Determination of Cr(VI) in leather residues using graphite/paraffin composite electrodes modified with reduced graphene oxide nanosheets.

In this study, we determined the Cr(VI) in samples of tanned leather residues by differential pulse voltammetry (DPV) using graphite/paraffin composite electrodes modified with reduced graphene oxide nanosheets (referred to as GPEs/nsRGO). After the modification, the composite electrodes were characterized by two electrochemical techniques (i.e., cyclic voltammetry, CV, and electrochemical impedance spectroscopy, EIS), scanning electron microscopy, and Raman spectroscopy. The electroanalytical method was applied using the GPEs/nsRGO. An analytical curve was obtained in a Clark-Lubs buffer solution (pH = 1), with a linear concentration range from 25.0 to 392.0 µmol L-1 and a limit of detection (LOD) of 1.01 µmol L-1. The GPEs/nsRGO showed good reproducibility in their manufacturing process and good response repeatability with an RSD of 4.59% over twelve measurements. These composite electrodes showed excellent selectivity, which was demonstrated by analyses in the presence of metal ions (Ca2+, Zn2+, Mg2+, Fe3+, Co2+, Na+, and Cu2+) that did not interfere in the analysis of Cr(VI). The GPEs/nsRGO were applied to the determination of Cr(VI) in real samples of wet-blue leather and leather ash using DPV. This approach was validated using the sample recovery method, where it presented values from 95.6 to 108.2%. The proposed method showed satisfactory results compared to the literature and can be considered a good alternative for the determination of Cr(VI) in aqueous samples.

Physical Exercise for Individuals With Spinal Cord Injury: Systematic Review Based on the International Classification of Functioning, Disability, and Health.

Introduction: Considering the reduction of physical activity performed daily in people with spinal cord injury, it is necessary to analyze the interventions based on physical exercises in order to provide recommendations based on evidence. Objectives: To review and evaluate the literature on physical exercise interventions for individuals with SCI, based on the International Classification of Functioning, Disability and Health, as well as physiological parameters for exercise prescription. Method: A systematic review of the literature produced from August 2016 to February 2017 within the PubMed, Embase, Cochrane Library, and MEDLINE databases. Results: Two independent examiners conducted a search in which 223 articles were initially found. A third evaluator verified possible divergences and generated a final list of 25 articles that strictly met the inclusion criteria, 5 of which investigated the effects of aerobic exercise, 2 of resistance training, 2 of balance training, 12 of gait training, and 4 evaluating the combined effect of 2 or more forms of training. Conclusion: Considering studies classified as of high and moderate quality of evidence, positive effects were observed in the domains of structures and functions, in aerobic, resistance training and combined exercises, and in some studies with gait training. In the domain of activities and participation, positive effects were observed in the studies with gait training, balance training, and combined interventions.