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Oxidative treatment methods are valuable tools for the microbial safety of drinking water. However, the reaction of oxidants with natural substances or anthropogenic contaminants present in the raw water can potentially lead to the formation of harmful transformation products (TPs). The present paper proposes a tiered approach for the risk evaluation of TPs formed from pesticides residues during drinking water treatment. First, the concentrations of pesticides residues in raw water used for drinking water production are evaluated (step 1). Substances with a predicted concentration in raw water above 0.1 µg/L proceed further to a reactivity assessment, examining the behaviour in water treatment plants (step 2). Using information available in the scientific literature, prediction of structural elements in the TPs can be made and allow a worst-case assessment based on the Threshold of Toxicological Concern (TTC) (step 3). If concerns remain, experiments may be conducted to simulate water treatment (step 4). Because of their complexity and variability, experiments for the simulation of water treatment should focus on prioritized substances of potential concern. The test conditions should be realistic (i.e., close to EU-representative conditions in waterworks) and ozonation and chlorination should be combined with pre- and post-treatment steps, as is normally the case in European waterworks. As a first screening option, we propose to test the toxicity of the reaction mixture. If the treated water shows an enhanced toxicity, further experiments can be conducted to identify and quantify the major TPs (step 5). We propose to define major TPs as substances present at more than 10% of the initially applied test substance. For major TPs a tiered dietary risk assessment is conducted, starting with the TTC concept, and continuing with toxicity testing of the TP, according to EFSA and ECHA and internationally agreed guidance.

A molecular rotational resonance spectroscopy method for measuring the enantiomeric excess of pantolactone, an intermediate in the synthesis of panthenol and pantothenic acid, is presented. The enantiomers are distinguished via complexation with a small chiral tag molecule, which produces diastereomeric complexes in the pulsed jet expansion used to inject the sample into the spectrometer. These complexes have distinct moments of inertia, so their spectra are resolved by MRR spectroscopy. Quantitative enantiomeric excess (EE) measurements are made by taking the ratio of normalized complex signal levels when a chiral tag sample of high, known EE is used, while the absolute configuration of the sample can be determined from electronic structure calculations of the complex geometries. These measurements can be performed without the need for reference samples with known enantiopurity. Two instruments were used in the analysis. A broadband, chirped-pulse spectrometer is used to perform structural characterization of the complexes. The broadband spectrometer is also used to determine the EE; however, this approach requires relatively long measurement times. A targeted MRR spectrometer is also used to demonstrate EE analysis with approximately 15-min sample-to-sample cycle time. The quantitative accuracy of the method is demonstrated by comparison with chiral gas chromatography and through the measurement of a series of reference samples prepared from mixtures of (R)-pantolactone and (S)-pantolactone samples of known EE.

The cycloaddition of activated alkynes, among them 6-alkynylpterins, with the tributylphosphine-carbon disulfide complex followed by a Wittig reaction of the resulting ylid with carbonyl compounds or nitrosobenzene affords novel 2-alkylidene- or 2-(phenylimino)-1,3-dithioles in moderate to very good yields. The pterin-substituted species are potential intermediates in the synthesis of the molybdenum cofactor

The cycloaddition of activated alkynes, among them 6-alkynylpterins, with the tributylphosphine-carbon disulfide complex followed by a Wittig reaction of the resulting ylid with carbonyl compounds or nitrosobenzene affords novel 2-alkylidene- or 2-(phenylimino)-1,3-dithioles in moderate to very good yields. The pterin-substituted species are potential intermediates in the synthesis of the molybdenum cofactor

The identification of n-decyl alpha(1--6)isomaltoside as a main component of technical alkyl polyglucoside (APG) mixtures by the parallel use of liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) spectroscopy is described. Following enrichment on a styrene-divinylbenzene-based solid-phase extraction material, unknown components were separated by reversed-phase liquid chromatography (LC). Chemical characterization was achieved by both mass spectrometry and NMR spectroscopy. It is demonstrated that the combination of LC-MS with various NMR techniques is very suitable for stereochemical assignment of unknown components in technical APG mixtures.