Papers by Pilar Sotomayor
Anal. Methods, 2016
A biomimetic sensor is proposed as a promising new analytical method for the determination of cya... more A biomimetic sensor is proposed as a promising new analytical method for the determination of cyanide in different samples.
Reactive and Functional Polymers, 2016
In the present study new molecularly imprinted adsorbents based on poly(methacrylic acid) and pol... more In the present study new molecularly imprinted adsorbents based on poly(methacrylic acid) and poly(acrylic acid) have been synthesized, characterized and evaluated as selective materials for the adsorption of diuron. Morphological, textural data and the presence of functional groups in the polymer have been evaluated by means of SEM, nitrogen adsorption-desorption assays and FT-IR, respectively. Two functional monomers were evaluated for the MIP synthesis, methacrylic acid (MIP MAA) and acrylic acid (MIP AA), and the first one showed higher selectivity and better adsorption towards diuron in the presence of competitor molecules, carbofuran and 2,4-D. The experimental adsorption isotherm of diuron has been obtained at pH 7.0 in phosphate buffer (0.05 mol L −1):acetonitrile (1:2, v/v) medium and equilibrium time of 180 min. The respective maximum adsorption capacities (MAC) of MIP MAA and MIP AA were found to be 14.58 and 7.32 mg g −1. One should note that MAC of MIP AA and its respective blank polymer (NIP AA) was very similar to each other, while for the MIP MAA its MAC was significantly higher (14.58 mg g −1) than the MAC of NIP MAA (6.12 mg g −1). Such result demonstrates the great influence of monomer on the adsorption and selectivity of MIP. Adsorption kinetic data were well fitted to pseudo-first-order and intraparticle diffusion models, while the adsorption isotherms showed good fit to the isotherm of Langmuir-Freundlich for two sites (LF-2) and one site (LF-1), but the former one allowed insight into the adsorption mechanism with more details.
Sensors and Actuators B: Chemical, 2015
Abstract A new selective sensor based on molecularly imprinted polymers (MIPs) was developed for ... more Abstract A new selective sensor based on molecularly imprinted polymers (MIPs) was developed for the determination of hexazinone (HXZ) in environmental samples. MIPs were synthesized using a non-covalent approach, and selection of the monomers employed in the polymerization reaction was carried out by molecular modeling. Three functional monomers with high (2-vinylpyridine (MP17)) and intermediate (methacrylic acid (MP12) and acrylamide (MP5)) energies of binding to the template (HXZ) were selected for preparation of the MIPs, in order to conduct comparative studies and validate the theoretical data. For sensor construction, carbon pastes were modified with each MIP or NIP (non-imprinted polymer), and HXZ determination was performed using differential pulse adsorptive cathodic stripping voltammetry (DPAdCSV). All parameters affecting the sensor response were optimized. In HCl at pH 2.5, the sensor prepared with MP17 (5% w/w in the paste) showed a dynamic linear range between 1.9 × 10 −11 and 1.1 × 10 −10 mol L −1 , and a detection limit of 2.6 × 10 −12 mol L −1 , under the following conditions: accumulation time of 200 s at a potential of −0.5 V, scan rate of 50 mV s −1 , pulse amplitude of 60 mV, and pulse width of 50 ms. The sensor was selective in the presence of other similar compounds, and was successfully applied to the analysis of HXZ in river water samples.
Electrochimica Acta, 2014
Journal of Colloid and Interface Science, 2013
In a typical protocol for attaching DNA to a gold electrode, thiolated DNA is incubated with the ... more In a typical protocol for attaching DNA to a gold electrode, thiolated DNA is incubated with the electrode at neutral pH overnight. Here we report fast adsorption of non-thiolated DNA oligomers on gold electrodes at acidic pH (i.e., pH ~3.0). The peak-to-peak potential difference and the redox peak currents in typical cyclic voltammetry of [Fe(CN)6] 3are investigated to monitor the attachment. Compared with incubation at neutral pH, the lower pH can significantly promote the adsorption processes, enabling efficient adsorption even in 30 min. The adsorption rate is DNA concentration-dependent, while the ionic strength shows no influence. Moreover, the adsorption is base-discriminative, with a preferred order of A >C>>G, T, which is attributed to the protonation of A and C at low pH and their higher binding affinity to gold surface. The immobilized DNA is functional and can hybridize with its complementary DNA but not a random DNA. This work is promising to provide a useful time-saving strategy for DNA assembly on gold electrodes, allowing fast fabrication of DNA-based biosensors and devices.
Peroxidase was extracted from a natural source (turnip) and irradiated with 60 Co (0.1 kGy). It w... more Peroxidase was extracted from a natural source (turnip) and irradiated with 60 Co (0.1 kGy). It was then used in the construction of biosensors for hydrogen peroxide determination, in order to study the effect of the gamma irradiation on the performance of the biosensors. The biosensors were constructed using two immobilization procedures: crosslinking with glutaraldehyde and covalent binding through carbodiimide. The biosensor prepared using covalent binding through carbodiimide showed a higher sensitivity for H 2 O 2. A good enhancement in stability and sensitivity was obtained for the biosensors from irradiated material, when compared to biosensors prepared with non-irradiated enzyme. However, the initial linear response range (1.0 to10.0 mmol dm 23) and response time (0.5 s) were equal with or without irradiation.
A SiO2/Nb2O5 mixed oxide was prepared by a solgel processing method based on TEOS and NbCl5 as p... more A SiO2/Nb2O5 mixed oxide was prepared by a solgel processing method based on TEOS and NbCl5 as precursors and HCl as catalysts. A material having a specific surface area of 703 m2 g− 1, average pore diameter of 2.4 nm and 5 wt.% of Nb was obtained. An ...
... Construction and evaluation of an optical pH sensor based on polyanilineporous Vycor glass n... more ... Construction and evaluation of an optical pH sensor based on polyanilineporous Vycor glass nanocomposite. ... This work describes the preparation of a polyaniline (Pani)porous Vycor glass (PVG) nanocomposite and its use as sensing phase in an optical fibre pH sensor. ...
Electrochimica acta, 2003
The use of tris (2,2′-bipyridil) copper (II) chloride complex, [Cu(bipy)3]Cl2·6H2O, as a biomimet... more The use of tris (2,2′-bipyridil) copper (II) chloride complex, [Cu(bipy)3]Cl2·6H2O, as a biomimetic catalyst, is reported in the construction of an amperometric sensor for dopamine. The sensor was prepared modifying a glassy carbon electrode with a Nafion® membrane doped with the complex. The optimized conditions for the sensor response were obtained in 0.25 mol dm−3 Pipes buffer (pH 7.0) containing 150 μmol dm−3 H2O2, with an applied potential of −50 mV versus saturated calomel electrode (SCE). In these conditions, a linear response range between 9 and 230 μmol dm−3, with a sensitivity of 1.43±0.01 nA dm3 μmol−1 cm−2 and a detection limit of 4.8 μmol dm−3 were observed for dopamine. The response time for this sensor was about 1 s, presenting the same response for at least 150 successive measurements, with a good repeatability (4.8%) expressed as relative standard deviation for n=13. After its construction, this sensor can be used after 180 days without loss of sensitivity, kept at room temperature. The difference of the sensor response between four preparations was 4.2%. A detailed investigation about the sensor response for other eighteen phenolic compounds and five interfering species was performed. The sensor was applied for dopamine determination in pharmaceutical preparation with success.
Optodes based on bromothymol blue (BB) and bromocresol purple (BP) acid-base indicators were cons... more Optodes based on bromothymol blue (BB) and bromocresol purple (BP) acid-base indicators were constructed. The dyes were chemically immobilised on the surface of a bifurcated glass fibre optical bundle, which was previously silanised with 3aminopropyl-triethoxysilane. A PTFE/acrylic cell was specially constructed, allowing the use of the optodes as detector in flow analysis systems. The optodes were evaluated for their pH responses in different flow approaches, such as continuous flow, flow injection and monosegmented flow systems. A steady state signal was achieved in the continuous flow system. The effect of the flow rate and the injected volume on the signal amplitude were studied. Signals up to 69 and 77% for BB optode and up to 82 and 92% for the BP optode of the steady state signal can be obtained by employing flow injection and monosegmented flow systems, respectively. The sampling frequency can be improved and sample consume can be lowered by employing the monosegment flow approach.
In this work, magnetic molecularly imprinted polymers (MMIPs) were synthesized and tested for the... more In this work, magnetic molecularly imprinted polymers (MMIPs) were synthesized and tested for the determination of folic acid (FA) in different food samples. The MMIPs were polymerized at the surface of Fe 3 O 4 @SiO 2 magnetic nanoparticles (MNPs) using acrylonitrile (functional monomer), ethylene glycol dimethacrylate (EGDMA) as cross-linking agent and azobiisobutyronitrile (AIBN) as an radical initiator. The morphological, topological and chemical characteristics of the MMIPs were investigated by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and Fourier transform infrared (FTIR) techniques. The physico-chemical characterization, such as adsorption capacities and selectivity of MMIPs was investigated and compared with the respective MNIPs. The adsorption experimental data demonstrate that maximum adsorption capacity of MMIP at equilibrium was 8 mg g −1 and than the adsorption process of FA over MMIPs follows Freundlich adsorption isotherm model and pseudo-first-order reaction kinetic. For evaluation of this new proposed material, the recovery studies were carried out in spiked samples at different concentration levels and the obtained values were in the range of 95–104% for orange and for spinach the recoveries were between 99.5 and 102.5%. The relative standard deviations (RSD) for the recoveries were b0.5% for both samples. These results demonstrate that this novel MMIP material can be efficiently used for the selective extraction of folic acid from different food complex matrices.
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Papers by Pilar Sotomayor