Qualitative and quantitative analysis of highly-polar contaminants in Atlanta urban water.

BACKGROUND

Highly polar substances have fallen from the scope of investigations due to this lack of accumulation into organic materials and the analytical difficulty they present using "traditional" techniques. This study presents an integrated analytical approach combining liquid chromatography (LC) and travelling-wave ion mobility spectrometry (TWIMS) coupled with high-resolution mass spectrometry (HRMS) for the separation, detection, and quantification of 45 challenging contaminants in urban water matrices. The targeted analytes, including 41 very mobile compounds and 37 highly polar substances (log D < 0), represent compounds that are often poorly retained under conventional reversed-phase and HILIC LC conditions.

RESULTS

TWIMS was used to determine the CCS of 33 small organic molecules (120-500 Da). A ΔCCS threshold of ≥0.5 % was identified as sufficient for proper separation on second-generation IMS instruments (resolving power >300 Rp). In cases where LC provided inadequate retention, TWIMS proved to be an effective complementary technique by exploiting differences in molecular size, shape, and charge to resolve compounds based on their collision cross-section (CCS) values. Surface water samples from the Chattahoochee River and tap water from Midtown Atlanta (USA) were analyzed, revealing that over 50 % of the targeted contaminants were detected in at least one matrix. Notably, compounds such as naphthalene-1-sulfonic acid, nicotine, and several per- and poly-fluoroalkyl substances (PFAS) were consistently observed, highlighting their ubiquitous occurrence in urban water impacted by industrial activities and heavy traffic.

SIGNIFICANCE

The methodology employed not only improved the resolution and identification of small, highly polar molecules but also provided robust quantitative data essential for environmental monitoring and risk assessment. This approach underscores the potential of IMS as a valuable complementary tool to traditional LC-MS workflows in complex environmental analyses. Additionally, the data presented regarding the presence of highly polar substances in urban water matrices should inform stakeholders and implement preventive strategies.