Development and validation of QuEChERS-based extraction for quantification of nine micropollutants in wastewater treatment plant.

A modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was established for simultaneous quantification of eight pharmaceutical molecules (2-hydroxyibuprofen, diclofenac, ibuprofen, propranolol, ofloxacin, oxazepam, sulfamethoxazole, carbamazepine) and caffeine in environmental matrices. Analysis was performed by ultra-high-performance liquid chromatography with tandem mass spectrometry (UHPLC-MS-MS). Quantification was performed by using the 13C internal standard method for each molecule. Two methods were firstly optimized on freeze-dried waste activated sludge and then applied and validated on real complex matrices, which have contrasted physicochemical properties, i.e., clarified wastewater and primary sludge. The combination of acetate buffer with MgSO4 (protocol A) and citrate buffer with Na2SO4 (protocol B) was found necessary to recover the nine targeted compounds. Adding a higher salts quantity of Na2SO4 (protocol B) compared to MgSO4 (protocol A) is crucial to increase the ionic strength of the aqueous solution and to obtain comparable extraction recoveries of the targeted molecules. Adding two times solvent volume to the aqueous phase leads to increased absolute recovery for all molecules and both protocols. After demonstration of the final protocol's performance on the control matrix, its robustness was tested on the matrices of interest. As a result, the two proposed detection methods exhibit good reproducibility, high sensitivity, and high reliability.

A deeper investigation on carbohydrate cycling in Sinorhizobium meliloti.

Recycling of triose-phosphate and pentose-phosphate was previously reported on glucose in Sinorhizobium meliloti, a polysaccharide-synthesizing bacterium, but the metabolic basis of such processes remained unclear. In this work, we have used (13)C-labelling strategies to demonstrate that carbohydrate cycling in this organism is independent of the gluconate bypass, the alternative pathway for glucose assimilation involving its periplasmic oxidation into gluconate. Furthermore, carbohydrate cycling in S. meliloti is also observed on fructose, making the situation in this bacterium significantly different from that depicted for alginate-synthesizing species.