Biomedical subjects

P Ortega Barrales

Publications and source records attributed to P Ortega Barrales.

3 recordsLinked to original sources

PubMed2003

Continuous-flow separation and pre-concentration coupled on-line to solid-surface fluorescence spectroscopy for the simultaneous determination of o-phenylphenol and thiabendazole.

A novel and single flow-injection system combined with solid-surface fluorescence detection is proposed in this work for the resolution of a mixture of two widely used pesticides (o-phenylphenol and thiabendazole). The continuous-flow methodology is based on the implementation of on-line pre-concentration and separation of both analytes on the surface of C18 silica gel beads placed just inside the flow cell, implemented with gel-phase fluorimetric multi-wavelength detection (using 305/358 and 250/345 nm as excitation/emission wavelengths for thiabendazole and o-phenylphenol, respectively). The separation of the pesticides was possible owing to the different retention/desorption kinetics of their interactions with the solid support in the zone where the stream impinges on the solid material. No previous separation of the analytes before they reach the flow cell is needed thereby simplifying substantially both the procedure and the manifold. By using a sample volume of 2,600 microL, the system was calibrated in the range 0.5-16 and 5-120 ng mL(-1) with detection limits of 0.09 and 0.60 ng mL(-1) for thiabendazole and o-phenylphenol, respectively. The RSD values (n=10) were about 1% for both analytes. The proposed methodology was applied to environmental water samples and also to various commercial pesticide formulations containing both analytes. Recovery percentages were 97-103% and 98-102% for thiabendazole and o-phenylphenol, respectively.

Journal Article↗

PubMed2003

A flow injection sensor for simultaneous determination of sulfamethoxazole and trimethoprim by using Sephadex SP C-25 for continuous on-line separation and solid phase UV transduction.

A flow-through sensor based on integration of spectrophotometric detection and the different kinetics of retention/elution of analytes on a solid support is proposed for the simultaneous determination of sulfamethoxazole (SMZ) and trimethoprim (TMP). The solid support (Sephadex SP C-25) fills both, a microcolumn placed on-line and the sensing microzone. The intrinsic absorbance of both compounds is monitored directly on the solid phase at 269 nm and so, no derivatization step is required. Using two alternate solutions, 10(-4) M hydrochloric acid and 0.20 M NaAc/HAc (pH 5.0) buffer, the sensor responds linearly in the measuring range of 50-250 and 10-70 microg ml(-1) with detection limits of 9.5 and 0.6 microg ml(-1) (500 microl of sample volume) for SMZ and TMP, respectively. The main advantages of the sensor are simplicity, rapidity and low reagents consumption. Its application to SMZ and TMP determination in synthetic samples and pharmaceutical preparations is demonstrated. The results obtained by the proposed method were compared with those obtained by a standard HPLC method.

Chromatography, High Pressure Liquid↗

PubMed2001

Simultaneous determination of thiamine and pyridoxine in pharmaceuticals by using a single flow-through biparameter sensor.

For the first time, an UV-photometric flow-through sensing device has been developed for the simultaneous determination of two cationic species (thiamine and pyridoxine). The sensor is based on the retention of the analytes on a cationic ion-exchanger gel placed in the detection zone itself into a quartz flow-cell. A double discrimination is used for detecting the analytes: (a) a double and simultaneous working wavelength, performed by the use of a diode array detector; and (b) a temporary sequentiation in the arrival of the analytes to the sensing zone by on line separation using a cationic ion-exchanger (the same used in the sensing zone) placed into a minicolumn just before the flow cell. Pyridoxine is determined the first (by measuring its intrinsic absorbance at 293 nm) because it passes through the minicolumn while thiamine is strongly retained on it. Then, thiamine is conveniently eluted from the precolumn and its intrinsic UV absorbance measured at 255 nm. In both cases, transitory signals were obtained because both the carrier (in the case of the pyridoxine) and the eluting (in the case of thiamine) solutions used also eluted the respective analyte from the sensing zone. Using 1000 microl of sample, the analytical signal showed a very good linearity in the range 2-30 microg ml(-1) for both analytes with detection limits of 0.10 and 0.084 microg ml(-1) for thiamine and pyridoxine, respectively. The optosensor was satisfactorily applied to the determination of these two analytes in pharmaceuticals.

Flow Injection Analysis↗