Determination of aluminium using different techniques based on the Al(III)-morin complex.

Three different methods for the determination of Al(III) in aqueous samples were compared. The different described procedures were based on the formation of the Al(III)-morin complex. UV-Vis spectrophotometry, spectrofluorimetry and differential pulse adsorptive stripping voltammetry (DPAdSV) techniques were compared under optimized experimental conditions. The DPAdSV method showed a better performance for the analysis of Al(III) in terms of capability of detection (70 nM) in comparison with the value obtained for UV-Vis spectrophotometric (300 nM) and spectrofluorimetic (110 nM) techniques. Thus, DPAdSV method was selected for the analysis of aluminium in river, tap and bottled water samples under the following optimized experimental conditions: pH = 4.4, deposition potential = +243 mV, deposition time = 210 s, giving satisfactory results.

Simultaneous determination of cadaverine and putrescine using a disposable monoamine oxidase based biosensor.

The selective and simultaneous amperometric determination of putrescine (Put) and cadaverine (Cad) has been carried out using a novel design of screen-printed carbon electrode (SPCE) with two working electrodes connected in array mode. A mixture of 3% of tetrathiafulvalene (TTF), as mediator, and carbon ink was used for the construction of the screen-printed working electrode. The employment of different amounts of monoamine oxidase (MAO) enzyme on these modified TTF/SPCEs and the use of gold nanoparticles (AuNPs) allowed performing the simultaneous determination of both analytes. The amperometric detection has been performed by measuring the oxidation current of the mediator at a potential of+250 mV vs. screen-printed Ag/AgCl reference electrode. A linear response in the Cad concentration range from 19.6 till 107.1 µM and from 9.9 till 74.1 µM for Put was obtained at the MAO/AuNPs/TTF/SPCE biosensor. This device showed a capability of detection of 9.9 and 19.9±0.9 µM (n=4 α=ß=0.05) and a precision of 4.9% and 10.3% in terms of relative standard deviation for Put and Cad, respectively. The developed biosensor was successfully applied to the simultaneous determination of Put and Cad in octopus samples.

Screen-printed biosensors for glucose determination in grape juice.

An approach to the glucose determination by amperometric biosensing in wine industry applications is presented. Integrated screen-printed biosensors based on horseradish peroxidase (HRP) and glucose oxidase (GOx) have been developed. The experimental design methodology has been used to find the optimum conditions of the experimental variables, in such a way that a chronoamperometric response specific for glucose was recorded. Under these conditions, repeatability and reproducibility of the modified electrodes have been analyzed. The detection limit for glucose has been calculated taking into account the probability of false positive (alpha) and negative (beta), reaching a medium value of 4.37+/-0.21 micromol dm-3 (alpha=beta=0.05, and a replicate n=4). The biosensor was applied to the determination of glucose in white wine samples.