This study describes the development of an analytical methodology based on the use of microchip electrophoresis (ME) devices integrated with capacitively coupled contactless conductivity detection (C4D) for the separation and detection of inorganic anions in post‐blast explosive residues. The best separation condition was achieved using a running buffer composed of 35 mmol/L lactic acid, 10 mmol/L histidine and 0.070 mmol/L cetyl(trimethyl ammonium) bromide. For C4D measurements, the highest sensitivity was obtained applying a 700 kHz sinusoidal wave with excitation voltage of 20 Vpp. The separation of Cl−, NO3−, NO2−, SO42−, ClO4− and ClO3− was performed within ca. 150 s with baseline resolution and efficiencies between 4.4 × 104 and 1.7 × 105 plates/m. The found limits of detection ranged between 2.5 and 9.5 μmol/L. Last, real samples of post‐blast explosive residues were analyzed on the ME‐C4D devices obtaining successfully the determination of Cl−, NO3− and SO42−. The achieved concentration values varied between 12.8–72.5 mg/L for Cl−, 1.7–293.1 mg/L for NO3− and 1.3–201.3 mg/L for SO42−. The data obtained using ME‐C4D devices were in good agreement with the concentrations found by ion chromatography. The approach reported herein has provided short analysis time, instrumental simplicity, good analytical performance and low cost. Furthermore, the ME‐C4D devices emerge as a powerful and portable analytical platform for on‐site analysis demonstrating to be a promising tool for the crime scene investigation.
A photometric flow titration based on the redox reaction between KMnO4 and minoxidil is described. The best titration results were observed at 3.20 x 10-4 mol L-1 KMnO4 and 1.00 x 10-3 mol L-1 minoxidil, using the minoxidil solutions as titrant. The flow rate was fixed at 17 mL min-1 and the titrant was added to the system in aliquots of 500 µL, the color changes were monitored at 550 nm. The method was applied to commercial samples and compared with the results from a chromatographic procedure. Recoveries from 97.6 to 102.8 % were observed depending on the sample. Comparison with the chromatographic procedure reveled relative errors of 3.5 - 4.0 %.
The water bodies of São Carlos/SP receive domestic sewage besides industrial and agricultural wastewaters, so that it was proposed in this work the identification of possible correlations between the waterways anthropogenic contamination and the pollution sources. Twenty-seven sampling points were chosen -strategically located -in order to analyze the following parameters: pH, conductivity, dissolved oxygen, temperature, and total dissolved solids in the water; nutrients (total Kjeldahl nitrogen, total phosphorus, and organic carbon) and metals (Cr, Cu, Mn, Fe, Co, Ni, Cd, Pb, Zn, and Al) in the water and sediments; anions (F -, Cl -, Br -, NO 2 -, NO 3 -, SO 4 2-, and PO 4 3-) and cations (Li + , Na + , K + , NH 4 + , Mg 2+ , and Ca 2+ ) in the water. From the set of data obtained in the analyses, it has been proposed the calculation of a quality index (IQA SC ), so that the quantification of the water quality could be performed, during the summer (rainy weather) and the winter (dry weather). It was observed through the values of the indices that the seasonality is very important for the quality of watercourses in the city, so that during the rainy season the water quality is better than in the dry one in the majority of the sampling points. The Spearman correlation was used in order to distinguish if nutrients, ions, and metals could come from the same source of pollution or if the contributions are of naturally origin. Chemometric analyses (HCA and PCA) were also performed for better interpreting the results, due to the large amount of data.The method of refolding the augmented matrix was important for, through the analyzed data, separating geographical and temporal scores. Through the HCA, the separation of the majority of the groups according to the sampling campaigns was achieved. In one or two groups only the mixture of sampling campaigns were observed. The PCA differentiated some groups of samples, allowing the association of the parameters to anthropogenic or natural sources. By analyzing the obtained results, it could be concluded that the Gregório Stream (inside the urban perimeter), the Tijuco Preto Stream (near its spring), the Água Quente Stream after receiving the sewage of Cidade Araci Suburb, and some points of Monjolinho River are impacted by the presence of domestic sewage.
A photometric flow titration based on the redox reaction between KMnO 4 and minoxidil isdescribed. The best titration results were observed at 3.20 x 10 -4 mol L -1 KMnO 4 and 1.00 x 10 -3 mol L -1minoxidil, using the minoxidil solutions as titrant. The flow rate was fixed at 17 mL min -1 and the titrantwas added to the system in aliquots of 500 μL, the color changes were monitored at 550 nm. The methodwas applied to commercial samples and compared with the results from a chromatographic procedure.Recoveries from 97.6 to 102.8 % were observed depending on the sample. Comparison with thechromatographic procedure reveled relative errors of 3.5 - 4.0 %.
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