99.4 +/-0.2, 100.7+/-0.10, and 99.8+/-0.1% for sensors 1-4, respectively. The results obtained by the proposed procedures were statistically analyzed and compared with those obtained by using a reported method. The 4 proposed sensors were also applied successfully to the determination of the drug in tablets and in biological fluids. Average recoveries obtained by using sensors 1, 2, 3, and 4 for drug assay of tablets were 99.6+/-0.6, 100+/-0.7, 99.7+/-0.4, and 99.5+/-0.8%, respectively. The presence of tablet excipients did not interfere with the determination of the drug or with the accuracy and precision of the 4 proposed methods. The methods were also used to determine the drug in the presence of its degradates and thus could be used as stability-indicating methods.     

Spectrophotometric determination of diphenhydramine hydrochloride in pharmaceutical preparations and biological fluids via ion-pair formation

A simple, sensitive and accurate spectrophotometric method has been described for the assay of diphenhydramine hydrochloride (DPH) in raw material and in biological samples. The method is based on extraction of DPH into dichloromethane as ion-pair complexes with patent blue (PB), eriochrome black T (EBT), methyl orange (MO) and bromocresol purple (BCP) in acidic medium. The coloured species exhibited absorption maxima at 632, 514, 428 and 414 nm for PB, EBT, MO and BCP, with molar absorptivity values of 1.32 × 10⁵, 2.36 × 10⁴, 3.68 × 10⁴ and 3.07 × 10⁴ l mol^?1 cm^?1, respectively. The reaction conditions were optimized to obtain the maximum colour intensity. Beer’s law was obeyed with a good correlation coefficient (0.9982–0.9993) in the concentration ranges 0.5–3, 2.0–16, 2.0–10 and 1.0–10 μg ml^?1 for PB, EBT, MO and BCP methods, respectively. The composition ratio of the ion-association complexes was found to be 1:1 in all cases as established by Job’s method. The conditional stability constant (K_f) and the free energy changes (ΔG°) were determined for all complexes formed. The proposed method was successfully applied for the determination of DPH in tablets and human urine with good accuracy and precision. Statistical comparison of the results with those obtained by the official method showed good agreement and indicated no significant difference in accuracy and precision.     

Spectrofluorimetric determination of paroxetine hydrochloride in its formulations and human plasma

A sensitive spectrofluorimetric procedure for the determination of paroxetine-HCl in pharmaceutical formulations and human plasma has been described. The native fluorescence of the drug has been studied under different conditions. Maximum fluorescence intensity was obtained in methanol at 340 nm using 290 nm for excitation. Different surfactants showed negative effect on the fluorescence intensity of paroxetine-HCl. Regression analysis of Beer's plot showed good correlation (r=0.9999) between fluorescence intensity and concentration over the range of 0.05-0.40 microg ml-1 with lower limit of detection (LOD) of 0.015 microg ml-1. The drug was successfully determined in its tablets with average % recovery of 98.00+/-0.99% which was in accordance with those given by a compendial method. The method was also applied to the determination of paroxetine-HCl in spiked human plasma with average recovery of 77.70+/-1.06%.     

Spectrofluorimetric determination of 2-amino-5-chlorobenzophenone impurity in chlordiazepoxide hydrochloride

2-Amino-5-chlorobenzophenone (5×10^?8?3×10^?5 g ml^?1) is determined by oxidation to 2-chloro-9-acridanone with cerium (IV) in phosphoric acid solution followed by spectrofluorimetric measurement at λ(em) = 465 nm with λ(ex) = 405 nm. The chlordiazepoxide does not react, thus the procedure is useful for quality control.     

Molecularly imprinted polymer based potentiometric sensor for the determination of hydroxyzine in tablets and biological fluids

Molecular imprinting is a useful technique for the preparation of functional materials with molecular recognition properties. In this work, a biomimetic potentiometric sensor, based on a non-covalent imprinted polymer, was fabricated for the recognition and determination of hydroxyzine in tablets and biological fluids. The molecularly imprinted polymer (MIP) was synthesized by precipitation polymerization, using hydroxyzine dihydrochloride as a template molecule, methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylat (EGDMA) as a cross-linking agent. The sensor showed a high selectivity and a sensitive response to the template in aqueous system. The MIP-modified electrode exhibited a Nernstian response (29.4 ± 1.0 mV decade⁻¹) in a wide concentration range of 1.0 × 10⁻⁶ to 1.0 × 10⁻¹ M with a lower detection limit of 7.0 × 10⁻⁷ M. The electrode demonstrated a response time of ∼15 s, a high performance and a satisfactory long-term stability (more than 5 months). The method has the requisite accuracy, sensitivity and precision to assay hydroxyzine in tablets and biological fluids.     

盐酸二甲双胍的毛细管电泳法快速测定

建立了毛细管电泳高频电导法快速测定片剂中盐酸二甲双胍的方法。考察了缓冲溶液、有机溶剂添加剂、毛细管长度以及分离电压和进样条件等因素对分离检测的影响。在最佳条件下5.0 min内即可实现盐酸二甲双胍分离检测,盐酸二甲双胍的线性范围为1.50μg/mL~130μg/mL,检出限为1.0μg/mL。该方法成功地测定了盐酸二甲双胍片剂中的盐酸二甲双胍。     

Two selective HPTLC methods for determination of some angiotensin II receptor antagonists in tablets and biological fluids

Two simple, selective, precise and highly sensitive high‐performance thin‐layer chromatography (HPTLC) methods have been developed and validated for analysis of five angiotensin II receptor antagonists, namely losartan, irbesartan valsartan, candesartan and olmesartan, which are widely used in clinical practice. HPTLC of the drugs was performed on pre‐coated silica gel HPTLC plates 60 F₂₅₄ by development using a mobile phase composed of chloroform–acetone–glacial acetic acid (7.8:1.5:0.7m v/v/v), which was suitable for all of the studied drugs. The first method depended on utilizing reflectance/fluorescence mode for detection while the second method depended on using 2,3,5,6‐tetrachloro‐1,4‐benzoquinone as spraying reagent for the first time to form orange spots scanned at 460 nm. A good linear relationship was obtained over the concentration ranges of 1.2–60 and 360–3000 ng/band while detection and quantification limits were in the ranges of 0.07–0.43, 45.2–140.49 and 0.21–1.29, 137.05–425.74 ng/band for reflectance/fluorescence and reflectance/absorbance methods respectively. The developed methods were applied successfully for their determination in tablets and spiked human plasma for reflectance/fluorescence method with good accuracy and precision, and so can be applied in the pharmacokinetic and bioavailability studies.     

Determination of cefuroxime axetil in tablets and biological fluids using liquid chromatography and flow injection analysis

In the present work, the separations of calixarene derivatives have been investigated using both high-performance liquid chromatography (HPLC) and nonaqueous capillary electrophoresis (NACE) techniques. HPLC-1 method with LC-318 (pore size = 300 Å) column and MeCN mobile phase was optimized for the separation of calixarenes. At the flow-rate of 1 ml/min p-nitrocalix[6]arene, calix[4]arene and calix[6]arene could be well baseline and symmetrically separated within 5 min. For the separation of p-tert-butylcalix[n]arenes (n = 4, 6, 8), HPLC-2 and NACE methods have been optimized. The optimal conditions in HPLC-2 method included NH₂ column and MeCN mobile phase, and p-tert-butylcalix[n]arenes (n = 4, 6, 8) were baseline separated within 10 min at 0.8 min/min. The optimal conditions for NACE method employed MeCN-H₂O (8:2, v/v) as the nonaqueous medium and 120 mM Tris/HCl (pH 9.0) as the buffer, and p-tert-butylcalix[n]arenes (n = 4, 6, 8) were successfully baseline resolved within 16 min. With the detection at 280 nm, the calibration lines were linear in the ranges of 1-200 μg/ml for calixarene derivatives by HPLC-1 and HPLC-2 methods, and of 2.5-200 μg/ml for p-tert-butylcalix[n]arenes (n = 4, 6, 8) by NACE method, respectively. The detection limits (S/N = 3) and recoveries ranged from 0.5 to 1.4 μg/ml and from 98.1 to 102.4% by both HPLC-1 and HPLC-2 methods, and from 1.3 to 2.0 μg/ml and from 97.9 to 105.1% by NACE method, respectively. The intra-day reproducibility of the methods was determined with satisfactory results. The proposed HPLC and NACE methods were accurate and reproducible, and could be utilized to separate and determine calixarene derivatives.     

Spectrophotometric determination of proteins in biological fluids

A comparative analysis of procedures of the spectrophotometric determination of total protein with various organic dyes, Bromocresol Green, Bromophenol Blue, and Pyrogallol Red, in biological fluids is presented. It is shown that the results of determination with various dyes can differ because of the specific features of reagent interaction with the components of biological fluids. A new organic reagent, Bromopyrogallol Red, possessing equal sensitivity to different protein fractions (albumins and globulins) and ensuring a minimum error of the determination of total protein in clinical examinations using calibration solutions of various compositions is proposed. A procedure for the determination of total protein in biological fluids is developed and tested on real samples of urine and blood serum.     

A simple spectrophotometric method for the determination of nylidrin hydrochloride, isoxsuprine hydrochloride and salbutamol sulphate in pharmaceutical preparations

A simple spectrophotometric method for the determination of nylidrin hydrochloride, isoxsuprine hydrochloride and salbutamol sulphate is described, based on measurement of the orangeyellow species produced when the drugs are coupled with diazotized benzocaine (p-aminoethyl benzoate) in trimethylamine medium. The method is applicable over the range 1-12 mug ml for isoxsuprine hydrochloride and nylidrin hydrochloride and 1-8 mug ml for salbutamol sulphate. The method is a modification of the Bratton-Marshall reaction and is simple, reproducible, accurate and more sensitive than those cited in the literature.