Multiresidue microextraction-GC-MS/MS for emerging tire rubber contaminants in urban waters

Tire rubber contains many chemicals that can enter aquatic ecosystems through tire wear particles or leachates from crumb rubber surfaces. The antiozonant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) and its transformation product, 6PPD-quinone, are of particular concern due to their toxicity associated with aquatic species mortality. Other relevant compounds from the PPD family are DPPD and IPPD. Vulcanizing and crosslinking agents, including benzothiazole, 2-mercaptobenzothiazole, N-cyclohexylbenzothiazole-2-sulfenamide (CBS) and hexamethoxymethylmelamine (HMMM), together with alkyl organophosphate esters and alkyldimethylamines are also of great interest. This work aimed to develop an analytical method for detecting and quantifying 11 emerging tire rubber contaminants in urban waters. The method is based on solid-phase microextraction (SPME) using commercial fibers followed by gas chromatography coupled to tandem mass spectrometry (GC-MS/MS). SPME parameters were optimized via multivariate design to efficiently extract all analytes. The method was successfully validated for linearity, precision, and accuracy, with mean recoveries of 84-105%. In all the urban water samples analyzed, 6PPD and 6PPDQ were detected. To our knowledge, this is the first time that GC-MS/MS has been applied to the analysis of most of these compounds, including PPDs, as well as the first proposal of SPME for the extraction and analysis of many of these compounds. This is also the first investigation of these substances in real water samples originating from recycled tire rubber surfaces as a potential source of contamination. Due to its simplicity, this multiresidue method, which includes antiozonants, vulcanizing, and crosslinking agents, can be easily implemented in any routine laboratory.