Maha F. El-Tohamy

Determination of the anti‐viral drug Ribavirin in dosage forms via micelle‐enhanced spectrofluorimetric method

A simple and sensitive spectrofluorimetric method was developed for the determination of Ribavirin in pharmaceutical formulations. The proposed method was based on the fluorescence spectral behaviour of Ribavirin in a sodium dodecyl sulfate (SDS) micellar system. In an aqueous acetate buffer solution of pH 4.0, the fluorescence intensity of Ribavirin was significantly enhanced by about 217% in the presence of SDS. Fluorescence intensity was measured at 396 nm after excitation at 270 nm for Ribavirin. The fluorescence-concentration plot was rectilinear over the range of 0.01-3.0 µg/mL for Ribavirin with a lower detection limit of 5.02 x 10(-3) µg/mL. The method was successfully applied to the analysis of the drug in its commercial capsules. Results were in good agreement with those obtained with the official method. The application of the proposed method was extended to stability studies of Ribavirin after exposure to different forced degradation conditions such as acidic, alkaline, photo and oxidative conditions according to ICH guidelines.

Disposable screen-printed sensors for determination of duloxetine hydrochloride

A screen-printed disposable electrode system for the determination of duloxetine hydrochloride (DL) was developed using screen-printing technology. Homemade printing has been characterized and optimized on the basis of effects of the modifier and plasticizers. The fabricated bi-electrode potentiometric strip containing both working and reference electrodes was used as duloxetine hydrochloride sensor. The proposed sensors worked satisfactorily in the concentration range from 1.0 × 10-6-1.0 × 10-2 mol L-1 with detection limit reaching 5.0 × 10-7 mol L-1 and adequate shelf life of 6 months. The method is accurate, precise and economical. The proposed method has been applied successfully for the analysis of the drug in pure and in its dosage forms. In this method, there is no interference from any common pharmaceutical additives and diluents. Results of the analysis were validated statistically by recovery studies.

Application of silver nanoparticles to the chemiluminescence determination of cefditoren pivoxil using the luminol–ferricyanide system

A new simple, accurate and sensitive sequential injection analysis chemiluminescence (CL) detection method for the determination of cefditoren pivoxil (CTP) has been developed. The developed method was based on the enhancement effect of silver nanoparticles on the CL signal arising from a luminol-potassium ferricyanide reaction in the presence of CTP. The optimum conditions relevant to the effect of luminol, potassium ferricyanide and silver nanoparticle concentrations were investigated. The proposed method showed linear relationships between relative CL intensity and the investigated drug concentration at the range 0.001-5000 ng/mL, (r = 0.9998, n = 12) with a detection limit of 0.5 pg/mL and quantification limit of 0.001 ng/mL. The relative standard deviation was 1.6%. The proposed method was employed for the determination of CTP in bulk drug, in its pharmaceutical dosage forms and biological fluids such as human serum and urine. The interference of some common additive compounds such as glucose, lactose, starch, talc and magnesium stearate was investigated. In addition, the interference of some related cephalosporins was tested. No interference was recorded. The obtained sequential injection analysis-CL results were statistically compared with those from a reported method and did not show any significant differences.

A high throughput gold nanoparticles chemiluminescence detection of opioid receptor antagonist naloxone hydrochloride

AbstractBackgroundThe opioid antagonist agent naloxone hydrochloride (NLX) is a drug that has high affinity for opiate receptors but do not activate these receptors. Owing to the role of this drug to block the effects of exogenous administered opioids and endogenous released endorphians we can deduce the importance of developing sensitive analytical methods for detection of such drug. In the present study gold nanoparticles (AuNPs) was employed for enhancing the chemiluminescence (CL) signals arising from luminol-ferricyanide reaction in the presence of naloxone hydrochloride using sequential injection chemiluminescence analysis (SIA).MethodIn the present study gold nanoparticles (AuNPs) was employed for enhancing the chemiluminescence (CL) signals arising from luminol-ferricyanide reaction in the presence of naloxone hydrochloride using sequential injection chemiluminescence analysis (SIA).ResultsThe developed method was examined under optimum experimental conditions and the obtained results revealed a linear relationship between the relative CL intensity and the investigated drug at a concentration range of 1.0×10−9-1.0×10−2 mol L−1, (r = 0.9993, n=9) with detection and quantification limits of 1.6×10−11 and 1.0×10−9 mol L−1, respectively. The relative standard deviation was 0.9%.ConclusionThe proposed method was employed for the determination of the investigated drug in bulk powder, its pharmaceutical dosage forms and biological fluids. The interference of some metals and amino acids on the CL intensity was investigated. Also the interference of some related pharmacological action drugs was tested. The obtained results of the developed method were statistically treated and compared with those obtained from other reported methods. Graphical AbstractUtility of gold nanparticles in luminol-potassium ferricyanide chemiluminescence system for determination of naloxone hydrochloride.

A label-free electrochemical immunosensor based on gold nanoparticles and graphene oxide for the detection of tumor marker calcitonin

A label-free ultrasensitive electrochemical immunosensor has been designed for the detection of calcitonin, a medullary thyroid carcinoma tumor marker. The immunosensor was fabricated by deposition of gold nanoparticles and graphene oxide on the activated surface of a glassy carbon electrode. The incorporation of the nanocomposite leads to the increased surface area of the immunosensor, which translates into an enhanced sensitivity. The modified surface of the immunosensor improves the loading of anti-calcitonin capture antibody. Furthermore, the gold nanoparticles and graphene oxide nanocomposite are coupled with the sensor surface through aryldiazonium salts via covalent bonds, which stabilizes the sensing interface. The anti-calcitonin detection antibodies are immobilized on the sensor surface that is modified using ferrocene-graphene oxide molecules for detecting calcitonin level. The signal of the modified sensor is determined based on the shift of peak current, which is a consequence of the change in surface charge due to the antigen–antibody sandwich-type immunoreaction. Under optimized conditions, the output peak current shift was directly proportional to the calcitonin concentration, with a dynamic linearity range from 0.001 to 1.0 ng mL−1 and a detection limit as low as 0.7 pg mL−1. The designed immunosensor exhibited an acceptable selectivity for the detection of human calcitonin with a high sensitivity at low concentrations.

Eu(III)-Sensitized Luminescence Probe for Determination of Tolnaftate in Pharmaceuticals and Biological Fluids.

A highly selective, sensitive, accurate, and reproducible luminescence procedure for determination of antifungal drug tolnaftate was developed. The introduced method was based on the formation of Europa Universalis III (Eu(III))-tolnaftate complex using sodium sulfite as a deoxygenated agent in the presence of acetate buffer (pH = 6) and micellar solution of anionic surfactant sodium dodecyl sulfate. The optimum conditions (effect of pH, buffer, surfactant, Eu(III), and sodium sulfite concentrations) for the luminescence signal were investigated and optimized. The luminescence signals were recorded at λex = 270 nm and λem = 460 nm. The method has a good linear response (0.2-130 μg/mL(-1)) between the luminescence intensity and the concentrations of the drug (r = 0.999), with a LOD 0.07 μg/mL(-1) and LOQ 0.2 μg/mL(-1). The luminescence signals of Eu (III)-tolnaftate-sodium dodecyl sulfate were found to be 200-fold more sensitive without the presence of micelle solution. The interferences of some additives, metals, amino acids, sugars, and other related pharmacological action drugs were examined and no interference was recorded. The proposed method was used for quick and simple determination of tolnaftate in its pharmaceuticals and biological fluids.

Gold nanoparticle-enhanced luminol/ferricyanide chemiluminescence system for aristolochic acid-I detection in medicinal plants and slimming products

ABSTRACT Aristolochic acid-I (AA-I) is commonly present as a natural product in medicinal plants such as Asarum and Radix aristolochiae. The misuse of some slimming products and dietary, supplements containing AA-I as a regulator has been reported to cause cancer, acute hepatitis and renal failure. Hence, quality control and quantification of AA-I in these products at a trace level are significantly necessary. In this approach, a simple and accurate sequential injection analysis (SIA) chemiluminescence (CL) detection method was employed for AA-I determination. Gold nanoparticles were used to enhance the CL signal of luminol-ferricyanide-AA-I reaction. The results showed that the proposed method displayed linear relationship of 10–20,000 ng mL−1, (r = 0.9992) with 10 and 3  ng mL−1 as the minimum quantification and detection limits, respectively. The possible interferences such as some common metals, additives and related pharmacological action compounds were tested. The recorded SIA-CL results were statistically assessed and compared to those obtained from other published methods. GRAPHICAL ABSTRACT

Utility of gold nanoparticles in luminescence determination of trovafloxacin: comparison of chemiluminescence and fluorescence detection

Two novel sensitive sequential injection chemiluminescence analysis and fluorescence methods for trovafloxacin mesylate detection have been developed. The methods were based on the enhancement effect of gold nanoparticles on luminol-ferricyanide-trovafloxacin and europium(III)-trovafloxacin complex systems. The optimum conditions for both detection methods were investigated. The chemiluminescence signal was emitted due to the enhanced effect of gold nanoparticles on the reaction of luminol-ferricyanide-trovafloxacin in an alkaline medium. The response was linear over a concentration range of 1.0 × 10(-9) to 1.0 × 10(-2) mol/L (%RSD = 1.3), (n = 9, r = 0.9991) with a detection limit of 1.7 × 10(-10) mol/L (S/N = 3). The weak fluorescence intensity signal of the oxidation complex of europium(III)-trovafloxacin was strongly enhanced by gold nanoparticles and detected at λex = 330 and λem = 540 nm. Fluorescence detection enabled the determination of trovafloxacin mesylate over a linear range of 1.0 × 10(-8) to 1.0 × 10(-3) mol/L (%RSD = 1.2), (n = 6, r = 0.9993) with a detection limit of 3.3 × 10(-9) mol/L. The proposed methods were successfully applied to the determination of the studied drug in its bulk form and in pharmaceutical preparations. The results were treated statistically and compared with those obtained from other reported methods.

A SENSITIVE SEQUENTIAL INJECTION ANALYSIS (SIA) DETERMINATION OF MEMANTINE HYDROCHLORIDE USING LUMINOL-HYDROGEN PEROXIDE INDUCED CHEMILUMINESCENCE DETECTION

ABSTRACT A fully automated sequential injection analysis (SIA) method for chemiluminescence (CL) determination of Al-zheimer’s drug memantine hydrochloride was developed and presented. The employing of SIA injection analysis facilitates fluidic handling and lowering the consumption of sample and reagents. The basic CL reaction was based on the emission of CL radiation due to the reaction of luminol with hydrogen peroxide in basic medium. The CL emission has been monitored using FIAlab system. The optimum conditions and characterizations were optimized using a computer-aided simplex method. Under the optimal conditions the linear calibration graph was obtained within the range of 0.0001-1.0 µg mL -1 , (r=0.9996) with detection limit of 3.3x10 -5 µg mL along with relative standard deviation 1.8 % (n). The flow rates were 120 -1µL s -1 , for the aspiration into the holding coil and 80 µL s for detection. The sample frequency throughput was 103 h -1 . The proposed CL method was successfully applied for determination of the tested drug in pure form and its pharmaceutical formulations. The interference of some common additive compounds such as glucose, lactose, starch, talc and magnesium stearate was investigated. No interference was recorded. The obtained SIA results were statistically compared with those obtained from a reported method and did not show any significant difference.

ELECTROCHEMICAL SENSORS FOR DIRECT DETERMINATION OF SIMVASTATIN IN PHARMACEUTICAL FORMULATIONS AND BIOLOGICAL FLUIDS

The construction and performance characteristics of simvastatin (SIM) selective electrodes were developed. Three types of electrodes: plastic membrane I, coated wire II, and coated graphite rod III were constructed based on the incorporation of simvastatin with phosphotungstic (PTA) or phosphomolybdic (PMA) acids and mixed ion pair (PTA/PMA) for the three electrodes, respectively. The influence of membrane composition, kind of plasticizer, type of ion-pair, pH of the test solution, soaking time, and foreign ions on the electrodes was investigated. The electrodes showed a Nernstain response with a mean calibration graph slope of 56.24±0.43, 55.44±0.14 and 58.93±0.34 mV decade-1 at 25oC over simvastatin concentration range from 1.0 x 10-6-5.0 x 10-2, 9.0 x 10-6-5.0 x 10-3 and 9.0 x 10-7-1.0 x 10-2 mol L-1, with detection limit of 5.0 x 10-7, 3.9 x 10-6 and 3.2 x 10-7 mol L-1 for electrode I, II and III, respectively. The pH range for the proposed electrodes was 4-7. The influence of possible interfering species such as common inorganic cations, many sugars, amino acids and a pharmacologically related drug ‘ezetimibe’ was studied. Statistical student’s t-test and F test showed insignificant systematic error between proposed and official methods.