Chlorhexidine residues in sludge from municipal wastewater treatment plants: analytical determination and toxicity evaluation.

In this work, a procedure for the sensitive and selective determination of chlorhexidine in sludge from municipal sewage treatment plants (STPs) based on matrix solid-phase dispersion (MSPD) and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was optimized and validated. Analysis of sewage sludge samples, obtained from different STPs in Northwest Spain from 2018 to 2021, showed that chlorhexidine was ubiquitous in this environmental compartment with concentrations between 0.3 and 16 µg g-1. The toxicity of this pollutant was assessed in in vitro assays considering three different model organisms: Candida albicans, Escherichia coli, and Staphylococcus aureus. C. albicans was the most sensitive of the tested microorganisms to chlorhexidine with a lethal threshold concentration of 0.1 mg L-1. Thus, the lowest observed sludge residue was 3 times higher than the acute toxicity threshold measured for C. albicans. Moreover, E. coli and S. aureus were also affected at chlorhexidine concentrations around 1.8 mg L-1 and 0.5 mg L-1, respectively. So, chlorhexidine residues might affect the population of microorganisms existing in STPs. In addition, the potential phytotoxicity of the compound was evaluated with germination experiments using different model seeds. At the evaluated dose (10 µg g-1 dried soil), chlorhexidine did not affect the germination of Sorghum saccharatum, Lepidium sativum, or Sinapis alba seeds. Thus, amending agriculture soils with chlorhexidine containing sludge is unlikely to affect the germination of plants.

Determination of human metabolites of chlorinated phosphorous flame retardants in wastewater by N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide-derivatization and gas chromatography-high resolution mass spectrometry.

The analysis of wastewater for the determination of human biomarkers of exposure (human metabolites) is a non-intrusive, economic and complementary alternative to the analysis of urine in the monitoring of human exposure to chemicals of concern. This study provides the first gas chromatography-based method for the determination of three metabolites of chlorinated organophosphorous flame retardants (OPFRs: bis(2-chloroethyl) phosphate, bis(chloropropyl) phosphate and bis(1,3-dichloro-2-propyl) phosphate) in wastewater. A solid-phase extraction procedure based on the use of mixed-mode reversed-phase weak anion exchange sorbents was optimized including a fractionated elution of OPFRs and their metabolites. Analytes derivatization was investigated by comparing two silylating reagents, N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide and N-methyl-N-(trimethylsilyl)trifluoroacetamide, the first one providing better results. Determination was performed by gas chromatography-high resolution mass spectrometry with a quadrupole-time-of-flight system (GC-QTOF) in order to improve selectivity. Furthermore, the use of GC-QTOF combined with the specific ion obtained from silylated metabolites (m/z 154.9924) can be exploited to screen for other phosphate ester metabolites. Under final conditions, the overall method performance was satisfactory, affording method detection limits ranging from 1.1 to 4.6 ng/L, percentages of recovery from 90% to 110%, and relative standard deviations below 13%. The analysis of composite raw wastewater samples collected over 24 h in the NW of Spain allowed to quantify, for the first time in this matrix, the metabolite bis(chloropropyl) phosphate at levels over 60 ng/L.

Healthy effect of different proportions of marine ω-3 PUFAs EPA and DHA supplementation in Wistar rats: Lipidomic biomarkers of oxidative stress and inflammation.

Dietary intervention with ω-3 marine fatty acids may potentially modulate inflammation and oxidative stress markers related with CVD, metabolic syndrome and cancer. The aim of this study was to evaluate whether different proportions of ω-3 EPA and DHA intake provoke a modulation of the production of lipid mediators and then, an influence on different indexes of inflammation and oxidative stress in a controlled dietary animal experiment using Wistar rats. For such scope, a lipidomic SPE-LC-ESI-MS/MS approach previously developed was applied to determine lipid mediators profile in plasma samples. The effect of ω-3 fatty acids associated to different ratios EPA:DHA was compared with the effect exerted by ω-3 ALA supplementation from linseed oil and ω-6 LA from soybean oil. CRP showed a tendency to greater inflammatory status in all ω-3-fed animals. Interestingly, ratios 1:1 and 2:1 EPA:DHA evidenced a noteworthy healthy effect generating a less oxidative environment and modulating LOX and COX activities toward a decrease in the production of proinflammatory ARA eicosanoids and oxidative stress biomarkers from EPA and DHA. In addition, the ability of 1:1 and 2:1 fish oil diets to reduce lipid mediator levels was in concurrence with the protective effect exerted by decreasing inflammatory markers as ω-6/ω-3 ratio in plasma and membranes. It was also highlighted the effect of a higher DHA amount in the diet reducing the healthy benefits described in terms of inflammation and oxidative stress. Results support the antiinflammatory and antioxidative role of fish oils and, particularly, the effect of adequate proportions EPA:DHA.