Optimization and validation of LLE-LTP to determine florpyrauxifen-benzyl herbicide in water samples by HPLC-DAD

Florpyrauxifen-benzyl is a systemic herbicide which acts on weeds of common occurrence in rice cultivation areas using flooded or rainfed systems. The Brazilian Health Regulatory Agency (ANVISA) authorized the commercialization of this pesticide, but did not establish guidelines with an extraction and quantification method of residues of this compound as a form of environmental monitoring. Therefore, the present study aimed to optimize and validate the liquid-liquid extraction with low temperature purification (LLE-LTP) to determine florpyrauxifen-benzyl content in water samples by high performance liquid chromatography with diode array detection (HPLC-DAD). The recovery ranged from 95.84 to 105.4% with a relative standard deviation less than 1.5. LLE-LTP was selective, precise, accurate, linear in the range from 4.00 to 150 µg L^-1, and the limit of quantification was 4.00 µg L^-1. The stability study of the compound in water revealed its degradation in 25 days and DT₅₀ in approximately 5 days. LLE-LTP coupled to HPLC-DAD presented itself as a simple, easy and efficient method of extracting and analyzing it in water samples.

Catharanthus roseus potential for phyto-stabilizing metals in sewage sludge

This work evaluated the potential of Catharanthus roseus in phytoremediation of As, Ba, Cd, Cu, Cr, Ni, Pb, Se and Zn in sewage sludge-based substrates. C. roseus was cultivated for 108 days in a treatment containing sewage sludge:vermiculite (70:30%) and in the control with 100% commercial substrate. The plants cultivated in sludge showed approximately four times greater height, number of leaves and stem diameter, as well as 89% higher fresh mass than those of the control. The highest concentrations of the metals were obtained in the roots of plants grown in the sludge, and ranged from 2.04 (Cd) to 1121 mg kg^-1 (Zn). Cu, Cd and Zn had a higher bioconcentration factor than 1 in both treatments. On the other hand, the translocation factor value in the control was greater than 1 for Ba, Cd, Cu, Ni, Se and Zn. The results showed that C. roseus was efficient in the phytoremediation of the evaluated metals, in which the translocation process was progressive in the treatment that presented higher metal content.

Easy and fast extraction methods to determine organochlorine pesticides in sewage sludge, soil, and water samples based at low temperature

Organochlorine pesticides present in sewage sludge can contaminate soil and water when they are used as either fertilizer or agricultural soil conditioner. In this study, the technique solid-liquid extraction with low temperature purification was optimized and validated for determination of ten organochlorine pesticides in sewage sludge and soil samples. Liquid-liquid extraction with low temperature purification was also validated for the same compounds in water. Analyses were performed by gas chromatography-mass spectrometry operating in the selective ion monitoring mode. After optimization, the methods showed recoveries between 70% and 115% with relative standard deviation lower than 13% for all target analytes in the three matrices. The linearity was demonstrated in the range of 20 to 70 µg L^-1, 0.5 to 60 µg L^-1, and 3 to 13 µg L^-1, for sludge, soil, and acetonitrile, respectively. The limit of quantification ranged between 2 and 40 µg kg^-1, 1 and 6 µg kg^-1, and 0.5 µg L^-1 for sludge, soil, and water, respectively. The methods were used in the study of pesticide lixiviation carried out in a poly vinyl chlorine column filled with soil, which had its surface layer mixed with sludge. The results showed that pesticides are not leached into soil, part of them is adsorbed by the sewage sludge (4-40%), and most pesticides are lost by volatilization.