Study of a new solid carbon paste tyrosinase-modified amperometric biosensor for the determination of catecholamines by high-performance liquid chromatography

Advances in nanomaterial-based electrochemical biosensors for the detection of microbial toxins, pathogenic bacteria in food matrices

There is a growing demand to protect food products against the hazard of microbes and their toxins. To satisfy such goals, it is important to develop highly sensitive, reliable, sophisticated, rapid, and cost-effective sensing techniques such as electrochemical sensors/biosensors. Although diverse forms of nanomaterials (NMs)-based electrochemical sensing methods have been introduced in markets, the reliability of commercial products is yet insufficient to meet the practical goal. In this review, we focused on: 1) sources of pathogenic microbes and their toxins; 2) possible routes of their entrainment in food, and 3) current development of NM-based biosensors to realize real-time detection of the target analytes. At last, future prospects and challenges in this research field are discussed.

A zucchini-peroxidase biosensor applied to dopamine determination

A biosensor modified with peroxidase from crude extract of zucchini (Cucurbita pepo) was developed for the determination of dopamine in pharmaceutical samples. This enzyme catalyses the oxidation of dopamine to dopaminequinone, in presence of hydrogen peroxide, which the electrochemical reduction can be followed at a peak potential of -0.02 V. The recovery of dopamine from the samples ranged from 94.8% to 106% and a rectilinear analytical curve for dopamine concentration from 5.0 x 10(-4) to 3.0 x 10(-3) mol L-1 (r=0.9982) was obtained. The detection limit was 2.6x10(-5) mol L-1 and the relative standard deviation was less than 1.2% for 7.9 x 10(-4) mol L-1 dopamine in 0.1 mol L-1 phosphate buffer solution at pH 6.0 (n=10).

N-hydroxysuccinimidyl fluorescein-O-acetate as a fluorescent derivatizing reagent for catecholamines in liquid chromatography

A new amine-reactive derivatizing reagent, N-hydroxysuccinimidyl fluorescein-O-acetate (SIFA), was developed for catecholamine (CA) analysis in liquid chromatography. The reactivity of this reagent with the CAs norepinephrine (NE), epinephrine (E), and dopamine (DA) was investigated in detail. In aqueous methanol containing 32 mmol/L pH 9.0 H3BO3-Na2B4O7 buffer, SIFA reacted with NE, E, and DA under mild conditions. The derivatives were separated in 20 min on a C18 column with a mobile phase of methanol/water (38:62, v/v) containing 10 mmol/L pH 5.0 H3cit-Na2HPO4 buffer. At lambda(ex)/lambda(em) = 490/516 nm, the detection limits were 3.2, 12, and 56 fmol, respectively, with a signal-to-noise ratio of 3, which were comparable to those using 1,2-diphenylethylenediamine as the derivatizing reagent for CA analysis. Amino acids, aliphatic amines, and alcohols had no obvious interference with the determination. The proposed method has been applied to the determination of CAs in human urine, with recoveries of 95.3-103.9%.