Pollution sources affecting oxidative potential of fine aerosols from a Portuguese urban-industrial area

Trabalho apresentado em European Aerosol Conference 2023 (EAC2023), September 3−8, 2023, Malaga, SpainN/

ELECTROCATALYSIS OF ASCORBIC ACID ON THE GLASSY CARBON ELECTRODE CHEMICALLY MODIFIED WITH POLYANILINE FILMS.

Chemically modified electrodes prepared by electropolymerization of aniline on glassy carbon electrodes, exhibited good electrocatalytic properties towards ascorbic acid oxidation. The electrocatalytic response was evaluated by cyclic voltammetry with regard to pH, Blm thickness, ascorbic acid concentration, scan rate, electrolyte composition, rotation speeds of the electrode, and other variables. The location of the reactions taking place was discussed with experimental evidence that the cross-exchange reaction is the rate-determining step. Experiments in flowing streams were performed to characterize the electrode as an amperometric sensor for the determination of ascorbic acid. The electrode stability, precision, limit of detection and linear range were evaluated at a constant potential of 0.350 V (vs. Ag/AgCl). The limit of detection was 1.0 mu M (i.e., 1.76 ng injected), and the calibration plot was linear in the range 1.0 mu M-0.7 mM (correlation coefficient 0.999). The resulting modified electrode was found to retain 80 % of its initial response in flowing streams for 8 h of operating time

Heavy metal determination by biosensors based on enzyme immobilised by electropolymerisation.

The work describes the original application of biosensors based on enzyme immobilised by electropolymerisation to heavy metal determination. An inhibition detection scheme has been employed for detecting Hg2+ by an established glucose biosensor based on glucose oxidase immobilised in poly-o-phenylenediamine. The investigated enzymatic inhibition appears reversible and mixed, in agreement with data for the enzyme in solution. A low response time (<2 min) and a rapid recovery of response by EDTA seem the most interesting characteristics of the proposed biosensor at the present stage of development, along with the well known easy preparation of this kind of biosensors. The occurrence of a high response also for Cu2+ opens the possibility to apply the biosensor in total toxic metal content determination

Sulfide measurements by flow injection analysis and ion chromatography with electrochemical detection

Dissolved sulfide ions are separated and detected by using ion chromatography (IC) and electrochemical detection with a glassy carbon electrode modified by electrochemical deposition of palladium particles. The influence of various experimental factors such as pH, loading of palladium, applied potential and flow rate of mobile phase is evaluated. The effect of some common organic and inorganic compounds on the amperometric signal is also evaluated. Under optimal chromatographic conditions, the detection limit for sulfide (S/N=3) was 0.3\u3bcM (15pmol injected) and the calibration plot was linear for 0.5\u2013350\u3bcM sulfide (r=0.9964, n=16). The separation and detection of sulfides in human blood serum is presented as an example of an application to real specimens