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Analytica Chimica Acta (v.614, #1)
Conducting polymers in chemical sensors and arrays by Ulrich Lange; Nataliya V. Roznyatovskaya; Vladimir M. Mirsky (pp. 1-26).
The review covers main applications of conducting polymers in chemical sensors and biosensors. The first part is focused on intrinsic and induced receptor properties of conducting polymers, such as pH sensitivity, sensitivity to inorganic ions and organic molecules as well as sensitivity to gases. Induced receptor properties can be also formed by molecularly imprinted polymerization or by immobilization of biological receptors. Immobilization strategies are reviewed in the second part. The third part is focused on applications of conducting polymers as transducers and includes usual optical (fluorescence, SPR, etc.) and electrical (conductometric, amperometric, potentiometric, etc.) transducing techniques as well as organic chemosensitive semiconductor devices. An assembly of stable sensing structures requires strong binding of conducting polymers to solid supports. These aspects are discussed in the next part. Finally, an application of combinatorial synthesis and high-throughput analysis to the development and optimization of sensing materials is described.
Keywords: Abbreviations; CP; conducting polymer(s); PANI; polyaniline; PNMA; poly(; N; -methylaniline); p; -ABSA; poly(; p; -aminobenzene sulfonic acid); PPY; polypyrrole; PTH; polythiophene; P3MTH; P3HTH; P3OTH; poly(-3-methyl-,-3-hexyl-,-3-octyl-thiophene); PEDOT; polyethylenedioxythiophene; EDOT; ethylenedioxythiophene; PI; polyindole; PP; poly(; p; -phenylene); PPV; poly(; p; -phenylenevinylene); PPE; poly(; p; -phenyleneethynylene); PMNT; poly(3-(3′-; N; ,; N; ,; N; -triethylamino-1′propyloxy)-4-methyl-2,5-thiophene); PSS; polystyrenesulfonate; PVS; polyvinylsulfonate; PET; polyethylene terephthalate; PEG; polyethylenglycol; PAA; polyacrylic acid; AMPS; poly(2-acrylamido-2-methylpropane sulfonic acid); PA; polyacrylamide; HRP; horseradish peroxidase; GOx; glucose oxidase; LDH; lactate dehydrogenase; MIP; molecular imprintingConducting polymers; Chemical sensors; Electroactive polymers; Gas sensors; Combinatorial techniques; Electropolymerization; Sensor array
Sorbent- and liquid-phase microextraction techniques and membrane-assisted extraction in combination with gas chromatographic analysis: A review by Tuulia Hyötyläinen; Marja-Liisa Riekkola (pp. 27-37).
Approaches are described for on-line and off-line sample pretreatment of liquid samples utilising liquid- and adsorbent- and sorbent-phase microextraction methodologies with GC analysis. Solid-phase microextraction (SPME), stir-bar sorptive extraction (SBSE), on-line solid-phase extraction (SPE), liquid-phase microextraction (LPME) and membrane-assisted methods are critically evaluated and the applicability of each technique is demonstrated with examples.
Keywords: Microextraction; Solid-phase microextraction; Stir-bar sorptive extraction; Liquid-phase microextraction; Membrane-assisted extraction; Gas chromatography
Interference-free determination of thallium in aqua regia leaches from rocks, soils and sediments by D2-ETAAS method using mixed palladium–citric acid–lithium chemical modifier by Lenka Husáková; Tomáš Černohorský; Jitka Šrámková; Kateřina Hubáčková; Iva Doležalová (pp. 38-45).
The mixture of palladium (chloride) with citric acid and lithium is proposed as a new chemical modifier for the elimination of interference occurred during the determination of Tl in aqua regia extracts from rocks, soils and sediments by electrothermal atomic absorption spectrometry using instrumentation with deuterium-lamp background correction (D2-ETAAS). Palladium was preferred to rhodium and platinum as to analyte stabilization, citric acid served as an effective reducing agent facilitating formation of Pd–Tl stable covalent bonds playing an important role in the analyte stabilization. Citric acid in addition helps to remove most of interfering chloride at low temperature. The further addition of Li increased significantly the robustness of chemical modifier against strongly interfering ZnCl2 matrix by binding free chlorine into a more stable LiCl molecule. In the presence of the proposed chemical modifier the temperature for the final step of pyrolysis was adjustable up to 1000°C, without any noticeable loss of volatile Tl species and the interference of the rest chloride matrix was significantly reduced. The application of the modifier to direct determination of Tl in aqua regia extracts from rocks, soils and sediments has ensured the characteristic mass and LOD value for the original sample 13pg and 0.043μgg−1, respectively (10-μL aliquots of sample) and has enabled the use of matrix-free standard solutions for attaining accurate analysis. The accuracy was verified by the analysis of certified reference samples and by the comparison of results with those found by an inductively coupled plasma orthogonal acceleration time-of-flight mass spectrometer (ICP-oa-TOFMS) method.
Keywords: Thallium analyte; Chloride matrix; Electrothermal atomic absorption spectrometry; Chemical modifiers; Aqua regia; extraction; Rocks; Soils; Sediments
Second-order advantage from kinetic-spectroscopic data matrices in the presence of extreme spectral overlapping by María J. Culzoni; Héctor C. Goicoechea; Gabriela A. Ibañez; Valeria A. Lozano; Nilda R. Marsili; Alejandro C. Olivieri; Ariana P. Pagani (pp. 46-57).
Multivariate curve resolution coupled to alternating least-squares (MCR-ALS) has been employed to model kinetic-spectroscopic second-order data, with focus on the achievement of the important second-order advantage, under conditions of extreme spectral overlapping among sample components. A series of simulated examples shows that MCR-ALS can conveniently handle the studied analytical problem unlike other second-order multivariate calibration algorithms, provided matrix augmentation is implemented in the spectral mode instead of in the usual kinetic mode. The approach has also been applied to three experimental examples, which involve the determination of: (1) the antiparkinsonian carbidopa (analyte) in the presence of levodopa as a potential interferent, both reacting with cerium (IV) to produce the fluorescent species cerium (III) with different kinetics; (2) Fe(II) (analyte) in the presence of the interferent Zn(II), both catalyzing the oxidation of methyl orange with potassium bromate; and (3) tartrazine (analyte) in the presence of the interferent brilliant blue, both oxidized with potassium bromate, with the interferent leading to a product with an absorption spectrum very similar to tartrazine. The results indicate good analytical performance towards the analytes, despite the intense spectral overlapping and the presence of unexpected constituents in the test samples.
Keywords: Multivariate curve resolution; Kinetic-spectral data; Second-order advantage; Extreme spectral overlapping
Cloud point extraction and determination of trace trichlorfon by high performance liquid chromatography with ultraviolet-detection based on its catalytic effect on benzidine oxidizing by Hai-zhen Zhu; Wei Liu; Jian-wei Mao; Ming-min Yang (pp. 58-62).
4-Amino-4′-nitrobiphenyl, which is formed by catalytic effect of trichlorfon on sodium perborate oxidizing benzidine, is extracted with a cloud point extraction method and then detected using a high performance liquid chromatography with ultraviolet detection (HPLC-UV). Under the optimum experimental conditions, there was a linear relationship between trichlorfon in the concentration range of 0.01–0.2mgL−1 and the peak areas of 4-amino-4′-nitrobiphenyl ( r=0.996). Limit of detection was 2.0μgL−1, recoveries of spiked water and cabbage samples ranged between 95.4–103 and 85.2–91.2%, respectively. It was proved that the cloud point extraction (CPE) method was simple, cheap, and environment friendly than extraction with organic solvents and had more effective extraction yield.
Keywords: Trichlorfon; 4-Amino-4′-nitrobiphenyl; Cloud point extraction; Triton X-100; High performance liquid chromatography; Ultraviolet detection
Characterization of recognition sites for diethyl 4-nitrobenzylphosphonate, an organophosphate pesticide analogue by Anne-Marie Gué; Armand Lattes; Elisabeth Laurent; Monique Mauzac; Anne-Françoise Mingotaud (pp. 63-70).
In a first step towards chemical sensors using molecular imprinted materials, the complexing characteristics of diethyl 4-nitrobenzylphosphonate, an organophosphate pesticide analogue, have been studied. Two molecules have been assessed as potential interacting moieties, specifically a fluoroalcohol and an aromatic acid. The interactions have been first characterized by regular methods, such as1H,31P NMR and IR spectroscopy. These showed a stoichiometry 1/1 for both complexes and association constants, respectively, close to 40±10 and 12±2M−1. In a second step, isothermal titration calorimetry was used and a method was developed to obtain low-association constants. The association constant could be obtained for the fluoroalcohol ligand and was found equal to 63±0.7M−1. For the acidic molecule, an appropriate model could not be found, preventing the evaluation of this constant.
Keywords: Pesticides; Isothermal titration calorimetry; Molecular imprinted polymers; Sensors
Adsorption of a protein–porphyrin complex at a liquid–liquid interface studied by total internal reflection synchronous fluorescence spectroscopy by Yao-Ji Tang; Ying Chen; Zhe Chen; Tang-Tang Xie; Yao-Qun Li (pp. 71-76).
Interfacial analysis has attracted more and more attention owing to its fundamental and biological importance. Total internal reflection fluorescence (TIRF) spectroscopy is a useful method to study interfacial properties. The synchronous scanning fluorescence technique provides a selective tool to analyze a specific component in a complex system. The interaction and adsorption of bovine serum albumin (BSA) and meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) at toluene–water interface were studied successfully by the coupling technique of total internal reflection synchronous fluorescence (TIRSF). New methods are provided for the determination of the critical micelle concentration (cmc), apparent adsorption equilibrium constant ( Kad) and maximum amount of adsorption ( fmax) at the liquid–liquid interface. The results indicated that BSA could adsorb onto the toluene–water interface as a complex of BSA–TPPS in a ratio of 1:1 ratio based on Langmuir adsorption isothermal model. The cmc, apparent Kad and fmax for BSA at pH 3.1 were determined to be 1.0×10−4molL−1, 1.15×105Lmol−1 and 1.14×10−9molcm−2, respectively.
Keywords: Liquid–liquid interface; Total internal reflection fluorescence; Synchronous fluorescence; Porphyrin; Protein
Phosphate-selective fluorescent sensing microspheres based on uranyl salophene ionophores by Katarzyna Wygladacz; Yu Qin; Wojciech Wroblewski; Eric Bakker (pp. 77-84).
Optical dihydrogen phosphate-selective sensors that function on the basis of bulk optode principles and are based on two different uranyl salophene ionophores are reported here for the first time. The influence of the optode composition and measuring conditions such as sample pH on the optode response are characterized, along with sensor selectivity and long-term stability. Three plasticizers of different polarity are considered for optode fabrication: bis(2-ethylhexyl)sebacate (DOS), dodecyl 2-nitrophenyl ether ( o-NPDDE), o-nitrophenyloctylether ( o-NPOE). The compounds 9-(diethylamino)-5-(octadecanoylimino)-5H-benzo[ a]phenoxazine (ETH 5294, chromoionophore I) and 9-(diethylamino)-5-[(2-octyldecyl)imino]benzo[ a]phenoxazine (ETH 5350, chromoionophore III) are used as H+-selective fluoroionophores that also act as reference ionophores. The resulting optode-based sensors are compared with their ion-selective electrode (ISE) counterparts, and it is revealed that optodes are better suited for operation at physiological pH. The best optode performance was found for the two component optode sensors doped with ETH 5350 and phosphate ionophore(I). The linear range of these sensor was log a=−6.0 to −2.6. Dihydrogen phosphate-selective optode sensors of optimized composition are fabricated in microsphere format and preliminary measurements in diluted sheep blood samples are presented.
Keywords: Phosphate sensor; Optical sensors; Ionophore; Uranyl salophene; Microsphere sensors
Functional polyterthiophene-appended uranyl-salophen complex: Electropolymerization and ion-selective response for monohydrogen phosphate by Junghwan Kim; Dong Min Kang; Sung Chul Shin; Myong Yong Choi; Jineun Kim; Shim Sung Lee; Jae Sang Kim (pp. 85-92).
We have synthesized a bis(terthiophene)-appended uranyl-salophen complex, comprising N, N′-bis[4-(5,2′:5′,2″-terthiophen-3′-yl)salicylidene]-1,2-ethanediamine–uranyl complexes (TUS), and used it as a monomer for the electrochemical polymerizations (poly-TUS) on glassy carbon surfaces to prepare functionalized conducting polymer (CP) films. The poly-TUS films prepared from propylene carbonate/0.1M tetrabutyl ammonium perchlorate (TBAP) on a glassy carbon electrode have both the functionality of ion-to-electron transducers (solid contact) and Lewis-acidic binding sites for a monohydrogen phosphate (MHP) ion-selective electrode (ISE). The CP/poly-TUS sensor showed a linear range between 1.0×10−1 and 1.0×10−4.5M with a near-Nernstian behavior (−30.4mVdecade−1) at a pH of 8.2. The detection limit of the electrode was 10−5.0M and the response time was improved (<10s) compared to that of conventional ISEs (<20s). For comparison, a conventional ISE (with an internal aqueous solution) based on a TUS monomer/ o-nitrophenyl octylether ( o-NPOE)/polyvinyl chloride (PVC) liquid membrane with or without tridodecylmethylammonium chloride (TDMACl) as an additive was also constructed and its performance as an MHP-ISE were studied. The superior selectivity and sensitivity of the CP/poly-TUS sensor enabled the direct measurement of MHP in a wide variety of applications.
Keywords: Ion-selective sensor; Conducting polymer; Polyterthiophene derivatives; Monohydrogen phosphate ion-selective electrode
Disposable electrochemical DNA-array for PCR amplified detection of hazelnut allergens in foodstuffs by Francesca Bettazzi; Fausto Lucarelli; Ilaria Palchetti; Francesca Berti; Giovanna Marrazza; Marco Mascini (pp. 93-102).
An electrochemical low-density DNA-array has been designed and implemented to be used in combination with polymerase chain reaction (PCR) in order to investigate the presence of hazelnut major allergens (Cor a 1.04, Cor a 1.03) in foodstuff. Unmodified PCR products were captured at the sensor interface via sandwich hybridization with surface-tethered probes and biotinylated signalling probes. The resulting biotinylated hybrids were coupled with a streptavidin–alkaline phosphatase conjugate and then exposed to a α-naphthyl phosphate solution. Differential pulse voltammetry was finally used to detect the α-naphthol signal. The detection limits for Cor a 1.03 and Cor a 1.04 were 0.3 and 0.1nmolL−1, respectively (R.S.D. 10%). The optimized conditions were used to test several commercially available foodstuffs, claiming to contain or not the targeted nuts. The results were compared with those obtained with classical ELISA tests.
Keywords: Electrochemical genosensor; Food allergens; Hazelnut; Polymerase chain reaction; Screen-printed electrode; Array
Application of new sol–gel electrochemical sensors to the determination of trace mercury by G. Cabello-Carramolino; M.D. Petit-Dominguez (pp. 103-111).
The aim of this work was the synthesis and characterization of new modified sol–gel carbon composite electrodes and their application to the determination of trace mercury species with positive charge. Two types of modified electrodes were synthesized, sol–gel and sol–gel-PVSA carbon composite electrodes. In the last ones, poly(vinylsulfonic acid) (PVSA) was used as a functional polymer entrapped within the sol–gel material due to its cationic exchange properties. In a first stage, parameters affecting both, the sol–gel process and the electrode preparation were optimized. In a second stage, usefulness of developed electrodes applied to the determination of cationic mercury species was evaluated, optimizing the activation, preconcentration, measurement and regeneration steps. Developed electrodes showed very favourable electroanalytical properties for their use as amperometric sensors, such as small size, low cost, simple fabrication and handling, renewability and reusability. By means of an easy and low-cost methodology, satisfactory experimental results were obtained in Hg2+ determination. In this sense, developed analytical methodology showed adequate response times, linear concentration range up to three orders of magnitude (from 5.0×10−8 to 5.0×10−5M) and detection limits of 1.5×10−8M (3.0μgL−1). These results suggest that the incorporation of different receptor molecules at the sol–gel carbon composite material in combination with a selected electrochemical reaction could improve the detection limit achieved and obtain electrochemical sensors adapted to the determination of different species of mercury and other heavy metals.
Keywords: Sol–gel electrochemical sensors; Mercury; Cation-exchange
Preparation of molecularly imprinted solid phase extraction using bensulfuron-methyl imprinted polymer and clean-up for the sulfonylurea-herbicides in soybean by Kaijie Tang; Shangwei Chen; Xiaohong Gu; Haijun Wang; Jun Dai; Jian Tang (pp. 112-118).
A pre-treatment methodology based on the molecularly imprinted solid phase extraction (MI-SPE) procedure was developed for the determination of bensulfuron-methyl (BSM), tribenuron-methyl (TBM), metsulfuron-methyl (MSM) and nicosulfuron (NS) in soybean samples. A molecular imprinted polymer (MIP) was prepared by precipitation polymerization using BSM as the template molecule, α-methacrylic acid (MAA) as the functional monomer, trimethylolpropane trimethacrylate (TRIM) as the cross-linker and dichloromethane as the porogen. The binding behaviors of the template BSM and its analogues on the MIP were evaluated by high performance liquid chromatography (HPLC). Then, solid phase extraction (SPE) with a BSM molecularly imprinted polymer (BSM-MIP) as adsorbent was investigated and the optimum loading, washing, and eluting conditions for MI-SPE of the selected BSM, MSM, TBM, and NS were established. The optimized MI-SPE procedure was used to extract the sulfonylureas and a high recovery was obtained in the soybean samples.
Keywords: Molecularly imprinted solid phase extraction; Bensulfuron-methyl imprinted polymers; Sulfonylurea-herbicides; Soybean