Efficiency of a low-cost pyramid-shaped solar still for pesticide removal from highly contaminated water.

Water pollution by pesticides and other chemical contaminants is a subject of major importance due to the risk for human health and the environment. The search for remediation processes able to withdraw chemical contaminants from water and to allows water reuse is an urgent need. Herein, a simple and cheap system for pesticides removal was constructed and evaluated using water samples contaminated with two widely used herbicides (imazapic and imazethapyr, at g L-1 level). Operation parameters and process efficiency, in terms of removal rate in the reclaimed water and degradation rate of pesticides in the dry residue, were quantitatively determined. The model was tested in real-world field experiments and was able to remove more than 99.95% of both contaminants from a 10 L solution containing 4.16 ±â€¯0.94 g of imazethapyr and 1.31 ±â€¯0.17 g of imazapic, generating reusable water with minimum volume loss (<2.5%). Liquid chromatography coupled to mass spectrometry was used to determine the herbicides content in all samples and to estimate the degree of degradation of the substances as well as the occurrence of transformation products of imazapic and imazethapyr. The system efficiency in removing contaminants of emerging concern from surface water was also evaluated. The process have generated output water with undetected levels for two fungicides present in a local river in Southern Brazil.

Dissipation behaviour and dietary risk assessment of boscalid, triflumizole and its metabolite (FM-6-1) in open-field cucumber based on QuEChERS using HPLC-MS/MS technique.

BACKGROUND: To resist plant diseases, boscalid and triflumizole have been applied to cucumbers frequently. However, the residue and dietary risk assessment of these fungicides in cucumber should be given attention for food safety. RESULTS: An effective and highly sensitive method based on the liquid chromatography-tandem mass spectrometry technique for simultaneous multidetermination of boscalid, triflumizole and its metabolite (FM-6-1) in a cucumber ecosystem was established and validated. Field experiments were conducted in three different locations, where boscalid and triflumizole (35% suspension concentration) were applied at 253 g of active ingredient (a.i.) per hectare (the recommended high dosage) and 379.5 g a.i. ha-1 (1.5 times the recommended high dosage) in each location. The limits of quantification and the limits of detection of the proposed method ranged from 0.01 to 0.05 mg kg-1 and 3.9 × 10-5 to 7.5 × 10-4 mg L-1 respectively. The mean recoveries and relative standard deviations of these compounds were 80-105% and 1.0-6.1% respectively. The dissipation dynamics of compounds followed pseudo-first-order kinetic models remarkably, with a half-value period of 2.3-40.8 days. The residues of boscalid and triflumizole in cucumber at harvest were below 0.66 mg kg-1 and 0.07 mg kg-1 respectively. The results of the dietary risk assessments have shown a low dietary risk of compounds in cucumber with hazard ratios <1 and hazard index <1. CONCLUSION: These results from the experiments are the most important for putting a guide on reasonable usage of these fungicides under the open-field conditions in China. © 2018 Society of Chemical Industry.

Synthesis of novel chiral imidazolium stationary phases and their enantioseparation evaluation by high-performance liquid chromatography.

Two novel chiral stationary phases (CSPs) were prepared by bonding chiral imidazoliums on the surface of silica gel. The chiral imidazoles were derivatized from chiral amines, 1-phenylethylamine and 1-(1-naphthyl)ethylamine. The obtained CSPs were characterized by Fourier Transform Infrared (FT-IR) spectroscopy and elemental analysis (EA), demonstrating the bonding densities of CSP 1 and CSP 2 were 0.43 mmol g-1 and 0.40 mmol g-1, respectively. These two CSPs could be used to availably separate 8 pharmaceuticals, 7 mandelic acid/its derivatives, 2 1-phenylethylamine derivatives, 1 1,1'-bi-2-naphthol, and 1 camphorsulfonic acid in high-performance liquid chromatography (HPLC). It is found that CSP 1 could effectively enantioseparate most chiral analytes, especially the acidic components, while CSP 2 could enantiorecognize all chiral analytes, although a number of components did not achieve baseline separation. Additionally, the effects of mobile phase composition, mobile phase pH and salt content, chiral selector structures, and analyte structures on the enantiorecognitions of the two CSPs were investigated. It is found that high acetonitrile content in mobile phases was conducive to enantiorecognition. Mobile phase pH and salt content could alter the retention behaviors of different enantiomers of the same chiral compound, resulting in better enantioresolution. Moreover, both chiral selector structures and substituted groups of analytes played a significant role in the separation of chiral solutes.

Experimental assessment of electromigration properties of background electrolytes in capillary zone electrophoresis.

Electromigration dispersion (EMD) properties of background electrolytes (BGEs) used in capillary zone electrophoresis (CZE) are of key importance for the success of an analysis. The knowledge of these properties may serve well for the prediction of the asymmetry of peaks of analytes, for the prediction of unsafe regions where a strong interference of system zones may be expected, and for the selection of optimum conditions where the analytes of interest may give sharp and practically symmetric peaks. Present theories enable one to calculate and predict EMD properties of many BGEs but there is also a lot of BGEs that are beyond the present theoretical models as far as their composition and equilibria involved are considered. This contribution brings a method for assessment of EMD properties of any BGE from easily accessible experimental data. The method proposed is illustrated by model examples both for cationic and anionic separations. Imidazole acetate, histamine acetate, and histidine acetate served as model BGEs for cationic separations; as the model BGE for anionic separations, Tris-borate and sodium-borate BGEs have been selected since these buffers are frequently used and borate is well-known for its complexing equilibria in aqueous solutions.