Showing papers by "Juan A. Squella published in 2014"

Vibrating screen printed electrode of gold nanoparticle-modified carbon nanotubes for the determination of arsenic(III)

Abstract: A linear sweep anodic stripping voltammetric method using a carbon nanotube–gold nanoparticle-modified vibrating screen printed electrode for the determination of arsenic(III) is reported. The experiments were conducted with a 0.1 mol L−1 solution of H2SO4 in order to estimate the electrode area related to gold oxide formation. The results showed a clear reduction peak at approximately +0.85 V corresponding to the reduction of the gold surface oxide with a superficial area of 0.089 cm2. A vibrating motor was attached to the screen printed electrode to create a portable and autonomous system with enhanced mass transfer. The repeatability of the measurements was 2.4 % (n = 10) at the level of 0.5 mg L−1 of arsenic(III) under the best instrumental operating conditions. The peak current was linearly dependent on the arsenic(III) concentration, thus allowing the construction of a linear analytical curve in the range from 10 to 550 μg L−1 with the equation: −Ip (μA) = 0.05 + 134.59 [As(III) (μg L−1)], R2 = 0.99. The obtained detection and quantification limits were 0.5 (3 SD) and 1.5 (10 SD) μg L−1, respectively, using 120 s as the deposition time. It was shown that Cu(II) does not interfere in the detection of As(III) using the proposed method.

Multiwalled carbon nanotubes modified electrodes with encapsulated 1,4-dihydro-pyridine-4-nitrobenzene substituted compounds

Abstract: We report a voltammetric study of several nitroaromatic compounds such as the drugs: Nifedipine, Nitrendipine, Furnidipine and Nisoldipine in multiwalled carbon nanotubes (MWCNT) modified electrodes.All the compounds are strongly encapsulated in the three dimensional structure of the MWCNT and then reduced to the corresponding hydroxylamine deriva -tives. In the case of the modified electrode with MWCNT the answer in current are remarkably increased (approximately 40 times). This current multiplier effect is due to the nitro compounds are not only superficially adsorbed but this really encapsulated in the nanotube network covering the GCE.The nitro reduction peak was linearly dependent with the concentration of the nitroaromatic compound with detection limit (LOD) of 1.2 ∙10 -8 mol∙L -1 and a quantification limits (LOQ) of 3.9∙10 -8 mol∙L -1 for the case of Nitrendipine. All the studied nitrocompounds followed equivalents behaviours. Obviously from this result it is possible to postulate this technology as a very useful tool to develop analytical methods to determine these nitroaromatic drugs in real samples such as biological fluids.From the obtained results it is possible to conclude that for the studied 1,4-dihydropyridine-4-nitrobenzene substituted compounds a greater difficulty of reduc-tion implies a greater ability to encapsulation.