Determination of 6PPD-Quinone in Aqueous Matrices Using Solid Phase Extraction With Various Polymeric Sorbents and Liquid Chromatography with Tandem Mass Spectrometry (LC/MS/MS)

Innovative Solutions for Water Testing
Poster Presentation

Prepared by A. Cocozza
UCT, 2731 Bartram Rd, Bristol, PA, 19007, United States


Contact Information: [email protected]; 215-781-9255

ABSTRACT

The degradation of tires on roadways is known to release numerous chemicals into the environment, posing ecological and health risks. To combat this, the presence of 6PPD (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) gained attention due to its role as a rubber antioxidant. However, studies now show that through reactions with environmental oxidants such as ozone, this compound forms 6PPD-quinone (6PPD-Q), a highly reactive and toxic compound that can pose risks to ecosystems and human health. It has popularly been linked to the mortality of coho salmon as they migrate upstream to spawn, so much so that only a few hours of exposure of the salmon to contaminated stormwater has proven lethal. Considering these recent discoveries, the EPA released an official Draft Method 1634 in January 2024 to extract and analyze 6PPD-Q in water. This method uses an extracted internal standard (EIS) to measure the concentration of 6PPD-Q by isotope dilution and a native internal standard (NIS) to measure the efficiency of the extraction procedure.
This application outlines the SPE extraction and analysis of water samples using quality control protocols outlined in draft method 1634, comparing both UCT’s Enviro-Clean® polymeric highly-crosslinked divinylbenzene SPE cartridges and UCT’s Enviro-Clean® polymeric hydrophilic-lipophilic-balance SPE cartridges. A sample preparation method was optimized by modifying the procedures outlined in the draft method. Both cartridges demonstrated efficient recoveries over a 3-day method detection limit study and mid-level demonstration of capability studies, with the divinylbenzene cartridges achieving cleaner extracts. Both cartridges were also tested using tap water, and with these tests, it was discovered during the experiment that the pH of the sample is crucial to the extraction procedure in field samples.
Using UCT’s SelectraCore® C18 HPLC Column, an optimized analysis method was developed via LC-MS/MS. The core-shell technology of the column reduces backpressure and system downtime on the HPLC and improves chromatographic resolution. The LC method is shortened from the EPA’s outlined run time & injection volume to a 5-minute run time and 10 microliter injection volume. The MS/MS method reached sensitivity levels below the EPA’s lowest suggested standard and met all method criteria for linearity and reproducibility.