Rosana Badía

Molecularly Imprinted Polymers and Optical Sensing Applications

ABSTRACT The development of optical sensing approaches for analytes of biological, industrial, or environmental concern has reached an enormous significance. Different natural systems such as enzymes or antibodies have been employed in the development of these kind of sensors, but they often lack of stability. Molecular imprinting has become a universal tool for preparation of artificial and robust recognition materials mimicking natural systems. Molecular imprinting polymers (MIPs) are easily obtained by copolymerization of suitable functional monomers and crosslinkers in the presence of the target molecule. These polymers exhibit a tremendous thermal, chemical, and mechanical stability besides having selectivity similar to that of natural systems. Here we report an overview of molecular imprinting technique focussed to its sensing applications, emphasizing those systems based on an optical transduction.

FLUORIMETRIC MONITORING OF MOLECULAR IMPRINTED POLYMER RECOGNITION EVENTS FOR ALUMINIUM

ABSTRACT Novel molecular imprints were prepared against aluminium. Sensing materials were prepared via non-covalent imprinting technique, using the aluminium(III)–morin chelate as the template. Based on the fluorescent properties of the chelate, it was possible to design a selective optical flow-through sensor for Al3+. The affinity of the polymer binding sites was higher for aluminium than for other di- and trivalent ions (e.g., Be2+, Ca2+, Mg2+, Eu3+, Zn2+, Fe3+), suggesting that the nature of the metal ion, its ionic radius, and the metal–morin stoichiometry play important roles in the ionic recognition.

Selective fluorescent chemosensor for fructose

A chemosensing system for the selective recognition of fructose based on a reverse photoinduced electron transfer process was developed. A fluorescent boronic acid, m-dansylaminophenylboronic acid, reacts with fructose to produce an electron transfer, which results in the fluorescence quenching of the dye. The addition of the sugar shifted the pKa from 8.13 to 7.80. A possible sensing mechanism is proposed. The analytical figures determined in a batch approach were detection limit 5 × 10–6M, repeatability of 1% at the 1 × 10–4M fructose level and linear calibration up to 3 × 10–4M. A flow injection system was also examined and after the experimental conditions had been optimized a selectivity study showed that only galactose (at a 1:2 fructose to galactose molar ratio) gave a positive deviation. Several food samples were analysed by the proposed flow injection procedure and the results agreed with those obtained using an enzymatic kit for food analysis.

Comparative study of the micellar enhanced spectrophotometric determination of β-lactamic antibiotics by batch and flow injection analysis using a multisimplex design

A study has been made on the spectrophotometric determination of the beta-lactamic antibiotics, amoxicillin and ampicillin, in micellar media using Cu ions as catalyst. Batch and flow injection approaches were compared. Multisimplex design was used to determine the optimal values of the flow injection analysis (FIA) system. Chemical (buffer, pH and Cu(II) concentrations) and physical (flow rate, temperature and reaction coil length) variables were considered. The analytical performance characteristics were as follows: the detection limits for batch and flow-through systems were 2.5 x 10(-7) and 2 x 10(-6) M, respectively, and a relative standard deviation less than 1% was found for both methods. The proposed FIA methodology was satisfactorily applied to the determination of the antibiotics in pharmaceutical formulations.

Room-Temperature Phosphorescent Complexes with Macromolecular Assemblies and Their (Bio)chemical Applications

A number of metal complexes, including hydroxyquinolines, phthalocyanines, porphyrins, chlorophyls, and others, phosphoresce at room temperature in the presence of macromolecular assemblies such as micelles, vesicles, proteins, and nucleic acids. The aim of this review is to illustrate the applicability of these systems to a variety of analytical problems through the discussion of representative examples. Finally, recent developments and likely prospects in the field of room temperature phosphorescent complexes, such as probes of vascular disorders, are also considered.

Molecularly Imprinted Polymers for Optical Sensing Devices

A problem of paramount importance in analytical chemistry is selectivity, particularly at low analyte concentrations in the presence of interfering substances. The sensitive and selective determination of a large number of trace compounds in complex samples is of great relevance in many fields such as biotechnology, the environment, food and pharmacentrical industries and health care for diagnosis or treatment of diseases.

A sensitive probe for oxygen sensing in gas mixtures, based on room-temperature phosphorescence quenching

The dye Erythrosine B (which gives room-temperature phosphorescence, RTF) has been covalently bound to a silica-based amino-functionalized exchanger. The resulting material turned out to be extremely useful as a luminescent probe for oxygen. The photochemical properties and the analytical performance of the RTF probe have been studied by use of a gas flow-injection analysis system, which incorporates a convenient exponential dilution chamber for gas sample introduction. The possible origin of the non-linear Stern-Volmer quenching response observed is thoroughly discussed in terms of the quenching and lifetimes. The proposed sensing material is particularly suitable for measuring oxygen in gas mixtures at extremely low concentrations. The detection limit attained was 0.00006% (0.6 ppm) of oxygen in dry argon (making the system one of the more sensitive optosensors for oxygen published so far). A typical precision of ± 0.2%, at the 0.025% oxygen level, was achieved. Response times were less than 2 s for full signal change and no hysteresis effects were noticed. A possible mechanism for the observed oxygen RTF quenching in the new sensing material is proposed.

Tuning the Performance of Room Temperature Phosphorescence Sensing Materials for Oxygen Using Factorial Designs

ABSTRACT The effects of three experimental factors (pH, precursors, alcohol) on the sensing characteristics of these materials were screened by means of two-level factorial designs. The resulting materials turned out to be useful as luminescent probes for the measurement of dissolved and gaseous oxygen. The photochemical properties and the analytical performance of the RTP sensing phases have been studied by using both gas flow-injection analysis and continuous liquid flow-through systems. The proposed sensing materials were particularly suitable for measuring dissolved oxygen in natural waters. The detection limit attained was 0.004 mg.ml−1 and a typical precision of ± 1.0% al a 0.6 mg.ml−1 oxygen level was achieved. Response time for 90% of the final RTP value was less than 90s in a continuous flow mode. No hysteresis effects were noticed.

Screening of a molecularly imprinted sol–gel library for nafcillin recognition

Properties of tailored imprinted sol–gels are extremely dependent on the synthesis conditions and on the nature of the reagents used due to the diversity of combinatory interactions among the sol–gel components and the large number of chemical requirements for the sol–gel process. In this paper, methyltrimethyl orthosilicate was used as precursor to create molecularly imprinted polymers against the β-lactamic antibiotic nafcillin under different experimental conditions. A 22 member–library of imprinted sol–gels against nafcillin, and the respective control materials, was produced. Screening of the library members was performed by room temperature phosphorescence (RTP) flow-injection analysis and by batch RTP re-binding assays. A 22 factorial experimental design was also performed in selected sub-libraries of imprinted sol–gels as a function of the template and the additive concentrations, both using acid and basic catalysis.

Room-temperature phosphorimetry of carbazole in anthracene

Room-temperature phosphorimetry (RTP) using thallium(I) as the heavy atom was applied to the determination of carbazole in a high-purity anthracene. The results were compared with those obtained by spectrofluorimetry and RTP precision parameters were calculated.