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A novel and simple biosensor based on poly (indoleacetic acid) film-modified electrode (PIAA/CPE) was fabricated by electrochemical polymerization of indoleacetic acid on a carbon paste electrode (CPE) through cyclic voltammetry. The resulting electrode was characterized by scanning electron microscopy, and the electrochemical behaviors of dopamine (DA) and epinephrine (EP) at the electrode were studied. It was illustrated that PIAA/CPE had excellent electrochemical catalytic activities toward DA and EP. The anodic peak currents (I pa ) were dramatically enhanced by about seven-fold for DA and ten times for EP at PIAA/CPE. Thus, the determinations of DA and EP were carried out using PIAA/CPE successfully. The linear responses were obtained in the range of 3.0×10 −7 ∼7.0× 10 −4 and 1.0×10 −6 ∼8.0×10 −4 mol L −1 with the detection limits (3σ) of 1×10 −7 and 4×10 −7 mol L −1 corresponding with DA and EP, respectively. Moreover, the cathodic peaks of DA and EP were well-separated with a potential difference about 325 mV in pH 5.3 phosphate-buffered saline, so simultaneous determination of DA and EP was carried out in this paper. Additionally, the interference studies showed that the PIAA/CPE exhibited excellent selectivity in the presence of ascorbic acid (AA). With good selectivity and sensitivity, the present method has been successfully applied to the determination of DA and EP in pharmaceutical samples.

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Poly (methyl red) film was deposited on a carbon paste electrode (CPE) through cyclic voltammetry (CV) and a novel and simple biosensor (PMR/CPE) for highly sensitive and selective determination of dopamine (DA) was fabricated. The polymer film was characterized by scanning electron microscopy (SEM) and the electrochemical behavior of DA at PMR/CPE was studied. It was illustrated that the polymer film had excellent electrochemical catalytic activity towards DA. The anodic peak current of DA was dramatically enhanced by about four folds at PMR/CPE and the standard rate constant (Ks) for DA could be calculated to be 4.686 s −1 . Moreover, the separation of oxidation peak potentials of DA and uric acid (UA) was 140 mV, and no oxidation peak for ascorbic acid (AA) appeared at PMR/CPE. Thus, the sensitive and selective determination of DA was carried out successfully. The linear response was obtained over two concentration internals: 1.00 × 10 −8 ∼1.00 × 10 −7 mol L −1 and1.00 × 10 −7 ∼1.00 × 10 −3 mol L −1 with a low detection limit (S/N = 3) of 5 × 10 −9 mol L −1 . With favorable selectivity and sensitivity, the present method has been successfully applied to the determination of DA in pharmaceutical samples.DA is an important neurotransmitter belonging to the catecholamine groups, which plays very significant roles in contacting the nervous systems and exhibits potent physiological functions and pharmacological characteristics. Extreme abnormalities of DA in biological fluids may lead to several diseases such as Schizophrenia, Huntington's disease, and Parkinsons disease. 1 Therefore, it is highly desirable to develop simple and rapid methods for the determination of DA with high selectivity and sensitivity in routine analysis.Various strategies have been reported to detect DA sensitively and selectively, such as fluorescence, 2, 3 HPLC, 4-6 spectrophotometry, 7 and electrochemistry. 8-11 DA possesses high electrochemical activity, so voltammetric method based on chemically modified electrodes (CMEs) for its detection have received significant interests in recent decades. However, the selectivity for the electrochemical detection of DA has experienced great challenges, because the coexisted AA and UA can be oxidized at similar potentials resulting in an overlap of the voltammetric responses. Therefore, many attempts have been made in order to improve the selectivity of the electrodes. Generally, composite films based on nanomaterials, Nafion and polymer film were employed to distinguish DA in the presence of AA and UA effectively. 12-14 Zhang et al. 12 casted poly (styrene sulfonic acid) sodium salt/single-wall carbon nanotube on the surface of glassy carbon electrode and the electrochemical behavior DA was investigated. Wang et al. 13 combined poly (3-methylthiophene) with Nafion/singlewalled carbon nanotubes film for highly selective and sensitive determination of DA. Chen et al. 14 modified glassy carbon electrode using multi-wall carbon nanotubes, quercetin and Nafion, and the modified electrode was used for th...

The use of bronate affinity adsorbents is a new separation method that appeared recently with great potential for specific extraction of cis-diol-containing compounds. In this work,a new strategy for the facile construction of boronic acid-functionalized Fe3 O4 magnetic nanoparticles (Fe3 O4 @FPBA MNPs) with a high capacity was described. The extraction capacity of the Fe3 O4 @FPBA MNPs was determined to be 66.0 ± 2.7 µmol/g for catechol and 80.6 ± 2.0 µmol/g for dopamine, being higher than that for the reported methods. The Fe3 O4 @FPBA MNPs were used to extract four cis-diol drugs: caffeic acid isopropyl ester, caffic acid bornyl ester, isopropyl 3-(3,4-dihydroxyphenyl)-2-hydroxypropanoate and 3-(3, 4-dihydroxyphenyl)-2-hydroxylpropionic acid - from the spiked rabbit plasma, and the recoveries of four drugs were between 87.29 and104.37% with relative standard deviations ranging from 1.34 to 8.81%. Under the most favorable conditions, the solid-phase extraction combined with HPLC-UV for the analysis of four drugs in plasma could eliminate interferences from endogenous components of the biological fluids and exhibited sufficient precision and accuracy. These results showed that the prepared Fe3 O4 @FPBA MNPs were qualified for efficiently enriching and determining the trace cis-diol substances from biological samples.

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