Biomedical subjects

A Ruiz-Medina

Publications and source records attributed to A Ruiz-Medina.

4 recordsLinked to original sources

PubMed2005

Resolution of biparametric mixtures using bead injection spectroscopic flow-through renewable surface sensors.

A new, sensitive and simple bead injection spectroscopy-flow injection analysis (BIS-FIA) sensor with spectrophotometric detection, using a commercially available flow-cell, is described to the determination of biparametric mixtures. As an analytical model, the metallic mixture Cu(II) and Zn(II) has been chosen. The flow-cell (Hellma 138-OS) is filled by injecting in the flow system 300 microl of a homogeneous bead suspension of an anion exchanger gel (Sephadex QAE A-25) previously loaded with the chromogenic reagent 2-carboxyl-2-hydroxy-5-sulfoformazylbenzene (Zincon). A sequential reaction of Cu(II) and Zn(II) with Zincon to form two complexes is performed on the bead sensing support and the absorbance is monitored at 627 nm, after two successive injections from the mixture solution. The sample containing these metal ions is injected into the first carrier (deionized water, pH 5.9), and Cu(II) selectively reacts with Zincon on the beads, developing the analytical signal. Then, 600 microl of 2 M HCl is injected to decompose the complex, and the carrier solution is changed. At pH 11 (second carrier) both Cu(II) and Zn(II) react with the chromogenic reagent, the absorbance now corresponding to both analytes. The eluent is again injected to descompose both complexes. After three analyses the sensing bead surface is not regenerated. Then, beads are automatically discarded from the flow cell by reversal of the flow, and instantaneously transported out of the system. So the procedure exploits the combination of the concepts of flow-through renewable sensors with bead injection spectroscopy. Using a sample volume of 1000 microl, the calibration graph for Cu(II) is linear over the range 0.05 to 1 microg ml(-1) and for Zn(II) from 0.1 to 1.8 microg ml(-1) in the presence of each other. RSDs (%) lower than 5% are obtained for both analytes. The sensor is satisfactorily applied to individual determination or mixture resolution in waters, pharmaceuticals, soils and human hair samples.

Azo Compounds↗

PubMed2002

A flow-through solid-phase spectroscopic sensing device implemented with FIA solution measurements in the same flow cell: determination of binary mixtures of thiamine with ascorbic acid or acetylsalicylic acid.

A continuous and simple UV-photometric flow-through optosensor has been developed for the simultaneous determination of a binary mixture of two species with different electric charges present at very different concentrations - ascorbic acid (or acetylsalicylic acid) and thiamine. The sensing device is based on the selective sorption and determination of a cationic analyte on a cation-exchange gel (Sephadex SP-C25) while the other, anionic, analyte is determined in the solution among the interstices of the cation-exchange gel in the same flow cell. The analytes arrive in sequence at the sensing zone, which detects their intrinsic absorbance at 253 nm, as a result of on-line separation by use of a minicolumn filled with the same cation-exchange gel as in the cell, and placed before the flow cell. Thiamine is retained in the minicolumn whereas ascorbic acid or acetylsalicylic acid pass through it and produce their signal as a result of absorbance in the interstitial solution among the resin beads. Thiamine is then eluted from the precolumn, transported to the flow cell, and temporarily retained in the sensing zone from this eluted solution. Calibration graphs were linear over the range 3-50, 25-400, and 300-3000 microg mL(-1) (600 microL sample volume) and the relative standard deviations were 2.56, 1.85, and 1.25 % for thiamine, ascorbic acid, and acetylsalicylic acid, respectively. The proposed method was satisfactorily applied to the determination of binary mixtures of thiamine with ascorbic acid or acetylsalicylic acid in pharmaceutical preparations and semi-synthetic samples.

Ascorbic Acid↗

PubMed2001

Flow-through UV spectrophotometric sensor for determination of (acetyl)salicylic acid in pharmaceutical preparations.

The solid phase spectrophotometry technique, in which the absorbance of the species of interest sorbed on a solid support is measured directly, was applied to the determination of salicylic acid using flow injection-analysis. Salicylic acid was determined by monitoring of its intrinsic absorbance at 297 nm sorbed on Sephadex QAE A-25 resin placed in an appropriate flow-through cell. The method proposed improves the selectivity compared with the corresponding solution-phase method and the sensitivity is increased by a factor of 30 or more. The flow-through sensor proposed allows working with several calibration lines simply by varying the sample volume injected. Thus, linear dynamic ranges from 1 to 20 and from 2 to 40 microg ml(-1) can be obtained by using 1000 and 300 microl, respectively, with detection limits being 0.064 and 0.135 microg ml(-1). Relative Standard Deviations (RSDs) of 0.52 and 0.38%, and sampling frequencies of 18 and 25 h(-1), respectively, were also achieved. The sensor also allows the indirect determination of acetylsalicylic acid previous hydrolysis on-line to salicylic acid. For acetylsalicylic acid, a linear dynamic range from 5 to 120 microg ml(-1) and 25 h(-1) of sampling frequency (300 microl of sample volume) were obtained. The proposed flow-through sensor has been successfully applied to the determination of both analytes in pharmaceutical preparations.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2001

A flow-through optosensing device with fluorimetric transduction for rapid and sensitive determination of dipyridamole in pharmaceuticals and human plasma.

A flow-through optosensor with fluorimetric transduction has been prepared for the sensitive and selective determination of dipyridamole in aqueous solutions and biological fluids. The method is based on a monochannel flow-injection analysis system using Sephadex QAE A-25 resin, placed into a Hellma 176-QS fluorimetric flow-through cell, as an active sorbing substrate. The native fluorescence of dipyridamole fixed on the solid sorbent is continuously monitored at wavelengths of 305 and 490 nm for excitation and emission, respectively. After obtaining the maximum fluorescence intensity, the eluent solution (KH(2)PO(4)/NaOH buffer solution, c(T)=0.05 mol l(-1), pH 6.0) is allowed to reach the flow cell, the analyte is removed, and the resin support is regenerated. When an NaOH (10(-4) mol l(-1))/NaCl (0.1 mol l(-1)) solution is used as carrier solution, at a flow-rate of 1.56 ml min(-1), the sensor responds linearly in the measuring range of 10-500 microg l(-1) with a detection limit of 0.94 microg l(-1) and a throughput of 22 samples per hour (300 microl of sample volume). The relative standard deviation for ten independent determinations (200 microg l(-1)) is less than 0.82%. The method was satisfactorily applied to the determination of dipyridamole in pharmaceutical preparations and human plasma.

Chemistry, Pharmaceutical↗