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Sensors and Actuators B 168 (2012) 370– 375

Contents lists available at SciVerse ScienceDirect

Sensors and Actuators B: Chemical

j o ur nal homep a ge: www.elsev ier .com/ locate /snb

eusable phosphorescent probes based on molecularly imprinted polymers forhe determination of propranolol in urine

drián Álvarez, José Manuel Costa, Rosario Pereiro, Alfredo Sanz-Medel ∗

epartment of Physical and Analytical Chemistry, University of Oviedo, Julian Claveria 8, E-33006 Oviedo, Spain

r t i c l e i n f o

rticle history:eceived 22 December 2011eceived in revised form 29 March 2012ccepted 10 April 2012vailable online 21 April 2012

a b s t r a c t

The combination of the molecular imprinting techniques with room temperature phosphorescent detec-tion was applied to the development of a simple and easy to regenerate probe for the determination ofthe beta-blocker propranolol in urine samples.

First, bulk brominated polyurethanes were synthesized to ensure the applicability of the imprintingmethodology with phosphorescent detection to the target molecule and then the polymerization was

eywords:olecular imprinting

ropranololhosphorescencenalytical probesrine analysis

carried out onto glass slides to generate thin molecularly imprinted films. The analyte recognized by theimprinted-polymeric layer exhibited intense phosphorescence with a maximum at 520 nm for an excita-tion wavelength of 314 nm. Under optimized experimental conditions, the detection limit achieved was22 �g/L of propranolol, whereas the limit of quantification was 73 �g/L of propranolol and the responsewas linear at least up to 1 mg/L of propranolol. Finally, these reusable probes were successfully appliedto urine samples analysis.

. Introduction

Propranolol is a non-selective beta-blocker mainly indicatedor the treatment of several pathologies such as hypertension,ngina pectoris, arrhythmia and myocardial infarction, having also

local anesthetic effect. The World Anti-Doping Agency (WADA)as included many beta-blockers in the list of banned substances inport for the year 2011 [1], propranolol being one of them. Althoughhe prohibition does not affect all sports, the presence of propra-olol in urine or serum is not permitted in many competitions (e.g.

n archery and shooting).Urine analysis is a routine way to detect the presence of many

rugs and illicit substances [2]. Thus, sensitive and selective meth-ds fulfilling the minimum required performance levels (MRPLs)emanded by the WADA in urine are needed to ensure reliableesults. As in the case of other beta-blocker substances, there iso established threshold concentration value in urine for propra-olol but the WADA establishes a MRPL of 500 �g/L, although theytate that the so-called ‘adverse analytical findings’ can be foundven below that level [3].

Several luminescent analytical methodologies have been devel-ped for the control of propranolol in water and urine based on theeasurement of its native luminescence emission, including room

∗ Corresponding author. Tel.: +34 985103474.E-mail addresses: adralv 82@yahoo.es (A. Álvarez), asm@uniovi.es

A. Sanz-Medel).

925-4005/$ – see front matter © 2012 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.snb.2012.04.038

© 2012 Elsevier B.V. All rights reserved.

temperature phosphorescence (RTP) [4,5]. However, RTP methodsoften require the addition of high concentrations of a heavy atomsalt and/or surfactants (in order to generate micelles). This bringsabout higher costs of the analysis and generation of an importantvolume of wastes, which constitutes an environmental drawback.Therefore, analyte immobilization on solid surfaces can be consid-ered as a very positive alternative for RTP [6].

In the last decade, molecular imprinting has proved to be oneof the simplest, most straightforward, and cost-effective strate-gies to develop artificial receptors for organic compounds [7,8].Moreover, the use of molecularly imprinted polymers (MIPs)has demonstrated to be a promising alternative to enhance theselectivity of luminescence optosensing systems. In fact, severalattempts have been made to develop MIP-based optosensors forcontrol of many different organic species such as pesticides [9,10]employing luminescent detection. Particularly, the combinationof MIPs with RTP has allowed a high selectivity for the targetmolecules [11,12].

On the other hand, the development of chemical or biochemicalanalytical tests providing analytical information in a rapid, sim-ple and cheap way is continuously pursued. In this context, severalinteresting approaches have been proposed in recent years leadingto disposable and/or portable sensors in the form of polymeric filmsor strips [13–16]. Desirable advantages of these sensing schemes

include ease of handling, low costs, lower response times, capa-bility to obtain on-site results thus avoiding the need to transportsamples to the laboratory or store large sample volumes, and lessgeneration of waste products.

Actuators B 168 (2012) 370– 375 371

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A. Álvarez et al. / Sensors and

Here we propose a combination of molecularly imprinted poly-ers based on brominated monomers with a phosphorescent

etection scheme to develop a simple, selective and sensitiveptosensing system for the routine determination of propranololn urine. Polyurethane has been previously employed in the devel-pment of MIPs for the fluorescent detection of several naphthaleneerivatives [17] being structurally similar to propranolol. Herehe native phosphorescent emission from propranolol, selectivelyetained in the MIP, is induced by including a heavy atom, a usefultrategy demonstrated in some of our previous work [11,12]. Afterynthesis, the bulk MIP sensing materials were analytically charac-erized using a flow-injection system. Further, the polymers weremmobilized onto the surface of a glass slide, in order to developimple and low cost probes for the detection of propranolol.

. Materials and methods

.1. Chemicals and materials

Propranolol hydrochloride, ethyl acetate, pindolol, nadolol,lbumin from chicken egg (min. 98%), creatinine hydrochloride,etrahydrofuran, toluene, chloroform, dimethyl sulfoxide, acetone,nd acetonitrile were purchased from Sigma–Aldrich (Milwaukee,I, USA). 3,3′-5,5′-Tetrabromobisphenol A, phloroglucinol and qui-

ine were obtained from Fluka Chemie (Steinheim, Germany).Diphenylmethane 4,4′-diisocyanate (MDI), acetic acid, sodium

ydroxide, sodium chloride, sodium hydrogen carbonate andodium sulfite were obtained from Merck (Darmstadt, Germany).ethanol, ethanol and urea were obtained from Prolabo. Potassium

hloride was obtained from Panreac (Madrid, Spain) and potassiumihydrogen phosphate was obtained from Calbiochem.

All chemicals were of analytical grade and used as received,ithout further purification. Freshly prepared ultrapure deionizedater (Milli-Q3 RO/Milli-Q2 system, Millipore, UK) was used in all

he experiments.

.2. Molecularly imprinted polymer synthesis procedure

MIPs with a heavy atom in their structure were synthesized (theresence of a heavy atom, such as bromide, in the final polymerictructure of the MIP was found to be necessary in order to obtainnalytically useful RTP signals from the recognized analytes) usingetrabromobisphenol A and MDI as functional monomers.

First, bulk polymerization was carried out in the presencef a template molecule (typically the analyte or a derivativeith a similar structure of the analyte). The analyte, propranololydrochloride, cannot be used directly as it is poorly soluble inany organic solvents such as tetrahydrofuran. In contrast, its free

asic form is highly soluble in those non polar solvents used asorogens – solvents that generate a porous polymeric structurehen evaporated – during the polymerization. Thus, prior to the

ynthesis itself, propranolol hydrochloride was transformed in itsree base, by means of neutralization with a saturated solutionf sodium hydrogencarbonate followed by extraction with ethylcetate.

Polymerization mixtures were prepared in glass vials by addi-ion of the appropriate amounts of the solid functional monomersnd cross-linker together with propranolol as template molecule,nd then dissolved in tetrahydrofuran. Different MIP-based sens-ng materials were prepared by varying the amount of templatepropranolol as free base), functional monomers, cross-linker and

olvent.

The finally selected bulk imprinted polymer (MIP) was thatne exhibiting higher recognition capabilities (higher RTP signalsbtained for the recognition of propranolol in an aqueous sample)

thesized onto glass slides. The reproducibility expressed as standard deviation ofthe intensities recorded at � = 520 nm was 3.7%.

with a negligible contribution of unspecific adsorptions of the ana-lyte or other species (instead of just selective recognition inside thespecific sites in the polymeric structure) to the RTP signal. Thus,the selected MIP was obtained from a polymerization carried outby mixing 25.4 mg propranolol (free base), 30.0 mg phloroglucinol,454.0 mg tetrabromobisphenol A and 236.8 mg MDI dissolved in5 mL tetrahydrofuran. To obtain the bulk polymers, after sonicationthe mixtures were stored uncovered in absence of light during 4days until complete evaporation of the organic solvent was reached(constant weight). The solid material finally obtained was groundin an agate mortar, washed with acetonitrile and dried at 45 ◦Cuntil constant weight was reached. The ground polymer was dry-sieved and particles with diameters between 160 and 200 �m werefinally selected. Control non imprinted polymers (NIPs) were alsoprepared and treated in the same way, except that no templatemolecule was added for their synthesis.

In the case of the polymers synthesized as layers onto glassslides, the slides were first cut to the desired size and then theirsurface was activated by washing with 5 M sodium hydroxide andthen rinsed with ethanol and distilled and de-ionized Milli-Q water,ensuring the surface of the slides was completely clean beforedrying them overnight in an oven at 100 ◦C. Then, a spin coatingprocedure [18] was employed to obtain thin homogeneous poly-meric layers. The MIP layer finally selected was prepared usinga polymerization mixture containing 30.7 mg of propranolol (freebase) as template molecule, 50.0 mg of phloroglucinol, 454.0 mgof tetrabromobisphenol A and 87.6 mg of MDI dissolved in 5 mLtetrahydrofuran. Higher amounts of MDI led to polymers that eas-ily detached from the glass slides thus becoming useless, whereaspoorer recognition capabilities toward the analyte were observedwith lower amounts of template molecule.

To carry out the synthesis of the MIP layers deposited onto theglass slides, a pre-polymerization mixture was prepared and keptunder sonication, as in the case of the bulk polymers, and differentvolumes of polymerization mixture were tested also at differentturning speeds. Finally, a fixed volume of 50 �L of the mixture waschosen to be statically deposited on the glass slides, which wereimmediately accelerated to a selected turning speed of 700 rpmduring half a minute and later left drying in the absence of light dur-ing 2 days. Lower volumes of mixture and lower turning speeds didnot ensure a complete covering of the slides, whereas higher vol-umes and higher turning speeds lead to a higher volume of wastedpre-polymerization mixture. Moreover, although at higher speedsthinner films can be obtained, the desired thickness together with

a good adherence of the polymer to the glass slide were achieved atthe selected speed. A good reproducibility in the synthesis proce-dure was achieved: as can be seen in Fig. 1 all the resulting polymer

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72 A. Álvarez et al. / Sensors and

oatings gave rise to very similar phosphorescence signals from theetained template molecule, with a reproducibility in the RTP sig-als from the propranolol retained (expressed as relative standardeviation) of less than 4% for eight different batches of MIPs.

.3. Template removal

Although for bulk polymers the template could be removed bysing methanol, in the case of the polymers synthesized as thinlms the procedure had to be significantly different, as their poly-erization process does not take place in the same conditions.ethanol caused polymer detaching from the glass surface, mak-

ng it useless. Different methanol/water mixtures were also tested.nfortunately, low fractions of methanol were not able to remove

he template, whereas when employing high content of methanolhe sensing polymers tended to detach from the glass surface.ther solvents were assayed for this purpose, including ethanol,cetone, acetonitrile, chloroform, dimethylformamide and toluene.nly this latter solvent provided acceptable removal of the tem-late without the undesired detaching of the polymer from thelass surface. A 6 h long Soxhlet extraction procedure was needed tonsure a good removal of the template, while keeping the integrityf the polymers attached to the glass surface (even under such con-itions, approximately 5% of trapped template molecules could note removed from the MIP).

.4. Solutions

Standard solutions (200 �g/L) of propranolol hydrochlorideere prepared by dissolving the appropriate amount of the solid

ubstance in ethanol and stored in the dark at 4 ◦C for a maximumeriod of two weeks. The same procedure was employed for thereparation of solutions containing pindolol, nadolol and quinine.olutions of albumin and creatinine were prepared in Milli-Q water.

For the experiments with the bulk polymer, working solutions50 mL) of each compound, all of them containing 8 mM sodiumulfite as an oxygen scavenger [19] and 2% ethanol, were preparedaily by dilution with deionized Milli-Q water of the standard solu-ions.

In the case of the experiments with the thin polymeric filmsn glass slides, as real urine showed a certain matrix effect on theecognition of the analyte (probably due to the high amount of saltsresent in the matrix), it was found necessary to prepare the stan-ards in a medium quite similar to real urine in terms of pH and

onic strength. Therefore, synthetic urine was prepared in Milli-Qater as detailed by Kark et al. [20], thus finally containing 18.2 g/Lrea, 7.5 g/L NaCl, 4.5 g/L KCl, 4.8 g/L NaH2PO4, 2.0 g/L creatininend 50 mg/L chicken egg albumin. This synthetic urine was storedt 4 ◦C during a maximum period of one week. Working solutionsere prepared daily by dilution of the propranolol standard solu-

ions. In all cases, the pH was adjusted by adding 1 M phosphateuffered saline solution at pH 7.

.5. Instrumentation

The flow-injection system used for the characterization of theulk polymer has been described elsewhere [11,21]. The polymerarticles were packed in a luminescence flow-through quartz cell of.5 mm light path, which was placed inside the sample holder of the

uminescence spectrometer, and the carrier solution was pumpedhrough at a constant flow rate of 1.5 mL/min. Propranolol solutions3 mL) or methanol (2 mL) were injected into the carrier flow by

eans of two six-way injection valves.RTP data were collected using a Varian Cary Eclipse lumi-

escence spectrometer. Different instrumental variables wereptimized to obtain the maximum sensitivity for propranolol

ators B 168 (2012) 370– 375

detection. Finally selected instrumental values were: both excita-tion and emission slits were set at 10 nm, a delay time of 0.1 ms (theshortest allowed by the software of the luminescence spectrometerused) and a gate time of 2 ms were selected, and the photomulti-plier tube voltage was set at 800 V, although before the removalof the template molecule good signals were achieved even whenmeasuring at 600 V, and even without deoxygenation.

A conventional quartz cell with a 10-mm light path was usedfor the phosphorescence measurements in the glass slides, placeddiagonally in a fixed position inside the cell. This was top covered,while absence of oxygen inside was ensured by the continuousintroduction of argon at a low flow rate. For analyte recognitionexperiments, sensing slides were introduced during 30 min in vialswith 25 mL of the working solutions, favoring diffusion of the ana-lyte by means of magnetic stirring.

3. Results and discussion

3.1. MIP-based propranolol recognition

It is well known that a requirement to obtain analytically usefulRTP signals is a rigid environment for the phosphor, thus minimiz-ing possible nonradiative deactivation processes from the excitedtriplet state. This can be achieved by the retention of the targetanalyte inside a polymeric structure (e.g. in the cavity of the MIP).

In our experiments, before the removal of the template fromthe bulk brominated MIPs, their particles were packed in the flowcell and their phosphorescence spectrum was recorded while acarrier solution was passed through it. Under such conditions anintense propranolol phosphorescence peak (maximum emission at525 nm) with �ex = 317 nm was observed, even in the absence of adeoxygenating agent. This fact suggests that propranolol moleculesshould be tightly retained in the polyurethane template cavities,which ensure a rigid environment for the phosphor (thus pro-tecting RTP even from quenching by dissolved oxygen). However,particularly after initial template removal, chemical deoxygenationbecame necessary for the measurement of low RTP signals. Also, theremoval of propranolol after each corresponding sample injection(i.e. the regeneration of the MIP for a subsequent analysis) was pos-sible by simply passing 2 mL of methanol through the packed MIP,between successive sample injections.

In the case of thin layer films on glass slides, much higherphosphorescence intensities were observed (maximum emissionat 520 nm with �ex = 314 nm) in comparison to the bulk polymerin similar conditions and greater difficulties were experienced toremove the template molecules from the polymeric structure. Thiscould be ascribed to a much tighter confinement of propranolol inthe polymeric cavities due to a faster polymerization. As result, theremoval of the template could not be achieved in the same condi-tions as in the bulk polymers and strong washing conditions wereneeded to remove most of the template molecule as detailed in Sec-tion 2. As a result of such template extraction procedure, a slightlydetectable RTP emission was still measured (due to the residualpropranolol retained in the MIP) as shown in Fig. 2.

Experiments carried out with samples and propranolol stan-dards using the slides once the initial template was removed,showed that the retained analyte is also easily removed with asimple washing step under Milli-Q water, after which they wereleft drying at room temperature thus regenerating the active phasefor at least five subsequent uses without any detectable detach-ing of the polymeric layer from the glass surface. Moreover, it has

been observed that a deoxygenated environment was favorable forRTP measurements, leading to a significant increase in the observedphosphorescence lifetimes for the MIPs (as can be seen in Fig. 3),and signals were stable with time.

A. Álvarez et al. / Sensors and Actuators B 168 (2012) 370– 375 373

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The effect of pH on the MIPs performance (both, for bulk andayer films) was studied in the interval 4–8, the pH range to beound normal in urine. Higher RTP intensities were reached with aH value of 5–7, whereas at lower or higher pH values the intensityecreased noticeably. Considering the buffering capabilities of thehosphate solution, we finally selected pH 7.

Another optimized parameter was the response time of theensing materials (MIP films deposited onto glass slides) for theetection of propranolol in an aqueous sample. For such pur-ose, several 500 �g/L propranolol solutions were prepared inynthetic urine, and different polymeric-layered glass slides wereeft immersed in these standard solutions with slow magnetic stir-ing, as previously described. Although slightly higher responsesere obtained at higher times, 30 min were finally selected because

he improvement in the signals did not justify longer immersionimes of the slides in the solutions.

.2. Analytical characterization of the MIPs for propranololptosensing

The analytical performance of the synthesized bulk brominatedIPs, using the proposed flow system, was evaluated under the

elected experimental conditions. First, it was found that highly

ntense RTP responses to the analyte, even at low concentration lev-ls, were observed in the imprinted polymer, whereas the responsef the control non-imprinted polymer in the same conditions was

ig. 3. Phosphorescence decay curves for the retained propranolol in the polymericlms. The black lines represent the emission from the propranolol retained in theIPs, being the continuous line corresponding to the absence of oxygen and the

ashed line that corresponding to the presence of oxygen. The gray lines (continuousnd dashed one) represent the RTP observed for the NIP: no difference was observedn this latter case between absence and presence of oxygen.

Fig. 4. Comparison of the responses of the bulk MIP (black line) and NIP (gray line)to 3 mL injections of 0.5 mg/L of propranolol. Regeneration with 2 mL methanol.

negligible, as can be seen in Fig. 4. Increasing concentrations ofthe analyte brought about increased RTP signals and so calibrationgraphs were obtained from triplicate 3 mL injections of aqueousstandards of increasing propranolol concentrations following thegeneral procedure. The calibration curve was linear up to 500 �g/Lof analyte with a regression coefficient of r = 0.9980. The repeata-bility of the proposed method, evaluated as the standard deviationof ten replicates of a sample containing 300 �g/L propranolol wasabout 5%. The detection limit, calculated as the concentration ofanalyte which produced an analytical signal 3 times the standarddeviation of the blank signal (IUPAC criterion), was 22 �g/L pro-pranolol, whereas the limit of quantification, calculated as theconcentration of analyte which produced an analytical signal 10times the standard deviation of the blank signal, was 73 �g/L pro-pranolol. In the case of the thin layer MIP a similar detection limitwas achieved with a linear range up to 1 mg/L (r = 0.9971). As canbe seen, the detection limit values obtained were clearly below theMRPLs established by the WADA, although slightly worse than RTPin solution methods [4,5].

The effect of ionic strength on the recorded signals was alsoevaluated: different solutions containing 300 �g/L of propranololwere prepared together with NaCl concentrations ranging from 0to 20 g/L. It was observed that increasing ionic strengths from 5 to20 g/L had no influence on the RTP signal observed for MIPs ontoa glass slide or for the bulk polymer. Thus, a medium such as thedescribed synthetic urine used to prepare the standard solutions,minimized eventual matrix effects due to the composition of realurine. Moreover, a bit higher and more reproducible signals thanjust Milli-Q water were secured.

Also, no significant changes in the analytical response to pro-pranolol were observed when working with MIPs synthesized ondifferent days with the same synthesis procedure. This suggests avery good reproducibility in the laboratory synthesis.

The main analytical characteristics of the proposed systemturned out to be comparable to those of previously reported meth-ods for the RTP detection of this analyte in solution. In fact, thedetection limit achieved was in the same order of magnitude, but

with the key advantage of the simplicity of the measurements andthe avoidance of using high concentrations of surfactants or heavyatoms.

374 A. Álvarez et al. / Sensors and Actuators B 168 (2012) 370– 375

nd some potential interferents studied.

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Table 1Recoveries in spiked urine samples (n = 3 replicates per sample).

Added (�g/L) Recovery (%)

Bulk polymer600 96 ± 5500 96 ± 7

Thin polymeric layer250 101 ± 8

Fig. 5. Structures of propranolol a

.3. Selectivity

To check the analytical selectivity for propranolol detectionf the MIP-based RTP method several potential interferents weressayed in the proposed RTP determination: pindolol, nadolol anduinine (structures shown in Fig. 5). Competition assays were car-ied out by analyzing solutions containing together propranolol,indolol, nadolol and quinine all of them at the same concentrationseither 250 �g/L or 500 �g/L each), finding no significant differ-nces in the obtained signals (measured at 520 nm) when comparedo the corresponding solutions containing just propranolol. More-ver, it was observed that the presence of typical concentrations oflbumin (50 mg/L) and glucose (70 mg/L) in urine did not produceoticeable changes in the propranolol RTP signals.

Using the same experimental conditions employed for its corre-ponding MIP, the NIP did not produce significant phosphorescenceignals in the same concentration levels (alone or together withhe interferents tested). The above results proved that the RTPptosensing systems proposed here, using either bulk particles orIPs onto a glass slide, show a high selectivity for propranolol

eterminations. At least for the interferents concentration levelsested, selectivity observed was also superior to that in previ-us RTP methods reported [5] (e.g. no significant interference wasetected for glucose at higher concentrations).

.4. Analysis of urine samples

The real applicability of the two proposed RTP optosensors (flowystem with bulk polymer and thin MIP layered slides) for theetermination of traces of propranolol in urine samples was evalu-ted. Urine samples were centrifuged during 15 min at 10,000 rpmnd a temperature of 4 ◦C. To analyze them with the bulk MIP theyere conditioned by diluting 2 times with Milli-Q water, ensuring

he presence of 8 mM Na2SO3 pH 7, and spiked with different con-entrations of propranolol. It should be mentioned that the sampleilution step, required when using bulk polymers for propranololensing, was not necessary when using the MIP onto glass slides.ecovery studies were carried out using the proposed sensing sys-em.

Table 1 summarizes the results obtained for the analyses ofhree replicates of six doped urine samples. The last column in

able 1 shows very good recoveries for the determination of pro-ranolol in the concentration ranges investigated, demonstratinghe usefulness of these MIP-based RTP optosensors for propranololetermination in human urine.

350 94 ± 10500 98 ± 8

4. Conclusions

A selective optosensing of the beta-blocker propranolol inhuman urine, based on MIP technology and RTP detection, hasbeen successfully demonstrated. The “heavy-atom effect” seemsto be more efficient if the imprinted polymer contains bromine oriodine in its solid structure as it induces strong RTP most efficientlywhen the analyte is retained into the MIP specific cavities. Thisstrategy gives rise to simpler, reusable, and thus more environmen-tally friendly, methodologies as compared to those phosphorescentmethodologies using the heavy atom in solution [4,5].

RTP is highly selective of those luminescent molecules, they aretightly retained in a rigid environment (MIP cavities in this case)and they stay close to the heavy atoms present in the polymericstructure. Possible spectral interferences from other phosphorsin the sample (that could be adsorbed onto the MIP surface) arereduced or even eliminated. Moreover, in this way the analyte ispreconcentrated in the MIP cavities.

The RTP proposed sensing systems allow for a simple, selective,and low-cost determination of propranolol. Particularly, the poly-meric film synthesis onto glass slides provides a reusable probe,which could be coupled to a portable device. This probe offers com-parable performance in terms of sensitivity to previously describedmethods for propranolol detection in water or urine but improvesportability and sample throughput.

Acknowledgments

Financial support from the Spanish Ministry of Education andScience (research project CTQ2006-02309) and FEDER program co-

financing funds are gratefully acknowledged. A.A.D. acknowledgesthe Ph.D. scholarship from the Asturias Government (Ref. BP07-061).

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Biographies

Alfredo Sanz-Medel is full professor in analytical chemistry since1982 and the head of the “Analytical Spectrometry” Research Group(http://www.unioviedo.es/analyticalspectrometry) at the University of Oviedo(Spain). He is author or co-author of more than 500 scientific publications ininternational journals, several patents, and books. His current research interestsinclude new atomic detectors and ion sources for ultra-trace analysis, newmolecular optical sensors (particularly those based on the use of MIPs and quantumdots), and hybrid techniques (coupling a separation unit and an atomic detector)for ultra-trace and trace metal speciation to solve biological and environmentalproblems and for proteomics. He has been an editor of Analytical and BioanalyticalChemistry since 2002.

Rosario Pereiro is full professor in analytical chemistry at the Department of Physi-cal and Analytical Chemistry (University of Oviedo, Spain). She has co-authored over130 articles in international peer-reviewed journals, 12 book chapters, the book“Atomic Absorption Spectrometry: An Introduction” (Coxmoor, 2008) and severalpatents. At present, her research interests are mainly oriented toward two broadfields: 1. Analysis of thin layers, implants, polymers and nanostructured materialsusing glow discharges and laser ablation-ICP-MS, among other techniques. 2. Syn-thesis of nanostructured sensing phases for recognition of compounds of biologicaland environmental concern.

José Manuel Costa-Fernández is a senior lecturer in analytical chemistry at theDepartment of Physical and Analytical Chemistry of the University of Oviedo (Spain).He is author or co-author of more than 70 research articles, several reviews,two patents and different chapters in several books. His research interests aremainly focused into instrumental development and application of photolumi-nescent techniques (fluorescence and phosphorescence) to the development ofnew bioanalytical methodologies and fiber optic (bio)sensors, based onnanomaterials.

Adrián Álvarez Díaz is a Ph.D. student in analytical chemistry at the University ofOviedo. In October 2006, he joined the “Analytical Spectrometry” Research Group

working under the supervision of Dr. Jose Manuel Costa-Fernández and Dr. RosarioPereiro on the line of research “Functional materials based on the synthesis ofmolecularly imprinted polymers, fluorescent conjugated polymers and luminescentnanoparticles for the development of optosensors”.