P-chloranilic Acid Research Articles

Development of Visible Spectrophotometric Methods for the Determination of Tricyclic Antidepressants Based on Formation of Molecular Complexes with p-Benzoquinones

Tricyclic antidepressants are commonly employed in the management of major depressive disorders. The present work describes two visible (VIS) spectrophotometric techniques that utilize the formation of charge transfer complexes between four antidepressant compounds, namely, amitriptyline hydrochloride (AMI), imipramine hydrochloride (IMI), clomipramine hydrochloride (CLO), and trimipramine maleate (TRI) acting as electron donors and two p-benzoquinones, namely, p-chloranilic acid (pCA) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), serving as electron acceptors. The stoichiometry of the compounds produced exhibited a consistent 1:1 ratio in all instances, as established by Job’s method. Molar absorptivities, equilibrium association constants, and several other spectroscopic properties were determined for all complexes. The developed spectrophotometric techniques were validated intra-laboratory and successfully applied for quantitative assessment of the four antidepressant active ingredients in several commercial pharmaceutical formulations. The methods are relatively simple, fast, and use readily available laboratory instrumentation, making them easily applicable by most quality control laboratories worldwide.

SPECTROPHOTOMETRIC METHODS FOR THE QUANTITATIVE DETERMINATION OF MEMANTINE HYDROCHLORIDE IN PURE FORM AND PHARMACEUTICAL FORMULATIONS

Objective: Three simple, sensitive, accurate, and precise spectrophotometric methods have been developed and validated for the determination of Alzheimer’s disease drug memantine HCl (MEM) in pure form and pharmaceutical formulations. Methods: The method was based on the formation of charge transfer complex between MEM as n-electron donor and various π-acceptors quinalizarin (Quinz) in methanol, p-chloranilic acid (p-CA) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) in acetonitrile as chromogenic reagents which showed an absorption maximum at 558, 532 and 840 nm using Quinz, p-CA and TCNQ, respectively. The optimization of the reaction conditions such as the type of solvent, reagent concentration and reaction time were investigated. Results: Under the optimum conditions, beer’s law is obeyed in the concentration ranges 4.0–24, 10–160 and 5.0–50 μg/mlusing Quinz, p-CA and TCNQ, respectively with good correlation coefficient (r2 ≥ 0.9995) and with a relative standard deviation (RSD% ≤ 1.11). For more accurate analysis, Ringbom optimum concentration ranges were found to be between 8.0–20, 15–140 and 10–45 μg/ml using Quinz, p-CA and TCNQ, respectively. The limits of detection were found to be 1.2, 2.70 and 1.45 µg/ml and the limits of quantification were found to be 4.0, 9.0 and 4.83 µg/ml for Quinz, p-CA and TCNQ, respectively. A Job's plot of the absorbance versus the molar ratio of MEM to each of the acceptors under consideration indicated (1:1) ratio. Conclusion: The methods were successfully applied to the determination of MEM in its pharmaceutical formulations and the validity assessed by applying the standard addition technique. Results obtained by the proposed methods for the pure MEM and commercial tablets agreed well with those obtained by the reported method.

Application of two charge transfer complex formation reactions for selective determination of metformin hydrochloride in pharmaceuticals and urine

BackgroundMetformin hydrochloride (MFH) is a biguanide class anti-diabetic drug used to treat type-2 diabetes mellitus. Its reaction with two charge-transfer complexing agents, p-chloranilic acid (PCA) and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) in acetonitrile medium to yield coloured products measurable at wavelengths of maxima 530.0 and 460.0 nm, respectively, was conveniently used to develop two spectrophotometric methods for analyses of bulk sample and tablets.ResultsThe effect of solvent, reagent concentration and reaction time to form charge-transfer (CT) complexes was meticulously studied and optimized. Under optimised conditions, the absorbance at the respective wavelength of maximum versus concentration of MFH was in linear correlation for the range from 8.0 to 320.0 and from 1.6 to 64.0 μg mL-1 in PCA and DDQ methods, respectively, and correspondingly, the values of molar absorptivity of 0.733 × 103 and 0.257 × 104 L mol-1 cm-1 and Sandell sensitivity of 0.3620 and 0.0644 μg cm-2. The quantification (QL) and detection (DL) limits were 2.67 and 0.88 μg mL-1 for PCA method, and 0.33 and 0.11 μg mL-1 for DDQ method.ConclusionThe new methods were emerged as repeatable and reproducible, with replicate measurements for intra- and inter-day variations as showed by obtained RSD values of < 2%. Within a day and between day relative errors were ≤ 2.18%. Methods were also validated for robustness, ruggedness and selectivity and agreeing results were produced. The methods were used to analyse MFH-containing tablets very accurately and precisely as reflected by the mean recovery value close to 100% and lower RSD values, respectively. Analysis of spiked human urine yielded excellent mean recoveries, indicating the absence of interference from endogenous substances.

Simultaneous Spectrophotometric Estimation of Azithromycin and Ofloxacin using π-Acceptors as Analytical Reagents

In this study, two sensitive and precise spectrophotometric methods have been developed for the simultaneous determination of azithromycin and ofloxacin in pure mixture and in pharmaceutical binary dosage forms. A new concept of area under curve (AUC) is proposed for simultaneous estimation of two drugs by these methods. Method A involves the use of DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone) as analytical reagent and the AUC between 390nm and 690nm for DDQ was used for determination. Method B involves the use of p-CA (p-chloranilic acid: 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone) as an analytical reagent and the AUC between 400nm and 700nm for p-CA was used for determination. The methods developed and construction of calibration curves using two analytical reagents viz., DDQ and p-CA are described. Optical and analytical parameters for the individual and simultaneous determination of azithromycin and ofloxacin using AUC are tabulated. These methods have been validated and compared with HPLC methods in terms of standard deviation, t-test and F-test.

Validated spectrophotometric determination of maduramicin ammonium using three charge transfer complexation reactions

Direct spectrophotometric determination of Maduramicin ammonium (MAD) represents an analytical challenge since it is a weak UV-absorbing and lacking a strong chromophore. This work represents the first spectrophotometric determination of MAD as no direct spectrophotometric or colorimetric determination methods for MAD are available in the literature. The present study illustrates the development of three simple, rapid and inexpensive colorimetric methods for the routine quality control analysis of MAD based on the formation of colored charge transfer complexes with three electron acceptors namely p-chloranilic acid (p-CA), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and picric acid (PA). The color products of MAD with p-CA, DDQ and PA were measured at 519, 588 and 405nm respectively. The proposed methods were validated in terms of linearity, ranges, precision, accuracy, robustness and limits of detection and quantification. MAD was effectively determined over concentration ranges of 100-1000, 25-250 and 30-150μg/mL using p-CA, DDQ and PA, respectively with good linearity as shown by the values of correlation coefficients not less than 0.9991. The developed methods were successfully implemented in the assay of MAD powder pharmaceutical formulation for veterinary use.

Simultaneous Spectrophotometric Determination of Lamivudine and Stavudine using π-Acceptors as Analytical Reagents

Two new sensitive and precise spectrophotometric methods have been proposed and developed for the simultaneous estimation of lamivudine and stavudine in pure mixture and in pharmaceutical binary dosage forms. A new concept of area under curve (AUC) is proposed for simultaneous estimation of two drugs by these methods. Method A involves the use of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as analytical reagent and the AUC between 390 nm and 690 nm for DDQ was used for determination. Method B involves the use of p-chloranilic acid: 2,5-dichloro-3,6-dihydroxy-1,4- benzoquinone (p-CA) as an analytical reagent and the AUC between 400 and 700 nm for p-chloranilic acid was used for deter-mination. The methods developed and construction of calibration curves using two analytical reagents viz., DDQ and p-chloranilic acid are described. Optical and analytical parameters for the individual and simultaneous determination of lamivudine and stavudine using AUC are tabulated. The methods have been validated and compared with HPLC methods in terms of standard deviation, t-test and F-test.

Spectrophotometric Analysis of Azithromycin and Clarithromycin in Tablets and Human Plasma Using p-Chloranilic Acid

A novel spectrophotometric method for rapid estimation of clarithromycin and azithromycin in authentic sample, pharmaceutical dosage forms and in human plasma was developed using p-chloranilic acid. The method depends on charge transfer reaction between p-chloranilic acid and the mentioned drugs. Linearity was observed over a concentration range of 5 to 50 μg/mL-1 clarithromycin and azithromycin. The results indicate that the proposed method is very sensitive, rapid, accurate, selective, and reproducible. The method was validated according to ICH guidelines. The method has been successfully applied for the analysis of marketed formulations and spiked human plasma.

Development of optical detection for antibiotic residues: oxytetracycline in freshwater aquaculture

This study satisfies the primary need for a simple monitoring scheme for antibiotic residue content in freshwater systems to regulate and prevent immunization of aquaculture species to antibiotics. A series of antibiotic solutions with decreasing concentrations (from 5ppm to 1ppm) were prepared, with each solution containing fixed amounts of the reagents (p-Chloranilic acid in acetonitrile solution, and pure acetonitrile) and a buffer solution to distinctly simulate the environmental conditions of actual freshwater systems. Using the UV-Vis Spectrophotometer with the optimum wavelength of 519nm, the stability, repeatability, and sensitivity tests were performed, where relative standard deviation (RSD) values of less than 10% were obtained. The limit of detection was also calculated to be 0.54ppm, using the RSD result from the sensitivity test. Actual freshwater sample was gathered and subjected to a repeatability test using the same working wavelength. Results showed that the trend in the absorbance reading for the real water sample differed with the laboratory standard samples. This shift may have been caused by other interfering chemicals used in aquaculture that were present in the sample. Modified detection method of Oxytetracycline (OTC) in freshwater was made to provide solution to the main objective.

SPECTROPHOTOMETRIC METHOD FOR THE DETERMINATION AMIKACIN IN PURE AND PHARMACEUTICAL DOSAGE FORM

Objective: The aim of the study was to develop an easy, sensible and rapid method for the estimation of amikacin in both pure and marketed formulation using the spectrophotometric method.Methods: Due to lack of chromophoric group in the amikacin, it was derivatized with 0.1 mmol chloranillic acid reagent. For the estimation of amikacin, Shimadzu UV-1700 model spectrophotometer with UV probe software was used. The method was based simple on charge transfer complexation of the drug with a p-chloranilic acid reagent to give a purple coloured product which was measured at 524 nm against blank solution.Results: The derivatised product of amikacin was detected at a wavelength of 524 nm. Linearity was observed with the concentration range of 20-100 µg/ml with a regression coefficient of 0.9803. Results of all the parameters were within the acceptance criteria with % RSD less than 2.Conclusion: The spectroscopic method was validated as per ICH guidelines and was found to be applicable for routine quantitative analysis of amikacin in marketed formulations also. The results of linearity, precision, accuracy LOD and LOQ were within the specified limits. The method is highly sensitive, robust, reproducible and specific.

Spectrophotometric methods based on charge transfer complexation reaction for the determination of some antifungal drugs in pure and dosage forms

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

Analytical Study for the Charge-Transfer Complexes of Risperidone in Pure and Dosage Forms

Two simple, accurate and sensitive spectrophotometric methods were carried out to investigate through charge-transfer reactions of risperidone (RIS) as n-electron donor with various π acceptors: 7, 7, 8, 8-tetracyanoquinodimethane (TCNQ) and p-chloranilic acid (pCA). The absorbance of reaction product was measured at 842 and 520 nm for TCNQ and pCA reagents respectively. Different experimental parameters affecting the reactions were carefully studied. The reaction pathway was postulated. The proposed spectrophotometric method was utilized for the analysis of RIS in pure form as well as in its pharmaceutical preparations. Under the optimum reaction conditions, Beer’s law is obeyed over the concentration range of 1-12 µg mL-1 and 10-180 µg mL-1 for TCNQ and pCA respectively. The limit of assays detection (LOD) is 0.114 µg mL-1 and 2.55 µg mL-1 for TCNQ and pCA respectively. The mean recovery percentage was 99.72 ± 1.06 and 100.50 ± 1.07 for TCNQ and pCA respectively. The results were compared favorably with those obtained by comparison method. The proposed method was validated statistically according to ICH guidelines.

Spectroscopic study of charge transfer complexation between doxepin and π–acceptors and its application in quantitative analysis

Charge transfer complexes of the doxepin with π – acceptors such as 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), tetracyanoquinodimethane (TCNQ) and p-chloranilic acid (p-CA) have been studied spectrophotometrically. The stoichiometry of the reactions was studied by Job's method of continuous variations which show that the complexation ratio was 1:1 (acceptor: donor) for DDQ, TCNQ and p-chloranilic acid with doxepin base. The data were discussed in terms of association constant (K), molar absorptivity (ε), free energy change (ΔG), oscillator strength (f), transition dipole moment (μEN), resonance energy (RN) and ionization potential (ID). Three simple, fast and sensitive spectrophotometric methods were proposed for the quantification of doxepin hydrochloride in pure form and drug formulations. The methods (A, B and C) were based on the reaction of doxepin base as n-donor with DDQ, TCNQ and pCA resulting in coloured species which absorbed maximally at 570nm, 840nm and 530nm, respectively. Beer's law was obeyed in the concentration range of 5–45μgmL−1, 40–360μgmL−1, and 40–400μgmL−1 for the methods A, B, and C, respectively. A series of variables were studied to optimize the reaction conditions. The developed methods were successfully applied for the determination of doxepin in its formulations with high accuracy and precision and without interference from common excipients.

Validated spectrophotometric methods for determination of sodium valproate based on charge transfer complexation reactions

This work presents the development, validation and application of four simple and direct spectrophotometric methods for determination of sodium valproate (VP) through charge transfer complexation reactions. The first method is based on the reaction of the drug with p-chloranilic acid (p-CA) in acetone to give a purple colored product with maximum absorbance at 524nm. The second method depends on the reaction of VP with dichlone (DC) in dimethylformamide forming a reddish orange product measured at 490nm. The third method is based upon the interaction of VP and picric acid (PA) in chloroform resulting in the formation of a yellow complex measured at 415nm. The fourth method involves the formation of a yellow complex peaking at 361nm upon the reaction of the drug with iodine in chloroform. Experimental conditions affecting the color development were studied and optimized. Stoichiometry of the reactions was determined. The proposed spectrophotometric procedures were effectively validated with respect to linearity, ranges, precision, accuracy, specificity, robustness, detection and quantification limits. Calibration curves of the formed color products with p-CA, DC, PA and iodine showed good linear relationships over the concentration ranges 24–144, 40–200, 2–20 and 1–8μg/mL respectively. The proposed methods were successfully applied to the assay of sodium valproate in tablets and oral solution dosage forms with good accuracy and precision. Assay results were statistically compared to a reference pharmacopoeial HPLC method where no significant differences were observed between the proposed methods and reference method.

Validated Spectrophotometric Methods for the Determination of Oxybuprocaine Hydrochloride

Simple, rapid, accurate and reliable spectrophotometric methods were developed and validated for determination of Oxybuprocaine hydrochloride (OXY) in pure form and in pharmaceutical preparation. The methods depend on charge transfer reaction of OXY as n-electron donor with p-chloranilic acid (p-CA), 2, 3 – dichloro 5, 6 – dicyano 1, 4 benzoquinone (DDQ) and iodine as π and σ acceptors, respectively. These reactions were studied under various conditions and the optimum parameters were selected. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9996, 0.9997, and 0.9998) were found between absorbance of the formed complexes and concentrations of OXY in the range of 20.0 220.0 μg/mL, 10.0-80.0 μg/mL and 4.0-44.0 μg/mL for (p-CA), DDQ and iodine methods, respectively. The methods were successfully applied for the determination of OXY in pure form and in dosage form. Job’s method was applied to determine the stoichiometry of the reactions. No significant difference was found at p = 0.05 when the obtained results of the proposed methods were statistically compared with those obtained by an official method.

Application of Charge Transfer Reactions for the Quantitative Spectrophotometric Determination of Cyclophosphamide in Pure and Pharmaceutical Formulation

Abstract: The present investigation describes two simple, sensitive and validated spectrophotometric methods for the determination of Cyclophosphamide (CP) in pure and formulated forms. The methods are mainly based on the formation of charge transfer (CT) complex, with the reagents 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) (Method A) and p-Chloranilic acid (PCA) (Method B), hence a sta-ble, 1:1 stoichiometric complex was obtained, which shows orangeyellow and pink colors, respectively. The produced chromogens optical densities were measured at 352 and 522 nm, respectively. The Beer’s law was tested in the range of 2-16 and 5-50 µg mL -1 . The optical characteristics such as molar absorptivity (ɛ), and San-dell’s sensitivity values were calculated. Other analytical parameters like, Limit of Detection (LOD), Limit of Quantifica-tion (LOQ), accuracy and precisions were evaluated. The proposed methods were successfully applied for the determina-tion of the CP in tablet formulation with higher accuracy, better recoveries and less than 2% relative standard deviation.

Application of π receptors to the spectrophotometric determination of naftidrofuryl oxalate in pure form and its pharmaceutical preparation

Three different spectrophotometric methods are developed for the determination of naftidrofuryl oxalate (NAF) in pure form and its pharmaceutical preparation. The methods are based on charge transfer complexation reactions of NAF as n-electron donor with either p -chloranilic acid (PCA) or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) or tetracyano ethylene (TCNE) as π-receptors to give highly colored anion radicals species. The colored products were quantified spectrophotometrically at 515, 588 and 396 nm in PCA, DDQ and TCNE methods, respectively. Under the optimized experimental conditions, Beer's law is obeyed over the concentration ranges of 75.0-300.0, 25.0-150.0 and 15.0- 50.0 μg/mL NAF for PCA, DDQ and TCNE methods, respectively. The proposed methods were applied successfully to the determination of NAF in pure form and its commercial tablets with good accuracy and precision. Statistical comparison of the results was performed using Student's t-test and F-ratio at 95% confidence level, showing that there is no significant difference between the reference and the proposed methods with regard to accuracy and precision. Further, the validity of the proposed methods was confirmed by standard addition technique.

Spectrophotometric determination of Epinastin hydrochloride in bulk and in Pharmaceutical dosage form

Three rapid, selective and sensitive spectrophotometric methods have been proposed for the quantitative determination of Epinastin hydrochloride (EPH) in bulk and ophthalmic solutions. The methods are based on the charge transfer complexation of EPH as n-electron donor with Iodine as σ-acceptor (method-A), and also with 2, 3-dichloro-5, 6-dicyano-1, 4-benzoquinon (DDQ) (method-B) and p-chloranilic acid (p-CA) (method-C) as π -acceptors. The CT complexes exhibited absorption bands at 366nm, 585nm and 514 nm for method-A, method-B and method-C respectively. Under the optimized experimental conditions, Beer's law is obeyed over the concentration ranges of 20-120 μg/ml for method-A, 15-75 μg/ml for method-B and 25-125 μg/ml for method-C.The coefficient of correlation was found to be 0.998 for three methods. The effect of reagent concentrations, polarity of solvent and effect of reaction time have been studied and optimized. The stoichiometric relationship was determined by Job's continuous method and is found to be 1:1 in each case. The methods have been validated in terms of ICH guidelines and applied to the quantification of EPH in pure form

Analytical Study for the Charge-Transfer Complexes of Rosuvastatin Calcium with π-Acceptors

Studies were carried out to investigate the charge-transfer (CT) reaction of ROS-Ca, as a n-electron donor with various π-acceptors: tetracyanoethylene, p-chloranilic acid, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, 2,3,5,6-tetrabromo-1,4-benzoquinone, 1,3,5-trinitrobenzene, 2,3,5,6-tetrachloro-1,4-benzoquinone, 7,7,8,8-tetracyano-quinodimethane, and 2,4,7-trinitro-9-fluorenone. Different colored CT complexes were obtained. The reaction mechanism and site of interaction were determined by ultraviolet-visible spectrophotometric techniques and computational molecular modeling. The formation of the colored complexes was utilized in the development of simple, rapid and accurate spectrophotometric methods for the determination of ROS-Ca. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9984–0.9995) were found between the absorbances and the concentrations of ROS-Ca in the range of 2–200 μg mL−1. The limits of detection ranged from 0.41 to 12.24 μg mL−1. No interference could be observed from the additives commonly present in the tablets or from the drugs that are co-formulated with ROS-Ca in its combined formulations. The methods were successfully applied to the analysis of tablets with good accuracy and precision; the recovery percentages ranged from 99.54–100.46 ± 1.58–1.82%. The results were compared favorably with the reported method. The proposed methods are practical and valuable for routine application in quality control laboratories for determination of ROS-Ca in its bulk form and tablets.

Different validated methods for determination of cefditoren pivoxil

Six, sensitive, precise and accurate methods have been developed for the determination of cefditoren pivoxil (CP). The first two methods were based on the formation of charge transfer colored complex between CP and p-chloranilic acid (p-CA) or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in the concentration range of 50.00–225.00 μg mL−1 and 75.00–250.00 μg mL−1, respectively. The influence of different parameters on color formation was studied to determine optimum conditions for the visible spectrophotometric methods. The other four methods were adopted for determination of the studied drug in the presence of its acid degradation products including two spectrophotometric methods, namely, first derivative (D1) and first derivative of ratio spectra (DD1), and two chromatographic methods, namely, thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC), as stabilityindicating techniques. The degradation products were identified by infrared and mass spectroscopy. All the proposed ...

Spectrophotometric Determination of Valsartan using p-Chloranilic Acid as π-Acceptor in Pure and in Dosage Forms

The aim of this work was to develop a simple, sensitive and extraction free spectrophotometric method for the quantitative estimation of valsartan in both pure and in pharmaceutical preparations. The developed method is based on the charge transfer complexation reaction between valsartan (VRT) as n- electron donor and pchloranilic acid (p-CA) as π-acceptor. VRT reacts with p-CA in methanol to produce a bright pink colored complex with a maximum absorption at 530 nm. Beer's law was obeyed in the concentration range of 5-50 µg/mL. The linear regression equation of the calibration graph is A = 0.0081+0.0092C with a regression coefficient (r) of 0.9976 (n = 7). The molar absorptivity is calculated to be 2.06 × 10 3 L mol –1 cm –1 and the Sandell sensitivity is 0.1025 μg cm –2 . The limits of detection (LOD) and quantitation (LOQ) values are calculated according to ICH guidelines. The method developed is successfully applied to the determination of VRT in dosage forms.