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In situ enzymatic generation of bimetallic nanoparticles, mainly Au/Pt, overcomes the drawbacks (continuous absorbance drift, modest LOQ, and long-time reaction) observed when AuNP alone are produced. In this study, Au/Pt nanoparticles have been characterized by EDS, XPS, and HRTEM images using the enzymatic determination of tyramine with tyramine oxidase (TAO) as a model. Under experimental conditions, the Au/Pt NPs show an absorption maximum at 580 nm which can be related to the concentration of tyramine in the range 1.0 × 10-6M to 2.5 × 10-4M with a RSD of 3.4% (n = 5, using 5 × 10-6M tyramine). The Au/Pt system enables low LOQ (1.0 × 10-6 M), high reduction of the absorbance drift, and a significant shortening of the reaction time (i.e., from 30 to 2 min for a [tyramine] = 1 × 10-4M); additionally, a better selectivity is also obtained. The method has been applied to tyramine determination in cured cheese and no significant differences were obtained compared to a reference method (HRP:TMB). The effect of Pt(II) seems to involve the previous reduction of Au(III) to Au(I) and NP generation from this oxidation state. Finally, a three-step (nucleation-growth-aggregation) kinetic model for the generation of NPs is proposed; this has enabled us to obtain a mathematical equation which explains the experimentally observed variation of the absorbance with time.

Brotizolam and Midazolam, psychotropic drugs belonging to thienotriazolodiazepine and imidazobenzodiazepine families, have been determined by flow injection analysis with photometric detection. At pH 7, signals showed to be rectilinear from 1.27 × 10-6 M to 1.07 × 10-4 for brotizolam and from 1.53 × 10-6 M to 1.07 × 10-4 M for midazolam. Methods developed were applied to the determination of both drugs in their formulations (Lendormin and Dormicum). © 1988, Taylor & Francis Group, LLC. All rights reserved., SCOPUS: ar.j, info:eu-repo/semantics/published