Automated, High-Throughput Analysis of Tire-Derived p-Phenylenediamine Quinones (PPDQs) in Water by Online Membrane Sampling Coupled to MS/MS.

The tire-derived contaminant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6-PPDQ) was recently identified as a potent toxin to coho salmon (Oncorhynchus kisutch). Studies investigating 6-PPDQ have employed solid-phase extraction (SPE) or liquid-liquid extraction (LLE) with liquid chromatography-mass spectrometry (LC-MS), providing excellent sensitivity and selectivity. However, cleanup and pre-enrichment steps (SPE/LLE) followed by chromatographic separation can be time- and cost-intensive, limiting sample throughput. The ubiquitous distribution of 6-PPDQ necessitates numerous measurements to identify hotspots for targeted mitigation. We recently developed condensed phase membrane introduction mass spectrometry (CP-MIMS) for rapid 6-PPDQ analysis (2.5 min/sample), with a simple workflow and low limit of detection (8 ng/L). Here, we describe improved quantitation using isotopically labeled internal standards and inclusion of a suite of PPDQ analogues. A low-cost autosampler and data processing software were developed from a three-dimensional (3D) printer and Matlab to fully realize the high-throughput capabilities of CP-MIMS. Cross-validation with a commercial LC-MS method for 10 surface waters provides excellent agreement (slope: 1.01; R2 = 0.992). We employ this analytical approach to probe fundamental questions regarding sample stability and sorption of 6-PPDQ under lab-controlled conditions. Further, the results for 192 surface water samples provide the first spatiotemporal characterization of PPDQs on Vancouver Island and the lower mainland of British Columbia.

Aqueous naphthenic acids and polycyclic aromatic hydrocarbons in a meso-scale spill tank affected by diluted bitumen analyzed directly by membrane introduction mass spectrometry.

With the increasing use of unconventional, heavy crude oils there is growing interest in potential impacts of a diluted bitumen (DB) spill in marine and freshwater environments. DB has the potential to release several toxic, trace organic contaminants to the water column. Here, the aqueous concentrations and compositions of two classes of organic contaminants, naphthenic acids (NAs) and polycyclic aromatic hydrocarbons (PAHs), are followed over 8 weeks after a simulated spill of DB (10 L) into a freshwater mesocosm (1200 L) with river sediment (2.4 kg). These complex samples contain biogenic dissolved organic matter, inorganic ions, petroleum contaminants, suspended sediments, and oil droplets. We report the first use of condensed phase membrane introduction mass spectrometry (CP-MIMS) as a direct sampling platform in a complex multi-phase mesocosm spill tank study to measure trace aqueous phase contaminants with little to no sample preparation (dilution and/or pH adjustment). CP-MIMS provides complementary strengths to conventional analytical approaches (e.g., gas- or liquid chromatography mass spectrometry) by allowing the entire sample series to be screened quickly. Trace NAs are measured as carboxylates ([M-H]-) using electrospray ionization and PAHs are detected as radical cations (M+•) using liquid electron ionization coupled to a triple quadrupole mass spectrometer. The DB-affected mesocosm exhibits NA concentrations from 0.3 to 1.2 mg/L, which rise quickly over the first 2 - 5 days , then decrease slowly over the remainder of the study period. The NA profile (measured as the full scan in negative-electrospray ionization at nominal mass resolution) shifts to lower m/z with weathering, a process followed by principal component analysis of the normalized mass spectra. We couple CP-MIMS with high-resolution mass spectrometry to follow changes in molecular speciation over time, which reveals a concomitant shift from classical 'O2' naphthenic acids to more oxidized analogues. Concentrations of PAHs and alkylated analogues (C1 - C4) in the DB-affected water range from 0 to 5 µg/L. Changes in PAH concentrations depend on ring number and degree of alkylation, with small and/or lightly alkylated (C0 - C2) PAH concentrations rising to a maximum in the first 4 - 8 days (100 - 200 h) before slowly decaying over the remainder of the study period. Larger and heavily alkylated (C3 - C4) PAH concentrations generally rise slower, with some species remaining below the detection limit throughout the study period (e.g., C20H12 class including benzo[a]pyrene). In contrast, a control mesocosm (without oil) exhibited NA concentrations below 0.05 mg/L and PAHs were below detection limit. Capitalizing on the rapid analytical workflow of CP-MIMS, we also investigate the impacts of sample filtration at the time of sampling (on NA and PAH data) and sample storage time (on NA data only).

A Direct Mass Spectrometry Method for the Rapid Analysis of Ubiquitous Tire-Derived Toxin N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine Quinone (6-PPDQ).

The oxidative transformation product of a common tire preservative, identified as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6-PPDQ), has recently been found to contribute to "urban runoff mortality syndrome" in Coho salmon at nanogram per liter levels. Given the number of fish-bearing streams with multiple stormwater inputs, large-scale campaigns to identify 6-PPDQ sources and evaluate mitigation strategies will require sensitive, high-throughput analytical methods. We report the development and optimization of a direct sampling tandem mass spectrometry method for semiquantitative 6-PPDQ determinations using a thin polydimethylsiloxane membrane immersion probe. The method requires no sample cleanup steps or chromatographic separations, even in complex, heterogeneous samples. Quantitation is achieved by the method of standard additions, with a detection limit of 8 ng/L and a duty cycle of 15 min/sample. High-throughput screening provides semiquantitative concentrations with similar sensitivity and a full analytical duty cycle of 2.5 min/sample. Preliminary data and performance metrics are reported for 6-PPDQ present in representative environmental and stormwater samples. The method is readily adapted for real-time process monitoring, demonstrated by following the dissolution of 6-PPDQ from tire fragments and subsequent removal in response to added sorbents.