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Electrochemically Reduced Graphene Oxide-Based Screen-Printed sensors Article Electrochemically Reduced Graphene Oxide-Based Screen-Printed Electrodes for Total Tetracycline Determination by Adsorptive Transfer Stripping Differential Pulse Voltammetry 1,2 1 2, 2, Anabela S. Lorenzetti , Tania Sierra , Claudia E. Domini *, Adriana G. Lista y, Agustin G. Crevillen 3 and Alberto Escarpa 1,4,* 1 Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering, University of Alcala, E-28871 Alcala de Henares, Spain; [email protected] (A.S.L.); [email protected] (T.S.) 2 INQUISUR, Department of Chemistry, Universidad Nacional del Sur (UNS)-CONICET, Av. Alem 1253, Bahía Blanca 8000, Argentina; [email protected] 3 Department of Analytical Sciences, Faculty of Sciences, Universidad Nacional de Educación a Distancia (UNED), E-28040 Madrid, Spain; [email protected] 4 Chemical Research Institute “Andrés M. del Río” (IQAR), University of Alcalá, E-28805 Alcalá de Henares, Spain * Correspondence: [email protected] (C.E.D.); [email protected] (A.E.) In memoriam. y Received: 11 November 2019; Accepted: 19 December 2019; Published: 21 December 2019 Abstract: Disposable electrochemically reduced graphene oxide-based (ERGO) screen-printed electrodes (SPE) were developed for the determination of total tetracyclines as a sample screening approach. To this end, a selective adsorption-detection approach relied on adsorptive transfer stripping differential pulse voltammetry (AdTDPV) was devised, where the high adsorption capacity and the electrochemical properties of ERGO were simultaneously exploited. The approach was very simple, fast (6 min.), highly selective by combining the adsorptive and the electrochemical features of tetracyclines, and it used just 10 µL of the sample. The electrochemical sensor applicability was demonstrated in the analysis of environmental and food samples. The not-fully explored AdTDPV analytical possibilities on disposable nanostructured transducers become a new tool in food and environmental fields; drawing new horizons for “in-situ” analysis. Keywords: tetracycline; adsorption; graphene; adsorptive and electrochemical selectivity; disposable sensors; sample screening 1. Introduction Graphene is a carbon allotrope composed of a single layer of carbon with partially filled sp2-orbitals above and below the plane of the sheet. This nanomaterial has attracted the attention of scientific community due to its amazing features, such as large surface area (2630 m2/g for a single layer), high mechanical strength, and high elasticity (Young’s modulus 1100 GPa); and excellent thermal ≈ (5 103 Wm 1 K 1) and electrical conductivity (charge carrier mobility > 200,000 cm2 V 1 s 1 for freely × − − − − suspended graphene) [1]. Graphene has been successfully used in all analytical steps: sample preparation, separation, and detection [1–3]. Regarding sample preparation, graphene has been applied in solid phase extraction and solid phase microextraction because of its excellent adsorption ability [4,5]. These applications were mainly focused on the extraction of benzene derivatives, which can easily interact, by π–π stacking Sensors 2020, 20, 76; doi:10.3390/s20010076 www.mdpi.com/journal/sensors Sensors 2020, 20, x FOR PEER REVIEW 2 of 11 Sensors 2020, 20, 76 2 of 12 stacking with graphene thanks to its large electron delocalization. For example, benzene derivatives such as polycyclic aromatic hydrocarbons [6], tetracyclines [7], sulphonamides antibiotics [8], among withothers, graphene were extracted thanks to by its graphe large electronne-based delocalization. sorbents. Respect For example, to the benzeneuse of graphene derivatives for such direct as polycyclicelectrochemical aromatic sensing, hydrocarbons this nanoma [6],terial tetracyclines provides [ 7(i)], high sulphonamides heterogeneous antibiotics electron [8 transfer], among rate, others, (ii) wereelectrocatalytic extracted byproperties graphene-based against sorbents.several molecule Respects to(due the to use the of high graphene number for directof atoms electrochemical localized in thesensing, edges/defects), this nanomaterial and (iii) provides high surface (i) high to heterogeneous volume ratio electronthat increases transfer sensitivity rate, (ii) electrocatalytic [2,9]. Taking propertiesadvantage againstof this features, several molecules a plenty of (due electroche to the highmical number sensors of were atoms developed localized exclusively in the edges based/defects), on grapheneand (iii) high for surfacedirect todetection volume ratioof H2 thatO2, increasesascorbic acid, sensitivity uric [acid,2,9]. Takingdopamine, advantage and several of this features,phenol- containinga plenty of electrochemicalcompounds, among sensors others were developed [9,10]. Fu exclusivelyrthermore, basedthe combination on graphene forof directscreen-printed detection electrodeof H2O2, ascorbic(SPE) technology acid, uric and acid, graphene dopamine, is a andcutting-edge several phenol-containing strategy for “in situ” compounds, analysis and among for developingothers [9,10]. new Furthermore, point-of-care the combinationtesting (POC) of screen-printeddevices. SPE technology electrode (SPE) provides technology reliable and single-use graphene devices,is a cutting-edge which strategycan be foreasily “in situ”modified analysis [11], and and for developinggraphene newprovides point-of-care an improvement testing (POC) of electroanalyticaldevices. SPE technology performance provides [10]. reliable single-use devices, which can be easily modified [11], and grapheneOn the other provides hand, antetracyclines improvement are ofa kind electroanalytical of antibiotics performance with a chemical [10]. structure derived from a hydronaphthaceneOn the other hand, containing tetracyclines four are fused a kind rings of antibiotics(see Figure with 1). aAll chemical of them structure also contain derived a phenol from a grouphydronaphthacene that is electroactive containing [12]. four This fused group rings of an (seetibiotics Figure has1). Allbeen of exhausti them alsovely contain employed a phenol in human group andthat isanimal electroactive medicine [12]. and This groupalso as of antibioticsan additive has in been animal exhaustively feed because employed of inits human broad andspectrum animal antimicrobialmedicine and activity also as anand additive low cost in [13]. animal Within feed this because family, of tetracycline its broad spectrum (TET), oxytetracycline antimicrobial activity(OTC), chlortetracyclineand low cost [13]. (CTC), Within and this doxycy family,cline tetracycline (DOX) (TET),are the oxytetracycline most prescribed (OTC), in the chlortetracycline veterinary world (CTC), [14]. Theand doxycyclineintensive use (DOX) and abuse are the of mostantibiotics, prescribed in general, in the and veterinary tetracyclines, world [in14 ].particular, The intensive has led use to and an increaseabuse of of antibiotics, bacterial instrains general, resist andant tetracyclines, to antimicrobial in particular, agents, causing has led a to public an increase health ofalarm bacterial worldwide strains [15].resistant For these to antimicrobial reasons, a lot agents, of countries causing legislated a public health to establish alarm maximum worldwide residual [15]. For limits these (MRL) reasons, in animal-deriveda lot of countries food legislated [14]. Moreover, to establish the maximum presence of residual tetracyclines limits (MRL)is not limited in animal-derived to foodstuff food but also [14]. toMoreover, environmental the presence through of tetracyclineswastewater because is not limited sewage to foodstutreatmentff but plants also cannot to environmental fully remove through them wastewater[15]. because sewage treatment plants cannot fully remove them [15]. Figure 1. Chemical structures of studied tetracyclines. Several analytical techniques have been successfullysuccessfully employed for determination of residual tetracyclines such as separation separation techniques techniques (HPLC, (HPLC, CE), CE), spectropho spectrophotometrytometry or or ELISA ELISA [14]; [14]; however, however, they present present some some drawbacks drawbacks such such as as a acomplicated complicated sample sample pretreatment pretreatment process process and/or and/ orthe the need need of aof trained a trained lab lab technician technician [16]. [16 ].In In this this sense, sense, sensors sensors are are an an attractive attractive alternative alternative or complementary analytical toolstools for for tetracycline tetracycline detection detection because becaus of theire of inherenttheir inherent advantages advantages such as highsuch selectivity, as high selectivity,rapid detection, rapid anddetection, in-situ and applications in-situ applications [17]. In fact, [17]. sensors In fact, are sensors ideal candidates are ideal forcandidates developing for developingsample-screening sample-screening methods, namely methods, methods namely used methods to detect used theto detect presence the presence of an analyte of an oranalyte class or of classanalytes of analytes at the level at the of interest.level of interest. A screening A screen methoding method is the first is the method first method that is appliedthat is applied to sample to sampleanalysis analysis with the with purpose the purpose to confirm to theconfirm presence the orpresence absence or of absence antibiotic of residues.antibiotic This residues. procedure This procedureshould be simple,should fast,be simple, cheap, andfast, sensitive.cheap, and In addition,sensitive.
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