Spectrophotometric determination of carbamazepine and mosapride citrate in pure and pharmaceutical preparations

Simple, rapid and sensitive spectrophotometric methods were developed for the determination of carbamazepine and mosapride citrate drugs in pure and pharmaceutical dosage forms. These methods are based on ion pair and charge transfer complexation reactions. The first method is based on the reaction of the carbamazepine drug with Mo(V)–thiocyanate in hydrochloric acid medium followed by an extraction of the coloured ion-pair with 1,2-dichloroethane and the absorbance of the ion pair was measured at 470 nm. The second method is based on the formation of ion-pairs between mosapride citrate and two dyestuff reagents namely bromothymol blue (BTB) and bromocresol green (BCG) in a universal buffer of pH 4 and 3, respectively. The formed ion-pairs are extracted with chloroform and methylene chloride and measured at 412 and 416 nm for BTB and BCG reagents, respectively. The third method is based on charge transfer complex formation between mosapride citrate (electron donor) and DDQ (π-acceptor reagent) and the absorbance of the CT complexes was measured at 450 nm. All the optimum conditions are established. The calibration graphs are rectilinear in the concentration ranges 10–350 for carbamazepine using Mo(V)–thiocyanate and 4–100, 4–60 and 10–150 μg mL^?1 for mosapride citrate using BTB, BCG and DDQ reagents, respectively. The Sandell sensitivity (S), molar absorptivity, correlation coefficient, regression equations and limits of detection (LOD) and quantification (LOQ) are calculated. The law values of standard deviation (0.04–0.09 for carbamazepine using Mo(V)–thiocyanate and 0.022–0.024, 0.013–0.018 and 0.013–0.020 for mosapride citrate using BTB, BCG and DDQ, respectively) and relative standard deviation (0.630–2.170 for carbamazepine using Mo(V)–thiocyanate and 0.123–1.43, 0.102–0.530 and 0.226–1.280 for mosapride citrate using BTB, BCG and DDQ, respectively) reflect the accuracy and precision of the proposed methods. The methods are applied for the assay of the two investigated drugs in pharmaceutical dosage forms. The results are in good agreement with those obtained by the official method.     

A new spectrophotometric method for the determination of finasteride in tablets

A simple, rapid, accurate, precise and sensitive colorimetric method for the determination of finasteride in tablets is described. The proposed methods are based on the formation of ion-pair complexes between the examined drug with bromophenol blue (BPB), bromocresol green (BCG) and bromothymol blue (BTB), which can be measured at the optimum lambda(max). Beer's law is obeyed in the concentration ranges 3.0-15.0, 3.0-15.0 and 5.0-20 microg/mL with BPB, BCG and BTB, respectively. The detection limits of FIN was found to be 1.16 microg/mL for BPB, 1.17 for BCG, 1.76 microg/mL for BTB. All the methods gave similar results and were validated for selectivity, linearity, precision and sensitivity. The proposed methods were directly and easily applied to the pharmaceutical preparation with accuracy, resulting from recovery experiments between 100.11 and 100.33% for BPB, 100.17 and 100.67% for BCG and 100.33 and 100.60% for BTB methods. The low relative standard deviation values indicate good precision and high recovery values indicate accuracy of the proposed methods. The proposed methods have been applied to the determination of drug in commercial tablets. Results obtained from the analysis of commercial preparations with the proposed methods are in good agreement with those obtained with the official HPLC method.     

Spectrophotometric determination of diphenhydramine hydrochloride in pharmaceutical preparations and biological fluids via ion-pair formation

A simple, sensitive and accurate spectrophotometric method has been described for the assay of diphenhydramine hydrochloride (DPH) in raw material and in biological samples. The method is based on extraction of DPH into dichloromethane as ion-pair complexes with patent blue (PB), eriochrome black T (EBT), methyl orange (MO) and bromocresol purple (BCP) in acidic medium. The coloured species exhibited absorption maxima at 632, 514, 428 and 414 nm for PB, EBT, MO and BCP, with molar absorptivity values of 1.32 × 10⁵, 2.36 × 10⁴, 3.68 × 10⁴ and 3.07 × 10⁴ l mol^?1 cm^?1, respectively. The reaction conditions were optimized to obtain the maximum colour intensity. Beer’s law was obeyed with a good correlation coefficient (0.9982–0.9993) in the concentration ranges 0.5–3, 2.0–16, 2.0–10 and 1.0–10 μg ml^?1 for PB, EBT, MO and BCP methods, respectively. The composition ratio of the ion-association complexes was found to be 1:1 in all cases as established by Job’s method. The conditional stability constant (K_f) and the free energy changes (ΔG°) were determined for all complexes formed. The proposed method was successfully applied for the determination of DPH in tablets and human urine with good accuracy and precision. Statistical comparison of the results with those obtained by the official method showed good agreement and indicated no significant difference in accuracy and precision.     

Extraction-spectrophotometric determination of amprolium hydrochloride using bromocresol green, bromophenol blue and bromothymol blue

A new procedure for the determination of amprolium hydrochloride by reaction with bromocresol green (BCG), bromophenol blue (BPB) and bromothymol blue (BTB) has been developed. The method consists of extracting the yellow ion-pair formed into chloroform from aqueous medium. The ion-pairs have absorption maxima at 420, 410 and 415 nm with molar absorptivities of 3.64 × 10⁴, 3.12 × 10⁴ and 2.31 × 10⁴1 mol^–1 cm^–1 for BCG, BPB and BTB, respectively. The method obeys Beer's law over the concentration ranges 0.6–12.0, 0.12–8.8 and 1.2–11.3 ag/ml amprolium hydrochloride for BCG, BPB and BTB, respectively. The method is simple, precise (relative standard deviation 0.665–2.210%), accurate (recovery 97.8–100.8%) and easily applied for pharmaceutical quality assurance for amprolium hydrochloride in raw materials and in formulated veterinary soluble powder.     

Spectrophotometric determination of gatifloxacin in pure form and in pharmaceutical formulation

Simple, rapid, and extractive spectrophotometric methods were developed for the determination of gatifloxacin (GT) in bulk and pharmaceutical dosage form. These methods are based on the formation of yellow ion-pair complexes between the basic nitrogen of the drug and three sulphonphthalein acid dyes, namely; bromocresol green (BCG), bromocresol purple (BCP), bromophenol blue (BPB) and bromothymol blue (BTB) in phthalate buffer pH 3.0, 3.4 and 3.2, using BCG, BCP and (BPB or BTB), respectively. The formed complexes were extracted with chloroform and measured at 415, 417, 412 and 414 nm for BCG, BPB, BCP and BTB, respectively. The analytical parameters and their effects on the reported systems are investigated. The reactions were extremely rapid at room temperature and the absorbance values remains unchanged at 48 h for all reactions. Beer's law was obeyed in the ranges 2.0-20, 2.0-14 and 2.0-16 microg mL(-1) for BCG, BCP and (BPB or BTB), respectively. The composition of the ion pairs was found 1:1 by Job's method. Beer's law validation, accuracy, precision, limits of detection, limits of quantification. The proposed methods have been applied successfully for the analysis of the drug bulk form and its dosage form. The results were in good agreement with those obtained by the official and reported methods.     

Spectrophotometric microdetermination of anti-Parkinsonian and antiviral drug amantadine HCl in pure and in dosage forms

Two simple, rapid, sensitive, low-cost, and accurate methods (A and B) for the microdetermination of amantadine HCl (AMD) in pure form and in pharmaceutical formulations are developed. Method A is based on the formation of tris (o-phenanthroline)-iron(II) complex (ferroin) upon reaction of amantadine HCl with an iron (III)-o-phenanthroline mixture in sodium acetate-acetic acid buffer media. The ferroin complex is spectrophotometrically measured at λ_max 509 nm against reagent blank. Method B is based on the reduction of Fe (III) by the drug which forms colored complex (λ_max 521 nm) with 2,2′-bipyridyl. Optimizations of the experimental conditions are described. Beer’s law is obeyed in the concentration ranges 0.4–10 and 0.6–22 μg mL^?1 using 1,10-phenanthroline and 2,2′-bipyridyl, respectively. The developed methods have been successfully applied for the determination of AMD in bulk drugs and in pharmaceutical formulations. The common excipients and additives did not interfere in their determinations.     

UV–Second Derivative Spectrophotometric and Colorimetric Methods for the Determination,Validation and Thermogravimetric Analysis of New Oral Antidiabetic Pioglitazone in Pure and Pharmaceutical Preparations

Abstract

Three rapid, sensitive, and simple spectrophotometric methods have been developed for the determination of pioglitazone in pure and pharmaceutical preparations.

For the first method, UV-spectrophotometry, standard solutions were measured at 270.2 nm. The first method was linear from 5.0–20.0 µgmL^?1. The linearity was found to be 5.0–20.0 µgmL^?1. For the second method, the distances between two extremum values (peak-to-peak amplitudes), 272.0 and 287.4 nm were measured in the second order derivative-spectra of standard solutions. Calibration curves were constructed by plotting d² A/dλ² values against concentrations, 2.0–12.0 µgmL^?1 of pioglitazone standards in acetonitrile. The detection limits of pioglitazone were 0.10 and 0.16 µgmL^?1 for UV and derivative spectrophotometric methods, respectively. The third method was based on the formation of an ion association complex with bromocresol green (BCG), bromocresol purple (BCP), bromophenol blue (BPB), and bromothymol blue (BTB). The assay was linear over the concentration range of 20.0–100.0 µgmL^?1 for BCG, 10.0–100.0 µgmL^?1 for BCP, 20.0–120.0 µgmL^?1 for BPB, and 10.0–100.0 µgmL^?1 for BTB. The detection limits of pioglitazone was found to be 0.14 µg mL^?1 for BCG, 0.32 for BCP, 1.24 µgmL^?1 for BPB, and 0.22 µgmL^?1 for BTB. The thermal analysis of the pioglitazone was studied by Thermogravimetric Analysis-Differential Scanning Calorimetry (TGA-DSC) techniques. Enthalpy change of pioglitazone was found to be 85.16 J/g. The proposed methods were validated according to the ICH guidelines (1996) with respect to specificity, linearity, limits of detection and quantification, accuracy, precision, and robustness. The results demonstrated that the procedure is accurate, precise, specific, and reproducible (percent relative standard deviation <2%), while being simple and less time consuming. The three proposed methods have been successfully applied to the assay of pioglitazone in pure and in pharmaceutical preparations. The results compared with those obtained by an ultraviolet spectrophotometric method using t and F tests.     

Simultaneous determination of five commercial cationic dyes in stream waters using diatomite solid-phase extractant and multivariate calibration

A simple spectrophotometric method was developed for the simultaneous determination of five commercial cationic dyes at 2.0?8.5 μg L^?1 level after using diatomite as solid-phase extractant. The method is based on preconcentration of the five dyes on natural diatomite solid-phase extractant and on multivariate calibration using partial least squares method (PLS-1). Compared with commonly used chromatographic or electrophoretic methods the developed method is simple and sensitive. With enrichment factors between 89 and 96, diatomite outperformed zeolite and activated carbon for dyes preconcentration. Before preconcentration and using PLS-1 method, the cationic dyes were simultaneously analyzed with linear ranges of 0.18–4.5, 0.32–5.0, 0.23–4.5, 0.45–8.0 and 0.82–12.0 mg L^?1 for crystal violet, malachite green, methylene blue, safranine O, and thioflavin T, respectively. The detection limits of dyes were estimated using Lorber’s method and found to be within the range 43–245 μg L^?1. The proposed SPE/PLS-1 method was applied to spiked stream water samples with good accuracy (79–91%) and precision (RSD 1.8–7.3%) but with slightly lower enrichment factors (80–92).     

Utility of oxidation–reduction reaction for the spectrophotometric determination of amlodipine besylate

A simple, rapid, accurate, precise and sensitive spectrophotometric method for the determination of amlodipine besylate (ADB) in bulk sample and in dosage forms is described. The method is based on oxidation of the drug by potassium permanganate in acidic medium and determine the unreacted oxidant by measuring the decrease in absorbance for five different dyes; methylene blue (MB), acid blue 74 (AB), acid red 73 (AR), amaranth dye (AM) and acid orange 7 (AO) at a suitable λ_max 663, 609, 511, 520, and 484 nm, respectively. Regression analysis of Beer's law plots showed good correlation in the concentration ranges 1.0–24, 0.9–22, 1.2–26, 0.9–12.8 and 1.0–14 μg ml^?1, respectively. The apparent molar absorptivity, Sandell sensitivity, detection and quantitation limits were calculated. For more accurate results, Ringbom optimum concentration ranges were 1.2–22.4, 1.1–20, 1.4–24.5, 1.0–12.3 and 1.3–13.2 μg ml^?1, respectively. Statistical treatment of the results reflects that the proposed procedures are precise, accurate and easily applicable for the determination of amlodipine besylate in pure form and in pharmaceutical preparations.     

Copper(II)–neocuproine reagent for spectrophotometric determination of captopril in pure form and pharmaceutical formulations

A simple, rapid, sensitive and accurate spectrophotometric method for the determination of captopril in pure form and pharmaceutical formulations is developed. The procedure is based on the reaction of copper(II) with captopril in the presence of neocuproine (NC) (2,9-dimethyl-1,10-phenanthroline) reagent in acetate buffer at pH 5.0. Copper(II) is reduced easily by captopril to Cu(I)–neocuproine complex, which shows an absorption maximum at 448 nm. Beer’s law was obeyed in the concentration range 0.3–3.0 μg mL^?1 with a minimum detection limit (LOD) of 0.039 μg mL^?1 and a quantification limit (LOQ) of 0.129 μg mL^?1. For more accurate results, Ringbom optimum concentration ranges was 0.5–2.7 μg mL^?1. The apparent molar absorbtivity and Sandell sensitivity were calculated. The validity of the proposed method was tested by analyzing the pure and pharmaceutical formulations and compared well with those obtained by the official method and demonstrated good accuracy and precision.     

Spectrophotometric determination of 6-aminopenicillanic acid using bromophenol blue and bromothymol blue

Two simple, selective and sensitive spectrophotometric methods are described for the determination of 6-aminopenicillanic acid (6-APA). The methods are based on the reaction of 6-APA with either bromophenol blue (BPB) or bromothymol blue (BTB), to give orange-red and green species, respectively. The coloured products are quantified spectrophotometrically at 625 and 616 nm for BPB and BTB, respectively. The optimization of the different experimental conditions is described. No interferences from different -lactams and common degradation products were observed in the determination of 6-APA using BTB, while flucloxacillin, dicloxacillin, adrenaline, vitamin C, urea and common degradation products in any percentage interfere on using BPB only. The BTB method was better than the BPB method, because of its wider range of determination (0.4–20 g ml^–1 vs. 0.4–7.2 g ml^–1 on using BPB), higher molar absorptivity and Sandell sensitivity (3.27 × 10³l mol^–1 cm^–1 and 0.099 g cm^–2 vs. 2.82 × 10³lmol^–1 cm^–1 and 0.115 g cm^–2), greater stability (3 and 10 days on using BTB and BPB, respectively) and better selectivity. The results were compared with those given by the Official United States Pharmacopeial XXI method.     

Spectrophotometric determination of sildenafil citrate in pure form and in pharmaceutical formulation using some chromotropic acid azo dyes

Two simple and highly sensitive spectrophotometric methods were developed for the quantitative determination of the drug sildenafil citrate (SC), Viagra, in pure form and in pharmaceutical formulations, through ion-associate formation reactions (method A) with mono-chromotropic acid azo dyes, chromotrope 2B (I) and chromotrope 2R (II) and ion-pair reactions (method B) with bi-chromotropic acid azo dyes, 3-phenylazo-6-o-carboxyphenylazo-chromotropic acid (III), bis-3,6-(o-hydroxyphenylazo)-chromotropic acid (IV), bis-3,6-(p-N,N-dimethylphenylazo)-chromotropic acid (V) and 3-phenylazo-6-o-hydroxyphenylazo-chromotorpic acid (VI). The reaction products, extractable in methylene chloride, were quantitatively measured at 540, 520, 540, 570, 600 and 575 nm using reagents, I–VI, respectively. The reaction conditions were studied and optimized. Beer's plots were linear in the concentration ranges 3.3–87.0, 3.3–96.0, 5.0–115.0, 2.5–125.0, 8.3–166.7 and 0.8–15.0 μg mL^?1 with corresponding molar absorptivities 1.02 × 10⁴, 8.34 × 10³, 6.86 × 10³, 5.42 × 10³, 3.35 × 10³ and 2.32 × 10⁴ L mol^?1 cm^?1 using reagents I–VI, respectively. The limits of detection and Sandell's sensitivities were calculated. The methods were successfully applied to the analysis of commercial tablets (Vigoran) and the recovery study reveals that there is no interference from the common excipients that are present in tablets. Statistical comparison of the results was performed with regard to accuracy and precision using Student's t- and F-tests at 95% confidence level. There is no significant difference between the reported and proposed methods with regard to accuracy and precision.     

Heteroassociation of the bromine-containing anions of sulfophthaleins in aqueous solution

The ability of bromine-containing anions of sulfophthalein dyes, such as bromophenol blue (BPB), bromocresol green (BCG), bromocresol purple (BCP), bromothymol blue (BTB), as well as non-substituted phenol red (PhR), to form heteroassociates in aqueous solution was investigated. Singly and doubly charged anions BPB, BCG, BCP, BTB, and PhR (HAn^-, An^2-) are capable of forming stable heteroassociates of composition Ct⁺•HAn^- and (Ct+)2•An^2- with cationic polymethine dyes (Ct+), such as pinacyanol and quinaldine red. The enthalpies of formation of the dye ions and heteroassociates were calculated by semiempirical methods, and the most probable structure of heteroassociates was determined.     

Design and characterization of Cu(II) complexes from 2-benzoylpyridine benzhydrazone: Crystallographic evidence for coordination versatility

The syntheses and characterization of six copper(II) complexes of 2-benzoylpyridine benzhydrazone in the form of [Cu(BPB)₂], [Cu(BPB)Cl]·H₂O, [Cu(BPB)Br], [Cu₂(BPB)₂](ClO₄)₂·4H₂O, [Cu(BPB)N₃]·H₂O, and [Cu(BPB)NCS]·H₂O·CH₃OH are reported. The analytical methods used for the characterization of complexes include partial elemental analyses, IR, electronic and EPR spectra, conductivity measurements, magnetic susceptibility measurements and single crystal X-ray diffraction. From the crystal structure, it is clear that the hydrazone adopts the E conformation about the azo bond to attach to the metal through the N_py–N_azo–O chelating system. In the EPR spectra of complexes in DMF at 77 K four hyperfine quartets in the parallel region could be resolved and a half field signal is observed at 1500 G for complex [Cu₂(BPB)₂](ClO₄)₂·4H₂O in polycrystalline state at 298 K which gives evidence for its binuclear nature indicating a weak interaction between the two Cu(II) ions.     

Quantitative determination of lansoprozole in capsules and spiked human urine by spectrophotometry through ion-pair complex formation reaction

Two simple, rapid and sensitive extraction-free spectrophotometric methods are proposed for the determination of lansoprazole (LAN) in bulk drug and in its capsule formulation. The methods are based on the interaction of LAN in dichloromethane (DCM) with acidic sulfonphthalein dyes, namely, bromocresol purple (BCP) in method A and bromothylmol blue (BTB) in method B to form stable, yellow-colored, ion-pair complexes peaking at 400 and 430 nm, respectively. The parameters that affect the reaction were carefully optimized, and under the optimized conditions, linear relationships were obtained in the ranges of 0.5–15.0 and 1.25–20.0 μg mL^?1 LAN for method A and method B, respectively. The molar absorptivity values are calculated to be 2.10 × 10⁴ and 1.50 × 10⁴ L mol^?1 cm^?1 for method A and method B, respectively. The composition of the ion-pairs was found to be 1:1 by Job’s method of continuous variations and the conditional stability constant (log K_f) of the complexes has been calculated. The proposed methods were applied successfully to the determination of LAN in capsules as well as in spiked urine sample with good accuracy and precision. The results obtained by the proposed methods were compared favorably with those of the reference method.     

Direct determination of bromine in plastic materials by means of solid sampling high-resolution continuum source graphite furnace molecular absorption spectrometry

This work investigates the potential of high-resolution continuum source graphite furnace molecular absorption spectrometry for the direct determination of bromine in polymers, which could be interesting in view of the current regulations restricting the use of organobrominated compounds. The method developed is based on the addition of Ca (300 μg) and Pd (30 μg) to favor the formation of CaBr, which is monitored at the main molecular “lines” (rotational spectra) found in the vicinity of 625.315 nm.It was found that accurate results could be obtained for all the samples investigated (polyethylene, polypropylene and acrylonitrile butadiene styrene certified reference materials) using any of the lines studied and constructing the calibration curve with aqueous standards. Furthermore, the combined use of the main four CaBr lines available in the spectral area simultaneously monitored permits to easily expand the linear range up to 2000 ng, provides a limit of detection of 1.8 ng (1.8 μg g^− 1 for a mass of 1 mg) and further improves precision to values between 3–7% RSD. Overall, the method proposed seems suited for the fast and simple control of these types of samples (approximately 10 min for sample are required), circumventing the traditional problems associated with sample digestion (e.g., losses of volatile compounds), and providing sufficient sensitivity to easily comply with regulations.     

New,simple and validated kinetics spectrophotometric method for determination of moxifloxacine in its pharmaceutical formulations

The objective of this research was to develop a kinetic spectrophotometric method for determination of moxifloxacine (MOXF) in pure form and pharmaceutical formulations. The method was based on the formation of a colored N-vinyl chlorobenzoquinone derivative of MOXF by its reaction with 2,3,5,6-tetrachloro-1,4-benzoquinone in presence of acetaldehyde.The formation of the colored product was monitored spectrophotometrically by measuring the absorbance at 652 nm. Factors affecting the reaction were studied and optimized. The stoichiometry of the reaction was determined, and the reaction pathway was postulated. The activation energy of the reaction was calculated and found to be 6.65 kJ mol^?1. Under the optimized conditions, the initial rate and fixed time (at 5 min) methods were utilized for constructing the calibration graphs. The graphs were linear in concentration ranges 5–100 and 15–150 μg ml^?1 with limit of detection of 2.0 and 5.0 μg ml^?1 for the initial rate and fixed time methods, respectively. The analytical performance for both methods was fully validated, and the results were satisfactory. No interference was observed from the excipients that are commonly present in the pharmaceutical formulations. The proposed method was successfully applied to the determination of MOXF in its pharmaceutical formulations. The label claim percentages were 101.25 ± 0.73% and 100.92 ± 0.65% for the initial rate and fixed time method, respectively. Statistical comparison of the results with those obtained by a reference spectrophotometric method showed excellent agreement between the accuracy and precision of the two methods. The proposed method has great value in its application to the analysis of MOXF in quality control laboratories.     

Molecular Stark-effect spectroscopy of Prodan and Laurdan in different solvents and electric dipole moments in their equilibrated ground and Franck–Condon excited state

The results from electrooptical absorption measurements (EOAM) on the ground and excited Franck–Condon state dipole moments of Prodan and Laurdan in 1,4-dioxane and cyclohexane are presented. The ground and excited Franck–Condon state electric dipole moments as well as the respective transition moment of both probes are parallel. The electric dipole moments of Prodan and Laurdan in the ground state in cyclohexane and 1,4-dioxane have values within the range (15.7–16.5) × 10⁻³⁰ C m. On optical excitation the dipole moments increase by (42.1–49.5) × 10⁻³⁰ C m. The obtained results are compared with the values of the dipole moments of Prodan and Laurdan determined by other methods.     

UV-absorption and fluorimetric methods for the determination of alprazolam in pharmaceutical formulation

The development of UV and fluorescence spectrophotometric methods for the quantitative determination of alprazolam in dosage forms using As(III)?SDS system. The two simple and sensitive, spectrophotometric and spectrofluorimetric methods were developed for the determination of alprazolam (ALP) in tablets. These methods are based on formation of ALP?As(III) complex in the presence of SDS. The UV-spectrum of 30% methanolic solution of ALP (5 × 10^?5 M) at pH 6.5 (Mclivaine buffer) was run between 200 and 380 nm. The absorption spectrum of ALP exhibits two peaks with a λ_max. at 255 nm and a weak band at 325 nm. When the spectra of the drug were run at varying pH in the region 200–380 nm, one isosbestic point at 290 nm was observed, which indicated the presence of two ionic conditions in solution. The complex exhibited an absorption maximum at 265 nm and emission peak at 520 nm with respect to the excitation wavelength of 325 nm. The spectrophotometric method was found to be linear in 8.0–17.0 μg ml^?1 range with detection limit of 13.520 μg ml^?1, while 0.05–9.5 μg ml^?1 range was with detection limit of 1.048 × 10^?2 μg ml^?1 by spectrofluorimetric method. The mean percentage recovery of the added quantity was found to be 99.54 (spectrophotometric method) and 100.22 (spectrofluorimetric method) and the %RSD are lower than 0.478 and 0.296 determined spectrophotomerically and spectrofluorimtrically, respectively. This indicates that the proposed method is accurate. The apparent ionization constant of ALP was found to be 9.29. The spectra, experimental conditions were set followed by determination stoichiometry, stability constant and thermodynamic parameters of the As(III), Co(II), Ni(II), and Zn(II) complexes with ALP at pH 6.5. The proposed methods have been successfully applied to the assay of ALP in tablets and the results were statistically evaluated.     

Simultaneous quantification of nimesulide,phenylpropanolamine, caffeine and chlorpheniramine in rat plasma by RP–HPLC/PDA method and application to pharmacokinetic studies in healthy rat subjects

Simultaneous determination of nimesulide, phenylpropanolamine, chlorpheniramine and caffeine in rat plasma by reversed-phase high performance liquid-chromatography (RP–HPLC) with photodiode array (PDA) detection method was developed and validated. Sample preparation based on a simple extraction procedure consisting of deproteination and extraction with methanol solution followed by volume make up with the aqueous component of the mobile phase obtained best recoveries of the analytes. The chromatographic conditions were optimized and the analytes were separated on XBridge™ C₁₈ (3.5 μm, 4.6 × 150 mm) column in isocratic elution with the mobile phase composition of acetonitrile and 10 mM ammonium acetate buffer (pH 4.0, 0.1% formic acid) (18:82 v/v%) at the flow rate of 1 mL min⁻¹ and the effluents were monitored in the wavelength range of 220–275 nm. The method was linear for all analytes over the following concentration (ng mL⁻¹) ranges: nimesulide 250–4000; phenylpropanolamine 100–1500; chlorpheniramine 20–500; and caffeine 10–100. Acceptable precision, accuracy and recoveries were obtained for quality control (QC) samples at three concentrations (low QC, middle QC and high QC). The percentage of relative standard deviation (% RSD) of Inter and intra-run precision of all molecules was <15% and the percentage of accuracy was 100 ± 10. The analytes were more stable in rat plasma at different storage conditions. Finally the method was efficiently applied to pharmacokinetics study in rat plasma.