Enrichment-free analysis of anionic micropollutants in the sub-ppb range in drinking water by capillary electrophoresis-high resolution mass spectrometry

Abstract

Reversed-phase liquid chromatography (RPLC) used for water analysis is not ideal for the analysis of highly polar and ionic contaminants because of low retention. Capillary electrophoresis (CE), on the other hand, is perfectly suited for the separation of ionic compounds but rarely applied in environmental analysis due to the weak concentration sensitivity when coupled to mass spectrometry (MS). However, novel interface designs and MS technology strongly improve the sensitivity. Here, a method is presented enabling the screening of anionic micropollutants in drinking water without sample pretreatment by coupling of CE to an Orbitrap mass spectrometer by a nanoflow sheath liquid interface. Targeted analysis of halogenated acetic acids, trifluoromethanesulfonic acid, and perfluorooctanoic and perfluorooctanesulfonic acid was conducted in drinking water samples which were chlorinated for disinfection. A bare fused silica capillary with an optimized background electrolyte (BGE) for separation consisting of 10% acetic acid with 10% isopropanol with large volume sample injection and optimized interface parameters offer limits of quantification in the range of < 0.1 to 0.5 μg/L with good linearity (R 2 > 0.993) and repeatability (14% standard deviation in area). Concentrations of the target analytes ranged from 0.1 to 6.2 μg/L in the water samples. Masses corresponding to halogenated methanesulfonic acids have been found as suspects and were subsequently verified by standards. Mono-, dichloro-, and bromochloro methanesulfonic acid were quantified in a range of 0.2 to 3.6 μg/L. Furthermore, five sulfonic acids, four organosulfates, and the artificial sweeteners acesulfame and cyclamate as well as inorganics such as halides, halogenates, phosphate, and sulfate could be determined as suspects among more than 300 features in a non-targeted screening. Overall, this approach demonstrates the great potential of CE-nanoESI-MS for the screening of ionic contaminants in environmental samples, complementary to chromatographic approaches.

Persistent, mobile and toxic (PMT) and very persistent and very mobile (vPvM) substances pose an equivalent level of concern to persistent, bioaccumulative and toxic (PBT) and very persistent and very bioaccumulative (vPvB) substances under REACH

“…Current analytical measurements for the most mobile substances are not widely available (the "analytical gap") and thus many go unnoticed and undetected in the water cycle ("the monitoring gap"). However, progress has been made to address this analytical gap and methods such as hydrophilic interaction liquid chromatography [23], supercritical fluid chromatography [24], mixed-mode liquid chromatography [25] and capillary electrophoresis [26] have now made it possible to analyse some of the most mobile substances. This progress also contributes to closing the monitoring gap as more of the most mobile substances can be detected.…”

Capillary electrophoresis-mass spectrometry for the direct analysis of glyphosate: method development and application to beer beverages and environmental studies

“…In addition, the choice of the BGE is more limited as the requirements for MS compatibility are even higher than for sheath liquid interfaces. A compromise may be the sheath flow interface using electrokinetic pumping [102] or nanoESI [103]; however, its applicability to GLP still has to be shown. Comparing our method to LC-MS-based approaches, matrix effects were low despite the negligible sample preparation with degassing only.…”

“…The separation of the strong acids DFA and TFA was not sufficient. Just recently, Höcker et al [103] demonstrated the separation of strong acids (e.g., chlorinated and brominated acetic acids) using a new CE-nanoESI-MS method with LOQs below 0.5 μg/L. For a broad screening of strong organic acids, further BGE modifications may be necessary, adapting pH and possibly the addition of organic solvents.…”

Rapid biomonitoring of perfluoroalkyl substance exposures in serum by multisegment injection‐nonaqueous capillary electrophoresis‐tandem mass spectrometry

“…[49][50][51] However, perfluorinated anionic surfactants possess strong adsorption properties that contribute to band broadening and/or poor resolution in CE when using aqueous BGE conditions with inadequate organic modifier content. 42 As a result, a nonaqueous BGE system was used for separation of PFASs in this work, which was composed of 70% v/v acetonitrile, 15% v/v methanol, and 5% v/v isopropanol;…”