Amr L. Saber

On-line solid phase extraction coupled to capillary LC-ESI-MS for determination of fluoxetine in human blood plasma

An instrumental setup including on-line solid phased extraction coupled to capillary liquid chromatography-electrospray ionization-mass spectrometry (SPE-capLC-ESI-MS) has been constructed to improve the sensitivity for quantification of fluoxetine hydrochloride in human plasma. Prior to injection, 0.5 mL of plasma spiked with metronidazole (internal standard) was mixed with ammonium formate buffer for effective chloroform liquid-liquid extraction. The method was validated in the range 5-60 ng mL(-1) fluoxetine, yielding a correlation coefficient of 0.999 (r(2)). The within-assay and between-assay precisions were between (8.5 and 11%) and (6.6 and 7.5%), respectively. The method was used to determine the amount of fluoxetine in a healthy male 14 h after an intake of one capsule of the antidepressant and anorectic Flutin, which contains 20mg fluoxetine per each capsule. Fluoxetine was detected, and the concentration was calculated to 9.0 ng mL(-1) plasma. In the preliminary experiments, conventional LC-UV instrumentation was employed. However, it was found that employing a capillary column with an inner diameter of (0.3mm I.D. x 50 mm, Zorbax C(18)) increased the sensitivity by a factor of approximately 100, when injecting the same mass of analyte. Incorporating an easily automated C(18) reversed phase column switching system with SPE (1.0mm I.D. x 5.0mm, 5 microm) made it possible to inject up to 100 microL of solution, and the total analysis time was 5.5 min.

Study on solid phase extraction and spectrophotometric determination of vanadium with 2,3-dichloro-6-(2,7-dihydroxy-1-naphthylazo)quinoxaline

A sensitive, selective and rapid method has been developed for the determination micrograms per liter level of vanadium ion based on the rapid reaction of vanadium(V) with 2,3-dichloro-6-(2,7-dihydroxy-1-naphthylazo)quinoxaline (DCDHNAQ) and the solid phase extraction of the colored complex with C18 cartridge. The DCDHNAQ reacts with V(V) in the presence of citric acid-sodium hydroxide buffer solution (pH 3.3) and benzyldimethyl tetradecylammonium chloride (zephiramine) medium to form a violet complex of a molar ratio 1:2 [V(V) to DCDHNAQ]. This complex was enriched by solid phase extraction with C18 cartridge and the enrichment factor of 100 was obtained by elution of the complex from the cartridge with acetonitrile. The molar absorptivity and Sandell sensitivity of the complex are 2.45x10(5) L mol(-1) cm(-1) and 0.0208 ng cm(-2) at 573 nm in the measured solution. Beers law is obeyed in the range of 0.01-0.45 microg mL(-1), whereas Ringbom optimum concentration ranges found to be 0.025-0.425 microg mL(-1). The detection and quantification limits are 3.2 and 9.9 microg L(-1), respectively in the original samples. This method was applied to the determination of vanadium(V) in steel, soil, water and biological samples with good results.

Three Spectrophotometric Methods for the Determination of Oxomemazine Hydrochloride in Bulk and in Pharmaceutical Formulations Using Bromocresol Green, Congo Red, and Methyl Orange

Abstract Three simple, sensitive, and highly accurate spectrophotometric methods have been developed for the determination of oxomemazine hydrochloride (OXO‐HCl) in bulk and in pharmaceutical formulations. These methods are based on the formation of yellow ion‐pair complexes between the examined drug and bromocresol green (BCG), congo red (CR), and methyl orange (MO) as reagents in universal buffer solution of pH 3.0, 5.5, and 3.5, respectively. The formed complexes were extracted with chloroform and measured at 413, 495, and 484 nm, respectively for the three systems. The best conditions of the reaction were studied and optimized. Beers law was obeyed in the concentration ranges 2.0–18.0, 2.0–14.0, and 2.0–16.0 µg ml−1 with molar absorptivity of 4.1×104, 1.1×104, and 3.5×104 mol−1cm−1, for the BCG, CR, and MO methods, respectively. Sandells sensitivity, correlation coefficient, detection, and quantification limits are also calculated. The proposed methods have been applied successfully for the analysis of the drug in pure and in its dosage forms. No interference was observed from common pharmaceutical excipients and additives. Statistical comparison of the results with those obtained by HPLC method shows excellent agreement and indicates no significant difference in accuracy and precision.

Selective potentiometric method for determination of flucloxacillin antibiotic

Abstract A new and rapid potentiometric method for determination of flucloxacillin is developed. The method involves development of a flucloxacillin sensor with a membrane consisting of Aliquat 336S-flucloxacillin as an electroactive material in poly vinyl chloride matrix membrane plasticized with orthonitrophenyl-octylether or dioctylphthalate. The sensor shows fast, stable and reproducible response over the concentration range of 1.0 × 10−5–1.0 × 10−2 M flucloxacillin with anionic slopes of 60.7 ± 0.3 and 61.2 ± 0.2 and pH ranges of 6–11 and 7–11 for o-nitrophenyloctylether (o-NPOE) and dioctylphthalate (DOP) plasticized based membrane sensors, respectively. The response time of the sensor is stable and fast (7 s). The sensor exhibits high selectivity towards flucloxacillin in presence of amoxicillin, ampicillin, dicluxacillin, pencillin, many anions and drug excipients and diluents. Validation of the method according to the quality assurance standards shows suitability of the proposed sensors for use in the quality control assessment of the drug. Results with average recoveries of 99.6% and 99.7% and mean standard deviations of ±1.2% and ±1.5% for o-NPOE and DOP plasticized based membrane sensors, respectively, of the nominal are obtained which compare fairly well with data obtained using the British Pharmacopoeia method.

Utility of Ion-Pair and Charge Transfer Complexation for Spectrophotometric Determination of Domperidone and Doxycycline in Bulk and Pharmaceutical Formulations

Four simple, sensitive, and accurate spectrophotometric methods (A-D) have been developed for the determination of domperidone (I) and doxycycline (II) in bulk and in pharmaceutical formulations. The first two methods (A and B) are based on the formation of yellow ion-pair complexes between the examined drugs with bromocresol green (BCG) and methyl orange (MO) as chromophoric reagents in Britton-Robinson (B-R) universal buffer of pH 3.0 and 2.2, respectively. The formed complexes were extracted with chloroform and measured at 420 nm and 424 nm for I and II using BCG, respectively and 480 nm for the studied drugs using MO. The last two methods (C and D) are based on charge transfer complex formation between the studied drugs and tetracyanoethylene (TCNE); and 7,7,8,8-tetracyanoquinodimethane (TCNQ). Different variables affecting the reactions were studied and optimized. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9992 - 0.9998) were found between the absorbance and the concentration of I in the range of 1.4-22.4μg mL −1 , whereas that for II in the range 1.4-25.5μg mL −1 . For more accurate analysis, Ringbom optimum concentration range was found to be between 3.0-21.5 and 3.0-23.5μg mL −1 , for I, and II, respectively. Sandell’s sensitivity, correlation coefficient, and limits of detection and quantification were calculated for each method. A Job’s plot of the absorbance versus the molar ratio of drug to each of formed complex under consideration indicated (1:1) ratio. No interference was observed from common pharmaceutical excipients and additives. Statistical comparison of the results with those obtained by the official method shows excellent agreement and indicates no significant difference in accuracy and precision.

Utility Spectrophotometric and Chromatographic Methods for Determination of Antidepressant Drug Sulpiride in Pharmaceutical Formulations and Plasma

Validated spectrophotometric and chromatographic methods have been developed for determination of the antidepressant drug sulpiride (SUL) in pharmaceutical formulation and plasms. The new spectrophotometric methods were based on the formation of sulpiride yellow ion-pair complex with bromocresol green (BCG), congo red (CR) or methyl orange (MO) in Britton-Robinson universal buffer of pH 3.0, 5.0 or 2.5, respectively. The formed complexes with BCG, CR and MO were extracted with chloroform and their absorbencies were measured at 420 nm, 515 nm, and 480 nm, respectively. Beer’s law was obeyed over the concentration ranges of 2-14.0, 2-16.0, and 2-14.0 μg/ mL sulpiride with BCG, CR and MO, respectively. The molar absorpativity (e) of the formed colored complexes with BCG, CR and MO was 4.10×104, 2.10×104 and 3.50×104 L moL-1 cm-1 and the estimated limit of detection (LOD) of sulpiride was found to be 0.044, 0.095 and 0.064 μg/mL, respectively. In the developed high performance liquid chromatographic method (HPLC), quantitation of sulpiride was carried out on C18 reversed phase column (250×4.0 mm, 5 μm) using a mobile phase of acetonitril: methanol: water: Britton-Robinson (B-R) universal buffer of pH 9 (20: 20: 40: 20, v/v/v/v) delivered at a flow rate of 0.6 mL/min with UV-detection at 225 nm. Calibration graph of bulk sulpiride was linear over the concentration range of 0.034-110 μg/mL. The described spectrophotometric and HPLC methods have been applied successfully for the analysis of sulpiride in its dosage form without interference from common excipients. Statistical comparison of their results with those obtained using a reported membrane selective electrode method showed excellent agreement and indicated no significant differences in accuracy and precision.

Novel Ionophore for Aluminum Ion Sensors: Synthesis and Analytical Characterization

A new and rapid potentiometric method to quantify aluminum ions concentration was developed. The method involves the development of an aluminum ion sensor with a membrane consists of diethyl (2-azobenzoic acid) malonate (DAM) as a novel ionophore in poly (vinyl chloride) matrix membrane plasticized with orthonitrophenyl-octyl ether or dioctylphthalate. The structure of the synthesized ionophore (DAM) was identified using Fourier transform infrared, ¹H Nuclear magnetic resonance, and elemental analysis. The proposed electrode reveals a Nernstian response over Al³⁺ ion in a concentration range 1 × 10^-7-1 × 10^-2 mol L^-1 with the cationic slopes of 19.6 ± 0.3 and 19.3 ± 0.2 mV decade^-1, and the limits of detection 5 × 10^-8 and 7 × 10^-8 mol L^-1 aluminum(III) for orthonitrophenyl-octyl ether and dioctylphthalate-based membrane sensors, respectively. The electrodes showed good discrimination toward Al³⁺ ion in the presence of the most common cations. The electrodes show response in a short time (10 s) for the entire concentration range and used for 11 weeks without significant variation in potentials. To evaluate the application of the investigated electrodes was used to determine Al³⁺ ion at different collected samples from environmental sources. In addition, these sensors have been used as indicator electrodes in the potentiometric titration of Al³⁺ ion against Ethylenediaminetetraacetic acid.