Glassy carbon electrode, which is used to electrochemically determine the content of buformin, is modified with an electropolymerized film of p-aminobenzoic acid in pH 7.0 acetate buffer solution (ABS). The polymer showed an excellent electrocatalytic activity for the reduction of buformin. In pH 7.0 ABS, the cathodic peak current increased linearly over three concentration intervals of buformin, and the detection limit (S/N=3) was 2.0×10−9g/mL. The method was successfully applied to directly determine buformin in tablets with standard addition recoveries of 95.8–102.5%. The proposed method is simple, cheap and highly efficient.

A novel renewable immunosensor was created comprising a temperature-controlled surface composed of poly(n-isopropylacrylamide) (PNIPAAm)–antibody conjugates that could reversibly bind the antigen. Bovine serum albumin (BSA) and the corresponding antibody (anti-BSA) were chosen as a model antibody–antigen system to demonstrate the concept. The thermally responsive PNIPAAm conjugated to anti-BSA displayed a controllable conformation change between an expanded and a collapsed form, below and above its characteristic phase transition temperature, i.e. low critical solution temperature (LCST). This showed a remarkable change in the bioaffinity of the conjugate for BSA. Thus, a renewable anti-BSA surface was generated for re-binding of the target antigen at the thermally controllable PNIPAAm–anti-BSA conjugated surface. The temperature-controlling strategy resulted in the regeneration of immunosensors on which immobilized anti-BSA antibodies retained their activity and specificity for more than 30 reproducible assays. The level of dissociation reached 89%, which is comparable with established recovery methods, while offering easer handing. The controlled binding and dissociation were monitored by quartz crystal microbalance (QCM), confocal fluorescence, native electrophoresis, laser-induced fluorescence, and electrochemical impedance methods.

Novel superparamagnetic core-shell imprinting microspheres (MCSIMs) were synthesized using magnetite microspheres with 350 nm diameter and 70 nm thickness silica gel to form core-shell Fe(3)O(4)/SiO(2) composite for template phenylephrine (Phen) recognition and high efficiency separation. Compared to the previous imprinting recognition, the main advantage of this strategy lies in two aspects: one is the high stability and monodispersity of the MCSIMs structure, the other is the use of superparamagnetic Fe(3)O(4)/SiO(2) microspheres as an immobilization matrix and separation tool, thus greatly simplifying time-consuming washing steps. The affinity and selectivity of the MCSIMs were monitored by QCM and electrochemistry measurements. Imprinting microspheres have a remarkable affinity to Phen over that of structurally related molecules, including DA, EP, Phe and Tyr. The relative binding selectivity for different analytes estimated from amperometric signals was Phen : DA : EP = 40 : 5 : 1. The MCSIMs sensor showed a high sensitivity (400 microA mM(-1)), short response time (reaching 98% within 10 s), and broad linear response range from 1 microM to 0.1 mM and low detection limit (0.1 microM). Additionally, the results of control experiments showed that only negligible signal was obtained for non-imprinting microspheres. This could be reasonably attributed to the unique surface pores, charges and especially the nature of the functional groups inside MCSIMs cavities.

A highly sensitive and reproducible lead sensor based on a cyclodextrin-modified gold electrode was created. A self-assembled monolayer (SAM) of thiolated β-cyclodextrin (6-(2-mercapto-ethylamino)-6-deoxy-β-cyclodextrin (MEA-β-CD)) was prepared and modified on a gold electrode (MCGE) for specific Pb2+-sensing. Thus the mercury-free sensors for Pb2+ assay based on MCGE were established. A linear calibration response for Pb2+ was found in the range of 1.7×10−8M to 9.3×10−7M. The detection limit was 7.1×10−9M (with S/N>3), which was 10 times lower than other reported methods of detection Pb2+ with CD. The measurement results via this method for real blood samples were well agree with those obtained by ICP-AES, and thus presented a novel strategy in design of specific lead sensors with high sensitivity and stability for analysis of trace Pb2+ in real blood samples.

Haloperidol (i.e. HPD) and hydroxyzine (i.e. HXY), two effective and important tranquilizers with low redox activity, were found to generate an irreversible anodic peak at about +0.86 V (vs. SCE) or two anodic peaks at about +0.83 and +0.91 V in 0.05 M NaH₂PO₄-Na₂HPO₄ (pH=7.0) buffer solution with a multi-walled carbon nanotubes-modified glassy carbon electrode (i.e. MWNTs/GC), respectively. Their sensitive and quantitative measurement based on the first two anodic peaks was established under the optimum conditions. The anodic peak current was linear to HPD and HXY concentration from 1×10-7 to 2.5 ×10-5 M and 5×10-8 to 2.5 ×10⁻5 M, the detection limits obtained were 8×10-9 and 5×10-9 M, separately. The modified electrode exhibited some excellent characteristics including easy regeneration, high stability, good reproducibility and selectivity. The method proposed was successfully applied to the detection of HPD and HXY in drug tablets and proved to be reliable compared with ultraviolet spectrophotometry. The modified electrode was characterized by electrochemical methods.

A poly-ABSA/SWNTs composite-modified electrode was fabricated by electropolymerizing aminobenzene sulphonic acid (ABSA) on the surface of glassy carbon electrode (GCE) modified with single-wall carbon nanotubes (SWNTs). SWNTs provide a 3D porous and conductive network for the polymer immobilization. The nanocomposite film was characterized by scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS). The results indicated that this composite-modified electrode had strong electrocatalytic activity toward the oxidation of trifluoperazine (TFP). TFP could effectively accumulate on the modified electrode and generate a sensitive anodic peak at 0.72V (versus SCE) in pH 6.1 phosphate buffer solution. Under the selected conditions, the anodic peak current of TFP was linear with its concentration within the range from 1.0x10(-7) to 1.0x10(-5)molL(-1) and 1.0x10(-5) to 1.0x10(-4)molL(-1), and the detection limit was 1.0x10(-9)molL(-1) (S/N=3). This method was successfully applied to the detection of trifluoperazine in drug samples and the recovery was satisfactory. In comparison with the SWNTs/GCE or poly-ABSA/GCE prepared in the similar way, this composite-modified electrode exhibited better catalytic activity.

A series of binuclear, divalent nickel and copper acetylacetonato complexes of the type [M(acac)-(mu-C6H2(=NAr)(4))M(acac)] (M = Ni, Cu) have been synthesized by reaction of the corresponding M(acac)(2) precursor with various bulky steric hindrace pi-acceptor N-substituted 2,5 -diamino-1,4-benzoquinonediimines C6H2(NHAr)(2)(=NAr)(2) (1a, Ar = 4-C6H4Me; 1b, Ar = 2-C6H4Me; 1c, Ar = 2,6-C6H3Me2), which are metalated and become bridging ligands. The ligands and complexes were determined by IR and UV-visible spectra and element analysis. Cyclic voltammetric behavior of complexes 2c and 3c has been tested. The molecular. structures of the ligand 1c and the complexes [Ni(acac) {mu-C6H2(=N(4-methylPh))(4))Ni(acac)]) (2a), [Ni(acac)[,mu-C6H2(=N(2,6-dimethyl-Ph))(4)}Ni(acac)]) (2c), and [Cu(acac)-1,{mu-H-6(2)(=N(2,6-dimethyl-Ph))(4))Cu(acac)]) (3c) have been determined by X-ray diffraction. The coordination geometry around the metal ions of the Ni and Cu complexes is square-planar, and a complete electronic delocalization of the quinonoid :pi-system occurs between the metal centers over the two N=C-C=C=N halves of the ligand. In the presence of MAO as cocatalyst, all the Ni complexes exhibited high activities both for addition polymerization of norbornene and for methyl methacrylate (MMA) polymerization, which produce syndiotactic-rich poly(methyl methacrylate) (PMMA) with broad molecular weight distribution; however, the Cu complexes show moderate activities for norbornene polymerization and are inactive for MMA polymerization.

Phenylephrine (i.e. PHE) and chlorprothixene (i.e. CPT), two effective and important antipsychotic drugs with low redox activity, were found generating an irreversible anodic peak at about +0.89V (vs. SCE) and +1.04V in 0.05M HAc–NaAc (pH 5.0) or NH2CH2COOH–HCl (pH 2.4) buffer solution at poly(4-aminobenzene sulfonic acid) modified glassy carbon electrode (i.e. poly(4-ABSA)/GC), respectively. Sensitive and quantitative measurement for them based on the anodic peaks was established under the optimum conditions. The anodic peak current was linear to PHE and CPT concentrations from 1×10−7 to 1.5×10−5M and 2×10−6 to 4.5×10−5M, the detection limits obtained were 1×10−8 and 1×10−7M, separately. The modified electrode exhibited some excellent characteristics including easy regeneration, high stability, good reproducibility and selectivity. The method proposed was successfully applied to the determination of PHE and CPT in drug injections or tablets and proved to be reliable compared with ultraviolet spectrophotometry. The modified electrode was characterized by electrochemical methods.

Clomipramine, an important tricylic antidepressant drug with low redox activity, was effectively electrocatalyzed on poly-aminobenzene sulfonic acid/Pt nano-clusters modified glassy carbon electrode (i.e., poly-ABSA/Pt/GCE) and generated a sensitive anodic peak at about 0.80 V in pH 8.1 PBS. ABSA was electropolymerized on the surface of GCE modified with Pt nano-clusters. Pt nanoparticles provide a 3 D and conductive structure for the polymer immobilization. The resulting sensor exhibited a considerable enhancement in voltammetric response characteristics: extending the linear range and lowering the detection limit. The anodic peak current of clomipramine was linear with its concentration over two concentration intervals, ViZ., 1.0 x 10(-7)similar to 4.0 x 10(-6) M and 4.0 x 10(-6)similar to 4.0 x 10(-5) M, with the detection limit of 1.0 x 10(-9) M (S/N = 3). This method was successfully applied to the determination of clomipramine in drug tablets and proved to be reliable compared with UV.

The stable electroactive thin film of rhein has been investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Electrochemical impedance spectroscopy of the electrodeposited film derived from rhein indicated the electrode reaction was kinetically controlled in the region of higher frequency, the charge transfer resistance was 2.6×103 Ω cm2 and capacitance value was 13.2 μF cm2 . The electrodeposited film derived from rhein exhibited a good electrocatalytic activity for myoglobin (Mb) reduction. In 0.30 mol dm−3 H2SO4solution, the catalysis currents were proportional to the concentrations of Mb over the range of 1.5×10−7–1.3×10−5 mol dm−3. The detection limit is 1.0×10−7 mol dm−3 (S/N=3). The relative standard deviation is 4.8% for eight successive determinations of 5.0×10−7 mol dm−3 Mb.

The electrochemical properties of ascorbic acid at a poly (ferric acid) modified electrode was studied. The modified electrode gives a relative reversible redox peak in 0.10 mol/L PBS (pH 6.6) over the potential range from -0.2 to 0.6 V (vs. Ag/AgCl), which the formal potential is 0.128 V (vs. Ag/AgCl). The modified electrode shows electrocatalytic activity toward ascorbic acid in 0.1 mol/L phosphate buffer solution, and the electro catalytic currents were proportional to concentrations of the ascorbic acid in the range of 0.01～5.0 mmol/L. The heterogeneous rate constant for oxidation of ascorbic acid at the poly (ferric acid) modified electrode surface was also determined and found to be about 8.60×10~3 mol~(-1)·L·s~(-1).

A film of single-wall carbon nanotubes (SWNTs) and didodecyldimethylammonium bromide (DDAB) is prepared by casting a solution of SWNTs and DDAB onto the surface of a gold electrode. The electrochemical behavior of the film is investigated by electrochemical impedance spectroscopy and cyclic voltammetry. In a 0.10 M phosphate buffer solution of pH 7.0, the film-modified electrode gives a pair of redox peaks in cyclic voltamograms, with the anodic and cathodic peak potentials of 0.095 and 0.042 V. The peak currents change linearly with the scan rate at 30–500 mV/s. The modified electrode has an excellent electrocatalytic activity towards the oxidation of ascorbic acid (AA). The catalysis currents are proportional to the AA concentration in the range of 5.0 × 10−4 to 3.2 × 10−2 M. The linear-regression equation is i (µA) = 1.2079 + 1.3987 × 103cAA (M), with a correlation coefficient of 0.9995. The detection limit is 2.2 × 10−4 M (signal-to-noise ratio of 3). The Michaelis-Menten constant (Km) is 1.0 × 10−4 M by the Lineweaver-Burk equation.

Direct electrochemistry of hemoglobin (Hb) immobilized on the PSS/SWNTs film modified Au electrode was studied. The immobilized Hb displayed a couple of stable and well-defined redox peaks with the formal potential (E0′) of about 0.117V (versus SCE) in a 0.1M phosphate buffer solution (PBS) of pH 7.0. The dependence of E0′ on the solution pH indicated that the direct electron transfer reaction of Hb was that the electrons transfer was accompanied by an equal number of protons in reaction process. Both single-wall carbon nanotubes (SWNTs) and poly(styrene sulfonic acid) sodium salt (PSS) could accelerate the electron transfer between Hb and the electrode. Using the PSS/Hb/SWNTs film modified Au electrode, the interaction between Hb and ribavirin was studied.

O-aminobenzoic acid (o-ABA) film is deposited on glassy carbon electrode (GCE) by electropolymerization in pH 7.0 phosphate buffer solution (PBS). The polymeric film shows an excellent electrocatalytical activity on the oxidation of dopamine (DA). Difference pulse voltammetry (DPV) was performed to determine DA in an excess of ascorbic acid (AA). The oxidation peak potentials of DA and AA recorded are 144 mV and -52 mV, respectively. In pH 7.0 PBS, the anodic peak current of DA increases linearly over two concentration intervals, viz., 1.0x10(-7)-1.0x10(-5) mol L(-1) and 1.0x10(-5) - 2.0x10(-4) mol L(-1), with correlation coefficient, 0.9966 and 0.9960, respectively. The relative standard deviation of 10 successive scans is 2.8 % for 1.0x10(-6) mol L(-1) DA and the recovery is 96 % - 101 %. The interference of AA and DOPAC with the determination of DA could be eliminated because of the very distinct attracting interaction between DA cations and the negatively poly (o-ABA) film in pH 7.0 PBS. The proposed method exhibits good recovery and reproducibility.

A glassy carbon electrode was modified with electropolymerized films of sulfosalicylic acid in PBS solution of pH 7.4 by cyclic voltammetry(CV).The modified electrode showed an excellent electrocatalytical effect on the oxidation of dopamine.In PBS of pH 7.4,dopamine displays two reduction peaks and two oxidation peaks.Its peak potential shifted negatively with the increasing of solution pH.The oxidation peak current increased linearly with concentration of dopamine: The linear regression equations were ipa(10μA)=0.2355+ 0.3055 c(mol/L) with coefficient correlation r =0.9930 in concentration range of 3×10~(-7)-9×10~(-6)mol/L,and ipa(10μA)=2.356+0.069 C(mol/L) with coefficient correlation r=0.9913 in concentration range of 10~(-5)-10~(-4)mol/L.The detection limit obtained by differential pulse voltammetry was 3.0×10~(-7) mol/L.The experimental results showed that the modified electrode could diminish the interference of ascorbic acid.The proposed method can be applied to the detection of dopamine in samples.The recovery was in the range of 97.7%-101.6%.

A glassy carbon electrode (GCE) is modified with electropolymerized film of p-aminobenzene sulfonic acid (p-ABSA) in pH 7.0 acetate buffer solution (ABS). Cyclic voltammetry (CV), different pulse voltammetry (DPV) and amperometric curve were used to study the electrochemical properties of the polymer film. The polymer film-modified electrode is used to electrochemically detect dopamine (DA) in the presence of ascorbic acid (AA). Polymer film showed excellent electrocatalytic activity for the oxidation of DA and AA. The DA and AA anodic peak potential values at the modified electrode are 196 and −8mV, respectively, which can be obtained from DPV recordings. In pH 7.0 ABS, the anodic peak current increases linearly over three concentration intervals of DA, viz., 1.0×10−7–1.0×10−6, 1.0×10−6–1.0×10−5 and 1.0×10−5–1.0×10−4moll−1, with the correlation coefficient, 0.9984, 0.9973 and 0.9921, respectively, and the detection limit (S/N=3) is 2.0×10−8moll−1. AA has no interference with the determination of DA because of the very distinct attracting interaction between DA cations and the negatively poly(p-ABSA) film. The proposed method exhibits good recovery and reproducibility.

A glassy carbon electrode (GCE) was modified with electropolymerized films of amidosulfonic acid in pH 7.0 phosphate buffer solution (PBS) by cyclic voltammetry (CV). The modified electrode showed an excellent electrocatalytical effect on the oxidation of dopamine (DA). In pH 7.0 PBS, the anodic peak current increased linearly with the concentration of DA in the range of 5.0×10−7∼ 1.0×10−4 mol dm−3, with a correlation coefficient of 0.9932, and a detection limit (S/N=3) of 1.0× 10−7 mol dm−3. The relative standard deviation of 10 successive scans was 2.5% for 1.0×10−6 mol dm−3 DA. The interference of ascorbic acid (AA) with the determination of DA could be eliminated because of the very distinct attracting interaction between DA cations and the negatively poly(amidosulfonic acid) film in pH 7.0 PBS. The proposed method exhibited good recovery and reproducibility.

Poly (acridine red) modified glassy carbon electrode was used for the detection of dopamine in the presence of ascorbic acid in a pH 7.4 phosphate buffer solutions (PBS) by cyclic voltammetry and differential pulse voltammetry.The major difficulty of the overlapped oxidation potential of ascorbic acid could be overcome through the distinct attractive ability of poly (acridine red) film to cationic dopamine and anionic ascorbic acid.The results showed that the dopamine anodic peak current and the concentration of dopamine had a linear relationship in the range of 1.0×10 -7 ~ 1.0×10 -4 mol dm -3 .The detection limit (S/N=3) obtained by differential pulse voltammetry was 1.0×10 -9 mol dm -3 .The relative standard deviation of 10 successive scans was 2.07 % for 1.0×10 -6 mol dm -3 DA.Ascorbic acid had hardly interference with the determination of dopamine.The proposed method exhibits good recovery and reproducibility.