New Spectrophotmetric Methods for Determination of Cephapirine Na

Three sensitive and accurate spectrophotometric procedures were developed for the analysis of cephapirine sodium in pure form and in its pharmaceutical formulation. Method A: A kinetic method based on the observation that in acidic medium cephapirine reduces sodium molybdate to molybdenum blue, the absorbance of which is proportional to the amount of antibiotic present at a fixed time of 40 minutes; the formed product was spectrophotometrically measured at 780 nm. The concentration of drug calculated using its calibration by fixed concentration and rate constant methods is feasible with the calibration equations obtained, but the fixed time method proved to be more applicable. Method B is based on chetale formation with palladium(II) chloride in buffered medium as the interaction between metal ions and ligand anions or moleules capable of the formation of complexes which results in the development of colors suitable for the characterization of quantitative determination of metal or ligand. Metals containing easily excited d or f electrons were suitable for the formation of colored complexes. Method C, is based on the formation of colored complex between palladium(II), eosin and cephapirine Na. Sodium lauryl sulphate is used as surfactant to increase the solubility and intensity of the formed complex. Under optimum conditions, the complexes showed maximum absorption at Δ370 and Δ550 for methods B and C, respectively. Apparent molar absorpitivities were 5.2 × 10³, 5.5 × 10³, 1.4 × 10⁴; Sandell's sensitivities were 1.17 × 10^?3, 1.24 × 10^?3, 3.1 × 10^?3, for methods A, B and C, respectively. The solution of the products obeyed Beer's Law in the concentration ranges 10–70, 20–70, 2–48, μg mL^?1 for methods A, B, and C. The proposed methods were applied to the determination of the drug in pure or pharmaceutical preparations. The results obtained were compared statistically with those given by the official method.     

Kinetic and Spectrophotometric Determination of Thioctic Acid in Bulk and Pharmaceutical Formulations

Three simple and sensitive spectrophotometric methods were developed for the determination of thioctic acid in bulk and in its pharmaceutical preparations using iron(III) as an oxidizing agent. Method A is based on kinetic investigation of oxidation reaction of the drug with iron(III) and a subsequent chelation of the produced iron(II) with ferricyanide to form prussian blue colored product at room temperature for a fixed time of 15 minutes at 750 nm. Methods B and C are based on oxidation of the studied drug with iron(III). The equivalent iron(II) produced is allowed to react with either o‐phenanthroline or bipyridyl to give colored species measurable at 510, 522 nm, respectively. Regression analysis of Beer‐Lambert plots showed a good correlation in the concentration ranges of 0.4–4 μg/mL with a detection limit of 0.095 μg/mL for method A and 0.5–5 μg/mL with detection limits 0.137 and 0.127 for method B and C, respectively. The three methods were successfully applied for the determination of the drug in its dosage forms. The percentage recoveries were 99.88 ± 1.40, 99.98 ± 1.26 and 100.64 ± 1.07, respectively.     

Spectrofluorimetric determination of melamine formaldehyde in solid and liquid forms and in wastewater

A new, simple and sensitive spectrofluorimetric method for determination of trace amount of melamine formaldehyde (MF) was developed. In phosphate buffer solution of pH 7.4 MF can remarkably quench the luminescence intensity of toluylene red (NR) at λ_em = 590 nm due to formation of NR-MF ion associate complex. The luminescence intensity of NR-MF complex was in proportion to the concentration of MF and used as photo probe for its determination. The dynamic range for the determination of MF is 7.5–52.5 ppm with detection limit of 4.4 ppm. The method is relatively free from interferences from coexisting substances and used successfully for the determining of MF in powder and liquid forms and in wastewater produced from MF industries. The average recoveries and standard deviations of 98.3 ± 0.6, 98.1 ± 0.6 and 97.3 ± 0.5% were achieved for determination of MF in solid, liquid forms and wastewater, respectively     

Study on the Catalytic Effects of Ruthenium on the Oxidation of Basic Dyes by Kio4 and its Analytical Applications

ABSTRACT

Three sensitive catalytic spectrophotometric methods have been developed for the determination of ruthenium(III), based on its catalytic effects on the oxidation reactions of three basic dyes: nile blue (NB), butyl rhodamine B (BRB) and methylene blue (MB), by KIO⁴ in acidic medium at 90±0.5 °C. The above reactions are followed spectrophotometrically by measuring the decrease in the absorbance at 630 nm, 555 nm and 670 nm for the catalytic reactions of NB, BRB and MB, respectively. The working curves for the three recommended reaction-rate methods are linear in the concentration range over 0.0080-1.2 and 0.0080-0.72 μg/L for NB and BRB methods, and 0.0-1.2 and 1.2-5.6 μg/L for MB method. Almost no foreign ion interfered in the determination at less than 10-fold concentration of Ru(III). The methods are highly sensitive, more selective and very stable, and have been successfully applied for the determination of trace amount of ruthenium in some ore and metallurgy products. The kinetic parameters and the catalytic reaction mechanism have also been studied.     

Liquid Chromatographic Determination of Dimetridazole and Ronidazole in Feeds

Abstract

A simple high performance liquid chromatographic (HPLC) procedure for the simultaneous determination of dimetridazole and ronidazole in turkey feeds is described. The drugs are extracted from feeds by carbon-tetrachloride/dimethylformamide (80:20) at 60°C during 30 mn and the extract is subjected to a partition by water. After centrifugation the eluate is chromatographed on a reverse phase column with ultaviolet detection at 316 nm. Recoveries from samples fortified at levels 2.02 to 7.07 ppm for ronidazole and 2.01 to 7.03 for dimetridazole were 99,6% ± 1,4 and 95,3% ± 1,8 (mean ± standard deviation), respectively.     

Spectrophotometric Determination of Esomeprazole Magnesium in Commercial Tablets Using 5‐Sulfosalicylic Acid and N‐Bromosuccinimide

Two simple, sensitive and economical spectrophotometric methods have been developed for the determination of esomeprazole magnesium in commercial dosage forms. Method A is based on the reaction of esomeprazole magnesium with 5‐sulfosalicylic acid in methanol to form a yellow product, which absorbs maximally at 365 nm. Method B utilizes the reaction of esomeprazole magnesium with N‐bromosuccinimide in acetone‐chloroform medium to form α‐bromo derivative of the drug peaking at 380 nm. Under the optimized experimental conditions, Beer's law is obeyed in the concentration ranges of 2‐48 and 10‐100 μg mL^?1 with molar absorptivity of 2.11 × 10⁴ and 4.57 × 10⁴L mol^?1 cm^?1 for methods A and B, respectively. The limits of detection for methods A and B are 0.35 and 0.46 μg mL^?1, respectively. No interference was observed from excipients commonly present in tablet formulations. Methods A and B are successfully applied to the commercial tablets for the estimation of esomeprazole magnesium with good accuracy and precision. The results compare favorably with the reference spectrophotometric method indicating no significant difference between the methods compared.     

Spectrophotometric Studies on the Chelate Formation between Zirconium(IV) and Chromotrope 2R

The composition and stability of the chelate formed between Zr(IV) and chromotrope 2R has been investigated using spectrophotometric methods. The chelate is violet in color and has λmax at 530 nm. The composition, determined by different methods is 1 : 1. The chelate is stable between pH 1.0-3.0. The value of log K as determined by two different methods are 4.48±0.2 and 4.21±0.1 and the values of free energy of formation are —6.21±0.2 and —5.83±0.1 respectively at 30°C. The system obeys Beer's Law over a concentration range of 2.50 to 20.0 ppm of zirconium. The effective range of photometric determination is 3.50 to 19.05 ppm of zirconium.     

Bioaccumulative and conchological assessment of heavy metal transfer in a soil-plant-snail food chain

Background

Alendronate (ALD) is a member of the bisphosphonate family which is used for the treatment of osteoporosis, bone metastasis, Paget's disease, hypocalcaemia associated with malignancy and other conditions that feature bone fragility. ALD is a non-chromophoric compound so its determination by conventional spectrophotometric methods is not possible. So two derivatization reactions were proposed for determination of ALD through the reaction with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) and 2,4-dinitrofluorobenzene (DNFB) as chromogenic derivatizing reagents.

Results

Three simple and sensitive spectrophotometric methods are described for the determination of ALD. Method I is based on the reaction of ALD with NBD-Cl. Method II involved heat-catalyzed derivatization of ALD with DNFB, while, Method III is based on micellar-catalyzed reaction of the studied drug with DNFB at room temperature. The reactions products were measured at 472, 378 and 374 nm, for methods I, II and III, respectively. Beer's law was obeyed over the concentration ranges of 1.0-20.0, 4.0-40.0 and 1.5-30.0 ??g/mL with lower limits of detection of 0.09, 1.06 and 0.06 ??g/mL for Methods I, II and III, respectively. The proposed methods were applied for quantitation of the studied drug in its pure form with mean percentage recoveries of 100.47 ± 1.12, 100.17 ± 1.21 and 99.23 ± 1.26 for Methods I, II and III, respectively. Moreover the proposed methods were successfully applied for determination of ALD in different tablets. Proposals of the reactions pathways have been postulated.

Conclusion

The proposed spectrophotometric methods provided sensitive, specific and inexpensive analytical procedures for determination of the non-chromophoric drug alendronate either per se or in its tablet dosage forms without interference from common excipients.

Graphical abstract

     

Inclusion as a driving force for the intramolecular charge transfer (ICT) fluorescence of p-(N,N-diphenylamino)benzoic acid methyl ester (DPABME) in α-cyclodextrin (α-CD) aqueous solution

A 1:1 inclusion complex between p-(N,N-diphenylamino)benzoic acid methyl ester (DPABME) molecule and α-cyclodextrin (α-CD) in aqueous solution is formed with a stabilization constant of ca. 45.65 ± 3.59 M^?1 at 25 °C. The formation of the complex is accompanied by enhancement of the long wavelength fluorescence at 510 nm (attributed to intramolecular charge transfer (ICT) due to twisting) relative to the normal fluorescence at 420 nm. In water, the long-wavelength fluorescence is hidden under the red tail of the normal fluorescence band due to quenching by non-radiative transition. Inclusion by CD reduces quenching and thus constitutes a driving force for DPABME to emit at longer wavelength via ICT process.     

Spectrophotometric determination of linezolid in pharmaceuticals on the basis of coupled redox-complexation reactions

The present study describes three simple and sensitive spectrophotometric methods developed for the determination of linezolid (LZD) in pure and tablet forms. These methods are based on the oxidation of LZD by ferric chloride in the presence of 1,10-phenanthroline (method A), or 2,2′-bipyridyl (method B), or potassium ferricyanide (method C). The colored complexes were measured at 510, 522 and 758 nm for methods A, B and C, respectively. In all the methods, the absorbance is found to increase linearly with increasing LZD concentration. Beer’s law is obeyed over the concentration ranges of 0.5–6.0, 0.5–9.0 and 1.0–9.0 μg/mL for methods A, B and C, respectively. The calculated molar absorptivity values are 5.8 × 10⁴, 3.6 × 10⁴ and 4.8 × 10⁴ L/mol cm for methods A, B and C, respectively, and the corresponding Sandell’s sensitivities are 5.8 × 10^?3, 9.8 × 10^?3 and 7 × 10^?3 μg/cm², respectively. The developed methods are applied successfully to the determination of LZD in the pharmaceutical formulations and the results tallied well with label claims.     

Dosage direct de submicrotraces de bore dans la soude de purete analytique par la methode fluorimetrique a l'hydroxy-2-methoxy-4-chloro-4'-benzophenone

A method based on the highly sensitive fluorescent reaction of boric acid with 2-hydroxy-4-methoxy-4'-chlorobenzophenone (H.M.C.B.), is described for the direct determination of traces of boron in “analytical grade” sodium hydroxide. In the nanogram range, the reliability of the H.M.C.B. method is satisfactory; the fluorescent reaction is not affected by up to 8% (v/v) of water. The sample is dissolved directly in concentrated sulfuric acid and no preliminary separation is needed. Interferences from other impurities of sodium hydroxide are negligible. Results for five different “analytical grade” reagents were: (0.9±0.2)·10^-6,(3.2±0.3)·l0^-6,(3.2±0.3)·^-6, (4.0±0.4)·10^-6and(2.0±0.16)·10^-6% B.     

Development of a Reversed-Phase Liquid Chromatographic Assay for the Quantification of Total Persipeptides in Fermentation Broth

The emergence and prevalence of multi-drug-resistant bacterial strains increase the potential for outbreaks of incurable infections. The discovery of novel antibiotics and pharmacological preparations requires the identification of novel bioactive small molecules. A specific, sensitive, and reliable quantification method using high-performance liquid chromatography (HPLC) with UV detection was developed for the determination of total persipeptides (A and B), which are cyclic pentapeptides found in the fermentation broth of Streptomyces zagrosensis UTMC 1154 that exhibit bioactivity against methicillin-resistant Staphylococcus aureus (MRSA). A simple liquid–liquid extraction (LLE) method using butanol was employed to extract persipeptides from the fermentation broth prior to HPLC analysis. The chromatographic separation of persipeptides and the internal standard, virginiamycin, was achieved with a gradient of acetonitrile and water on a C18 reversed-phase analytical column in a 25-min analytical run utilizing a flow rate of 0.8 mL min⁻¹ and detection at 210 nm. The whole assay was validated, and the method presented a linear response range with a regression coefficient of determination R ² of 0.9996 for the quantification of persipeptides in the concentration range of 3.9–250.0 µg mL⁻¹, as well as extraction recoveries ranging from 54.78 ± 9.83 % to 56.45 ± 16.33 %. The bias and the precision of the proposed method were <10 %. The detection and quantification limits for the persipeptides were 27 and 83 µg L⁻¹, respectively.

     

Structural and electrical characterisation of betaine-type,organic, molecular,thin evaporated films and LB multilayers

The structure and electrical properties of highly polar indandione-1,3 pyridinium betaine (IPB) derivatives have been studied in vacuum-evaporated thin films and Langmuir-Blodgett (LB) multilayer assemblies. Phase transitions induced by temperature and/or electric field have been observed in LB films of an amphiphilic derivative of IPB.The LB films of IPB, obtained at room temperature, form a Y-like structure which melts at about 50 °C to produce spherical domains, having Z-like structure, which remain stable up to 110 °C. Similar phase transitions can be induced by an electric field with ε ≥ 2 × 10⁵ V cm⁻¹ at room temperature. In the new Z-like phase of the IPB LB films, the electrical conductivity increases by some five or six orders of magnitude and the activation energy of dark conductivity decreases from 0.18 ± 0.03 eV to practically zero.The vacuum-evaporated IPB films yield low electrical conductivity (σ = 10⁻¹⁵–10⁻¹⁶S cm⁻¹), whereas in the LB multilayers a notable anisotropy of conductivity is observed. In case of coplanar cells the conductivity increases to σ = 10⁻⁸S cm⁻¹. In sandwich-type LB samples the conductivity value is similar to that of the vacuum-evaporated polycrystalline thin films.     

Studies on reaction of reduced lipoic acid with Mukaiyama reagent and its application for pharmaceutical and food analysis

A new sensitive method for the determination of lipoic acid (LA) in selected food items based on its reaction with Mukaiyama reagent (2-chloro-1-methylpyridinium iodide, CMPI) was developed. It was stated that CMPI reacts with reduced form of lipoic acid (dihydrolipoic acid, DHLA) and the stable product is produced. The spectrum of the labeled form of DHLA exhibits new band at 312?nm. Based on its spectral characteristics new spectrophotometric and UV–high-performance liquid chromatography (HPLC) methods of LA determination were elaborated. Both methods allowed determination of the analyte in the concentration range of 5?×?10^?6–1?×?10^?4?mol?L^?1 with limit of detection 0.39?×?10^?6 and 0.77?×?10^?6?mol?L^?1 for spectrophotometric and HPLC method, respectively. The practical usability of newly developed methods was checked by determination of lipoic acid contents in its pharmaceutical preparate Revitanerw. The proposed method was precise and accurate. The relative error of determination did not exceed ±0.067%. As chromatographic method allowed the determination of analyte in the presence of complex matrix, it was applied for assay of free fraction of α-lipoic acid in selected food items. A procedure of LA isolation from biological matrix was developed. The extraction with dichloromethane allowed quantitative recovery at 102.94?±?4.20%. The green barley appeared to be the richest source of LA.     

Simultaneous Determination of Propranolol Hydrochloride and Sodium Benzoate in Oral Liquid Preparations by HPLC

A simple, selective and sensitive HPLC–UV method for quantification of propranolol hydrochloride and sodium benzoate in oral liquid preparations was developed and fully validated. Separation was performed by Supelco Discovery^® C18 (25 cm × 4.6 mm, particles 5 μm) column. UV/VIS absorbance detector was set at wavelength 230 nm. Column oven was conditioned to 25 °C. Mobile phase was prepared by dissolving 1.6 g of sodium dodecyl sulphate and 0.31 g of tetrabutylammonium dihydrogen phosphate in 450 mL of ultrapure water; 1 mL of sulphuric acid (95–97 %) and 550 mL of acetonitrile were added. Sodium hydroxide solution (2.1 M) was used for adjusting pH to value 3.3 (±0.05). Retention times of sodium benzoate, propranolol hydrochloride and butylparaben (internal standard) were 2.2, 3.3 and 4.1 min, respectively. Newly developed method is suitable for simultaneous determination of propranolol hydrochloride and sodium benzoate in oral liquid preparations which are used for therapy of haemangiomas in paediatric patients. Method has been applied for stability testing of extemporaneous paediatric oral formulations containing propranolol hydrochloride.

     

Utility of p-chloranilic Acid and 2,3 Dichloro-5,6-dicyano p-Benzoquinone (DDQ) for the Spectrophotometric Determination of Triamterene

Abstract

Two simple and sensitive spectrophotometric procedures are suggested for analysis of triamterene. The first procedure is based on the reaction of triamterene with p-chloranilic acid (p-CA) in methylene chloride to form a highly stable coloured product, exhibiting maximum absorbance at λ 530 nm. Beer's law is obeyed in the range of 40–220 μg.ml^?1 with a mean percentage accuracy of 99.98 ± 0.446. Limit of determination is 20 μg.ml^?1. In the second procedure, the drug is determined via charge transfer complex formation with 2,3 dichloro-5,6-dicyano p-benzoquinone (DDQ) using methylene chloride as a solvent. Here the reaction product has two well defined maxima at 460 nm and 530 nm where each has been utilized for quantitative determination. Beer's law is obeyed in concentration ranges of 25–125 μg.ml^?1 and 25–150 μg.ml^?1 with mean percentage accuracies of 99.92 ± 0.449 and 100.00 ± 0.511 for both maxima. 460 and 530 nm. respectively. Limit of determination is 12.5 μg.ml^?1 at both maxima. Optimum conditions for each procedure have been studied and the stoichiometry of both reactions was ascertained using Job's method of continuous variation. The validity of the suggested procedures was assessed by applying the standard addition technique using the drug capsules. Both procedures are statistically analyzed as compared with BP method for analysis of triamterene (non aqueous titration) revealing good accuracy and precision as indicated by t and F tests.     

A Validated LC Method for Determination of Trace Impurities in Technical Triadimefon

A simple and sensitive liquid chromatography with ultraviolet detection (LC?CUV) method was developed for the determination of three impurities with a content over 0.1% (w/w) in technical triadimefon. A Gemini C₁₈ column (5 ??m, 250 mm × 4.6 mm i.d.) was used for the chromatographic separations. The samples were separated by gradient elution with water (solvent A) and methanol (solvent B) using the following conditions: 70% A isocratic for 12 min, linear to 0% A within 8 min, and isocratic for 10 min at 0% A with a flow rate of 1.0 mL min^?1. Chromatograms were recorded at an absorption wavelength of 280 nm. The chromatographic resolutions between triadimefon and its potential impurities A, B, and C were greater than 3. The developed LC method was validated with respect to linearity, accuracy, precision, and robustness. This method was successfully applied to analyze the impurities in commercial technical triadimefon. In addition, the structures of the three impurities were identified to be (A) 4-chlorophenol, (B) 1-(2,4-dichlorophenoxy)-3,3-dimethyl-1-(1H-1,2,4-triazol-1-yl)-2-butanone, and (C) 1,1-bis(4-chlorophenoxy)-3,3-dimethyl-2-butanone.     

Utility of certain nucleophilic aromatic substitution reactions for the assay of pregabalin in capsules

Background

Pregabalin (PG) is an anticonvulsant, analgesic and anxiolytic drug. A survey of the literature reveals that all the reported spectrophotometric methods are either don't offer high sensitivity, need tedious extraction procedures, recommend the measurement of absorbance in the near UV region where interference most probably occurs and/or use non specific reagent that don't offer suitable linearity range.

Results

Two new sensitive and simple spectrophotometric methods were developed for determination of pregabalin (PG) in capsules. Method (I) is based on the reaction of PG with 1,2-naphthoquinone-4-sulphonate sodium (NQS), yielding an orange colored product that was measured at 473 nm. Method (II) is based on the reaction of the drug with 2,4-dinitrofluorobenzene (DNFB) producing a yellow product measured at 373 nm. The different experimental parameters affecting the development and stability of the reaction product in methods (I) and (II) were carefully studied and optimized. The absorbance-concentration plots were rectilinear over the concentration ranges of 2-25 and 0.5-8 μg mL^-1 for methods (I) and (II) respectively. The lower detection limits (LOD) were 0.15 and 0.13 μg mL^-1 and the lower quantitation limits (LOQ) were 0.46 and 0.4 μg mL^-1 for methods (I) and (II) respectively.

Conclusion

The developed methods were successfully applied to the analysis of the drug in its commercial capsules. The mean percentage recoveries of PG in its capsule were 99.11 ± 0.98 and 100.11 ± 1.2 (n = 3). Statistical analysis of the results revealed good agreement with those given by the comparison method. Proposals of the reaction pathways were postulated.     

Improved spectrofluorimetric methods for determination of penicillamine in capsules

Two simple, sensitive and specific fluorimetric methods have been developed for the determination of Penicillamine (PNC), a sulphur containing compound. Method (I) involves the reaction of PNC with 2′,7′-bis(acetoxymercuri)-fluorescein (AMF) in the presence of Kolthoff’s buffer, pH 8.2, with subsequent measurement of fluorescence spectra at 520 nm (λ_Ex 497 nm). Method (II) is based on PNC being oxidized into penicillaminic acid using Cerium (IV) in an acidic medium. Method sensitivity has been improved using sodium triphosphate which enhances the luminescence intensity of Ce(III). Fluorescence spectra were then measured at 348 nm (λ_Ex 293 nm). The reaction conditions and the fluorescence spectral properties have been investigated for both methods. Under the described conditions, the proposed methods were applicable over the concentration ranges 0.0048 − 0.0288 μg mL⁻¹ and 0.096 − 0.288 μg mL⁻¹ with mean percentage recoveries 99.95 ± 1.29 and 100.04 ± 1.10 for methods I and II, respectively. The proposed methods were validated in terms of accuracy, precision, LOD and LOQ and robustness and then were successfully applied to the determination of PNC in bulk powder and in capsules as well as in the presence of the related disulphide. The results obtained were determined to be in good agreement with those obtained using a previously reported method.      

High Performance Liquid Chromatographic Determination of Diuretic-Antihypertensive Combination Products. II. Polythiazide and Reserpine

Abstract

A high performance liquid chromatographic method for the simultaneous determination of polythiazide and reserpine in tablets is described. Polythiazide, reserpine, and vanillin (an excipient) are separated isocratically on an octadecylsilane column using a methanol-water-acetic acid (55:44:1) mobile phase. The column effluent was monitored by ultraviolet ab-sorbance at 254 nm. Recoveries from synthetic formulations were 100.2 ± 1.7% for polythiazide and 98.7 ± 1.1% for reserpine.