Fakhr Eldin O. Suliman

A sequential injection method for the determination of aluminum in drinking water using fluorescence enhancement of the aluminum-morin complex in micellar media

Abstract A robust and simple sequential injection (SI) method for the assay of aluminum ions in natural water is described. The method is based on the enhancement of the fluorescence of the aluminum–morin complex in the presence of a non-ionic surfactant (Tween-20). The fluorescence of the complex is monitored at an emission wavelength of 495 nm with excitation at 425 nm. The pH, morin concentration and the aspirated sample volume were optimized simultaneously using a chemometric method. The optimum operating conditions are: 150 μl aspirated sample volume, 20 μM morin concentration, a pH of 4.5 and 0.8% Tween-20. Using these optimum conditions a linear calibration curve was obtained from 50 to 1000 ppb. The detection limit was 3 ppb and the maximum relative standard deviation (n=5) of the method was 2.9%. The method was successfully applied for the determination of aluminum ions in natural water samples.

A sequential injection spectrophotometric method for the determination of penicillamine in pharmaceutical products by complexation with iron(III) in acidic media

A simple, robust and sensitive sequential injection spectrophotometric method for the assay of penicillamine (PA) in pharmaceutical formulations is developed. The method was based on the complex formation when PA is reacted with iron(III) solution in hydrochloric acid media. The deep blue colored PA-iron(III) complex produced is monitored at a maximum wavelength of 600 nm. A five level orthogonal array design coupled to genetic algorithm was employed to obtain the optimum experimental conditions for the determination of PA using peak absorbance as the measure of the systems performance criterion. A linear dynamic range for the determination of PA of 25-300 ppm was obtained with a sampling frequency of 50 h(-1) and a relative standard deviation of less than 0.98%. The method was successfully applied to the determination of PA in pharmaceutical formulations.

A sequential injection method for the determination of piroxicam in pharmaceutical formulations using europium sensitized fluorescence.

A simple, selective and sensitive luminescence method for the assay of piroxicam (PX) in pharmaceutical formulation is developed. The method is based on the luminescence sensitization of europium (Eu(3+)) by complexation with PX. The signal for PX-EU is monitored at lambda(ex)=358nm and lambda(em)=615nm. Optimum conditions for the formation of the complex in methanol were 0.01M TRIS buffer and 0.2mM of Eu(3+) which allows the determination of 100-2000ppb of pX in batch method and 100-1000ppb with limit of detection (LOD) = 23.0ppb using sequential injection analysis (SIA). The relative standard deviations of the method range between 2 and 3% indicating excellent reproducibility of the method. The proposed method was successfully applied for he assay of PX in pharmaceutical formulations (Feldene capsules and tablets). Average recoveries of 101.0+/-0.3 and 98.8+/-2.7% were obtained for capsules in methanol using batch and sequential injection (SI) methods, respectively.

Determination of aminoglutethimide enantiomers in pharmaceutical formulations by capillary electrophoresis using methylated-β-cyclodextrin as a chiral selector and computational calculation for their respective inclusion complexes

A capillary electrophoretic method for the separation of the aminoglutethimide (AGT) enantiomers using methylated-beta-cyclodextrin (M-beta-CD) as chiral selector is described. Several parameters affecting the separation were studied, including the type and concentration of chiral selector, buffer pH, voltage and temperature. Good chiral separation of the racemic mixture was achieved in less than 9 min with resolution factor Rs=2.1, using a fused-silica capillary and a background electrolyte (BGE) of tris-phosphate buffer solution (50 mmol L(-1), pH 3.0) containing 30 mgm L(-1) of M-beta-CD. The separation was carried out in normal polarity mode at 25 degrees C, 16 kV and using hydrostatic injection. Acceptable validation criteria for selectivity, linearity, precision, and accuracy/recovery were included. The proposed method was successfully applied to the assay of AGT enantiomers in pharmaceutical formulations. The computational calculations for the inclusion complexes of the R- and S-AGT-M-beta-CD rationalized the reasons for the different migration times between the AGT enantiomers.

Enhancement of on chip chemiluminescence signal intensity of tris(1,10-phenanthroline)-ruthenium(II) peroxydisulphate system for analysis of chlorpheniramine maleate in pharmaceutical formulations.

The effect of detection chip geometry on chemiluminescence (CL) signal intensity of tris(1,10-phenanthroline)-ruthenium(II) peroxydisulphate system for analysis of chlorpheniramine maleate (CPM) in pharmaceutical formulations was investigated. It was observed that the design of the detection chip is very crucial and can play an important role in enhancing the CL signal intensity in this system. The CL signal intensity was enhanced 250% when a teardrop micromixer chip was used, compared to the commonly used serpentine chip geometry. The study was conducted using a multi-chip device. In this device, chip 1 was used to prepare and pump the reagent mixture, whereas chip 3 was used for pumping the sample. The two chips were connected to the teardrop chip (2) via silica capillary where detection took place. Non-linear regression curve fitting of the calibration data revealed that the calibration curves are best described by third order polynomial equation with excellent correlation coefficients (R(2)=0.9998) for the concentration range 7.69 × 10(-8) to 5.12 ×1 0(-5)mol L(-1). A linear response is also observed over the range 7.69 × 10(-8) to 1.28 × 10(-5)mol L(-1) (R(2)=0.9996) and the detection limit was found to be 5.49 × 10(-8)mol L(-1). The device was successfully used for the analysis of CPM in tablets and a multi-component cough syrup. Results were reproducible with relative standard deviation (RSD) of 0.6-1.1%.

Fluorimetric Determination of Aluminium using Sequential Injection Analysis (SIA): State of Our Art and Future Developments

Abstract This paper describes some of our recent advances and proposed future work in the area of fluorimetric determination of Al using sequential injection analysis (SIA). A rapid, automated system was developed with turnover times for sample analysis of <2 min, and attainable limits of detection of <1 ng/mL. The method is cost‐effective and highly competitive. It utilizes three different approaches: (i) molecular imprinted polymers (MIPs); (ii) micellar enhanced treatment; and (iii) renewable surface application. The merits and limitations of each approach are discussed, and the optimum conditions of analysis are presented. The overall sensitivity achieved was more than adequate for general analysis. Proposed new developments involve greater signal enhancement, and improved analytical strategy. The facility is capable of routine application, and is highly beneficial to developing countries in need of cost‐effective techniques for analysis of environmental samples, body fluids, and foodstuffs.

Capillary electrophoretic separation and computational modeling of inclusion complexes of β-cyclodextrin and 18-crown-6 ether with primaquine and quinocide

The antimalarial drug primaquine (PQ) and its contaminant, the positional isomer quinocide (QC) have been successfully separated using capillary electrophoresis with either beta-cyclodextrin (beta-CD) or 18-crown-6 ether (18C6) as chiral mobile phase additive. The interactions of the drugs with cyclodextrins and 18C6 were studied by the semiempirical method (Parametric Model 3) PM3. Theoretical calculations for the inclusion complexes of PQ and QC with alpha-CD, beta-CD and 18C6 were performed. Data from the theoretical calculations are correlated and discussed with respect to the electrophoretic migration behavior. More stable complexes are predicted for the PQ-beta-CD and PQ-18C6 complexes. The coelution of PQ and QC when alpha-CD was used as buffer additive can be explained by their comparable stabilities of the inclusion complex formed, while significant differences in the complexation stabilities of the drugs with beta-CD is responsible for their separation. The stronger hydrogen bonding in PQ-18C6 system is responsible for the separation between PQ and QC when 18C6 was used as chiral mobile phase additive.

Chemiluminescence determination of chlorpheniramine using tris(1,10-phenanthroline)–ruthenium(II) peroxydisulphate system and sequential injection analysis

A sequential injection (SI) method was developed for the determination of chlorpheniramine (CPA), based on the reaction of this drug with tris(1,10-phenanthroline)-ruthenium(II) [Ru(phen)(3)(2+)] and peroxydisulphate (S(2)O(8)(2-)) in the presence of light. The instrumental set-up utilized a syringe pump and a multiposition valve to aspirate the reagents [Ru(phen)(3)(2+) and S(2)O(8)(2-)] and a peristaltic pump to propel the sample. The experimental conditions affecting the chemiluminescence reaction were systematically optimized, using the univariate approach. Under the optimum conditions linear calibration curves of 0.1-10 microg/ml were obtained. The detection limit was 0.04 microg/ml and the relative standard deviation (RSD) was always < 5%. The procedure was applied to the analysis of CPA in pharmaceutical products and was found to be free from interferences from concomitants usually present in these preparations.

Enhancement of the chemiluminescence of penicillamine and ephedrine after derivatization with aldehydes using tris(bipyridyl)ruthenium(II) peroxydisulfate system and its analytical application

A novel sequential injection (SI) method was developed for the determination of penicillamine (PA) and ephedrine (EP) based on the reaction of these drugs with tris(bipyridyl)ruthenium(II) (Ru(bpy)(3)(2+)) and peroxydisulfate (S(2)O(8)(2-)) in the presence of light. Derivatization of PA and EP with aldehydes has resulted in a significant enhancement of the chemiluminescence emission signal by at least 25 times for PA and 12 times for EP, leading to better sensitivities and lower detection limits for both drugs. The instrumental setup utilized a syringe pump and a multiposition valve to aspirate the reagents, (Ru(bpy)(3)(2+) and S(2)O(8)(2-)), and a peristaltic pump to propel the sample. The experimental conditions affecting the derivatization reaction and the chemiluminescence reaction were systematically optimized using the univariate approach. Under the optimum conditions linear calibration curves between 0.2-24 microgmL(-1) for PA and 0.2-20 microgmL(-1) for EP were obtained. The detection limits were 0.1 microgmL(-1) for PA and 0.03 microgmL(-1) for EP. The procedure was applied to the analysis of PA and EP in pharmaceutical products and was found to be free from interferences from concomitants usually present in these preparations.

Spectrofluorimetric determination of aluminium using 2-hydroxy-1-naphthylidene-(8-aminoquinoline)

A sensitive and selective spectrofluorimetric method has been developed for the rapid determination of aluminium. This method is based on the complex formation between aluminium and 2-hydroxy-1-naphthylidene-(8-aminoquinoline) (HNAQ). The optimum conditions for the complex formation were a metal-to-ligand (M : L) stoichiometric ratio of 1:1, a pH of 5.5 and a 0.20 m acetate buffer. The fluorescence of the complex was monitored at an emission wavelength of 502 nm with excitation at 438 nm. Under these conditions, linear calibration curves were obtained in the ranges 0.05-1 and 1-5 ppm. The detection limit was 3.4 ppb for the former and 13.5 ppb for the latter. The maximum relative standard deviation of the method for an aluminium standard of 200 ppb was 1.5% (n = 5). This method was successfully applied for the determination of aluminium in drinking water, pharmaceutical antacid tablets and suspension samples.