An environmentally sensitive method for rapid monitoring of 6PPD-quinone in aqueous samples using solid phase extraction and direct sample introduction with liquid chromatography and tandem mass spectrometry

Abstract

The tire rubber antioxidant derivative N-(1,3-dimethylbutyl)-N′-p-phenyl-phenylenediamine-quinone (6PPD-Q) has been linked to toxic injury and death of coho salmon (Oncorhynchus kisutch) in Northeastern Pacific urban watersheds. The chemical is known to be lethal to coho salmon at relatively low and environmentally relevant concentrations. We have developed a new and environmentally sensitive method for rapid monitoring of 6PPD-Q at concentrations ranging from less than 2 ng L⁻¹ to over 1400 ng L⁻¹ in water samples collected from creeks. Sample analysis by liquid chromatography tandem mass spectrometry (LC-MS/MS) following solid phase extraction (SPE) or dilution and direct introduction (dilute-and-shoot or DnS) was investigated. Limits of quantification were 1.74 ng L⁻¹ for DnS-LC-MS/MS and 0.03 ng L⁻¹ for SPE-LC-MS/MS using 9.6 mL of water sample, which was 3.3 times lower than the lowest reported limit of quantification (0.1 ng L⁻¹) obtained with 500 mL of sample. The method used up to 99% less solvent during extraction than established procedures, leading to an equivalent reduction in the amount of waste generated. Sample storage space was also reduced due to the small volumes of sample required for analysis and the smaller bottles needed to collect these samples. The method was evaluated by comparing results with those obtained by a commercial laboratory using established procedures, which showed good agreement (r² = 0.982). This environmentally friendly and cost effective strategy for 6PPD-quinone analysis may be applied to other chemical monitoring studies in order to optimize sample storage and solvent usage while covering a wide range of analyte concentrations.