Interaction of toluene with polar stationary phases under conditions typical of hydrophilic interaction chromatography probed by saturation transfer difference nuclear magnetic resonance spectroscopy.

Toluene has been used as void volume (zero retention) marker since the inception of hydrophilic interaction chromatography (HILIC), based on the assumption that its hydrophobicity should prevent it from interacting with stationary phases envisioned to be covered by relatively thick layers of water. Recent work has shown that the void volumes of partly water-swollen HILIC phases are not identical to the volumes probed by toluene, yet the compound is still ubiquitously used as void volume marker. As part of our investigations of the retention mechanisms in HILIC, we probed the extent to which toluene is capable of penetrating into the water-enriched layer and to interact with the functional groups of three commercially available hydrophilic and polar stationary phases with different charge properties and water-retaining abilities, using saturation transfer difference 1H nuclear magnetic resonance (STD-NMR) spectroscopy at high resolution magic angle spinning (HR-MAS) conditions. The test solutions were 1000 ppm of toluene in deuterated acetonitrile and water mixtures, with and without addition of ammonium acetate, in order to mimic a set of conditions typically encountered in HILIC separations. Interactions between toluene and the functional groups on the stationary phases were probed by equilibrating the phases with these eluent mimics and measuring the transfer of magnetization from stationary phase protons to the protons of toluene. Our results show that toluene is indeed capable of traversing the water-enriched layers of all the three tested phases and of interacting with protons that are tightly associated with the stationary phases.

Evaluating gas chromatography with a halogen-specific detector for the determination of disinfection by-products in drinking water.

The occurrence of disinfection by-products (DBPs) in drinking water has become an issue of concern during the past decades. The DBPs pose health risks and are suspected to cause various cancer forms, be genotoxic, and have negative developmental effects. The vast chemical diversity of DBPs makes comprehensive monitoring challenging. Only few of the DBPs are regulated and included in analytical protocols. In this study, a method for simultaneous measurement of 20 DBPs from five different structural classes (both regulated and non-regulated) was investigated and further developed for 11 DBPs using solid-phase extraction and gas chromatography coupled with a halogen-specific detector (XSD). The XSD was highly selective towards halogenated DBPs, providing chromatograms with little noise. The method allowed detection down to 0.05 µg L-1 and showed promising results for the simultaneous determination of a range of neutral DBP classes. Compounds from two classes of emerging DBPs, more cytotoxic than the "traditional" regulated DBPs, were successfully determined using this method. However, haloacetic acids (HAAs) should be analyzed separately as some HAA methyl esters may degrade giving false positives of trihalomethanes (THMs). The method was tested on real water samples from two municipal waterworks where the target DBP concentrations were found below the regulatory limits of Sweden.