PERFORMANCE OF A PALLADIUM FILM ELECTRODE FOR THE DETERMINATION OF THALLIUM AND LEAD IN NATURAL WATER SAMPLE BY DIFFERENTIAL PULSE ANODIC STRIPPING VOLTAMMETRY

<p></p><p>The use of a palladium film electrode (PdFE) as an alternative electrode for the determination of thallium (Tl+) and lead (Pb2+) in water samples by anodic stripping voltammetry is proposed. Preliminary studies of the influence of the substrate were performed on the electrochemical behavior of PdFE prepared ex situ. Using a silver solid amalgam electrode as substrate (AgSAE), the effect of several parameters such as potential and deposition time, composition and pH of supporting electrolyte on the analytical response of PdFE for Tl+ by differential pulse anodic stripping voltammetry (DPASV) was initially investigated. Under best experimental conditions of deposition potential of −1.2 V and deposition time of 300s the analytical curve was linear in the Tl+ concentration from 3.0 to 100.0 µg L−1 with a relative standard deviation (RSD) <2.0%. The limit of detection (LOD) and limit of quantification (LOQ) were 0.89 µg L−1 and 2.96 µg L−1, respectively. The PdFE was successfully applied for the determination of Tl+ in water samples. Moreover, this electrode showed promising as a sensor for the simultaneous determination of Tl+ and Pb2+ and as a suitable alternative to the mercury electrode.</p><p></p

PERFORMANCE OF A PALLADIUM FILM ELECTRODE FOR THE DETERMINATION OF THALLIUM AND LEAD IN NATURAL WATER SAMPLE BY DIFFERENTIAL PULSE ANODIC STRIPPING VOLTAMMETRY

<p></p><p>The use of a palladium film electrode (PdFE) as an alternative electrode for the determination of thallium (Tl+) and lead (Pb2+) in water samples by anodic stripping voltammetry is proposed. Preliminary studies of the influence of the substrate were performed on the electrochemical behavior of PdFE prepared ex situ. Using a silver solid amalgam electrode as substrate (AgSAE), the effect of several parameters such as potential and deposition time, composition and pH of supporting electrolyte on the analytical response of PdFE for Tl+ by differential pulse anodic stripping voltammetry (DPASV) was initially investigated. Under best experimental conditions of deposition potential of −1.2 V and deposition time of 300s the analytical curve was linear in the Tl+ concentration from 3.0 to 100.0 µg L−1 with a relative standard deviation (RSD) <2.0%. The limit of detection (LOD) and limit of quantification (LOQ) were 0.89 µg L−1 and 2.96 µg L−1, respectively. The PdFE was successfully applied for the determination of Tl+ in water samples. Moreover, this electrode showed promising as a sensor for the simultaneous determination of Tl+ and Pb2+ and as a suitable alternative to the mercury electrode.</p><p></p

AVOCADO, SPENT COFFEE GROUNDS, LICURI AND COCONUT MILK FOR OIL EXTRACTION, BIODIESEL PRODUCTION, AND SPECTRAL ANALYSIS

<p></p><p>An undergraduate organic chemistry experiment for oil extraction and biodiesel production using alternative biomass was developed, whereby oils of avocado, coconut and spent coffee grounds were obtained and submitted to transesterification reaction with CH3OH under NaOH catalysis. Avocado and coffee oils were obtained by typical extraction and coconut oil was obtained through water evaporation of coconut milk in a domestic microwave oven. The commercial oil of licuri (Syagrus coronate), a Brazilian native biomass, was also converted to biodiesel. All four oils and four biodiesels were characterized by 1H-NMR and FTIR, and a comparative study of these spectra reveled that FTIR analyses alone provides enough information to discriminate between oil and biodiesel and confirm transesterification reaction. Besides, the unsaturation degree of all oils was determined by 1H-NMR. A mechanistic proposal concerning the role of NaOH catalysis is presented, excluding the sodium methoxide formation.</p><p></p