No abstract

An enhanced thiosemicarbazide(TSC)-H2O2 chemiluminescence (CL) system was established and proposed as a new analytical method for determination of beta-lactam antibiotics, ampicillin sodium and amoxicillin at microgram levels. The method is based on the inhibition of CL emission accompanying oxidation of TSC by H2O2 in alkaline medium. The effect of anionic, cationic, and non-ionic surfactants on the CL emission of the system was studied. Both N-cetyl-N,N,N-trimethylammonium bromide (CTMAB) and Triton X-100, unlike sodium dodecyl sulfate (SDS), reinforced the CL intensity and were efficient to approximately the same level. The effect of the presence of eight non-aqueous solvents on the CL system was also investigated. Upon addition of both of the non-ionic surfactant, Triton X-100, and the non-aqueous solvent, N,N-dimethyl formamide (DMF), the intensity of the CL reaction was increased 100-fold. This method allows the measurement of 25-545 microg amoxicillin, and 35-350 microg ampicillin sodium. The detection limits are 8 microg for amoxicillin and 9 microg for ampicillin sodium. The relative standard deviations of six replicate measurements of 200 microg amoxicillin and 200 microg ampicillin sodium were 1.9 and 2.1%, respectively. The effect of foreign species on the determination of amoxicillin and ampicillin sodium was also examined. The proposed method was successfully applied to the determination of ampicillin sodium and amoxicillin in some pharmaceutical dosage forms.

A simple and highly sensitive chemiluminescence (CL) method is reported for the determination of naphazoline hydrochloride (NH). It was found that the weak CL from the reaction of luminol and KIO4 in an alkaline medium could be highly amplified by cysteine-capped cadmium telluride quantum dots (QDs) and the enhanced CL was effectively quenched by NH and this finding was utilized as a basis for the determination of NH. The QDs were synthesized in aqueous medium and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-vis and photoluminescence spectroscopy. A possible mechanism was proposed for the CL system based on radical identification experiments, along with CL spectrum of the system. The experimental parameters were optimized by the reliable response surface methodology (RSM). Under the optimized experimental conditions, the proposed method allowed the determination of NH over the range of 5.0 × 10(-10) -2.0 × 10(-7) mol/L (r(2) = 0.9993, n = 10). The precision (RSD%) of the method, obtained from five replicate determinations of 2.0 and 150 nmol/L NH, was found to be 1.0% and 1.3%, respectively. The method was successfully applied to the determination of NH in pharmaceutical formulations and human urine and serum samples with results corroborated with the aid of those obtained from a standard method.

A cursory survey of the literature shows that although peroxidase-like activity is a well-known and well-applied property of CuO nanoparticles (CuO NPs), the oxidase-like activity of CuO NPs is a property that is somehow neglected to be incorporated in analytical applications.

A novel chemiluminescence (CL) reaction, captopril-H2O2, for determination of Cu(II) at nanogram per milliliter level in batch-type system has been described. The method relies on the catalytic effect of Cu(II) on the oxidation of captopril with hydrogen peroxide in alkaline medium. The optimization step was performed using univariate methodology and the factors studied were: pH and concentrations of the utilized reagents. Under the optimum conditions, calibration plot was linear in the range of 0.1-2.0 ppm. Limit of detection was 30 ppb and relative standard deviation for five replicate determinations of 0.8 ppm Cu(II) was 1.89%. The proposed method was successfully applied to the determination of Cu(II) in human scalp hair and cereals, rice and wheat, flour with satisfactory selectivity and sensitivity. The results were validated by comparison with a standard method (FAAS). The possible mechanism of the new CL reaction has also been discussed.