Time-Weighted Average SPME Analysis for in Planta Determination of CVOCs

The Potential of Phytoscreening for Plume Delineation at Contaminated Sites Has Promoted Interest in Innovative, Sensitive Contaminant Sampling Techniques. Solid-Phase Microextraction (SPME) Methods Have Been Developed, Offering Quick, Undemanding, Noninvasive Sampling Without the Use of Solvents. in This Study, Time-Weighted Average SPME (TWA-SPME) Sampling Was Evaluated for in Planta Quantification of Chlorinated Solvents. TWA-SPME Was Found to Have Increased Sensitivity over Headspace and Equilibrium SPME Sampling. using a Variety of Chlorinated Solvents and a Polydimethylsiloxane/carboxen (PDMS/CAR) SPME Fiber, Most Compounds Exhibited Near Linear or Linear Uptake over the Sampling Period. Smaller, Less Hydrophobic Compounds Exhibited More Nonlinearity Than Larger, More Hydrophobic Molecules. using a Specifically Designed in Planta Sampler, Field Sampling Was Conducted at a Site Contaminated with Chlorinated Solvents. Sampling with TWA-SPME Produced Instrument Responses Ranging from 5 to over 200 Times Higher Than Headspace Tree Core Sampling. This Work Demonstrates that TWA-SPME Can Be Used for in Planta Detection of a Broad Range of Chlorinated Solvents and Methods Can Likely Be Applied to Other Volatile and Semivolatile Organic Compounds. © 2012 American Chemical Society

Glyphosate has limited short-term effects on commensal bacterial community composition in the gut environment due to sufficient aromatic amino acid levels

Recently, concerns have been raised that residues of glyphosate-based herbicides may interfere with the homeostasis of the intestinal bacterial community and thereby affect the health of humans or animals. The biochemical pathway for aromatic amino acid synthesis (Shikimate pathway), which is specifically inhibited by glyphosate, is shared by plants and numerous bacterial species. Several in vitro studies have shown that various groups of intestinal bacteria may be differently affected by glyphosate. Here, we present results from an animal exposure trial combining deep 16S rRNA gene sequencing of the bacterial community with liquid chromatography mass spectrometry (LC-MS) based metabolic profiling of aromatic amino acids and their downstream metabolites. We found that glyphosate as well as the commercial formulation Glyfonova®450 PLUS administered at up to fifty times the established European Acceptable Daily Intake (ADI = 0.5 mg/kg body weight) had very limited effects on bacterial community composition in Sprague Dawley rats during a two-week exposure trial. The effect of glyphosate on prototrophic bacterial growth was highly dependent on the availability of aromatic amino acids, suggesting that the observed limited effect on bacterial composition was due to the presence of sufficient amounts of aromatic amino acids in the intestinal environment. A strong correlation was observed between intestinal concentrations of glyphosate and intestinal pH, which may partly be explained by an observed reduction in acetic acid produced by the gut bacteria. We conclude that sufficient intestinal levels of aromatic amino acids provided by the diet alleviates the need for bacterial synthesis of aromatic amino acids and thus prevents an antimicrobial effect of glyphosate in vivo. It is however possible that the situation is different in cases of human malnutrition or in production animals