Comparative analysis and application of novel spectrophotometric approaches and bioassay for fast macrolide quantification in table

A rapid , simple, accurate and sensitive spectrophotometric method was developed for determination of mebendazole ( MBL ) in pure form and in its pharmaceutical dosages. This method depend on oxidation of MBL with excess amount of N-bromosuccinimide ( NBS ) in acidic medium with standing for complete the reaction , and the oxidized MBL coupled with Rhodamine B to get red product related with MBL amount and measuring the absorbance of surplus dye at 570 nm. A linear calibration curve was obtained over the concentration range 2.5 – 30 μg.ml-1 with correlation coefficient of 0.9992. The molar absorptivity and sandell's sensitivity index values were determined to be 1.476 × 104 L.mol-1.cm-1 and 0.02 μg.cm-2. The limit of detection (LOD) and quantification (LOQ) were calculated to be 0.469 and 1.982 μg.ml-1, respectively . The proposed method has been successfully applied to the determination of MBL in available dosage form, the validity proposed method was confirmed by recovery study via standard addition technique.

Synthesis, and spectroscopic studies of charge transfer complex of 1,2-dimethylimidazole as an electron donor with π-acceptor 2,4-dinitro-1-naphthol in different polar solvents

This paper deals with the validation of a method for the determination of iron in spectrophotometric method in aqueous medium. The method is based on complex formation of iron with thioglycolic acid (TGA) in alkaline medium in presence of a masking agent to produce a red purple chelate that has an absorption maximum at 535 nm wavelength. Beer’s-Lambert’s law is obeyed and linear calibration curves were obtained for the concentration range of iron from 0.1 mg/L to 30 mg/L. The reaction is found to be spontaneous in alkaline medium. The limit of detection (LOD) and limit of quantification (LOQ) for the developed method are 0.0108 and 0.0345 respectively. Effect of different parameters like molar ratio of iron to different reagents and interferences, effect of time and effect of temperature of this method of determination were studied. It is found that this method is moderately sensitive and has been successfully applied for the determination of iron (III) in different fields like ceramic materials, clay, sand, glass, stone, soil, water, and any inorganic iron containing compound or alloys. A comparison report is made for Chevron gas field waste material and Certified Reference Material (CRM) of iron, which was done by Atomic Absorption Spectrophotometer (AAS) and Ultraviolet-visible (UV-Vis) spectrophotometer and found to be comparable.

Two simple, rapid and cost-effective methods based on titrimetric and spectrophotometric techniques are described for the assay of RNH in bulk drug and in dosage forms using silver nitrate, mercury(II)thiocyanate and iron(III)nitrate as reagents. In titrimetry, an aqueous solution of RNH is treated with measured excess of silver nitrate in HNO3 medium, followed by determination of unreacted silver nitrate by Volhard method using iron(III) alum indicator. Spectrophotometric method involve the addition a known excess of mercury(II)thiocyanate and iron(III)nitrate to RNH, followed by the measurement of the absorbance of iron(III)thiocyante complex at 470 nm. Titrimetric method is applicable over 4-30 mg range and the reaction stoichiometry is found to be 1:1 (RNH: AgNO3). In the spectrophotometric method, the absorbance is found to increase linearly with concentration of RNH which is corroborated by the correlation coefficient of 0.9959. The system obey Beer's law for 5-70 µg mL-1. The calculated apparent molar absorptivity and sandell sensitivity values are found to be 3.27 ´ 103 L mol-1 cm-1, 0.107 µg cm-2 respectively. The limits of detection and quantification are also reported for the spectrophotometric method. Intra-day and inter-day precision and accuracy of the methods were evaluated as per ICH guidelines. The methods were successfully applied to the assay of RNH in formulations and the results were compared with those of a reference method by applying Student's t and F-tests. No interference was observed from common pharmaceutical excipients. The accuracy of the methods was further ascertained by performing recovery tests by standard addition method.

The present study aims to develop a swift , simple, accurate and sensitive spectrophotometric method for determination of Ciprofloxacin Hydrochloride ( CPFX ) in pure and pharmaceutical formulations. The suggested method depend on oxidation of CPFX with known excess amount of N-bromosuccinimide ( NBS ) in acidic medium and after reaction is insured to be complete , the surplus NBS is estimated by de colorization of methylene blue dye and measuring the absorbance of surplus dye at 665 nm . A linear calibration curve was obtained over the concentration range 0.5 – 4.5 μg.ml-1 with correlation coefficient of 0.9993 . The molar absorptivity and sandell's sensitivity index values were determined to be 8.6 ×104 L.mol-1.cm-1 and 0.004276 µg.cm-2, respectively .The limit of detection (LOD) and quantification (LOQ) were calculated to be 0.0033 and 0.0111 μg.ml-1, respectively . The proposed method has been successfully applied to the determination of CIPH in available dosage form, the validity proposed method was confirmed by recovery study via standard addition technique .

Aim: To develop a swift , simple, accurate and sensitive spectrophotometric method for determination of mebendazole (MBZL) in pure and pharmaceutical formulations. Methods: The suggested method depend on oxidation of MBZL with known excess amount of N-bromosuccinimide ( NBS ) in acidic medium and after reaction is insured to be complete , the surplus NBS is estimated by de colorization of methyl orange (MO) dye and measuring the absorbance of surplus dye at 508 nm. A linear calibration curve was obtained over the concentration range 2.5– 25 μg.ml-1 with correlation coefficient of 0.9997. The molar absorptivity and sandell's sensitivity index values were determined to be 1.505 × 104 L.mol-1.cm-1 and 0.019607 μg.cm-2. The limit of detection (LOD) and quantification (LOQ) were calculated to be 0.3736 and 2.553 μg.ml-1, respectively. The proposed method has been successfully applied to the determination of MBZL in available dosage form, the validity proposed method was confirmed by recovery study via standard addition technique . Keywords: mebendazole ; N-bromosuccinimide ; Determination ;Spectrophotometry ; methyl orange

A new spectrophotometric method was developed for the determination of two important nitroimidazoles; metronidazole (MZ) and tinidazole (TZ). The method was based on the charge-transfer (CT) complexation reaction of reduced forms of metronidazole and tinidazole as n-electron donors and chloranilic acid (CAA) as π-electron acceptor to form a purple-colored complex with a new absorption band at 520 nm which was adopted as the analytical wavelength. Molar absorptivities of 2.741 × 10 2 L M -1 cm -1 and 2.681 × 10 2 L M -1 cm -1 were obtained for MZ and TZ, respectively. Optimization of reducing agent and time of reduction revealed the superiority of metal hydrides over reducing metals. Reduction of MZ and TZ was completed at 30 °C within 10 min. Optimizations of temperature and time for the complexation reaction revealed that the reaction was completed at 30 °C within 5 min. A 60:40 mixture of 1,4-dioxane:acetonitrile was found to be the best diluting solvent for optimal detector response. The complexes were stable at room temperatures for weeks. Beer’s law was observed in the concentration of 5-40 µg ml (MZ) and 4.8-79.2 µg ml -1 (TZ) with low limits of detection of 1.88 and 0.74 µg ml -1 , respectively. Overall recoveries of MZ and TZ from quality control samples were 103.19 ± 2.05 (%RSD = 1.99, n = 12) and 101.63 ± 1.41 (%RSD = 1.39) over three days. There was no interference from commonly utilized tablet excipients. No significant difference existed between the results of the new method and the BP titrimetric procedures (p > 0.05). The new CT procedure described in this paper is simple, fast, convenient, accurate and precise and has the novelty of carrying out the reactions at room temperature compared to previously described procedures. The new method could be adopted as an alternative procedure for the quality assessment of MZ and TZ in bulk and dosage forms.

Three simple, rapid, sensitive and cost-effective titrimetric and spectrophotometric methods were described for the determination of metoclopramide (MCP) in its pharmaceutical dosage forms and spiked human urine. The titrimetric methods were based on the diazotization reaction involving the primary amine group of MCP and NaNO2 in acid medium with visual (method A) and potentiometric (method B) end point detection. The spectrophotometric method (method C) depends upon the diazotization of MCP in acid medium followed by coupling with diphenylamine to give a red colored chromogen with a wavelength of maximum absorption at 530 nm. The experimental conditions were optimized. Both the titrimetric methods were applicable over the concentration range of 1.0-20.0 mg and the calculations were based on a 1 : 1 (MCP: NaNO2) reaction stoichiometry. In the spectrophotometric method, Beer's law was obeyed over the concentration range or 0.3-7.5 ug/mL with a molar absorptivity of 4.73 x 10^4 L/mol cm and Sandell's sensitivity being 0.007 μg/cm^2. The limit of detection and the limit of quantification were calculated to be 0.22 and 0.67 μg/mL, respectively. The proposed methods were applied to the determination of MCP in tablets, injection and also in spiked human urine.

The reactions of ketotifen fumarate (KT) with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as π acceptors to form charge transfer (CT) complexes were evaluated in this study. Experimental and theoretical approaches, including density function theory (DFT), were used to obtain the comprehensive, reliable, and accurate structure elucidation of the developed CT complexes. The CT complexes (KT-DDQ and KT-TCNQ) were monitored at 485 and 843 nm, respectively, and the calibration curve ranged from 10 to 100 ppm for KT-DDQ and 2.5 to 40 ppm for KT-TCNQ. The spectrophotometric methods were validated for the determination of KT, and the stability of the CT complexes was assessed by studying the corresponding spectroscopic physical parameters. The molar ratio of KT:DDQ and KT:TCNQ was estimated at 1:1 using Job’s method, which was compatible with the results obtained using the Benesi–Hildebrand equation. Using these complexes, the quantitative determination of KT in its dosage form was successful.

The formation of charge transfer (CT) complexes between bioactive molecules and/or organic molecules is an important aspect in order to understand ‘molecule-receptor’ interactions. Here, we have synthesized two new CT complexes, procainamide-chloranilic acid (PA-ChA) and procainamide-2,3-dichloro-5,6-dicyano-1,4-benzoquinone (PA-DDQ), from electron donor procainamide (PA), electron acceptor chloranilic acid (ChA), and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The structures of these two CT complexes were elucidated/characterized using FTIR, NMR, and many other spectroscopic methods. A stability study of each complex was conducted for the first time using various spectroscopic parameters (e.g., formation constant, molar extinction coefficient, ionization potential oscillator strength, dipole moment, and standard free energy). The formation of CT complexes in solution was confirmed by spectrophotometric determination. The molecular composition of each complex was determined using the spectrophotometric titration method and gave a 1:1 (donor:acceptor) ratio. In addition, the formation constant was determined using the Benesi–Hildebrand equation. To understand the noncovalent interactions of the complexes, density functional theory (DFT) calculations were performed using the ωB97XD/6-311++G(2d,p) level of theory. The DFT-computed interaction energies (ΔIEs) and the Gibbs free energies (ΔGs) were in the same order as observed experimentally. The DFT-calculated results strongly support our experimental results.

Three simple, sensitive, and accurate spectrophotometric methods have been developed for the determination of eletriptan hydrobromide (ELT) in pure and dosage forms. The first two methods are based on charge transfer complex formation between ELT and chromogenic reagents quinalizarin (Quinz) and alizarin red S (ARS) producing charge transfer complexes which showed an absorption maximum at 569 and 533 nm for Quinz and ARS, respectively. The third method is based on the formation of ion‐pair complex between ELT with molybdenum(V)‐thiocyanate inorganic complex in hydrochloric acid medium followed by extraction of the colored ion‐pair with dichloromethane and measured at 470 nm. Different variables affecting the reactions were studied and optimized. Beer′s law is obeyed in the concentration ranges 2.0–18, 1.0–8.0, and 2.0–32 μg mL−1 for Quinz, ARS, and Mo(V)‐thiocyanate, respectively. The molar absorptivity, Sandell sensitivity, detection, and quantification limits are also calculated. The correlation coefficients were ≥0.9994 with a relative standard deviation (R.S.D%.) of ≤0.925. The proposed methods were successfully applied for simultaneous determination of ELT in tablets with good accuracy and precision and without interferences from common additives, and the validity is assessed by applying the standard addition technique, which is compared with those obtained using the reported method.

A sensitive spectrophotometric method for the determination of nitrazepam in pure as well as in dosage form is described. The method is based on the reaction of reduced nitrazepam (RNZ) with p-bromanil in the presence of borate buffer solution of pH9 to form a pink color charge transfer(CT) complex of maximum absorption at 340 nm. Under the optimized reaction conditions, Beer’s law correlating the absorbance with nitrazepam concentration was obeyed in the range of 0.8-9.6 μg ml-1. The molar absorptivity was 1.977×104 L mol−1cm−1. The limits of detection was 0.093μg ml-1. The accuracy and precision of the method were satisfactory; the average recovery was 102% and values of relative standard deviations better than 1.5 %. The stoichiometry of the reaction was studied, and the reaction mechanism was postulated. The proposed CT complex formation method was successfully applied to the determination of nitrazepam in its pharmaceutical tablet with good accuracy and precision. The results obtained by the proposed method are compared with those obtained by the official method.

New simple and sensitive spectrophotometric and fluorimetricmethods have been developed and validated for the determination offluoxetine hydrochloride (FLX) in its pharmaceutical formulations. The spectrophotometric method was based on the reaction of FLXwith 1,2-naphthoquinone-4-sulphonate (NQS) in an alkaline medium(pH 11) to form an orange-colored product that was measured at 490nm. The fluorimetric method was based on the reaction of FLX with4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) in an alkalinemedium (pH 8) to form a highly fluorescent product that wasmeasured at 545 nm after excitation at 490 nm. The variablesaffecting the reactions of FLX with both NQS and NBD-Cl werecarefully studied and optimized. The kinetics of the reactionswere investigated, and the reaction mechanisms were presented. Under the optimum reaction conditions, good linear relationshipswere found between the readings and the concentrations of FLX inthe ranges of 0.3–6 and 0.035–0.5 μg mL−1 for thespectrophotometric and fluorimetric methods, respectively. Thelimits of detection were 0.1 and 0.01 μg mL−1 for thespectrophotometric and fluorimetric methods, respectively. Bothmethods were successfully applied to the determination of FLX inits pharmaceutical formulations.

Charge transfer complexes of some antifungal drugs fluconazole (FLU), sertaconazole nitrate (SER) and miconazole nitrate (MCO) as electron donor with the σ-acceptor iodine (I2) and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), p-chloranilic acid (p-CLA) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as π-acceptors in acetonitrile were investigated. The formation of the colored charge-transfer complexes were utilized in the development of simple, rapid and accurate spectrophotometric methods for the analysis of the cited drugs in pure forms and pharmaceutical formulations at 365 nm for MCO and SER using I2 method, at 460 nm for FLU and SER using DDQ method, at 535 and 530 nm for FLU and SER, respectively, using p-CLA method and at 842 nm for MCO and SER using TCNQ method. The optimum experimental conditions have been studied carefully and optimized. Beer’s law was obeyed over the concentration ranges of 2.0–28, 10–240 and 2.0–160 µg mL−1 for MCO, FLU and SER, respectively, with good correlation coefficients (0.9996–0.9999). Molar absorpitivity, Sandell sensitivity, relative standard deviation, limit of detection and quantification were calculated. The obtained data refer to high accuracy and precision of the proposed method. The obtained results were confirmed by inter and intra-day accuracy and precision with percent recovery of 99.1–100%, 99.3–101% and 99.1–101% for MCO, FLU and SER, respectively. These data were compared with those obtained using official methods for the determination of the cited drugs. The proposed methods were applied successfully for simultaneous determination of the cited drugs in their pharmaceutical formulations with good accuracy and precision and without interferences from common additives. KEY WORDS: Fluconazole, Sertaconazole nitrate, Miconazole nitrate, Charge transfer complexes, Spectrophotometry, Pharmaceutical formulations Bull. Chem. Soc. Ethiop. 2016, 30(3), 333-346.DOI: http://dx.doi.org/10.4314/bcse.v30i3.2

A rapid, simple, and sensitive spectrophotometric and high performance liquid chromatographic methods have been developed for the quantitative determination of metoclopramide hydrochloride MCP in both pure and dosage forms. The spectrophotometric method is based on diazotization of MCP and then coupling with 2,4-dihydroxyacetophenone in alkaline medium. The resulting azodye exhibits maximum absorption at 450 nm with a molar absorptivity of 2.48 X 104 l.mol-1.cm-1. Beer's law is obeyed over the range 10-300µg/25 ml, i.e., 0.4-12 ppm with a relative standard deviation (RSD)of better than±1.092% and relative error better than -1.1%. HPLC method has been developed for the measurement of MCP, the analysis was achieved on a C8 column using acetonitrile, water, and methanol in the ratio of 40:50:10 (V:V:V) (in the presence of 1% of sodium acetate) as a mobile phase by isocratic elution at 1 ml/min. flow rate, and detection was done spectrophotometrically at 308 nm. A linear relationship is obeyed over the range 0.18-0.8 ppm with a relative standard deviation (RSD) of better than 3.7% and relative error better than -1.6%. Both methods were applied successfully to the assay of MCP in pharmaceutical preparations in the form of syrup, injection, and tablet.