Research progress on analytical methods for the determination of <italic>p</italic>-phenylenediamine-based rubber antioxidants and their quinone transformation products

<italic>p</italic>-Phenylenediamine（PPD） compounds are widely used as antidegradants in the rubber industry due to their excellent antioxidant and antiozonant properties. However， increasing environmental concerns have arisen regarding their transformation products， especially quinone derivatives（PPD-Qs）， which are formed through oxidative processes under environmental conditions. These compounds have been frequently detected in various matrices， including air， water， sediment， soil， and biota， and have demonstrated significant ecological toxicity even at trace concentration. Accurate quantification of PPDs and PPD-Qs remains a significant analytical challenge due to their low environmental concentrations， high chemical reactivity， and matrix interferences. This review critically evaluates the current state-of-the-art analytical methodologies for the determination of PPDs and PPD-Qs across various environmental compartments. Emphasis is placed on the latest advancements in sample pretreatment techniques and instrumental detection methods that are suitable for complex and heterogeneous matrices. In gaseous and particulate samples， quartz fiber filters， passive samplers， and accelerated solvent extraction（ASE） have been employed for effective compound collection and extraction， with antioxidant protection（e.g.， glutathione） used to prevent analyte degradation. solid-phase extraction（SPE） based on hydrophilic-lipophilic balance（HLB） sorbents， as well as salting-out assisted liquid-liquid extraction（SALLE）， have achieved high recovery rates and reduced matrix effects. Passive monitoring approaches like diffusive gradients in thin films（DGT） have enabled long-term， time-integrated assessment of waterborne PPD-Qs under varying environmental conditions. For solid or semi-solid matrices such as soil， sediment， and biological tissues， ultrasound-assisted extraction（UAE）， gel permeation chromatography（GPC）， and modified QuEChERS methods have been widely adopted for high-efficiency extraction and purification. Instrumentally， gas chromatography-mass spectrometry（GC-MS） and liquid chromatography-tandem mass spectrometry（LC-MS/MS） remain the gold standards for sensitive and specific quantification. High-resolution mass spectrometry（HRMS）， such as Orbitrap platforms， enables non-targeted screening and structural elucidation of unknown metabolites and degradation products. In addition， emerging techniques such as condensed phase membrane introduction mass spectrometry（CP-MIMS） provide rapid， in situ detection with minimal sample pretreatment， showing great potential for real-time environmental monitoring. Electrochemical sensing platforms based on carbon-based or metal nitride-modified electrodes have also demonstrated promise due to their rapid response， cost-effectiveness， and field-deployable capabilities. However， challenges such as electrode fouling and selectivity limitations remain. In conclusion， this review integrates and evaluates a wide range of analytical approaches for detecting PPDs and PPD-Qs in complex environmental matrices. The comparative analysis of methodologies provides practical insights for optimizing analytical performance and advancing environmental surveillance. Future research should prioritize the development of automated， high-throughput， and green analytical platforms that are adaptable to field monitoring， risk assessment， and regulatory needs for emerging tire-derived contaminants.