Kinetic spectrophotometric determination of certain cephalosporins using oxidized quercetin reagent

A simple, precise and accurate kinetic spectrophotometric method for determination of cefoperazone sodium, cefazolin sodium and ceftriaxone sodium in bulk and in pharmaceutical formulations has been developed. The method is based upon a kinetic investigation of the reaction of the drug with oxidized quercetin reagent at room temperature for a fixed time of 30 min. The decrease in absorbance after the addition of the drug was measured at 510 nm. The absorbance concentration plot was rectilinear over the range 80–400 μg mL⁻¹ for all studied drugs. The concentration of the studied drugs was calculated using the corresponding calibration equation for the fixed time method. The determination of the studied drugs by initial rate, variable time and rate-constant methods was feasible with the calibration equations obtained but the fixed time method has been found to be more applicable. The analytical performance of the method, in terms of accuracy and precision, was statistically validated; the results were satisfactory. The method has been successfully applied to the determination of the studied drugs in commercial pharmaceutical formulations. Statistical comparison of the results with a well established reported method showed excellent agreement and proved that there is no significant difference in the accuracy and precision.     

A new reagent system for the highly sensitive spectrophotometric determination of selenium

Highly sensitive and simple spectrophotometric determination of selenium is described for the determination of selenium(IV) using a new reagent leuco malachite green. The method is based on the reaction of selenium(IV) with potassium iodide in an acidic condition to liberate iodine, the liberated iodine oxidizes leuco malachite green to malachite green dye. The green coloration was developed in an acetate buffer (pH 4.2–4.9) on heating in a water bath (∼ 40 °C). The formed dye exhibits an absorption maximum at 615 nm. The method obeys Beer’s law over a concentration range of 0.04–0.4 μg mL⁻¹ selenium. The molar absorptivity and Sandell’s sensitivity of the color system were found to be 1.67 × 10⁵ L mol⁻¹ cm-¹ and 0.5 ng cm⁻², respectively. The optimum reaction conditions and other analytical parameters have been evaluated. The proposed procedure has been successfully applied to the determination of selenium in real samples of water, soil, plant material, human hair, and cosmetic samples. The results were compared to those obtained with the reference method. Statistical analysis of the results confirms the precision and accuracy of the proposed method. In addition, the developed method is cost-effective and involves easily accessible instrumentation technique which can be used by ordinary research laboratories.     

Chlorophosphonazo-p-Cl,a new reagent for the spectrophotometric determination of scandium

Summary Chlorophosphonazo-p-Cl, A New Reagent for the Spectrophotometric Determination of Scandium The synthesis of chlorophosphonazo-p-Cl (CPApC) and a highly sensitive method with CPApC as a new reagent for the spectrophotometric determination of scandium are described. Scandium reacts with CPApC in nitric acid medium at pH 2 to form a 11-type complex which has a maximum absorption at 762 nm. Under the experimental conditions employed, the apparent molar absorptivity is 1.54×10⁵ l·mol^–1·cm^–1 and the relative standard deviation for 2.0g of scandium is 0.92%. The determination range is 0–6g of scandium in 25 ml of solution by using standard addition-deduction method. Scandium can be determined in the presence of reasonable amounts of rare earths.This work was supported by the Science Fund of the Chinese Academy of Sciences.     

Spectrophotometric method for assay of penicillins

Ninhydrin in 0.2M citrate buffer (pH 5) containing SnCl₂ is proposed as a new reagent for Spectrophotometric determination of penicillins and analysis of their pharmaceutical formulations. The method is based on acid hydrolysis of penicillins with 5M HCl and subsequent treatment with ninhydrin. The resulting violet colour exhibits maximum absorption at 570 nm.     

N,N-diethyl-N'-benzoylthiourea--a new spectrophotometric reagent for rhenium determination

The reagent N,N-diethyl-N'-benzoylthiourea produces a green complex with rhenium in hydrochloric acid medium in the presence of tin(II) chloride. The complex extracted into toluene shows an absorption maximum at 383 nm, obeys Beer's law from 1.5 to 22 micrograms ml-1 of rhenium while its molar absorptivity and Sandell sensitivity are 6.66 x 10(3) L mol-1 cm-1 and 0.028 microgram cm-2, respectively. It tolerates the presence of a large number of ions, including Mo(VI), W(VI) and some platinum metals. Job's and the mole ratio methods indicate that the rhenium metal and the chelating agent ratio of 1:2 in solution. The system has been applied to the determination of rhenium on synthetic samples and alumina based catalysts.     

Guaiacol as a new reagent for the spectrophotometric determination of uranium

Guiacol, i.e. o-hydroxyanisole, gives a distinct color reaction with U(VI) suitable for spectrophotometric determination of the metal. The complex formed in the reaction has an absorption maximum at 352 nm. Optimum pH for the color development ranges from 6.5 to 8.5. The molar absorptivity and Sandell's sensitivity of the method were found to be 3.75×10³ l·mol^–1·cm^–1 and 0.063 g·cm^–2, respectively. Many anions and cations do not interfere up to 100 ppm. The method has been made very specific by selective extraction of U(VI) with TBP from a mixture of different cations and anions in the presence of 60% NH₄NO₃ as salting out agent followed by developing the color in the non-aqueous phase by adding quaiacol in methanol at pH 6.5 to 8.5 An amount as low as 30 g of uranium (VI) per 10 ml of the solution could be satisfactorily determined with an RSD of ±2.0%. The method was applied to rock samples after U(VI) had been extracted from a sample solution into 25% TBP in hexane. Results obtained by the new method compare very well with those of conventional fluorimetric and radiometric assays. The features of the method include excellent precision, rapidity, good selectivity, and ease of performance.     

Micellanized spectrophotometric method for the determination of beryllium using haematoxylin

A simple and sensitized spectrophotometric method for the determination of trace amounts of beryllium has been described. The method is based on the formation of a ternary complex by the reaction of beryllium with haematoxylin in the presence of micellar medium (cationic surfactant, cetyltrimethylammonium bromide). The ternary complex of beryllium has a maximum absorbance at 592 nm and showed an excellent sensitivity (molar absorption coefficient of 7.07 x 10(4)L mol(-1)cm(-1) and the Sandell's sensitivity being 1.27 x 10(-4) microg cm(-2)) and reproducibility (within-day precision: R.S.D.相似文献   

Tungstophosphoric acid as a new reagent for the spectrophotometric determination of phenothiazines

A simple and rapid spectrophotometric method for the determination of phenothiazines based on the formation of a colored compound between tungstophosphoric acid and phenothiazines is described. The proposed method is successfully employed for the determination of phenothiazine drugs in various pharmaceutical products.     

Prochlorperazine bismethanesulfonate as a new reagent for the spectrophotometric determination of palladium

A simple, rapid, and selective method for the determination of palladium is described. The orange-red palladium(II)-prochlorperazine bismethanesulfonate complex in the presence of hydrochloric acid-sodium acetate buffer exhibits maximum absorbance at 480 nm with a molar absorptivity of 4.32 × 10³ liters mol^?1 cm^?1. The sensitivity of the reaction is 24.62 ng cm^?2. The system obeys Beer's law over the concentration range 0.4–20 ppm of palladium with an optimum concentration range of 1–19 ppm. The apparent stability constant of the complex is found to be log K = 5.3 ± 0.1 at 27 °C. The effects of pH, time, temperature, order of addition of reactants, reagent concentration, and interferences from various ions are reported. The proposed method offers the opportunity to carry out the determination at room temperature without the need for an extraction step. The method is also found to be suitable for the determination of palladium in jewelry alloy.     

A new polymeric chromogenic reagent for dual-wavelength spectrophotometric determination of iron(III)

By condensing chitosan with 7-(4-formyl-phenylazo)-8-quinolinol-5-sulfonic acid (FPAQS), a new polymeric chromogenic reagent C-FPAQS has been synthesized and its properties investigated. In acidic media (pH 2.7), C-FPAQS reacts with iron(III) to yield an orange complex with a molar absorptivity of 2.8 × 10⁴ lmol^–1 cm^–1 at 420 nm, and in the meantime a negative peak at 524 nm. The apparent molar absorptivity (420–524 nm) obtained by dual-wavelength measurements is 7.9 × 10⁴lmol^–1cm^–1 which is about two times higher than that by single-wavelength measurements at 420 nm Beer's law is obeyed in the range of 0–0.8 g ml^–1 for iron(III). The developed method has been satisfactorily used to determine iron at the 0.03 to 3% (ww) level in a nylon-6 and in a soil sample. Compared to the corresponding low-molecular weight FPAQS and other chromogenic reagents, C-FPAQS has not only good sensitivity but also largely increased acid solubility and improved selectivity for iron, which may be explained by the incorporation of FPAQS into an acid-soluble polymer.     

Neotetrazolium chloride: a new reagent for spectrophotometric determination of manganese

The interaction of Mn(VII) and the Neotetrazolium chloride has been examined. The ion-associate formed is extracted into 1,2di-chloroethane. The optimum conditions have been established. The molar absorptivity of the complex is (9.1+/-0.08)x10(5) l mol(-1) cm(-1). The sensitivity of the method is 6.04x1010(-5) mug cm(-2). It is possible to extract and determine manganese in the presence of large number of cations and anions. The characteristic values for the extraction and the aqueous phase equilibria were determined: extraction constant K(ex)=3.21x10(9), distribution constant K(D)=33 and association constant beta=9.72x10(7). The method is applicable to analysis of soils and steels.     

A new reagent for the colorimetric and spectrophotometric determination of phosphorus,arsenic and germanium

A new reagent for the colorimetric and spectrophotometric determination of phosphorus, arsenic and gurmanium is described. It contains Mo(Vl) amd Mo(V) in the ratio of 3 : 2 in an acid medium, 10N with respect to H₂SO₄ and 3N with respect to HCl.The absorption spectra, the influence of temperature, time, quantity of reagent and selectivity of the method have been studied. Beer's law is applicable up to 160 μg for P₂O₅, 220 μg for GeO₂ and 230 μg for arsenic, in 50 ml.     

Di-2-Pyridylketoxime,a new reagent for the spectrophotometric determination of iron(II)

Di-2-pyridylketoxime is proposed for the spectrophotometric determination of iron(II). The complex is stable and exhibits an absorption maximum at 534 nm in an alkaline citrate medium. Beer's law is obeyed and the molar absorptivity is 1.5·10³. Large amounts of copper and nickel can be tolerated. The method is simple, convenient and reproducible.     

o-Dianisidine: a new reagent for selective spectrophotometric, flow injection determination of chlorine.

A flow injection analysis (FIA) procedure for the determination of free chlorine in industrial formulations and water samples is proposed. The manifold is provided with a gas-diffusion unit which permits the removal of interfering species and also the preconcentration of chlorine. The determination of chlorine is performed on the basis of the oxidation by o-dianisidine as a chromogenic reagent to a coloured product which can be monitored at 445 nm. The method (for a preconcentration step of 60 s) is linear over the range 0.04-1.00 mg l(-1) of chlorine, the limit of detection is 0.04 mg l(-1), the reproducibility of the procedure (as RSD of the slope) is 3.7% for a series of four independent calibrations, the precision (as RSD of a series of 30 continuous FIA peaks of 0.56 mg l(-1) of chlorine) is 1.4% and the sample throughput is 40 h(-1). A detailed comparative study of the analytical characteristics of a single mono-channel reverse FIA assembly and the same system but provided with a Fluoropore membrane filter of 0.5 microm pore size was performed to check the advantages of the new approach in terms of sensitivity, selectivity and limit of detection.     

Benzeneacetaldehyde-4-hydroxy-alpha-oxo-aldoxime as a new analytical reagent for the spectrophotometric determination of cobalt

Benzeneacetaldehyde-4-hydroxy-α-oxo-aldoxime is proposed as a new sensitive and selective reagent for the spectrophotometric determination of cobalt. The reagent reacts with cobalt in the pH range 8.6–9.4 to form a yellow colored 1:3 chelate which is very well extracted in chloroform. Beer's law is obeyed in the concentration range 0.05–1.3 μg ml⁻¹ cobalt. The molar absorptivity of the extracted species is 2.746×10⁴ l mol⁻¹ cm⁻¹ at 390 nm. The proposed method is highly sensitive, selective, simple, rapid, accurate and has been satisfactorily applied for the determination of cobalt in synthetic mixtures, pharmaceutical samples, biological samples and alloys.     

2-(2-Thiazolylazo)-p-cresol as a spectrophotometric reagent for vanadium determination in the presence of ascorbic acid

The present work describes the use of 2-(2-thiazolylazo)-p-cresol (TAC) as a spectrophotometric reagent for vanadium determination. TAC reacts with vanadium(IV) in the presence of ascorbic acid, forming a red complex with absorption maximum at 525 nm. The following parameters were studied: complex stability, pH effect, amount of TAC, amount of acetate buffer, HEDTA effect, order of addition of reagents and Beer's law validity. TAC can be used for vanadium determination in the pH range 4.6–6.0, with molar absorptivity of 2.11 × 10⁴Lmole^–1 cm^–1 (at525nm). Beer's law is obeyed up to 2.0 g mL^–1. Many cation interferences can be easily eliminated by using HEDTA as a masking agent. Steel reference standards were used to test the proposed procedure and the accuracy and precision obtained were satisfactory.     

Evaluation of N-bromosuccinimide as a new analytical reagent for the spectrophotometric determination of fluoroquinolone antibiotics

Analytical studies were carried out, for the first time, to evaluate the use of N-bromosuccinimide (NBS) as an analytical reagent for the spectrophotometric determination of eleven therapeutically important fluoroquinolone antibiotics (FQA). The procedures involved the reaction of the FQA with NBS and subsequent measurement of the excess NBS by its reaction with p-phenylenediamine (PDA) to give a violet colored product that was measured at 530 nm. Different variables affecting the reaction (concentration of NBS, concentration of PDA, pH of reaction medium, reaction time, and the diluting solvents) were carefully studied and optimized. The molar ratio and mechanism of the reaction between each of the studied FQA with NBS were proposed using UV-vis, IR, and NMR techniques. Under the optimum reaction conditions, the analytical method was developed and validated. Beer's law was obeyed in the general concentration range of 3-25 microg/ml. The assay limits of detection and quantitation were 0.33-1.29 and 1.10-4.31 microg/ml, respectively. The precision of the method was satisfactory; the values of relative standard deviations did not exceed 2%. The proposed method was successfully applied to the analysis of the investigated FQA in their pure and pharmaceutical dosage forms without interference from the common excipients (label claim values were 99.85-100.17+/-0.13-0.59%). Interference from ascorbic acid, that is co-formulated as a stabilizer for the ampoule form, was avoided by its pre-oxidation with potassium bromate before applying the analytical procedure. The results obtained by the proposed method were comparable with those obtained by the official and reported methods.