Caracterização, gênese e uso de latossolos sob cerrado no município de Rio Paranaíba - MG

The main objective of this research was to study the morphological, physical, chemical, mineralogical and geomorphic characteristics of two soil types in the Rio Paranaíba área of Minas Gerais. Using descriptions based on current methods, the soil profile study was carried out in two trenches both two meters in depth. The landscape of this region consists of an extensive, flat plain where the Red Yellow Latosol is found. In addition, the Dusky Red Latosol is distributed on slopes between the basin of Parana-São Francisco and the plateau. Chemical analysis show that the Red Yellow Latosol presents an extremely low natural fertility and the high amounts of gibbsite indicates a highly advanced degree of weathering for this soil. Mecanization is difficult in the Dusky Red Latosol due to the steep relief. Thus, Dusky Red Latosol could be put to better use as land for pastures and perennial crops taking the necessary care to prevent erosion. The soils were classified respectively as Typic Acrustox and Acrustox according to the Soil Survey Staff (67) and were categorized as Dystrophic Red Yellow Latosol of a clayish texture, flat relief, with clayish substratum sediments and Dystrophic Dusky Red Latosol, of clayish texture, high relief, undulant substratum, with and volcanic tuffs in agreement with the criteria proposed by Bennema and Camargo (11) for the Brasilian Classification.

An alternative method for the simultaneous determination of copper and lead for quality control of sugar cane spirit using a nanotube-based sensor

The development of an electroanalytical method for simultaneous determination of copper and lead ions in sugar cane spirit (cachaça) using carbon paste electrode modified with ascorbic acid and carbon nanotubes (CPE-AaCNT) is described. Squarewave voltammetry (SWV) with anodic stripping was employed, and this technique was optimized with respect to the following parameters: frequency (50 Hz), amplitude (100 mV) and scan increment (9 mV). The analytical curves were linear in the range from 0.0900 to 7.00 mg L - 1 for lead and copper. The limits of detection were 48.5 and 23.9 µg L - 1 for lead and copper, respectively. The developed method was applied to the simultaneous determination of copper and lead in five commercial samples of sugar cane spirit. The results were in good agreement with those obtained by F AAS/GF AAS (flame atomic absorption spectrometry/graphite furnace atomic absorption spectrometry) and showed that CPE-AaCNT can be successfully employed in the simultaneous determination of these metals in real sugar cane spirit samples.

New voltammetry-based technique for the determination of tebuthiuron in crystal and brown sugar samples

Sugar is widely consumed worldwide and Brazil is the largest producer, consumer, and exporter of this product. To guarantee proper development and productivity of sugar cane crops, it is necessary to apply large quantities of agrochemicals, especially herbicides and pesticides. The herbicide tebuthiuron (TBH) prevents pre- and post-emergence of infesting weed in sugarcane cultures. Considering that it is important to ensure food safety for the population, this paper proposes a reliable method to analyse TBH in sugar matrixes (brown and crystal) using square wave voltammetry (SWV) and differential pulse voltammetry (DPV) at bare glassy carbon electrode and investigate the electrochemical behavior of this herbicide by cyclic voltammetry (CV). Our results suggest that TBH or the product of its reaction with a supporting electrolyte is oxidized through irreversible transfer of one electron between the analyte and the working electrode, at a potential close to +1.16 V vs. Ag |AgClsat in 0.10 mol L-1 KOH as supporting electrolyte solution. Both DPV and SWV are satisfactory for the quantitative analysis of the analyte. DPV is more sensitive and selective, with detection limits of 0.902, 0.815 and 0.578 mg kg-1, and quantification limits of 0.009, 0.010 and 0.008 mg kg-1 in the absence of the matrix and in the presence of crystal and brown sugar matrix, respectively. Repeatability lay between 0.53 and 13.8%, precision ranged between 4.14 and 15.0%, and recovery remained between 84.2 and 113% in the case of DPV conducted in the absence of matrix and in the presence of the crystal sugar matrix, respectively.

New voltammetry-based analytical method for indirect determination of procymidone in brazilian apples

Procymidone, a potentially carcinogenic and mutagenic pesticide, can contribute to environmental and human contamination when applied to apple crops. In this work, we propose a reliable and sensitive method to determine procymidone in Brazilian apples. The method involves differential pulse (DPV) and square-wave voltammetry (SWV) techniques on a glassy carbon electrode. In a supporting electrolyte solution of 0.5 mol L−1 NaOH, procymidone undergoes an irreversible one-electron oxidation at +1.42 V by cyclic voltammetric vs. Ag|AgCl, KCl 3 M reference electrode. The proposed DPV and SWV methods have a good linear response in the 8.00–20.0 mg L−1 range, with limits of detection (LOD) of 0.678 and 0.228 mg L−1, respectively, in the absence of the matrix. We obtained improved LOD (0.097 mg L−1) in the presence of apple matrix and the supporting electrolyte solution. We used three commercial apple samples to evaluate recovery, and we achieved recovery percentages ranging from 94.6 to 110 % for procymidone determinations. We also tested the proposed voltammetric method for reproducibility, repeatability, and potential interferents, and the results were satisfactory for electroanalytical purposes.