RESUMEN

A sensitive determination of a synthetic fluoroquinolone antibacterial agent, moxifloxacin (MOX), by an enhanced chemiluminescence (CL) method using a microfluidic chip is described. The microfluidic chip was fabricated by a soft-lithographic procedure using polydimethyl siloxane (PDMS). The fabricated PDMS microfluidic chip had three-inlet microchannels for introducing the sample, chemiluminescent reagent and oxidant, and a 500 µm wide, 250 µm deep and 82 mm long microchannel. An enhanced CL system, luminol-ferricyanide, was adopted to analyze the MOX concentration in a sample solution. CL light was emitted continuously after mixing luminol and ferricyanide in the presence of MOX on the PDMS microfluidic chip. The amount of MOX in the luminol-ferricyanide system influenced the intensity of the CL light. The linear range of MOX concentration was 0.14-55.0 ng/mL with a correlation coefficient of 0.9992. The limit of detection (LOD) and limit of quantification (LOQ) were 0.06 and 0.2 ng/mL respectively. The presented method afforded good reproducibility, with a relative standard deviation (RSD) of 1.05% for 10 ng/mL of MOX, and has been successfully applied for the determination of MOX in pharmaceutical and biological samples.

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RESUMEN

Luminescent properties of a terbium (Tb3+)-L-3, 4-dihydroxyphenylalanine (L-dopa) complex by binding to colloidal silver nanoparticles (Ag NPs) have been presented. Luminescence intensity of the L-dopa complex was dramatically enhanced about 6-7 times by introducing Ag NPs. The Ag NPs concentration on the luminescent intensity was regarded as a main factor that balancing between an enhancing and a quenching effect of the Ag NPs. It was observed that changing the concentration of L-dopa causes the change in luminescence intensity. Under the optimized condition, the luminescence intensity of the system was linearly related to the concentration of L-dopa. Based on this observation, L-dopa-Tb3+ complex containing Ag NPs has been applied for the determination of L-dopa in pharmaceutical formulation. Linear responses of luminescence intensity were observed in the concentration range of 0.25 to 1.5 nM (r = 0.9934) of L-dopa with limit of detection 0.042 nM. The performance of the system was tested using 1.0 x 10(-9) M of L-dopa, yielding a precision of 1.21% RSD for nine replicate measurements. The present method has been successfully applied to determine L-dopa in pharmaceutical samples.

RESUMEN

We present the enhancement of luminescence of europium complex, Eu(3+)-ciprofloxacin (CIP), in the presence of silver nanoparticles (Ag NPs) for the CIP determination. The increment of the luminescence intensity of the Eu(3+)-CIP complex with Ag NPs was obtained due to the transfer of resonance energy to the fluorophores through the interaction of the excited-state fluorophores and surface plasmon electron in the metal nano surface. The luminescence intensity of Eu3+ was enhanced by complexation with CIP at 614 nm after excitation at 373 nm corresponding to the 5D0-7F2 transitions of Eu3+ ion. Based on the above phenomenon, a sensitive and rapid spectrofluorimetric method has been developed for the CIP determination. Linearity of the calibration curve was obtained in the range of 2.0 x 10(-10)-1.0 x 10(-8) g mL(-1) with correlation coefficient of 0.9992. The limit of detection of CIP was found to be 1.9 x 10(-11) g mL(-1) with the relative standard deviation (RSD) of 1.19% for 5 replicate measurements of 5.0 x 10(-7) g mL(-1) of CIP. The present method has been successfully applied for CIP determination in pharmaceutical and biological samples.

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A simple and selective method to determine norfloxacin using an optical flow-through sensor has been developed. The present sensor was prepared by packing anionic ion exchange resin in a glass tube, followed by introducing KMnO(4) solution to the glass tube for immobilization on resin. The optical sensor is based on the emission intensity from the Tb(III) solution sensitized by norfloxacin. The excitation of norfloxacin occurred by the chemiluminescence from the reaction of KMnO(4) and Na(2)SO(4) solutions. The effects of pH, concentration of Tb(III) ion, KMnO(4) and Na(2)SO(4) solutions and flow rate of the norfloxacin solution on the chemiluminescence intensity were studied to find the optimum experimental conditions. The emission intensity increased linearly with increasing norfloxacin concentration from 1.0 x 10(-3) to 1.0 x 10(-8) M and the detection limit (3sigma) was 8.7 x 10(-9). The applicability of the present method was demonstrated by determination of norfloxacin in various pharmaceutical preparations and serum sample.

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