Formation Of Ion-pair Complex Research Articles

Studies on nano crystalline copper doped Nickel Zinc ferrites for optoelectronic applications

Investigation of optical and dielectric properties of nanocrystalline Ni0.65Zn0.35 Cu x Fe(2-2x/3) O4 (for x = 0.00–0.05 in steps of 0.01) ferrites synthesized using hydrothermal route is successfully carried out. Two distinct analytical spectroscopic methods with Dichloro – 5,6-Dicyano – 1,4-Benzo quinone (DDQ) and Bromo Phenol Blue (BPB) are adopted to observe the UV–visible absorption spectroscopy in the dispersed solutions of all samples. The formation of ion pair complex in the presence of BPB results in two distinct absorption edges in the visible region, around 440 nm and 580 nm in the present ferrite samples. Application of Tauc's formalism gives rise to two optical band gap values Eg1 and Eg2 in the range of 2.12–2.40 eV and 3.583–3.674 eV, respectively. The formation of charge transfer complex with all sample solutions in presence of DDQ reagent results in sharp absorption edges in the UV-region around 306 nm wavelength. An initial rise followed by continuous drop in band gap values ranging from 3.814 to 3.824 eV is observed from Tauc's plots. The optimum refractive index (n) values calculated for the three types of band gap values using empirical relations display the optical absorption potentiality of Ni–Cu–Zn nano ferrites in both Visible and UV – regions. Variation of band gap values is ascribed to the lattice strain effect, quantum confinement and narrowing band gap effects. Real part of dielectric constant (ε′), dielectric loss factor (tanδ) and ac-conductivity(σac) are studied for all samples at room temperature with in the frequency range of 42 Hz to 5 MHz. The values of ε′ and tanδ are observed to decrease with increase in frequency, while that of σac are found to increase with increase in frequency. Improved dielectric properties, existence of optical band-gap values observed in the present Ni–Cu–Zn ferrites promote these materials for their utility in optoelectronic devices and high frequency applications.

Spectroscopic strategies for quantitation of varenicline in pharmaceutical preparations and content uniformity testing.

Herein, two new facile methods were examined for varenicline determination using erythrosine. The latter is a food additive that has been recently investigated as a fluorescent dye for the determination of drugs. In the first method, the fluorescence of erythrosine B was quenched quantitatively by increasing the concentration of varenicline through ion-pair complex formation. This linear response was a basis for the spectrofluorimetric method used for varenicline quantitation in pure and dosage forms. The quenching is correlated with the concentration linearly over the range of 0.4–4.0 µg ml−1 at 550 nm after excitation at 528 nm with a correlation coefficient of 0.9993. Different parameters were investigated to reach the optimal conditions with the highest sensitivity and repeatability. The second method is depending on measuring the formed complex by spectrophotometry at 550 nm over the range of 1.0–10.0 µg ml−1 with an excellent correlation coefficient of 0.9999. The suggested methods were validated consistently with ICH guidelines, with acceptable results. The procedures were used to test the uniformity of content of Champix tablets. By comparing with the previous spectroscopic method, there was no significant difference as revealed from the calculated Student t-test and variance ratio F-test values.

Novel approaches of erythrosine B as a food dye-derived spectroscopic probe for assessing trospium chloride in raw material and dosage form.

Two facile spectroscopic methodologies were designed for estimating trospium chloride (TPM) in raw material and tablets with high operational reliability and selectivity. The methods were based on using erythrosine B (EB) as a spectroscopic tool for ion-pair complex formation with the drug. In a mild acidic medium of Britton Robinson buffer (pH4.0), the ionized hydroxyl group in the reagent interacted with the ionized amine in the studied drug. Method I was based on the spectrophotometric measuring of the absorbance of the reaction product at 557 nm. Method II was based on spectrofluorimetric measurement of the quenching effect of TPM on the inherent fluorescence of EB at 550 nm (λex. = 528 nm). The two methods showed linearity through ranges 1.0-10.0 and 0.5-10.0 μg/ml for Methods I and II, respectively. The suggested methods were exploited for analyzing TPM in Trospamexin® tablets and showed good applicability. The designed systems were validated as per International Conference on Harmonization guidelines. Experimental conditions were modulated to obtain the best sensitivities. The quenching mechanism was investigated and the quenching constant was computed relying on the Stern-Volmer equation. Environmental impact was appraised using novel metric green tools, GABI, and AGREE. The suggested systems excelled over other reported methods in terms of greenness, sensitivity, and cost-effectiveness.

A Simple Spectrophotometric Determination of Amoxicillin in Drug Samples

In this study, a fast and simple spectrophotometric method was developed for the determination of amoxicillin in drugs without any extraction steps. The developed method is based on the formation of a colored ion pair complex between bromocresol green and amoxycillin in dimethyl sulfoxide-acetonitrile (50 % v/v) medium. The absorbance of the bluish green complex is measured at a wavelength of 630 nm. The factors that affect the ion pair complex formation, such as time, reagent concentration, etc., have been optimized. Under the optimum conditions, the developed method had an average recovery of 98.16% with a relative standard deviation of 3.62 % and showed a very good linear behavior obeying Lambert-Beer's law in the range 1-18 µg mL-1 of amoxycillin concentration. The developed method has been successfully applied to both tablet and powder forms of pharmaceutical preparations. The standard addition method and statistical parameters were applied to test the accuracy of the proposed method, and the obtained results from the two methods showed good agreement with each other.

Simple spectrophotometric method for the determination of haloperidol from pharmaceutical formulations

A simple, sensitive, rapid, accurate and cost effective spectrophotometric method has been developed and validated for the estimation of haloperidol in bulk drug and for its pharmaceutical formulations. The proposed method is based on the formation of chloroform extractable ion pair complex of haloperidol with bromothymol blue. The absorbance of the coloured extractable ion pair complex is measured at the wavelength of maximum absorbance 420 nm against the reagent blank. Beer’s law is obeyed over a concentration range of 20 to 100 µg/ml of haloperidol, for a linear calibration curve. Results are statistically validated and found to be reproducible.

Development and Validation of Extractive Spectrophotometric Method for Estimation of Hydroxychloroquine Sulphate by using Smartphone Application

A simple, sensitive, accurate, precise and reproducible extractive spectrophotometric method was developed for estimation of Hydroxychloroquine Sulphate (HCQS) in bulk and pharmaceutical dosage form. The method is based on formation of ion pair complex of Hydroxychloroquine Sulphate with Bromocresol green dye in acidic medium. This complex extracted in chloroform and measured quantitatively at 421nm for estimation of Hydroxychloroquine Sulphate present in the sample. In this method estimation was also done by using Smartphone Application known as PhotoMetrix pro. Beer Lambert’s law obeyed over a range of 2-10 μg/ml for HCQS by UV spectrophotometric (r²=0.9988) and by SmartPhone Image analysis (r²=0.999) method. The developed method was successfully applied for estimation of Hydroxychloroquine Sulphate in three commercial product tablet dosage form without interference from common additives. The assay was found to be 100.09%, 100.8%, 98.6% by UV and 99.2%, 101.46%, 101.1% using PhotoMetrix for three formulation containing Hydroxychloroquine Sulphate. The developed method was also validated according to ICH Q2 guideline for linearity, range, accuracy, and precision. Comparison for both method UV and PhotoMetrix done by performing t-test, result shows that there is no significant difference between both method so PhotoMetrix can be used as alternative to UV for routine analysis of Hydroxychloroquine Sulphate.
 Keywords: Hydroxychloroquine Sulphate, Bromocresol green, Potassium Hydrogen Phthalate buffer, UV spectrophotometric, PhotoMetrix.

Determination of Omeprazole, Esomeprazole and Pantoprazole by Quenching the fluorescence of Eosin Y

A non-extractive, simple and sensitive spectrofluorimetric method with good selectivity has been described for the determination of the proton pump inhibitors namely; Omeprazole, Esomeprazole magnesium and Pantoprazole sodium that are used for the treatment of peptic ulcer disease. The method is based on the quenching the fluorescence intensity of the eosin Y dye, as the result of the ion-pair complex formation of the studied drugs with the dye in the presence of acetate buffer solution of pH 3.5. The quenching of the eosin Y fluorescence intensity was measured spectrofluorimetrically at 540 nm after excitation at 352 nm. At the optimum reaction conditions, the quenching values of fluorescence (∆F) and concentrations were rectilinear over the concentration ranges of 0.5–13.0, 0.7-15 and 0.3-15 µg/mL for Omeprazole, Esomeprazole magnesium and Pantoprazole sodium respectively. The recovery % values were in the range 99.92-100.56% and relative standard deviation values range was0.430-2.521 for all the studied drugs. The method was applied successfully for determination of above drugs in their pharmaceutical formulations as capsule, tablet and injectables. The method was free from interferences of common excipients.

التحديد الطيفي لأتورفاستاتين الكالسيوم في المستحضرات الصيدلانية عن طريق معقدات نقل الشحنة

تم وصف طريقة طيفية بسيطة وسريعة للتحليل الكمي (لاتورفاستاتين الكالسيوم) (ATV) في المواد الخام والأشكال الصيدلانية للأقراص. تعتمد الطريقة على تكوين معقد زوج شاردي أصفر اللون بين (الاتورفاستاتين الكالسيوم) و(البروموكريزول الأرجواني) في وسط من (ثنائي كلورومتان). تم تحسين العوامل المختلفة التي تؤثر على التفاعل مثل: تأثير المذيبات، الوقت، تركيز الكاشف، نسبة الارتباط، إلخ. تم قياس امتصاصية المعقد المتشكل بالطيف المرئي عند طول موجة امتصاص أعظمي عند 405 نانومتر. كان المجال الخطي واقعاً بين 3.02 – 42.33 ميكروغرام / مل، وأظهر تحليل الانحدار معامل ارتباط جيد R2 = 0.9994. كان حد الكشف (LOD) وحد القياس الكمي (LOQ) هو 0.463 ميكروغرام / مل و1.403 ميكروغرام / مل على التسلسل. نسبة متوسط الاسترداد بلغت (99.26 – 99.85) ٪ للاتورفاستاتين الكالسيوم. تم تطبيق هذه الدراسة على العلامة التجارية الصيدلانية السورية: (اتوراز 20ملغ و اتوراز 40 ملغ). تم تطبيق الطريقة بنجاح لتحديد الاتورفاستاتين الكالسيوم في المستحضر الصيدلاني على شكل أقراص. الطريقة المطبقة بسيطة ومباشرة وحساسة ولا تتطلب لاي عملية استخلاص الطريقة قابلة للتطبيق في التحليل الروتيني وضبط الجودة.

CHIẾT TRẮC QUANG XÁC ĐỊNH NIMODIPIN BẰNG SỰ HÌNH THÀNH PHỨC CẶP ION VỚI BROMTHYMOL XANH

A new spectrophotometric method was established for the determination of nimodipine (NMD) in pharmaceutical formulations. This method is based on the formation of a yellow ion-pair complex between the reduced nimodipine and bromothymol blue (BTB) in an acidic medium. Chloroform was used as an optimal solvent for the extraction of ion-pair complex and measured the absorbance of this complex at wavelengths of 414.5 nm. The effect of optimum condition via extracting solvent, volume of dye, shaking time, reaction ratio was studied. Beer’s law is obeyed in the concentration ranges of 4.0-50.0 μg/mL with a molar absorptivity of 1.50x104 L.mol-1.cm-1 and limit of detection (LOD) of 1.87 μg/mL. The accuracy and precision of the method were evaluated on an intra-day and inter-day basis. The relative error (%RE) and the relative standard deviation (%RSD) were < 5.0% while the recovery (%) was 99.05-103.25. The proposed method was applied successfully to determine nimodipine in pharmaceutical preparation (Nomitop, Bayer).

Spectrofluorimetric Determination of Some N. Containing Medicines Using Rhodamine 6G as a Chromogenic Reagent

A sensitive spectrofluorimetric method has been developed for the analysis of some medicines containing primary, secondary, and tertiary amino groups, namely Diclofenac (DIC), Domperidone (DOM), Famotidine (FAM), and Propranolol (PRO), in their pure and medicinal forms. The method is based on the quenching of the fluorescence intensity of rhodamine 6G (R6G) through the formation of ion-pair complexes between the above medicines and the R-6G reagent, which is measured at 552 nm after excitation at 402 nm. The calibration graphs were rectilinear in the concentration ranges of 0.10- 9.00, 0.05-15.00, 0.10-14.0 and 0.05-5.00 µg mL-1 for above medicines respectively. The recovery (%) values were ranged between 99.45%- 100.97%. The detection limits ranged in the concentration of 0.243-0.754 µg/mL, and the limits of quantitation were 0.806- 2.420 µgmL-1 for all drugs. The method was successfully applied for the determination of these drugs in their pharmaceutical preparations.

Spectroscopic Estimation of Doxylamine Succinate in Tablets and Human Plasma by Formation of Ion-pair Complex

Aim: To develop a simple spectroscopic method for estimation of doxylamine (DOX) succinate in its tablet dosage form and human plasma with the aid of an ion-pair complex formation.
 Methods: In this method, methyl orange (0.05 % w/v) dye was used to form an ion-pair complex in acetate buffer (1M; pH: 5.00) at 300 C ± 20C. The ion-pair complex formed was extracted with chloroform. The maximum absorbance for the ion-pair complex was measured at 420 nm.
 Results and discussion: The method conditions were obeyed Beer's law in the concentrations ranging from 5-25 µg/mL of DOX succinate with a correlation coefficient (r2) of 0.992. The ion-pair (drug-dye) complex was formed in a 1:1 ratio which was demonstrated by Jobs' method of continuous variation. The method was satisfied the validation criteria as per ICH (Q2R1) guidelines. Accuracy studies showed 99.06-100.9 % recovery of the analyte. The responses of the precision and robustness were found within acceptable limits (<2% RSD). The LOD and LOQ values were found as 0.31 and 0.939 µg/mL, respectively.
 Conclusion: The developed method was simple, specific, and economical and requires a short analysis time. Therefore it could be considered for precise analysis of DOX succinate in biological matrices.

KINETICS AND MECHANISM OF THE OXIDATION OF L-ASCORBIC ACID BY POTASSIUM TRISOXALATOFERRATE (III) TRIHYDRATE IN AQUEOUS HYDROCHLORIC ACID MEDIUM

The kinetics of the oxidation of K3[Fe(C2O4)3].3H2O by L-ascorbic acid has been studied in aqueous acidic medium. The stoichiometric studies showed that 1 mole of H2A was oxidized for every 2 moles of Fe(C2O4)33- reduced. Under pseudo-first order conditions of H2A >> Fe(C2O4)33-, the reaction was found to have first order dependence on each of the reactants, giving second order overall. The reaction rate was found to be directly dependent on acid concentration and increased with increase in ionic strength of reaction system. It was also evident that increase in dielectric constant of the reaction medium (D) enhanced the reaction rate and addition of CH3COO-, HCOO-, Mg2+and Li+ catalyzed the rate of the reaction. The oxidation of L-ascorbic acid by potassium trisoxalatoferrate (III) trihydrate is rationalized in terms of absence of ion pair complex formation with outer-sphere reaction pathway characteristics.

Non-extractive spectrophotometric determination of valsartan in pure form and in pharmaceutical products by ion-pair complex formation with bromophenol blue and methyl red

Two simple, rapid, green non extractive spectrophotometric methods are described for the estimation of valsartan in tablet dosage form. The determination is based on the ion-pair formation using the dyes, bromophenol blue (BPB) and methyl red (MR). Valsartan forms ion-pair complex selectively with the dyes, as indicated by the formation of a coloured complex with BPB at pH 5.5 with λmax at 424 nm and MR at pH 4.3 with λmax at 494 nm. For both methods, optimal spectrophotometric conditions were established. The linear relationship was found between absorbance at λmax and concentration of drug in the range 8–24 µg/mL for BPB and 4–20 µg/mL for MR. Regression analysis of Beer’s law plot at 424 nm yielded the regression equation, y = 0.0102x + 01636 (BPB) and at 494 nm y = 0.0222x – 0.0063 (MR). High values of correlations coefficient (R2 = 0.9988 (BPB) and R2 = 0.9991 (MR)) and small values of intercept validated the linearity of calibration curve and obedience to Beer’s law. The LOD and LOQ values were calculated to be 1.03 µg/mL and 3.43 µg/mL respectively (BPB) and 0.68 µg/mL and 2.26 µg/mL respectively (MR). Intra-day and inter-day accuracy and precision, robustness were in acceptable limits. The proposed methods were applied for the quantification of valsartan in tablets pertaining to three commercial formulations. Analytical eco-scale for greenness assessment of the proposed spectrophotometric methods showed that both methods corresponds to excellent green analysis with a score of 89.

Factorial design-assisted spectroscopic determination of oxybutynin hydrochloride.

In this study, we have developed two facile spectroscopic methods for quantifying oxybutynin (OBT) hydrochloride in its pure form and tablets using design of experiments (DOEs). The spectroscopic methods depended on the ion-pair complex formation between the tertiary amino group in the drug and eosin in 0.2 M acetate buffer of pH 4. Method I involves spectrophotometric measurement of the absorbance of the developed complex at 550 nm and showed linearity through 1.0–10.0 µg ml−1. Method II involves spectrofluorometric measurement of the quenching influence of OBT on the native fluorescence of eosin (λ excitation/λ emission of 304/548 nm) and showed linearity through 1.0–6.0 µg ml−1. Critical parameters were identified through preliminary trials and optimized using the DOE. Additionally, the quenching mechanism was investigated and the pathway of the reaction was postulated. The fluorescence quenching constant and thermodynamic parameters were explored using the Stern–Volmer plot and Van't Hoff graph, respectively. Assessments conducted via analytical ecoscale revealed the ‘excellent-greenness’ of the methodology. The two methods have the potentials of being green and fast compared with other reported methods.

Determination of Pitavastatin Calcium by Analytical Spectrophotometry

Simple and rapid spectrophotometric method for the quantitative analysis of Pitavastatin calcium (PTV) in raw material and tablets pharmaceutical formulation has been described. The method is based on the formation of yellow ion-pair complex between Pitavastatin calcium and Bromocresol purple (BCP) in chloroform medium. Different parameters affecting the reaction such as: effect of solvents, stability, reagent concentration, correlation ratio, etc. were optimized. The formed complex was quantified spectrophotometrically at absorption maximum 405 nm. Linearity range was 2.20 - 35.23 µg/mL, regression analysis showed a good correlation coefficient R2 = 0.9991. The limit of detection (LOD) and limit of quantification (LOQ) were to be 0.367 µg/mL and 1.112 µg/mL respectively. The average percent recovery was found to be (100.62 – 101.14) % for Pitavastatin Calcium. This study was applied on Syrian pharmaceutical trademark: (PAVACRIUM 4 & Londalop). The method was successfully applied for the determination of Pitavastatin calcium in tablets pharmaceutical formulation. The proposed method is simple, direct, sensitive and do not require any extraction process. Thus, this method could be readily applicable for the quality control and routine analysis.

Stir flat sheet membrane liquid phase microextraction for the selective chemiluminescence determination of ofloxacin and fleroxacin in human urine

Stir flat sheet membrane liquid phase microextraction procedure for the chemiluminescence determination of polar antibiotics (ofloxacin and fleroxacin) in human urine samples was developed. The microextraction procedure assumed simultaneous ion-pair complex formation between antibiotic and anionic dye in acidic medium, dispersion of extraction solvent by rotation of a stir flat sheet microporous membrane unit, mass-transfer of complexes from sample into microdroplets of extraction solvent followed by extract collection into the unit. After preconcentration the unit was immersed in alkaline aqueous solution for analytes re-extraction based on ion-pair complex decomposition followed by the chemiluminescence analysis of obtained aqueous phase. The developed microextraction procedure allowed to exclude matrix effects for the selective, simple, and rapid chemiluminescence determination of ofloxacin and fleroxacin in urine samples. The calibration graphs were linear over the concentration ranges of 0.1–25 mg L−1 for ofloxacin and fleroxacin. The LOD values, calculated from the blank tests based on 3σ, were 30 µg L−1 for ofloxacin and fleroxacin. The procedure was conveniently applied to the determination of fluoroquinolones in urine samples.

Non-extractive spectrophotometric determination of memantine HCl, clomipramine HCl and fluvoxamine maleate in pure form and in pharmaceutical products by ion-pair complex formation with rose bengal

The objective of this work is to develop a simple, sensitive and non-extractive spectrophotometric method for the determination of memantine HCl (MEM), clomipramine HCl (CLM) and fluvoxamine maleate (FLV). The proposed method was based on the formation of colored ion-pair complexes between the basic nitrogen of the target drugs and rose bengal (RB) dye in a weak acidic medium. The formed complexes were measured at 576nm for MEM, CLM and at 575nm for FLV. The reaction conditions were optimized to obtain the maximum color intensity. Beer's law was obeyed in the range of 2-20, 1-16 and 6-30μg/mL for MEM, CLM and FLV, respectively. The limit of detection (LOD) was 0.476, 0.185, 0.806 and the limit of quantitation (LOQ) was 1.443, 0.559 and 2.443 for MEM, CLM and FLV, respectively. The composition ratio of the ion-pair complexes was found to be 1:1 as determined by Job's method. The proposed method was applied successfully for the analysis of the cited drugs in pure and dosage forms. Results of the proposed method were statistically compared with the reported methods by applying student's t- and F-tests and no significant differences were observed.

Novel spectrofluorimetric determination of brigatinib in bulk powder and human urine samples via ion-pair complex formation using eosin Y

The developed spectrofluorimetric method was successfully applied to the analysis of brigatinib (BRG) in its bulk powder form, and human urine sample.It is based on the investigation of the fluorescence spectrum behavior of the BRG-eosin Y complex. The relative fluorescence intensity (RFI) was recorded at 560 nm after excitation at 480 nm. The principle of the proposed method was thoroughly explained. All experimental parameters affecting method development were optimized. Moreover, the obtained results were fully discussed and statistically analyzed. The molar ratio method was applied to study the stoichiometric relationship between BRG and eosin Y complex. The method revealed a ratio of 1:3 for BRG-eosin Y afforded the highest RFI. The developed method was validated over the concentration range of 62.5–4000 ng mL−1. The results were compared positively with the reported method.

Selective diammonium reagents hosted on nanofibers for recovery of iridium from rhodium: Theoretical and experimental studies

Quaternary diammonium-functionalized polyvinyl benzyl chloride nanofibers were done using different diamines such as ethylenediamine (EDA), tetramethylene diamine (TMDA), hexamethylenediamine (HMDA), octamethylenediamine (OMDA), 1,10-diaminodecane (DMDA) and 1,12-diaminododecane (DDMDA) with quaternization using methyl iodide, followed by conversion to a chloride form. These were called F-QUAT EDA, F-QUAT TMDA, F-QUAT HMDA, F-QUAT OMDA, F-QUAT DMDA and F-QUAT DDMDA, respectively. Materials characterization was supported using elemental analysis, FTIR, XPS, SEM-EDS, TG and BET analysis. Langmuir and Freundlich's models were applied to analyze the adsorption of [IrCl6]2− and [RhCl5(H2O)]2− onto the materials, and the Freundlich model was obeyed. The mass transfer kinetics were tested on the pseudo-first-order and pseudo-second-order equations, and the process obeyed the pseudo-second-order kinetics. Column studies for the sorption of [IrCl6]2− using the functional materials were carried out and the loading capacities were 5.98 mg/g, 7.95 mg/g, 15.23 mg/g, 21.71 mg/g, 32.94 mg/g and 9.70 mg/g for F-QUAT EDA, F-QUAT TMDA, F-QUAT HMDA, F-QUAT OMDA, F-QUAT DMDA and F-QUAT DDMDA, respectively. This was the order of an improvement in the methylene chain amongst the two ammonium groups up to ten carbons. Theoretically calculated electrostatic potential energies of the cations, dipole moments and solvation energies of the free cations and anions, energies for replacement of the chloride by [IrCl6]2−, and thermodynamic parameters for the formation of ion-pair complexes were used to explain this trend observed for the capacity of the functional reagents. The functional nanofibers displayed potential for use in selective recovery of iridium from rhodium.

Sensitive spectrophotometric determination of vardenafil HCl in pure and dosage forms

The present work aims to develop and validate a simple, rapid, cost-effective, sensitive and extractive spectrophotometric methods for the determination of phosphodiesterase type 5-inhibitor; vardenafil HCl (VARD) in pure and in dosage forms. The developed methods are based on the formation of ion-pair complexes between vardenafil HCl and dyes, namely, bromocresol green (BCG), bromocresol purple (BCP), bromophenol blue (BPB), bromothymol blue (BTB) and eriochrom black T (EBT) in acidic buffer solutions. Different factors affecting the reactions between VARD and the dyes were studied and optimized. The formed complexes were extracted with methylene chloride and measured at 418, 410, 415, 417 and 520nm using BCG, BCP, BPB, BTB and EBT, respectively. The beer's law was obeyed in the ranges 1.0-10, 1.0-16, 0.5-8.0, 2.0-20 and 1.0-14μgmL-1 for BCG, BCP, BPB, BTB and EBT, respectively under the optimum conditions. The composition of the ion-pairs was found 1:1. The molar absorptivity's, Sandell's sensitivity, limits of detection and the limits of quantification were calculated. Other method validation parameters, such as accuracy, intra-day and inter-day precision, robustness, ruggedness and selectivity, have been evaluated. The proposed methods have been applied successfully for the analysis of vardenafil HCl in pure and dosage forms. The reliability of the methods was further ascertained by performing recovery studies using the standard addition method. Statistical comparison of the results with the reported method was performed by applying student's t- and F-tests and no significant statistical differences were obtained.