Indirect spectrophotometric determination of sulfadiazine based on localized surface plasmon resonance peak of silver nanoparticles after cloud point extraction.

A novel, efficient, easy to use, environmentally friendly and cost-effective methodology is developed for the indirect spectrophotometric determination of sulfadiazine in different samples. The method is based on the micelle-mediated extraction of silver sulfadiazine and converting the silver content of the resultant surfactant-rich phase to the silver nanoparticles via generation of [Ag(NH3)2]+ followed by its chemical reduction using ascorbic acid. The changes in the amplitude of localized surface plasmon resonance peak of silver nanoparticles as a function of sulfadiazine concentration in the sample solution was monitored using fiber optic linear array spectrophotometry at 457nm. The experimental conditions were thoroughly investigated and optimized. Under the optimized condition, the developed procedure showed dynamic linear calibration within the range of 10.0-800.0µgL-1 with a detection limit of 2.8µgL-1 for sulfadiazine. The relative standard deviation of the method for six replicate measurements at 150.0µgL-1 of sulfadiazine was 4.7%. The developed method was successfully applied to the determination of sulfadiazine in different samples including well water, human urine, milk and pharmaceutical formulation.

A novel sensor for determination of naproxen based on change in localized surface plasmon peak of functionalized gold nanoparticles.

A highly selective and sensitive colorimetric sensor for the determination of naproxen (NAP) based on the aggregation of the thiolated ß-cyclodextrin (Tß-CD) functionalized gold nanoparticles (Tß-CD-Au NPs) in the presence of NAP and Zn2+is described. The hydrophobic end of NAP interacts with the immobilized Tß-CD on the Au NPs and forms the complex of Tß-CD:NAP while the Zn2+ ions form a 1:2 complex of (NAP)2Zn with the carboxyl groups of NAP resulting in the aggregation of functionalized gold nanoparticles. As a result of aggregation, the localized surface plasmon resonance (LSPR) band of functionalized gold nanoparticles around 520nm decreases and a new red shifted band at 650nm appears which increases gradually as the function of NAP concentration. The calibration graph derived from the intensity ratios of absorbance at 650nm to 520nm was linear in the concentration range of 4-180µgL-1of NAP. At the optimum conditions, the limit of detection (LOD) and quantification (LOQ) were found to be 0.6 and 2.1µgL-1, respectively and the relative standard deviation at 20µgL-1of NAP (n=5) was 2.5%. The selectivity and applicability of the method was verified through analyzes of the synthetic samples containing the major interference compounds reported in literature as well as tablets, wastewater and urine samples. The accuracy of the method was evaluated by recovery experiments and analysis of pharmaceutical tablets.

Development of a novel method for determination of mercury based on its inhibitory effect on horseradish peroxidase activity followed by monitoring the surface plasmon resonance peak of gold nanoparticles.

A highly sensitive and simple indirect spectrophotometric method has been developed for the determination of trace amounts of inorganic mercury (Hg(2+)) in aqueous media. The method is based on the inhibitory effect of Hg(2+) on the activity of horseradish peroxidase (HRP) in the oxidation of ascorbic acid by hydrogen peroxide followed by the reduction of Au(3+) to Au-NPs by unreacted ascorbic acid and the measurement of the absorbance of localized surface plasmon resonance (LSPR) peak of gold nanoparticles (at 530 nm) which is directly proportional to the concentration of Hg(2+). Under the optimum conditions, the calibration curve was linear in the concentration range of 1-220 ng mL(-1). Limits of detection (LOD) and quantification (LOQ) were 0.2 and 0.7 ng mL(-1), respectively and the relative standard deviation at 100 ng mL(-1) level of Hg(2+) was 2.6%. The method was successfully applied to the determination of mercury in different water samples.

Artificial neural network assisted kinetic spectrophotometric technique for simultaneous determination of paracetamol and p-aminophenol in pharmaceutical samples using localized surface plasmon resonance band of silver nanoparticles.

Spectrophotometric analysis method based on the combination of the principal component analysis (PCA) with the feed-forward neural network (FFNN) and the radial basis function network (RBFN) was proposed for the simultaneous determination of paracetamol (PAC) and p-aminophenol (PAP). This technique relies on the difference between the kinetic rates of the reactions between analytes and silver nitrate as the oxidizing agent in the presence of polyvinylpyrrolidone (PVP) which is the stabilizer. The reactions are monitored at the analytical wavelength of 420nm of the localized surface plasmon resonance (LSPR) band of the formed silver nanoparticles (Ag-NPs). Under the optimized conditions, the linear calibration graphs were obtained in the concentration range of 0.122-2.425µgmL(-1) for PAC and 0.021-5.245µgmL(-1) for PAP. The limit of detection in terms of standard approach (LODSA) and upper limit approach (LODULA) were calculated to be 0.027 and 0.032µgmL(-1) for PAC and 0.006 and 0.009µgmL(-1) for PAP. The important parameters were optimized for the artificial neural network (ANN) models. Statistical parameters indicated that the ability of the both methods is comparable. The proposed method was successfully applied to the simultaneous determination of PAC and PAP in pharmaceutical preparations.

Localized surface plasmon resonance sensor for simultaneous kinetic determination of peroxyacetic acid and hydrogen peroxide.

A new sensor for simultaneous determination of peroxyacetic acid and hydrogen peroxide using silver nanoparticles (Ag-NPs) as a chromogenic reagent is introduced. The silver nanoparticles have the catalytic ability for the decomposition of peroxyacetic acid and hydrogen peroxide; then the decomposition of them induces the degradation of silver nanoparticles. Hence, a remarkable change in the localized surface plasmon resonance absorbance strength could be observed. Spectra-kinetic approach and artificial neural network was applied for the simultaneous determination of peroxyacetic acid and hydrogen peroxide. Linear calibration graphs were obtained in the concentration range of (8.20×10(-5) to 2.00×10(-3) mol L(-1)) for peroxyacetic acid and (2.00×10(-5) to 4.80×10(-3) mol L(-1)) for hydrogen peroxide. The analytical performance of this sensor has been evaluated for the detection of simultaneous determination of peroxyacetic acid and hydrogen peroxide in real samples.