Analytical strategies for trace determination of fuel ethers: microextraction and hyphenated techniques

Fuel ethers, including methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME) and diisopropyl ether (DIPE), are widely used as gasoline oxygenates to improve combustion efficiency and reduce exhaust emissions. However, their high water solubility, environmental persistence, mobility, and potential toxicity have raised concerns regarding groundwater contamination and human exposure. This review critically evaluates advances in microextraction-based analytical methodologies for fuel ether determination published between 2010 and 2026, with particular emphasis on the integration of extraction strategies with advanced hyphenated analytical platforms. Comparative evaluation indicates that headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) remains one of the most versatile and extensively validated approaches, particularly for biomonitoring applications, with reported detection limits ranging from 0.0023 to 4.9 µg L⁻¹. For ultra-trace environmental analysis, purge-and-trap and HS-SPME coupled with GC-MS/MS provide the highest sensitivity, enabling sub-ng L^-¹ detection. Needle trap devices (NTDs) represent promising active sampling platforms, achieving enrichment factors up to 129; however, their application to fuel ether analysis remains limited, with only one identified study demonstrating their feasibility using GC-FID. Ion mobility spectrometry (IMS) provides rapid on-site screening capability but generally exhibits lower sensitivity, making it more suitable for preliminary assessment than confirmatory quantification. This review identifies three major challenges limiting broader implementation of advanced analytical technologies: (i) insufficient translation of emerging sorbent materials, including metal-organic frameworks (MOFs), molecularly imprinted polymers (MIPs), and covalent organic frameworks (COFs), into commercially available extraction devices; (ii) limited independent validation of sorbent durability and operational lifetime; and (iii) the absence of standardized fabrication procedures and quality-control protocols, particularly for NTDs. A tiered analytical framework is proposed, recommending GC-FID for routine screening, GC-MS for trace-level biomonitoring, and GC-MS/MS for ultra-trace environmental analysis. Future research should focus on standardization, interlaboratory validation, and the development of robust NTD-based approaches for environmental and occupational exposure monitoring.