Alaa S. Amin

Spectrophotometric determination of piroxicam and tenoxicam in pharmaceutical formulations using alizarin.

New spectrophotometric procedures have been established for the quantitation of piroxicam and tenoxicam. The procedures are based on the reaction between the examined drug and alizarin (I), alizarin red S (II), alizarin yellow G (III) or quinalizarin (IV) producing ion-pair complexes which can be measured at the optimum wavelength. The optimization of the reaction conditions is investigated. Beers law is obeyed in the concentration ranges 0.05-2.40 microg ml(-1), whereas optimum concentration as adopted from Ringbom plots was 0.12-2.25 microg ml(-1). The molar absorptivity, Sandell sensitivity, detection and quantification limits are also calculated. The correlation coefficient was >/=0.9990 (n=10) with a relative standard deviation (R.S.D.) of </=1.2, for ten determinations of 1.0 microg ml(-1). The methods are successfully applied to the determination of piroxicam and tenoxicam in their pharmaceutical formulations.

Colorimetric determination of β-blockers in pharmaceutical formulations

Abstract A simple, accurate, precise and sensitive colorimetric method for the determination of some β-blockers as atenolol (Ateno), metoprolol (Metop), sotalol (Sot) and nadolol (Nad) is described. This method is based on the formation of charge transfer complex with 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD–Cl) in methanolic–aqueous (for Ateno and Metop) or acetone–aqueous (for Sot and Nad) medium [30% (v/v)]. The orange color products are measured at 485, 470, 465 and 462 nm for Ateno, Metop, Sot and Nad, respectively. The optimization of various experimental conditions is described. Beers law is obeyed in the range 0.4–60 μg ml−1 while that obtained applying Ringbom is 0.8–56 μg ml−1. The molar absorptivity, Sandell sensitivity, detection and quantification limits are calculated. The results obtained showed good recoveries of 99.5±1.1, 100.3±1.2, 100.5±1.0 and 99.3±1.1% with relative standard deviations of 0.74, 0.98, 1.15 and 0.87% for Ateno, Metop, Sot and Nad, respectively. Applications of the proposed method to representative pharmaceutical formulations are successfully presented.

Utility of certain π-acceptors for the spectrophotometric determination of norfloxacin

Simple, rapid, accurate and sensitive spectrophotometric methods are described for the determination of norfloxacin. The methods are based on the reaction of this drug as a π-electron donor with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), 7,7,8,8-tetracyanoquinodimethane (TCNQ), p-chloranil (CL) or chloranilic acid (CLA) as π-acceptors to give highly coloured complex species. The coloured products are measured spectrophotometrically at 460, 843, 550 and 531 nm for DDQ, TCNQ, CL and CLA, respectively. Optimization of the different experimental conditions is described. Beers law is obeyed in the range 10–400 µg ml–1 and colours were produced in non-aqueous media and were stable for at least 3 h. Applications of the suggested methods to representative pharmaceutical dosage forms are presented and compared with the official method. Interferences from additives and common degradation products were investigated.

Spectrophotometric determination of iron in environmental and food samples using solid phase extraction

A simple, selective and highly sensitive extraction method has been developed for the determination of iron(II) spectrophotometrically after solid phase extraction. The absorbance is measured at λmax 644 nm. Beers law was obeyed up to 450 ng mL(-1) of iron. The molar absorptivity, Sandells sensitivity, detection and quantification limits were calculated and found to be 1.09×10(5) L mol(-1) cm(-1), 0.51 ng cm(-2), 1.98 and 6.0 ng mL(-1), respectively and compared with parameters obtained without using solid phase extraction method. After reduction of Fe(III) by addition of 2.0 mL of 10% hydroxylamine HCl, the system was applied to the total iron. The interference of various ions has been studied in detail and the statistical evaluation of the experimental results is reported. The proposed methods have been successfully applied for the determination of trace amount of iron in environment water, soil and botanical reference materials with recovery range (98.71-101.51%).

Cloud-point extraction, preconcentration and spectrophotometric determination of trace quantities of copper in food, water and biological samples.

A new, simple and sensitive cloud point extraction procedure was presented for the preconcentration and determination of copper(II) ion in food, water and biological samples. The analyte was complexed with a new synthesized reagent, 2-amino-4-(m-tolylazo)pyridine-3-ol (ATAP) as a new complexing agent and Triton X-114 as the surfactant. After centrifugation, dilution of the surfactant-rich phase with 0.4 mL of ethanol acidified with 1.0M HNO3 was performed after phase separation, and the copper contents were measured by spectrophotometry at λmax 608 nm. The influence of analytical parameters including concentration of complexing agent, Triton X-114, pH, equilibration temperature and time, centrifuge rate and time were optimized. The analytical characteristics of the method (e.g. linear range, molar absorptivity, Sandell sensitivity, optimum Ringbom concentration ranges limits of detection and quantification, preconcentration factor, and improvement factors) were obtained. Linearity was obeyed in the range of 4.0-115 ng mL(-1) of Cu(II) ion. The detection and quantification limits of the method were 1.20 and 3.94 ng mL(-1) of Cu(II) ion, respectively. The interference effect of some anions and cations was also tested. The method was applied for determination of copper in food, water and biological samples.

Utility of oxidation/reduction reaction for the determination of ranitidine hydrochloride in pure form, in dosage forms and in the presence of its oxidative degradates

Three simple, accurate and sensitive colorimetric methods (A, B and C) for the determination of ranitidine HCl (RHCl) in bulk sample, in dosage forms and in the presence of its oxidative degradates are described. The first method A is based on the oxidation of the drug by N-bromosuccinimide (NBS) and determination of the unreacted NBS by measurement of the decrease in absorbance of amaranth dye (AM) at a suitable lambda(max)=520 nm. The methods B and C involve the addition of excess Ce(4+) and determination of the unreacted oxidant by decrease the red color of chromotrope 2R (C2R) at a suitable lambda(max)=528 nm for method B or decrease the orange pink color of rhodamine 6G (Rh6G) at a suitable lambda(max)=526 nm for method C. Regression analysis of Beer-Lambert plots showed good correlation in the concentration ranges 0.2-3.6, 0.1-2.8 and 0.1-2.6 microg ml(-1) for methods A, B and C, respectively. The apparent molar absorptivity. Sandell sensitivity, detection and quantitation limits were calculated. For more accurate results, Ringbom optimum concentration ranges were 0.3-3.4, 0.2-2.6 and 0.2-2.4 microg ml(-1) for methods A, B and C, respectively. Analyzing pure and dosage forms containing RHCl tested the validity of the proposed methods. The relative standard deviations were </=1.38 with recoveries 98.9-101.0%.

Utilization of solid phase spectrophotometry for determination of trace amounts of beryllium in natural water

A simple, sensitive and accurate procedure for the determinations of trace amounts of beryllium has been developed, based on solid-phase spectrophotometry. Beryllium reacts with aurintricarboxylic acid (ATCA) in the presence of ethylene-diaminetetraacetic acid to give a complex with a high molar absorptivity (1.50 × 10 7 lm ol −1 cm −1 ), which is fixed on a dextran-type anion-exchange gel (Sephadex DEAE A-25). The absorbance of the gel, at 575 and 750 nm, packed in a 1.0 mm cell, is measured directly. Calibration is linear over the range 0.03–1.0 gl −1 with RSD of <2.4% (n = 8.0). The detection and quantification limits of the 500 ml sample method are 6.0 and 20 ng l −1 on using 90 mg. For 1000 ml sample the detection and quantification limits are 5.0 and 17 ng l −1 using 45 mg exchanger. Increasing the sample volume can enhance the sensitivity. The proposed methods have been applied to the determination of beryllium in tap, mineral and well water using the standard addition technique with recoveries of 100.13 ± 0.61, 99.47 ± 1.41 and 100.10 ± 1.53, and concentration levels of 0.032, 0.221 and 10.92 gl −1 , respectively.

The surfactant-sensitized analytical reaction of niobium with some thiazolylazo compounds

Abstract Cationic surfactants, such as cetylpyridinium bromide (CPB), sensitize the color reaction of Nb(V) with 1-(2-benzothiazolylazo)-2-hydroxy-3-naphthoic acid (Ia), 5-(benzothiazolylazo)2,5-naphthalenediol (Ib), 5-(2-benzothiazolylazo)8-hydroxyquinoline (Ic) and 4-(2- benzothiazolylazo)2, 2 -biphenyldiol (Id) reagents. The formation of a ternary complex of stoichiometric ratio 1:2:2 (Nb-R-CPB) is responsible for the observed enhancement in the molar absorptivity and the Sandell sensitivity of the formed complex, when a surfactant is present. The ternary complex exhibits absorption maxima at 649, 692, 661 and 612 nm, (e=3.35×104, 3.59×104, 4.46×104 and 2.79×104 l mol−1 cm−1) on using reagent Ia, Ib, Ic, and Id, respectively. Beer’s law is obeyed between 0.05 and 2.50 μg ml−1, while applying the Ringbom method for more accurate results is in the range from 0.20 to 2.30 μg ml−1. Conditional formation constants in the presence and absence of CPB for niobium complexes have been calculated. On the basis of a detailed spectrophotometric study, the nature of the chromophoric reagent–surfactant interaction and the peculiar features of the sensitization by CPB are discussed.

Utility of solid phase spectrophotometry for the modified determination of trace amounts of cadmium in food samples.

A modified selective, highly sensitive and accurate procedure for the determination of trace amounts of cadmium which reacts with 1-(2-benzothiazolylazo)-2-hydroxy-3-naphthoic acid (BTAHNA) to give a deep violet complex with high molar absorptivity (7.05×10(6)Lmol(-1) cm(-1), 3.92×10(7)Lmol(-1)cm(-1), 1.78×10(8)Lmol(-1)cm(-1), and 4.10×10(8)Lmol(-1)cm(-1)), fixed on a Dowex 1-X8 type anion-exchange resin for 10mL, 100mL, 500mL, and 1000mL, respectively. Calibration is linear over the range 0.2-3.5μgL(-1) with RSD of ⩽1.14% (n=10). The detection and quantification limits were calculated. Increasing the sample volume can enhance the sensitivity. The method has been successfully applied for the determination of Cd(II) in food samples, water samples and some salts samples without interfering effect of various cations and anions.

Atomic absorption spectroscopic, conductometric and colorimetric methods for determination of fluoroquinolone antibiotics using ammonium reineckate ion-pair complex formation.

Three accurate, rapid and simple atomic absorption spectrometric, conductometric and colorimetric methods were developed for the determination of norfloxacin (NRF), ciprofloxacin (CIP), ofloxacin (OFL) and enrofloxacin (ENF). The proposed methods depend upon the reaction of ammonium reineckate with the studied drugs to form stable precipitate of ion-pair complexes, which was dissolved in acetone. The pink coloured complexes were determined either by AAS or colorimetrically at lambdmax 525 nm directly using the dissolved complex. Using conductometric titration, the studied drugs could be evaluated in 50% (v/v) acetone in the range 5.0-65, 4.0-48, 5.0-56 and 6.0-72 microg ml-1 of NRF, CPF, OFL and ENF, respectively. The optimizations of various experimental conditions were described. The results obtained showed good recoveries of 99.15 +/- 1.15, 99.30 +/- 1.40, 99.60 +/- 1.50, and 99.00 +/- 1.25% with relative standard deviations of 0.81, 1.06, 0.97, and 0.69% for NRF, CPF, OFL, and ENF, respectively. Applications of the proposed methods to representative pharmaceutical formulations are successfully presented.