A comparative study among different types of modified electrodes for nitric oxide (NO) determination has been carried out. Detection limit, response time, reproducibility and selectivity versus some interferents as ascorbic acid, nitrite and dopamine were evaluated. Platinum (Pt) and glassy carbon (GC) electrodes have been assembled with homemade cellulose acetate membranes, commercially available membranes, Nafion and nonconducting polymers electrosynthesized directly onto the electrode surface. The most interesting results were obtained with a cellulose acetate membrane modified electrode and a Pt/poly[4,4 0 -dihydroxybenzophenone (4,4 0 -DHB)] electrode. The NO probes assembled showed a detection limit of 20 nmol/L and 40 nmol/L, respectively, for the cellulose acetate membrane modified electrode and for the Pt/poly[4,4 0 -dihydroxybenzophenone (4,4 0 -DHB)] electrode. A biological test on washed platelets stimulated by collagen was performed using the Pt/poly(4,4 0 -DHB) electrode.
This paper reports the optimisation of a competitive immunoassay (ELISA) to detect lactosylated proteins in milk samples. The assay employs monoclonal antibodies for lactosylated proteins produced in our laboratory and requires no pre-treatment of the samples other than a dilution step. Monoclonal antibodies were fully characterised in terms of selectivity and cross-reactivity with structurally related molecules and used in a competitive assay format with lactosylated standard proteins (lactosylated ovalbumin). The detection limit for lactosylated ovalbumin was 0.015 microgram ml-1 and the working range was from 0.010 to 40 micrograms ml-1. The data obtained indicate that the ELISA developed is applicable to diluted milk samples and is able to distinguish between milk samples that have undergone different heat treatments (UHT and pasteurised milk).
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