Showing papers by "Juan A. Squella published in 2013"

Sensitive determination of nitrofurantoin by flow injection analysis using carbon nanofiber screen printed electrodes

Abstract: In this work, a new method to quantify nitrofurantoin in aqueous media using a flow injection system connected to commercially available screen-printed carbon nanofibers was developed. A pretreatment of the screen-printed carbon nanofibers electrode with BrittonRobinson buffer/N,N-dimethylformamide was applied to enhance the ni- trofurantoin peak current signal in one step. The developed method was demonstrated to be sensible, reproducible, easy, and inexpensive. With a low detection limit, it is applicable to real samples. The results indicate that it is highly applicable for the detection of nitrofurantoin in several matrices. When urine samples without any pretreat- ment were analyzed, the method proved reproducible and sensible and had a low detection limit. The use of screen- printed electrodes has advantages over other modified electrodes as a glassy carbon due to its versatility.

Electrochemical Analysis of Nitrofurans Based on Flow Injection Analysis on Pretreated Commercial Carbon Nanofiber Screen Printed Electrodes: Determination in Chicken Muscle Samples

Abstract: A new method for the pre-treatment of a commercially available carbon-nanofibre screen-printed electrode (CNF-SPE) using a single one-step process was evaluated and applied for the analytical determination of nitrofurans. The optimal pre-treatment conditions were found to include a soaking process in Britton‐Robinson buffer/ Dimethylformamide (DMF) 70/30% solution for 15 min of activation time. Voltammetric curves were obtained for several biologically significant nitrofurans (furazolidone, nitrofurazone and nitrofurantoin) using the activated CNF-SPE, and a considerable increase in the peak current was observed. According to the chronoamperometric results, the calculated active area for a CNF-SPE activated with the pre-treatment was increased approximately 19 times compared to the active area of a non-activated electrode. Changes in the morphology of the electrode active area were observed in scanning electron microscopy (SEM) images after the activation pre-treatment. The carbon nanofibre surfaces became rougher and this increase in roughness was directly related to an enlargement of the electroactive area, with a corresponding increase in the active-site availability for the nitro compounds. The increase in the electrochemical activity of the activated surface was visualized with scanning electrochemical microscopy (SECM). In addition, a new approach to obtain SECM images on SPE is revealed. In order to apply the activated CNF-SPE, an analytical method using Linear-Sweep Voltammetry with a Flow Injection Analysis System (LSV-FIAS) was developed to analyze the nitrofurans in samples of chicken muscle, obtaining recoveries ranging from 97.2% to 102.7% and relative standard deviations between 1.9% and 5.2%.

Determination of arsenic (iii) by differential pulse polarography in the waters of camarones area, chile

Abstract: As (III) was determined by differential pulse polarography (DPP) in 1 mol L -1 HCl as supporting electrolyte. For quantification, the -0.35 V peak (versus Ag/AgCl) was chosen. The obtained detection and quantification limits were 2.7 (3 SD) and 8.9 (10 SD) μg L -1 respectively.The method was used for the determination of As (III) on surface water samples from Camarones River, located in Camarones area, province of Arica, Chile (this area’s water contain high levels of salinity). The results indicate that the proposed methodology is a suitable analytical alternative for As determination in natural waters with high levels of dissolved salts, as the waters of Camarones River. The method is not time consuming, nor tedious no prior treatment of the sample is required. The results show that As (III) concentrations in waters of Camarones River are about 10 times higher than the guide values established by WHO for water intended for human consumption. Keywords: Arsenic (III), surface water, differential pulse polarography.