Direct Spectrophotometric Method Research Articles

A non-extraction sequential injection method for determination of loratadine using formation of its ion-association complex with bromocresol purple in acetonitrile

The formation of an ion-association complex (IA) between sulfonephthalein dye and basic nitrogen-containing compound in an organic solvent medium has been for the first time used to develop an automated SIA method. In highly polar aprotic solvents, the tautomeric equilibrium for such dyes is strongly shifted towards the colorless lactonic form. The addition of a basic nitrogen-containing substance leads to the formation of IA with a highly colored quinonoid form, which is accompanied by an increase in the absorbance of the dye band at approximately 400 nm. Protonation of pyridine nitrogen in loratadine, structure and binding places of IA were shown using quantum-chemical calculations. The very simple, direct and non-extraction spectrophotometric SIA method with high throughput of 43 h−1 was developed based on the formation of IA between loratadine and bromocresol purple in the medium of acetonitrile used both as solvent and carrier. The calibration graph was linear in the concentration range from 1.0 to 20 mg L−1 with correlation coefficient of 0.9992. The developed method was successfully applied to the analysis of pharmaceutical formulations.

Different Eco-Friendly Spectrophotometric Approaches Including Direct and Manipulations of Zero and Ratio Spectra for Simultaneous Determination of Novel Nasal Spray Combination Used in Seasonal Allergic Rhinitis.

The presentation of rhinitis has drawn increasing attention in recent years due to the possibility of overlap or confusion between allergic rhinitis symptoms and those of COVID-19. Azelastine hydrochloride (AZH) and mometasone furoate (MOF) are two of the most efficient combinations for enhancing the symptoms of seasonal allergic rhinitis. This work concerns applying and validating different accurate and simple spectrophotometric approaches for simultaneous quantification of the binary mixture of AZH and MOF in raw material, laboratory-prepared mixtures, and pharmaceutical preparation. Moreover, assessment of the environmental impact of the applied approaches on the environment was also a key goal of this study. AZH was determined using the direct spectrophotometric (D0) method, while four reliable spectrophotometric approaches namely, induced dual wavelength (IDW), ratio subtraction (RS), ratio difference (RD), and ratio derivative (1DD) were used for MOF determination. The methods were validated in line with the International Conference of Harmonization standards. In the AZH range of (5-56 µg/mL) and MOF range of (2-20 µg/mL), the linearity of the proposed approaches was investigated with high accuracy findings. There were no significant differences between the obtained results and those of the reported method when compared statistically. Furthermore, the applied spectrophotometric methods were deemed to be eco-friendly according to Green Analytical Procedure Index (GAPI) and Analytical Greenness Calculator (AGREE) assessment metrics. The applied spectrophotometric methods are simpler, more eco-friendly, and take a shorter time to precisely estimate many measurements compared to the only reported chromatographic analysis. Neither publications of novel spectrophotometric methods nor reported green ones have been available for simultaneous determination of the binary mixture of AZH and MOF, so this work has a great significance and novelty in the area of pharmaceutical analysis.

Comparison of the optimized direct spectrophotometric serum prolidase enzyme activity assay method with the currently used spectrophotometric assay methods and liver fibrosis indexes to distinguish the early stages of liver fibrosis in patients with chronic hepatitis B infection.

The aim of this study was to optimize the currently used direct spectrophotometric serum prolidase enzyme activity (SPEA) assay method and compare its diagnostic accuracy with current precipitation and direct spectrophotometric assay methods, AST-to-ALT ratio, age platelet index, AST-to-platelet ratio index, cirrhosis discriminate score, Doha score, FIB-4, FibroQ, fibrosis index, Goteborg University Cirrhosis Index , King's score, and Pohl score for distinguishing Ishak F0 from F1-F3 in patients with chronic hepatitis B (CHB) infection. Liver biopsy results from 112 patients were included in this study. The SPEA values were 529(292-794) U/L, 671(486-927) U/L, and 1077(867-1399) U/L with the precipitation, current, and optimized direct spectrophotometric assay methods, respectively. According to multivariate logistic regression analysis optimized direct spectrophotometric SPEA was the only statistically significant parameter to predict the early stages of liver fibrosis. Optimized direct spectrophotometric SPEA assay method could be used to distinguish early stages of liver fibrosis in patients with CHB infection instead of the currentlyused spectrophotometric SPEA assay methods and other evaluated liver fibrosis indexes.

A Novel, Simple, and Reliable Spectrophotometric Determination of Total Hexavalent Chromium by Complexation with a New Reagent of Thiazole Linked to 2H-Chromen-2-One.

Hexavalent chromium is a known environmental contaminant and carcinogen. In the current work, a simple, rapid, and reliable direct spectrophotometric method was used for the determination of total Cr (VI) in environmental samples. Acid-base equilibria and ionization constant (pKa) of the new reagent 3-(2-(2-(4-(trifluoromethyl)benzylidene)hydrazineyl) thiazol-4-yl)-2H-chromen-2-one (thiazole linked to 2H-chromen-2-one, TFZ) were investigated. The value of pKa for the reagent was found to be 7.6 which was initially reported. The reaction of the TFZ ligand with Cr (VI) was optimized to produce a highly absorbent complex at 370 nm and pH 7.0 within 1 min. With a correlation coefficient of 0.9994, the linear concentration range ranges from 2 to 20,000 ng·mL-1. The detection limit and quantification limit were 0.73 and 2.43 ng·mL-1, respectively. The method has high precision with relative standard deviations less than 1.0 and high accuracy with recovery of 100 ± 2%. A large excess of cations and anions did not interfere with the determination of Cr (VI). The proposed method was successfully applied to the determination of Cr (VI) in cement samples. The current method could be useful for the routine analysis of Cr (VI) in environmental labs.

Simultaneous MEKC-DAD and smart spectrophotometric assays of thiocolchicoside and etoricoxib in challenging concentration ratio mixtures

Abstract Potent muscle relaxant (thiocolchicoside, TCC) and nonsteroidal anti-inflammatory drug (etoricoxib, ETXB) fixed-dose combination is formulated at relatively high 1:15 and 1:7.5 ratios for TCC and ETXB, respectively. Since the minor component (TCC) has lower absorptivity, assay of TCC/ETXB tablets presents an analytical challenge. The current study presents two novel methods: first is a micellar electrokinetic capillary chromatography (MEKC). Background electrolyte is borate buffer (40 mM, pH 9.2) containing 30 mM sodium dodecyl sulfate and methanol (ratio 80:20%, v/v), measured at 210 nm. Second is a direct double A max spectrophotometric method; minor component, TCC, is measured directly at its distant λ max (373 nm), at zero absorption of ETXB. Then, a ten-fold dilution step is carried out to eliminate TCC spectral interference and ETXB is determined at its λ max (282 nm). Both drugs’ concentrations disclose obedient linearities at 2–100 μg·mL−1 in MEKC, versus 3–25 and 40–350 μg·mL−1 for TCC and ETXB, respectively, in spectrophotometry. All ICH validation elements have been fulfilled for the developed methods. MEKC and spectrophotometric assays achieve accuracy, precision, selectivity, and robustness to be recommended for industrial quality control routine analysis of TCC/ETXB pills formulated at cited ratios or even higher.

A Robust Flow-Based System for the Spectrophotometric Determination of Cr(VI) in Recreational Waters.

A flow-based method for the spectrophotometric determination of chromium (VI) in recreational waters with different salinities was developed. Chromium can occur in the environment in different oxidation states with different related physiological properties. With regard to chromium, the speciation is particularly important, as the hexavalent chromium is considered to be carcinogenic. To achieve that purpose, the use of the diphenylcarbazide (DPC) selective colored reaction with the hexavalent chromium was the chosen strategy. The main objective was to develop a direct and simple spectrophotometric method that could cope with the analysis of different types of environmental waters, within different salinity ranges (fresh to marine waters). The potential interference of metal ions, that can usually be present in environmental waters, was assessed and no significant interferences were observed (<10%). For a complete Cr(VI) determination (three replicas) cycle, the corresponding reagents consumption was 75 µg of DPC, 9 mg of ethanol and 54 mg of sulfuric acid. Each cycle takes about 5 min, including the system clean-up. The limit of detection was 6.9 and 12.2 µg L−1 for waters with low and high salt content, respectively. The method was applied for the quantification of chromium (VI) in both fresh and marine water, and the results were in agreement with the reference procedure.

Simultaneous estimation of recently FDA approved co-formulated ophthalmic solution benoxinate and fluorescein: Application to aqueous humor

Nine simple, cost-effective, and sensitive spectrophotometric methods were developed to simultaneously assay benoxinate HCl and fluorescein sodium in their co-formulated eye drops without barring common excipients. A direct UV spectrophotometric method (method I) was developed for their FLU assay at 481 nm over the concentration range of 0.6–10.0 μg mL−1. Meanwhile, BEN was assayed over the concentration range of 1.0–25.0 μg mL−1 by different UV based methods, namely, conventional dual-wavelength method (DW) (method II), first derivative1D spectrophotometry (method III), second derivative2D spectrophotometry (method IV), ratio spectra difference spectrophotometry (method V), the first derivative of ratio spectra (method VI), ratio subtraction method (method VII), isosbestic point method (ISP) (method VIII) and absorption factor method (method IX). The performance of the proposed methods was assessed relying on the correlation coefficients, relative standard deviations, and limits of detection and quantitation. The variance ratio F-test and Student t-test showed no significant differences between the obtained results of the developed methods and those of reference methods. The proposed methods were also applied to determine studied drugs in commercial eye drops and aqueous humor.

The Direct Spectrophotometric Method Is Reliable for Initial Assessment of Total Bilirubin in Neonatal Venous Plasma.

To determine the consistency of bilirubin values between the direct spectrophotometric (DS) and colorimetric diazo (diazo) methods in neonatal venous plasma specimens. We measured the total bilirubin via the DS and diazo methods in 255 neonatal venous plasma specimens and compared the overall and subgroup results. Slight underestimation of total bilirubin values in most specimens using the DS method was observed, with higher mean biases found in higher concentrations. Significantly high positive correlations were found in all groups in which most of the different values were within the limits of agreement. DS cutoff of > 12 mg/dL showed 100% for all predictive indices in comparison with the diazo cutoff > 15 mg/dL. Measurement of total bilirubin in neonatal venous plasma using the DS method had favorable agreement and high correlation with the diazo method. Therefore, the direct spectrophotometric method can be used as a reliable screening method.

Development and Validation of Direct Spectrophotometric Method for the Estimation of Glimepiride

Aims: To develop simple, sensitive and direct spectrophotometric methods for the estimation of widely prescribed antidiabetic hypoglycemic agent Glimepiride in pure and pharmaceutical dosage form.&#x0D; Place and duration of study: Research Centre of Taywade Group of Institution Koradi, Nagpur affiliated to Rashtrasant Tukadoji Maharaj Nagpur University Nagpur between June 2020 and March 2021.&#x0D; Methodology: Two spectrophotometric methods were developed based on ion-pair formation of drug with Cresol Red dye (Method A) and Bromophenol Blue dye (Method B) in methanol and chloroform. The possible reaction mechanism was proposed with evaluation of statistical parameters. The methods were validated for its application to determine Glimepiride in bulk as well as in pharmaceutical formulations&#x0D; Results: The Beer's law was found linear in the range 10 - 60 µgml-1 at 450 nm for method A and 2 - 20 µgml-1 at 578 nm for method B, respectively. The linear regression equation obtained by applying least square regression analysis for Glimepiride were found to be Absorbance = 0.0136 x Concentration in µgml-1 + 0.028; R2 = 0.9965 for method A and Absorbance = 0.0428x Concentration in µgml-1 +0.0722; R2 = 0.9949 for method B. The Sandell's sensitivity was found to be 0.0696 and 0.0177 for method A and B respectively. The apparent molar absorptivity calculated to be for both methods were 6.6724 x103 and 2.0999 x104 l mol-1 cm-1.&#x0D; Conclusion: Two direct spectrophotometric methods for determination of Glimepiride have been developed successfully and validated for sensitivity, accuracy, precision, repeatability and robustness as per ICH guidelines. The developed methods are suitable for the routine estimation of Glimepiride in pure and dosage form.

Stability evaluation of Acetylsalicylic acid in commercial Aspirin tablets available in the Iraqi market ‎

Assay of acetylsalicylic acid(ASA) utilizing some brands of Aspirin tablets available in Iraqi pharmacies by using direct acid-base titration method and spectrophotometric method for the aim of evaluation of the stability of the active ingredient in their actual environment. Direct acid-base titration method was once used to discover the concentration of active components in aspirin samples then evaluate the result with the percentage of labeling as a reference value. Although the Spectrophotome

VALIDATION OF THE SPECTROPHOTOMETRIC PROCEDURE FOR DESLORATADINE ASSAY IN TABLETS APPLYING THE UNCERTAINTY CONCEPT OF THE STATE PHARMACOPOEIA OF UKRAINE

Aim. This work aimed to validate an assay procedure for desloratadine tablets by direct spectrophotometric method. Materials and methods. A pilot-scale batch of the pharmaceutical preparation Alerdez, film-coated tablets containing 5 mg of desloratadine, manufactured by PJSC SIC “Borshchahivskiy CPP”, Ukraine, was used as an object of the study. A UV-Vis spectrophotometer Lambda 25 (Perkin Elmer), analytical balance Mettler Toledo XP 205DR, and class A volumetric apparatus were used in the study. Validation of the procedure was performed following the metrological approach of the State Pharmacopoeia of Ukraine (SPhU), whose requirements for the target uncertainty and bias, which rest on the risk assessment of making incorrect decisions on compliance (a confidence level of 95 %), were translated into criteria for all validation characteristics recommended by ICH. All calculations were made in normalised coordinates. The linearity, accuracy and precision (repeatability) were studied in a single experiment using nine different concentrations that uniformly covered the range of ±30 % from the nominal concentration of desloratadine. For validation of the procedure, an SPhU reference standard of desloratadine was used. Results. The experiment design and validation characteristics being tested were in full compliance with ICH Q2(R1) recommendations. All performance characteristics conformed to the criteria recommended by the SPhU. Requirements for the target uncertainty (1.6 %) and bias for any systematic source of variation (≤0.51 %, negligible in relation to 1.6 %) were established. The analytical procedure was specific – the absorbance from the placebo solution was insignificant (A %=0.36). The procedure met the requirements for linearity, accuracy, and precision at the repeatability level. The residual standard deviation s0 was 0.34 (≤ 0.84); correlation index Rc was 0.9998 (≥0.9991); intercept а was 0.045 (less than its confidence interval ∆a=1.14). The confidence interval for recovery ∆Z, which was used as a precision estimate, was 0.55 % (less than the target uncertainty). The mean recovery, which was used as an accuracy estimate, statistically insignificantly deviated from 100% (|Zmean ‑ 100| = 0.022 %). The confidence interval for the intermediate precision ∆intra was 0.33 % (less than the target uncertainty). The developed analytical procedure was found to be robust. Conclusions. A spectrophotometric procedure suitable for the assay of desloratadine in film-coated tablets Alerdez with content limits of ±5 % was validated by the SPhU approach.

Optical spectral sensor for the assessment of uric acid kinetics during hemodialysis treatment

The dual-wavelength direct spectrophotometric method for uric acid determination in effluent dialysate and deep UV LED based optical spectral sensor for non-invasive online hemodialysis monitoring were developed. The time profiles of uric acid concentration in effluent dialysate were recorded for a group of 12 patients and 88 hemodialysis sessions by means of the sensor. The parameters of the double-pool kinetic model for each session were assessed and analyzed. The feasibility of online optical monitoring in the UV region as a useful and convenient tool for the experimental investigation of uric acid kinetics during hemodialysis was demonstrated.

Spectral characteristics of 5-hydroxymethylfurfural as a related substance in medicinal products containing glucose

Objectives: To study 5-hydroxymethylfurfural (5-HMF) spectral characteristics aiming at their future application in analytical procedures and their validation for the determination of 5-HMF in liquid products containing glucose after sterilization.Method: Direct spectrophotometric method for the determination of 5-HMF using the molar absorption coefficient at the absorption maximum (284 nm).Results and discussion: aqueous 5-HMF solutions have strong absorption in the ultraviolet range below 310 nm and give two absorption maxima at wavelengths of 229–230 nm and 284 nm. An excellent linear relationship between absorbance and 5-HMF concentration was observed in the concentration range of 2.0–10.0 mg/l. The linear dependence passes through the origin. The molar absorption coefficients of 5-HMF were determined and found to be 3007 mol−1•L•cm−1at 229–230 nm and 16070 mol−1•L•cm−1at 284 nm. The use of the molar absorption coefficient of 5-HMF stated in the Pharmacopeia of the United States of America for determining 5-HMF in polydextrose (16830 mol−1·L·cm−1at 283 nm) gives recovery results for model solutions of reference substance of 5-HMF that are acceptable from the point of view of the requirements of the State Pharmacopeia of Ukraine for methods of quantitative determination of impurities. However, other values of the molar absorption coefficient (17000 and 22700 mol−1•L•cm−1) given in the scientific publications are unsuitable for the quantitative determination of 5-HMF as an impurity in medicinal products.Conclusion: The molar absorption coefficient (16830 mol−1•L•cm−1at 284 nm) may be used to quantify 5-HMF as an impurity in medicinal products containing glucose. For a specific medicinal product, a full validation of the analytical procedure of the 5-HMF determination is required taking into account the composition of this product.

Fast Determination of the Main Reduced Sulfur Species in Aquatic Systems by a Direct and Second-Derivative Spectrophotometric Method

The determination of reduced sulfur species in aquatic systems is not an easy and fast task to accomplish regarding the numerous possible interferences and risks of oxidation that occur with the usual methods of quantification. The method presented here is a direct spectrophotometric method that can be used to quantify sulfides, sulfites, and thiosulfates in a simple and rapid way. The principle is based on the comparison of second-derivative absorbance spectra of the same sample at different pH (9.2, 4.7, and 1.0) and selected absorption wavelengths (250 and 278 nm). This method has been successfully tested and has demonstrated liability to (i) avoid the biases due to absorbance overlaps between the different major chemical species and (ii) keep, as a direct method, the advantages over indirect methods on interferences reduction. The limits of detections (LOD) reached for total sulfide, sulfite, and thiosulfate are 1.37, 7.32, and 1.92 µM, respectively. The method displays low accuracy mean and low relative standard deviation (&lt;4%) as well as a good linearity (R2 &gt; 0.999). Accordingly, this method represents a very robust alternative in terms of cost and rapidity for the quantification of reduced sulfur species in different aquatic environments, from freshwaters to saline and polluted systems.

Rapid and Sensitive Spectrophotometric Method for the Determination of the Trace Amount of Thallium (III) in Water and Urine Samples by New Oxidative Coupling Reaction

A very simple, sensitive and fairly selective direct spectrophotometric method is presented for the rapid determination of thallium(III) at trace level. The method is based on the oxidation of 2-hydrazono-3-methyl-2,3-dihydrobenzo[d]thiazole hydrochloride (MBTH) by thallium(III) in phosphoric acid medium to form a diazoniumcation, which couples immediately with 10,11-dihydro-5Hdibenzo[b,f]azepine (IDB) at room temperature giving a blue colored species having a maximum absorption at 660 nm. The reaction conditions and other important analytical parameters were optimized.The calibration curve was found to be linear over the range of 0.1-4 μg/mL with molar absorptivity of 4.5 × 104 L mol- cm-1 and Sandell’s sensitivity of 0.00454 μg cm-2. The relative standard deviation and limit of detection have been found to be 0.58% and 0.0147 μg/mL respectively. Almost all common anions and cations are found notto interfering in matrix level of the analytical process. The method has been successfully applied for the determination of thallium(III) in synthetic standard mixtures, water and human urine samples. The performance of proposed method was evaluated in terms of student’s t-test and variance ratio F-test, to find out the significance of proposed method over the reported methods.&#x0D; &#x0D;

Extraction-free spectrophotometric assay of the antitussive drug pentoxyverine citrate using sulfonephthalein dyes.

Pentoxyverine citrate (PEN-citrate) is an antitussive (cough suppressant) drug used for cough associated with illnesses like common cold. In this work, PEN-citrate is quantified by applying a simple, direct and accurate spectrophotometric method in pure form, pharmaceutical formulation (Cabella®, 2.13 mg/mL) and human serum samples. The formation of a stable yellow ion-pair with sulfonephthalein dyes; bromocresol green (BCG), bromophenol blue (BPB), bromothymol blue (BTB), bromocresol purple (BCP), bromochlorophenol blue (BChPB) and bromoxylenol blue (BXB), in three nonpolar solvents (chloroform, dichloromethane, acetonitrile) is used as the basis for this method. This is the first assay method reported for the quantification of PEN-citrate using the sulfonephthaleins as coloring agents. Diverse parameters were investigated in order to optimize the calibration curve conditions. The strategy was validated with respect to linearity range, precision, accuracy, specificity, robustness and limits of detection (LOD) and quantification (LOQ). In addition, solvents of different polarities were utilized to investigate the color reaction, light absorption and to allow for increasing the method sensitivity. Beer's law is obeyed over a wide concentration range (up to 42.05 μg/mL in case of BTB method). LOD and LOQ values reached 0.22 and 0.72 μg/mL, respectively, upon using BChPB. The relative standard deviation (%RSD) was ≤1.91% while correlation coefficient values (r) were ≥ 0.9974. High molar absorptivity values and low values of Sandell's sensitivity were obtained indicating that the proposed methods are highly sensitive. The validated methods were applied to the analysis of PEN-citrate in the dosage form and human serum samples where the drug was successfully resolved from the pharmaceutical additives and serum components with recoveries ≥98.98%.

Direct Spectrophotometric Determination of Cefuroxime Axetil in Pure Form and Pharmaceutical Dosage Forms.

A simple, direct and cost-effective spectrophotometric method for determination of cefuroxime axetil (CRXA) in pure and tablet dosage forms was applied. This method is based on formation of ion-pair complex ([CRXA]:[BTB]) between CRXA and bromothymol blue (BTB) in chloroform. Beer’s law in the optimum experimental conditions using [CRXA]:[BTB] complex is valid within a concentration range of 2.00-50.00 ?M (1.021–25.524 ?g.mL-1). The developed method is applied for the determination of CRXA in pure and its commercial tablets without any interference from excipients with average assay of 96.8 to 101.6% and the results are in good agreement with those obtained by the HPLC reference method. Associated drugs (sulbactam and linesolid) with cefuroxime axetil are considered to be interfere, while metronidazole can be considered as non-interfere.

Direct Spectrophotometric Determination of Glimepiride in Pure Form And Pharmaceutical Formulations Using Bromocresol Purple

A simple, direct and accurate spectrophotometric method has been developed for the determination of Glimepiride (GLM) in pure and pharmaceutical formulations by complex formation with bromocresol purple (BCP). The method involves the formation of a yellow ion-pair complex between BCP with glimepiride at pH&lt;3,8; after reacting GLM with Na2CO3 to give C24H33N4H+O5NaS which is extracted by chloroform. The formed complex [GLM]:[ BCP] was measured at lmax 418 nm against the reagent blank prepared in the same manner. Variables were studied in order to optimize the reaction conditions. Molar absorptivity (e) for complex was 20600 L.mol-1.cm-1. Beer’s law was obeyed in the concentration range of 1.226 – 46.608 mg.mL-1 in present of 5.0x10-4 mol/l of BCP with good correlation coefficient (R2= 0.9997). The relative standard deviation did not exceed 3.6%. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.15 and 0.46 mg.mL-1, respectively. The proposed method was validated for specificity, linearity, precision and accuracy, repeatability, sensitivity (LOD and LOQ) and robustness. The developed method is applicable for the determination of GLM in pure and different dosage forms with average assay of 98.8 to 102.0% and the results are in good agreement with those obtained by the RP-HPLC reference method.

Graphene coated iron oxide (GCIO) nanoparticles as efficient adsorbent for removal of chromium ions: Preparation, characterization and batch adsorption studies

Graphene coated iron oxide nanoparticles were prepared using microemulsion method for removal of Cr(VI) ions from aqueous solutions. Plausible interactions between the material and Cr(VI) ions were explored after adsorption and explained by characterizing through various analytical techniques such as Raman spectroscopy, LIBS, FTIR, TEM, EDX, SEM, particle size and zeta-potential measurements which confirmed 20% crystalline nature of GCIO, nanorange (50 nm) size of nanoparticles and great thermal stability. A simple, sensitive and highly selective direct spectrophotometric method was used for the determination of trace levels of Cr(VI) and various experimental parameters, such as the effect of time, pH, adsorbent dose, chromium concentration, temperature and composition of nanoparticles were studied on the adsorption of chromium. The equilibrium sorption data were fitted to various adsorption isotherm models and the as prepared GCIO adsorbent was found to follow the pseudo second order kinetics (R2 = 0.97) and Freundlich model isotherm (R2 = 0.97) with high adsorption capacity (352.1126 mg/g) for Cr(VI) adsorption. The nanoadsorbents were also found to be fairly reusable.

Development and Validation of Spectrophotometric Determination of Glimepiride in Pure and Tablet Dosage forms through Ion-Pair Complex Formation using Bromothymol Blue

A simple, direct and accurate spectrophotometric method has been developed for the determination of Glimepiride (GLM) in pure and pharmaceutical formulations by complex formation with bromothymol blue (BTB). The method involves the formation of a yellow ion-pair complex between BTB with glimepiride (C24H34N4O5S) at pH<3,8; after reacting GLM with Na2CO3 to give C24H33N4H+O5NaS which is extracted by chloroform. The formed complex [GLM]:[BTB] was measured at λmax 412 nm against the reagent blank prepared in the same manner. Variables were studied in order to optimize the reaction conditions. Molar absorptivity (e) for complex was 18024 L mol−1 cm−1. Beer's law was obeyed in the concentration range of 2.453 -49.062 μg.mL−1 in present of 5.0x10−4 mol.L−1 of BTB with good correlation coefficient (R2= 0.9995). The relative standard deviation did not exceed 3.8%. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.30 and 0.91 μg.mL−1, respectively. The proposed method was validated for specificity, linearity, precision and accuracy, repeatability, sensitivity (LOD and LOQ) and robustness. The developed method is applicable for the determination of GLM in pure and different dosage forms with average recovery of 99.5 to 101.6% and the results are in good agreement with those obtained by the RP-HPLC reference method.