Determination of Labetalol Hydrochloride in Drug Formulations by Spectrophotometry

A validated, selective and sensitive spectrophotometric method has been developed for the determination of labetalol hydrochloride in commercial dosage forms. The method is based on the coupling reaction of positive diazonium ion of 4‐aminobenzenesulfonic acid with phenolate ion of labetalol to form a colored azo compound which absorbs maximally at 395 nm. Under the optimized experimental conditions, the color is stable up to 2 h and Beer's law is obeyed in the concentration range of 0.8–17.6 μg mL^?1 with a linear regression equation of A = 4.84 × 10^?4 + 7.864 × 10^?2 C and coefficient of correlation, r = 0.9999. The molar absorptivity and Sandell's sensitivity are found to be 2.874 × 10⁴ L mol^?1 cm^?1 and 0.013 μg cm^?2 per 0.001‐absorbance unit, respectively. The limits of detection and quantitation of the proposed method are 0.08 and 0.23 μg mL^?1, respectively. The intra‐day and inter‐day precision variation and accuracy of the proposed method is acceptable with low values of standard analytical error. The recovery results obtained by the proposed method in drug formulations are acceptable with mean percent recovery ± RSD of 99.97 ± 0.52 ‐ 100.03 ± 0.63%. The results of the proposed method compared with those of Bilal's spectrophotometric method indicated excellent agreement with acceptable true bias of all samples within ± 2.0%.     

2‐Aminocyclopentene‐1‐Dithiocarboxylic Acid‐Naphthalene Adsorbent for the Preconcentration and Determination of a Trace Copper in Real Samples by Spectrophotometric Method

A solid uncharged complex produced from 2‐aminocyclopentene‐1‐dithiocarboxylic acid (synthetic reagent) on naphthalene provides a very sensitive, selective and economical method for the preconcentration and determination of trace amounts of copper in drug and alloy samples. The 2‐aminocyclopentene‐1‐dithiocarboxylate of copper is retained quantitatively on microcrystalline naphthalene in the pH range 2.8–3.3. After filtration the solid mass consisting of copper complex‐naphthalene is dissolved with 4 mL of dimethylformamide (DMF). The absorbance is measured at 462 nm with a spectrophotometer against the reagent blank and molar absorptivity found to be 2.8 × 10⁵ liter mol^?1 cm^?1. Beer's law is obeyed over the concentration range of 0.1–16.0 μg of copper in 4 mL of the dimethylformamide solution. Detection limit is 3 ng mL^?1 [signal to noise ratio = 2]. Ten replicate determinations on a sample containing 1 μg of copper gave a relative standard deviation of 0.76%. The interference of a large number of anions and cations have been studied and the optimized conditions developed were utilized for determination of copper in various real samples.     

Quantitative Analysis of Nicorandil in Commercial Tablets by Spectrophotometry

The main aim of this work is to develop and validate a spectrophotometric method for the determination of nicorandil in commercial tablets. The method is based on the reduction of the nitroxy ethyl group of nicorandil into carbonyl compound and nitrite ion by NH₄Cl and Zn dust. The nitrite ion thus formed reacts with potassium iodide and starch in dilute HCl medium to form a blue product, which absorbs maximally at 550 nm. Beer's law is obeyed in the concentration range 0.4‐4.0 μg mL^?1 with molar absorptivity of 7.92 × 10⁴L mol^?1 cm^?1. The detection limit is 0.017 μg mL^?1. The reaction conditions are optimized and validated as per the International Conference on Harmonisation guidelines (USA). The proposed method has been applied successfully for the determination of nicorandil in commercial tablets. The results of analyses are compared statistically with those of the author's spectrophotometric method, which confirmed that there is no significant difference between the methods compared.     

Analytical Applications of 2,6‐Diacetylpyridine‐bis‐4‐phenyl‐3‐thiosemicarbazone (2,6‐DAPBPTSC): Determination of Cd(II) in Foods and Water Samples

To the determination of trace amount of Cd(II) present in food and water samples, a selective and extractive spectrophotometric method were developed with 2,6‐diacetylpyridine‐bis‐4‐phenyl‐3‐thiosemicarbazone as a complexing agent. The yellowish orange colored metal complex, Cd(II)‐2,6‐DAPBPTSC with 1:1 (M:L) composition was extracted in to cyclohexanol at pH 9.5 and was shows maximum absorbance at λ_max 390 nm. This method obeys Beer's law in the range of 1.12‐11.25 ppm with 0.972 correlation coefficient of Cd(II)‐2,6‐DAPBPTSC complex, which is indicates linearity between the two variables. The molar absorptivity and sandell's sensitivity were found to be 6.088 × 10⁴ L mol^?1 cm^?1 and 0.0018 μg cm^?2, respectively. The instability constant calculated from Asmus' method (1.447 × 10^?4)at room temperature. The precision and accuracy of the method were checked by relative standard deviation (n = 5), 0.929 and its detection limit, 0.0060 μg mL^?1. The interfering effects of various cations and anions were also studied. The proposed method was successfully applied to the determination of Cd(II) in foods and water samples, and was evaluated its performance in terms of Student ‘t’ test and Variance ‘f’ test, which indicates the significance of present method. The inter comparison of the experimental values, using atomic absorption spectrometer (AAS), was also repoted.     

Spectrophotometric Determination of Thioctic Acid in its Dosage Forms through Complex Formation with Pd(II)

A simple and sensitive spectrophotometric method has been developed for the determination of thioctic acid in pharmaceutical preparations. The proposed method is based upon the formation of a complex with palladium(II) in acetate buffer of pH 4.8 with an absorption maximum at 318 nm. The absorbance obeyed Beer's law over the range of 2–20 μg mL^?1 with a minimum detection limit of 0.15 μg mL^?1 and molar absorptivity (ζ) of 7 × 10³ L mol^?1.cm^?1. The different experimental parameters affecting the development and stability of the color were carefully studied and optimized. The proposed method was successfully applied to the analysis of commercial tablets and ampoules. The results obtained were in good agreement with those obtained using a reference spectrophotometric method. A proposal of the reaction pathway is presented.     

Extractive Spectrophotometric Methods for Determination of Clarithromycin in Pharmaceutical Formulations Using Bromothymol Blue and Cresol Red

Two simple and sensitive extractive spectrophotometric methods have been described for the analysis of clarithromycin in pure form and in pharmaceutical formulations. The methods involved formation of yellow colored chloroform extractable ion‐association complexes of clarithromycin with bromothymol blue (BTB) and cresol red (CR) in buffered aqueous solution at pH 4. The extracted complexes showed maximum absorbance at 410 and 415 nm for BTB and CR, respectively. Beer's law is obeyed in the concentration ranges 0.1–20 μg mL^?1 and 2.0–20 μg mL^?1 of clarithromycin with molar absorptivity of 2.01 × 10⁴ and 4.378 × 10³ for BTB and CR, respectively. The composition ratio of the ion‐association complex was clarithromycin: BTB and CR = 1:1 as established by Job's method. The methods have been applied to the determination of drug in commercial formulations. The results of analysis were validated statistically and through recovery studies.     

Synthesis of New Reagent Benzyloxybenzaldehydethiosemicarbazone (BBTSC): Selective,Sensitive and Extractive Spectrophotometric Determination of Pd(II) in Water Samples and Synthetic Mixtures

A new reagent, benzyloxybenzaldehydethiosemicarbazone (BBTSC) was synthesized and a new method was developed for the simple, highly selective and extractive spectrophotometric determination of palladium(II) with BBTSC at wave length 365 nm. The metal ion formed a yellow colored complex with BBTSC in acetate buffer of pH 5.0, which was easily extractable into cyclohexanol with 1:1 (Metal: Ligand) composition. The method obeys Beer's law in the range of 5–60 ppm. The molar absorptivity and Sandell's sensitivity were found to be 0.4 × 10⁴ Lt. mol^?1 cm^?1 and 0.02661 μg cm^?2, respectively. The correlation co‐efficient of the Pd(II)‐BBTSC complex was 0.9657, which indicated an excellent linearity between the two variables. The repeatability of the method was checked by finding the relative standard deviation (RSD) (n = 10), which was 0.321% and its detection limit 0.016875 μg.mL^?1. The instability constant of the method was calculated by Asmus' method as 3.5714 × 10^?4. The interfering effect of various cations and anions were also studied. The proposed method was successfully applied for the determination of palladium(II) in synthetic and water samples. The results were compared with those obtained using an atomic absorption spectrophotometer, testing the validity of the method.     

Development of a Simple and Inexpensive Optical Absorption One‐Shot Sensor Membrane for Detection and Determination of Cyanide Ions in Water Samples

A new one‐shot optical cyanide ion sensor is proposed for determination of cyanide ions. The sensor was constructed by immobilizing crystal violet (CV) on triacetylcellulose membrane. The sensing mechanism involves reaction between cyanide ions and the immobilized CV at pH = 5.4, which results in a decrease in absorbance of the membrane at 600 nm. The sensor shows sufficient repeatability, reproducibility, operational lifetime of 3 weeks, and a response of less then 10 min under the optimum conditions and response time of 8 min. Cyanide can be determined in the concentration range of 50.0‐800 μg mL^‐1 with a detection limit of 5.0 μg mL^‐1. Most ions do not interfere with the determination of cyanide ions. The proposed sensor was successfully applied to the determination of cyanide in spiked water samples.     

Synthesis of New Reagent 2,6‐Diacetylpyridine Bis‐4‐Phenyl‐3‐Thiosemicarbazone (2,6‐DAPBPTSC): Selective,Sensitive and Extractive Spectrophotometric Determination of Co(II) in Vegetable,Soil, Pharmaceutical and Alloy Samples

New synthesized reagent 2,6‐diacetylpyridine bis‐4‐phenyl‐3‐thiosemicarbazone (2,6‐DAPBPTSC) is proposed as a sensitive and selective analytical reagent for the extractive spectrophotometric determination of cobalt(II). Cobalt(II) forms a reddish brown colored complex with 2,6‐DAPBPTSC, which is extracted into isoamylalcohol, under optimum conditions. The maximum absorption of the isoamylalcohol extract is measured at 400 nm. Beer's law is applied in the range 0.6‐6.0 ppm of cobalt(II). The molar absorptivity and Sandell's sensitivity of the complex is calculated as 2.2 × 10⁴ L mol^?1 cm^?1 and 2.68 × 10^?3 μg cm^?2, respectively. An adequate linearity with a correlation coefficient value of 0.969 is obtained for the Co(II)‐2,6‐DAPBPTSC complex. The instability constant of the complex, calculated from Asmus' method is 3.75 × 10^?4 The precision and accuracy of the method is checked with calculation of relative standard deviation (n = 5), 0.388 and the detection limit a value is 0.0028 μg mL^?1. The method is successfully employed for the determination of cobalt(II) in real samples, such as vegetables, soil, water samples, standard alloy samples, and the performance of the present method was evaluated in terms of Student ‘t’ test and Variance ‘f’ test, which indicates the significance of the present method is an inter comparison of the experimental values, using atomic absorption spectrometer (AAS).     

Simple determination of betaine,l‐carnitine and choline in human urine using self‐packed column and column‐switching ion chromatography with nonsuppressed conductivity detection

A sequential online extraction, clean‐up and separation system for the determination of betaine, l ‐carnitine and choline in human urine using column‐switching ion chromatography with nonsuppressed conductivity detection was developed in this work. A self‐packed pretreatment column (50 × 4.6 mm, i.d.) was used for the extraction and clean‐up of betaine, l ‐carnitine and choline. The separation was achieved using self‐packed cationic exchange column (150 × 4.6 mm, i.d.), followed by nonsuppressed conductivity detection. Under optimized experimental conditions, the developed method presented good analytical performance, with excellent linearity in the range of 0.60–100 μg mL⁻¹ for betaine, 0.75–100 μg mL⁻¹ for l ‐carnitine and 0.50–100 μg mL⁻¹ for choline, with all correlation coefficients (R²) >0.99 in urine. The limits of detection were 0.15 μg mL⁻¹ for betaine, 0.20 μg mL⁻¹ for l ‐carnitine and 0.09 μg mL⁻¹ for choline. The intra‐ and inter‐day accuracy and precision for all quality controls were within ±10.32 and ±9.05%, respectively. Satisfactory recovery was observed between 92.8 and 102.0%. The validated method was successfully applied to the detection of urinary samples from 10 healthy people. The values detected in human urine using the proposed method showed good agreement with the measurement reported previously.     

Kinetic Analysis of Cobalt in Veterinary Products

A novel kinetic method for the determination of trace amounts of Co(II) has been developed. The proposed method based on the catalytic effect of Co(II) on the oxidation of xylenol orange tetra sodium salt by H₂O₂ in the presence of cationic surfactant (N‐dodecylpyridinium chloride). Co(II) at μg.mL^?1 was determined spectrophotometrically by measuring the decrease in the absorbance of xylenol orange at 577 nm by the differential method. The method is precise, selective, and sensitive. The detection limit of the procedure was 0.058 μg.mL^?1. The relative standard deviation for the replicate determination (n = 6) of 0.7 μg.mL^?1 was 1.285%. The results compared satisfactorily with those of atomic absorption spectrometry. The method was successful for the analysis of Co(II) in veterinary and synthetic samples.     

Spectrophotometric Determination of Piroxicam via Chelation with Fe(III) in Commercial Dosage Forms

The objective of this work is to develop and validate spectrophotometric method for the determination of piroxicam in commercial dosage forms. The method is based on the chelation of the drug with Fe(III) to form pink coloured metal chelate at room temperature which absorbs maximally at 504 nm. Beer's law is obeyed over the concentration range of 8–160 μg mL^?1 (A = 1.07 × 10^?3 + 7.75 × 10^?3 C). Under the optimized experimental conditions, proposed method is validated as per the International Conference on Harmonisation guidelines. The limits of detection and quantitation for the proposed method are 0.775 and 2.348 μg mL^?1, respectively. The proposed method has been successfully applied to the determination of piroxicam in commercial dosage forms. The results are compared with the reference El‐Ries et al. spectrophotometric method.     

A Novel Spectrophotometric Method for the Determination of Levodopa with the Detection System of Potassium Ferricyanide‐Fe(III)

In this paper, a novel method has been established to determine levodopa with the detection system of potassium ferricyanide‐Fe(III). In the presence of potassium ferricyanide, it has been demonstrated that Fe(III) is reduced to Fe(II) by levodopa at pH 4.0. In addition, the in situ formed Fe(II) reacts with potassium ferricyanide to form soluble prussian blue (KFe^III[Fe^II(CN)₆]). Beer's law is obeyed in the range of levodopa concentrations of 0.01–4.00 μg mL^?1 at the maximal absorption wavelength of 735 nm. The linear regression equation is A = 0.0082 + 0.61365 C (μg mL^?1) with a correlation coefficient of 0.9996. The detection limit (3σ/k) is 9 ng mL^?1, and R.S.D. is 0.73% (n = 11). Moreover, the apparent molar absorption coefficient of indirect determination of levodopa is 1.2 × 10⁵ Lmol^?1cm^?1. The parameters with regard to determination are optimized, and the reaction mechanism is discussed. This method has been successfully applied to determine levodopa in pharmaceutical, serum and urine samples. Analytical results obtained with this novel assay are satisfactory.     

Study of the solid phase extraction and spectrophotometric determination of nickel using 5-(4′-chlorophenylazo)-6-hydroxypyrimidine-2,4-dione in environmental samples

A rapid, sensitive and selective method for the determination of nickel based on the rapid reaction of nickel(II) with 5-(4′-chlorophenylazo)-6-hydroxypyrimidine-2,4-dione (CPAHPD) and the solid phase extraction of the Ni(II)–CPAHPD complex with C18 membrane disks has been developed. In the presence of pH 6.8 buffer solution and cetylpyridinium bromide (CPB) medium, CPAHPD reacts with nickel to form a red complex of a molar ratio of 1:1 (nickel to CPAHPD). This complex was enriched by solid phase extraction (SPE) with C18 membrane disks. An enrichment factor of 100 was obtained by elution of the complex from the disks with the minimal amount of isopentyl alcohol. The molar absorptivity and Sandell sensitivity of the complex was 3.11 × 10⁵ L mol^?1 cm^?1 and 0.0189 ng cm^?2, respectively at 549 nm in the measured solution. Beer's law was obeyed in the range of 0.01–0.37 μg mL^?1, while that obtained by Ringbom plot was in the range of 0.025–0.35 μg mL^?1. The detection and quantification limits were calculated and found to be 0.003 and 0.01 μg mL^?1. The proposed method was applied to the determination of nickel in water, food, biological and soil samples with good results.     

Quantitation of Diltiazem Hydrochloride in Commercial Dosage Forms by Visible Spectrophotometry

A selective and sensitive visible spectrophotometric method has been described for the quantitation of diltiazem hydrochloride in commercial dosage forms. The method is based on the reaction of the tertiary amino group of the drug with sodium hypochlorite to form the chloro drug derivative, followed by the destruction of the excess hypochlorite by sodium nitrite and the subsequent development of blue color takes place by the reaction of chloro derivative of drug with starch and potassium iodide in sodium bicarbonate medium. The maximum absorbance of the resulting blue solution is read at 540 nm. Under the optimized experimental conditions, Beer's law is obeyed in the concentration range of 2.5–25.0 μg mL^?1 with a linear regression equation of A = 9.85 × 10^?4 + 4.90 × 10^?2 C and coefficient of correlation, r = 0.9999. The molar absorptivity is found to be 2.26 × 10⁴L mol^?1 cm^?1. The limits of detection and quantitation of the proposed method are 0.12 and 0.37 μg mL^?1, respectively. The proposed method has been successfully applied for the quantitation of diltiazem hydrochloride in commercial dosage forms. The results of the proposed method compared with those of Abdellatef's spectrophotometric method presented good mean recovery with acceptable true bias of all pharmaceutical samples within ± 2.0%.     

Simultaneous Determination of Nickel(II) and Copper(II) by Second‐Derivative Spectrophotometric Method in Micellar Media

A second‐derivative spectrophotometric method based on zero‐crossing over technique is developed in simultaneous determination of copper(II) and nickel(II) ions. Methylthymol blue (MTB) as a chromogenic reagent and cetyltrimethylammonium bromide as a surfactant were used, and measurements were carried out in buffered solution at pH 6 and at a temperature of 25 °C. The amplitude of derivative spectra was measured at wavelengths of 631.9 and 587.7 nm for the simultaneous determination of Ni²⁺ and Cu²⁺, respectively. Linearity was obtained in the range of 0.5–5.0 μg mL^?1 for both ions in the presence of 0.0–5.0 μg mL^?1 of the other ion as an interfering ion. IUPAC detection limits for Cu²⁺ and Ni²⁺ ions were obtained at 0.48 and 0.43 μg mL^?1, respectively. The proposed procedure has been applied successfully for the simultaneous determination of copper and nickel in synthetic binary mixtures and real samples.     

Flow Injection Analysis Spectrophotometric Determination of Platinum

Abstract

A new, simple, rapid, and selective procedure for the flow injection analysis (FIA) spectrophotometric determination of platement (Pt) is described. The method is based on the color reaction of Pt(IV) with SnCl₂ in the HCl medium. The mixed surfactants, i.e., cetylpyridinium chloride (CPC)+triton X‐100 (TX‐100) are used to enhance sensitivity of the method. The value of apparent molar absorptivity in the term of Pt is (3.00)×10³ L mol^?1 cm^?1 at absorption maximum, 405 nm. The detection limit (causing absorbance greater than 3×std. dev.) of the method is 150 ng/mL^?1. The optimum concentration range for the determination of Pt is 0.5–18 µg/mL^?1 with slope, intercept and correlation coefficient 0.0086, ?0.001, and +0.99, respectively. The sample throughput of the method is 120 samples/h^?1 at the flow rate of 3.7 mL/min^?1. The composition of the complex, and the reaction mechanism involved are discussed. The effect of FIA and analytical variables on the determination of the metal is optimized. The method has been tested for the analysis of Pt to the catalytic materials.     

Simultaneous Kinetic‐Potentiometric Determination of Hydrazine and Thiosemicarbazide by Partial Least Squares and Principle Component Regression Methods

Simultaneous determination of hydrazine (HZ) and thiosemicarbazide (TSC) by partial least squares (PLS) and principle component regression (PCR) was carried out based on kinetic data of novel potentiometry. The rate of chloride ion production in reaction of HZ and TSC with N‐chlorosuccinimide (NCS) was monitored by a chloride ion‐selective electrode. The experimental dada shows not only the good ability of ion‐selective electrodes (ISEs) as detectors for the direct determination of chloride ions but also for simultaneous kinetic‐potentiometric analysis using chemometrics methods. The methods are based on the difference observed in the production rate of chloride ions. The results show that simultaneous determination of HZ and TSC can be performed in their concentration ranges of 0.7‐20.0 and 0.5‐20.0 μg mL^?1, respectively. The total relative standard error for applying PLS and PCR methods to 9 synthetic samples in the concentration ranges of 0.8‐10 μg mL^?1 of TSC and 1.0‐12.0 μg mL^?1 of HZ was 4.62 and 4.98, respectively. The effects of certain foreign ions upon the reaction rate were determined for the assessment of the selectivity of the method. Both methods (PLS and PCR) were validated using a set of synthetic sample mixtures and then applied for simultaneous determination of HZ and TSC in water samples.     

Spectrophotometric Determination of Esomeprazole Magnesium in Commercial Tablets Using 5‐Sulfosalicylic Acid and N‐Bromosuccinimide

Two simple, sensitive and economical spectrophotometric methods have been developed for the determination of esomeprazole magnesium in commercial dosage forms. Method A is based on the reaction of esomeprazole magnesium with 5‐sulfosalicylic acid in methanol to form a yellow product, which absorbs maximally at 365 nm. Method B utilizes the reaction of esomeprazole magnesium with N‐bromosuccinimide in acetone‐chloroform medium to form α‐bromo derivative of the drug peaking at 380 nm. Under the optimized experimental conditions, Beer's law is obeyed in the concentration ranges of 2‐48 and 10‐100 μg mL^?1 with molar absorptivity of 2.11 × 10⁴ and 4.57 × 10⁴L mol^?1 cm^?1 for methods A and B, respectively. The limits of detection for methods A and B are 0.35 and 0.46 μg mL^?1, respectively. No interference was observed from excipients commonly present in tablet formulations. Methods A and B are successfully applied to the commercial tablets for the estimation of esomeprazole magnesium with good accuracy and precision. The results compare favorably with the reference spectrophotometric method indicating no significant difference between the methods compared.     

A Sensitive Spectrophotometric Determination of Nitrite in Water and Soil

A highly sensitive spectrophotometric method for the determination of nitrite in water and soil has been developed. The reaction of nitrite with acidified potassium iodide to liberate iodine which oxidizes leuco‐crystal violet (LCV) to form crystal violet having absorption maxima at 590 nm forms the bases of this method. In aqueous medium the system obeys Beer's law in the range of 0.1 to 1.0 μg per 25 mL (0.004–0.04 ppm), while in an extractive system the range is 0.025–0.25 μg in 100 mL (0.00025–0.0025 ppm). The molar absorptivity and Sandell's sensitivity were found to be 1.54 × 10⁶ 1 mol^?1 cm^?1 and 44 pg cm^?2, respectively.