ABSTRACT
This work demonstrates the development of electrochemical aptasensor using ochratoxin A (OTA) aptamers. Different aptamer coupling strategies were tested using polythiophene-carboxylic acid (PT3C) and polypyrrole-3-carboxylic acid (PP3C). The best sensitivity was recorded by polythiophene-3-carboxylic acid (PT3C) on screen-printed carbon electrode (SPCE) to attain the direct detection of OTA. The quantification of OTA was achieved by using electrochemical impedance spectroscopy. A good dynamic range 0.125-2.5â¯ngâ¯ml-1 was obtained for OTA with limit of detection (LOD) 0.125â¯ngâ¯ml-1 and Limit of quantification (LOQ) 0.3â¯ngâ¯ml-1 respectively. The good reproducibility was recorded with RSD% of 3.68. The obtained straight line equation was yâ¯=â¯0.4061â¯×â¯+ 1.03, râ¯=â¯0.99. For real sample applications, the developed aptasensors were demonstrated in coffee samples. The aptasensor displayed good recovery values in the range 88-89%, thus exhibited the effectiveness of proposed aptasensor for such complex matrices.
Subject(s)
Aptamers, Nucleotide/chemistry , Coffee/chemistry , Electrochemical Techniques , Ochratoxins/analysis , Thiophenes/chemistry , Carbon/chemistry , ElectrodesABSTRACT
A new biosensor for detection of phenols, based on tyrosinase immobilization with alumina sol-gel on Sonogel-Carbon transducer, has been developed. The electrode was prepared using high energy ultrasounds directly applied to the precursors. The alumina sol-gel provided a microenvironment for retaining the native structure and activity of the entrapped enzyme and a very low mass transport barrier to the enzyme substrates. Phenols are oxidized by tyrosinase biosensor to form a detectable product, which was determined at -300 mV vs. Ag/AgCl reference electrode. For phenol, the sensor exhibited a fast response which resulted from the porous structure and high enzyme loading of the sol-gel matrix. The linear range was from 5 x 10(-7)M to 3 x 10(-5)M, with a detection limit of 3 x 10(-7)M. The stability of the biosensor was also evaluated.
Subject(s)
Aluminum Oxide/chemistry , Biosensing Techniques/methods , Carbon/chemistry , Enzymes, Immobilized/metabolism , Monophenol Monooxygenase/metabolism , Phenols/chemistry , Agaricales/enzymology , Gels , Hydrogen-Ion Concentration , Microscopy, Electron, Scanning , Reproducibility of Results , Sensitivity and Specificity , Solutions , TransducersABSTRACT
The present work describes the development of a modified platinum electrode for stripping voltammetric determination of silver. The deposition of films based on electropolymerisation of the monomer thiophene was carried out by cycling the potential towards positive values between 0 and 1.6V. The preconcentration process of silver ions was initiated on the surface of the modified electrode by complexing silver with polythiophene (PTH) when a negative potential (-0.5V) was applied; then the reduced products was oxidized by means of differential pulse stripping voltammetry and the peak was observed at 0.17V. Parameters such as pH, supporting electrolyte and number of electropolymerisation cycles were studied. A linear relation between current peak and concentration of Ag(I) was obtained in the range 0.07-1.0mgL(-1). The detection limit for Ag(I) was evaluated to be 0.06mgL(-1). The reproducibility was tested carrying out 11 measurements at different electrodes and the relative standard deviation was 1.5%. The interference of several metals was investigated and showed negligible effect on the electrode response.
