Innovative Sample Preparation Strategies for Emerging Pollutants in Environmental Samples

Importance of the topic

Environmental sample preparation determines the reliability, sensitivity, and sustainability of contaminant monitoring across air, water, soils, sediments, and biota. Emerging pollutants such as microplastics and PFAS are persistent, widespread, and occur at concentrations ranging from percent levels down to parts-per-trillion, creating strong demands for high-selectivity preconcentration, field-deployable sampling, and low-waste workflows. Regulatory drivers (EPA, EEA, others) and growing concerns about ecological and human health effects are accelerating innovation in miniaturized, greener extraction formats and in novel sorbent chemistries that enable both on-site and laboratory analysis.

Aims and overview of the review

This review surveys advances in sample preparation for environmental analysis from roughly 2019–2024, emphasizing: (1) miniaturized extraction formats (SPME, TFME, MEPS, MEPS, PT-SPE, DLLME/LPME, MSPD, NTD), (2) new sorbent chemistries (MIPs, MOFs, COFs, aptamers, ionic liquids, DES), (3) emerging devices and deployment strategies (3D-printed samplers, lab-in-a-bottle, drones, robotic samplers, portable GC–MS and MS), and (4) sustainability metrics and green-sample-prep principles. Representative case studies are used to illustrate performance gains, field applications, and remaining challenges for gases, solids/semisolids, and aqueous matrices.

Methodologies and methodological trends

Key methodological advances described in the review include:

• Miniaturized solid-phase strategies: conventional SPE scaled to micro-SPE/MEPS/PT-SPE and thin-film and fiber SPME configurations that reduce solvent usage while enabling high preconcentration factors and automation compatibility.
• Liquid microextraction formats: DLLME, vortex-assisted LLMEs, and switchable solvent LPME variants to minimize solvent and sample volumes with rapid phase transfer.
• Matrix solid-phase dispersion (MSPD): combined disruption/extraction/clean-up for solids and sediments, with vortex-assisted and green-solvent implementations to reduce sample mass and solvent needs.
• Needle trap devices (NTDs) and in-tube extraction: compact sorbent-packed needles and tubes for active or passive gaseous sampling, compatible with field deployment and thermal desorption.
• Functional sorbent design: molecularly imprinted polymers, metal-organic and covalent organic frameworks, layered double hydroxides, nanocomposites, deep eutectic solvents and ionic liquids used as tailored extraction phases to enhance selectivity and capacity.
• Device integration and miniaturized platforms: 3D-printed sorbents and samplers, lab-in-a-bottle stirrers coated with MOFs, drone-deployed SPME/TFME, and robotic sampler arrays enabling automated, remote, or hazardous-area sampling.

Instrumentation used

The principal instrumental pairings and analytical tools discussed are:

• Chromatography coupled to mass spectrometry: GC–MS (including portable GC–MS), GC–MS/MS, LC–MS/MS, UPLC–HRMS for targeted and non-targeted analyses.
• Direct ionization / rapid MS: DART-MS and direct SPME–MS interfaces for ultra-rapid screening.
• Detectors for volatile/semi-volatile work: GC–FID, portable MS systems, thermal desorption accessories.
• Spectroscopy and imaging for particle identification: FTIR (including µ-FTIR) and Raman microscopy for microplastic identification and composition mapping; pyrolysis–GC–MS for bulk polymer characterization.
• Elemental tools: ICP-MS and continuum-source molecular absorption spectrometry where metals or inorganic species are targeted.
• Specialized sampling hardware: needle trap devices, cryogenic air samplers, lab-on-a-drone micropumps, 3D-printed stirrers and cartridges, magnetic levitation flow cells for particle separation, and portable/underwater SPME samplers for deep-sea work.

Main results and discussion

Across matrices, the reviewed literature shows consistent performance improvements and novel capabilities:

• Gaseous samples: Active and passive sorbent-based sampling remain fundamental. Innovations include drone-lab platforms (3D-printed micropumps for H2S with sub-µg·L⁻¹ sensitivity), drone- and robot-mounted SPME/NTD arrays coupled to portable GC–MS or portable MS for rapid on-site VOC profiling, and cryogenic samplers for PFAS in air particulates. NTDs packed with high-surface-area COFs produced low LODs for PAHs.
• Solids/semisolids: MSPD variants and CA-/VA-/UA-assisted SPME modalities reduced solvent consumption and sample mass while achieving ng·g⁻1-level detection for pharmaceuticals, PAHs, pesticides, and plastic-associated organics. Magnetic levitation and biphasic magnetic-trapping approaches enabled sequential density- and size-based fractionation of microplastics and simultaneous desorption of sorbed organics for downstream HPLC analysis.
• Aqueous samples: Lab-in-a-bottle and 3D-printed paddle stirrers coated with MOFs (e.g., MIL‑100(Fe)) provided low-µg·L⁻1 LODs for phenolics in wastewater while enabling in situ extraction. SPME and TFME devices (including drone deployment and submarine samplers) facilitated sampling in otherwise inaccessible environments. PFAS extraction benefited from ion-exchange–functionalized SPME coatings (HLB-WAX/PAN), achieving low- to sub-ng·L⁻1 detection limits when coupled to LC–MS/MS; direct SPME–MS approaches enabled extremely fast screening.

Performance metrics reported across selected studies included recoveries typically between 70–120% for many miniaturized formats, RSDs often <20% in validated method sets, and LODs down to low ng·L⁻1 or sub-ng·m⁻3 (air) depending on analyte and technique. The combination of tailored sorbents and device miniaturization repeatedly improved field portability and reduced waste compared with classical workflows.

Benefits and practical applications

Primary benefits identified are:

• Field deployability: drone- and robot-mounted samplers, portable GC–MS/MS, and lab-in-a-bottle concepts support remote, hazardous, or deep-water sampling with minimal sample handling.
• Reduced environmental footprint: solvent-free or low-solvent microextraction formats and greener sorbent choices (biomaterials, DES) align with green analytical chemistry metrics and lower lab waste and exposure risks.
• Higher selectivity and sensitivity: engineered sorbents (MIPs, MOFs/COFs, ion-exchange phases) enhance trace-level capture and reduce matrix interferences.
• Faster workflows: direct SPME–MS and rapid desorption techniques enable near-real-time screening useful for emergency response, industrial emission monitoring, and rapid site assessment.
• Versatile sample classes: methods are applicable across air, water, sediment, soil, and biota, enabling integrated environmental monitoring programs.

Future trends and potential uses

Anticipated directions and opportunities include:

• Deeper integration of miniaturized sampling with portable high-resolution mass spectrometry and on-board preconcentration for true point-of-need analytics.
• Expanded use of additively manufactured (3D-printed) sorbents and housings for bespoke sampler geometries and rapid prototyping at low cost.
• Increased deployment of autonomous and semi-autonomous platforms (drones, quadruped robots) for spatially resolved monitoring and rapid response in hazardous zones.
• Standardization and validation of miniaturized/green methods to meet regulatory requirements, including interlaboratory comparisons and robustness testing across diverse matrices.
• Continued development of selective sorbents that are robust, regenerable, and compatible with direct MS interfaces, together with life-cycle and greenness assessments (e.g., AGREE and related metrics).
• Novel separations for microplastics and associated pollutant profiling (e.g., bidimensional magnetic levitation coupled to targeted desorption), enabling combined particle fractionation and contaminant analysis.

Conclusions

Recent years have seen rapid, application-driven innovation in environmental sample preparation. Miniaturized extraction formats, advanced sorbent chemistries, and device integration (drones, 3D printing, robotic platforms) combine to deliver greater sensitivity, field portability, and sustainability than many traditional approaches. Challenges remain in method standardization, matrix complexity, ultratrace PFAS quantification, and scaling new methods for routine regulatory monitoring. Continued cross-disciplinary work—combining materials science, instrument miniaturization, and green-chemistry metrics—will be central to translating laboratory innovations into broadly adoptable environmental monitoring solutions.

References

Selected references cited in the review (representative, standard form):

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