Overview of SPE Technology/Method Development & New Trends in Sample Preparation

Importance of the Topic

Sample preparation is a critical step in analytical chemistry workflows that ensures reliable quantitative and qualitative data. Solid phase extraction (SPE) streamlines cleanup, concentrates analytes and removes matrix interferences in diverse samples such as biological fluids, environmental extracts and food matrices. Effective SPE improves sensitivity, protects chromatographic systems and enhances data quality.

Objectives and Study Overview

This review provides an overview of SPE technology, explores retention mechanisms, presents a systematic approach to SPE method development and highlights new trends in sample preparation. Case studies illustrate optimization of SPE protocols for pharmaceuticals and metabolites in serum and urine. Recent advances in sorbents and alternative extraction formats are also discussed.

Methodology and Instrumentation

SPE operates on chromatographic principles using cartridges or 96-well plates packed with reversed-phase, normal-phase, ion-exchange or mixed-mode sorbents. Key steps include conditioning, equilibration, sample loading, washing and elution. Instrumentation ranges from vacuum manifolds, flow-through 96-well plates and automated liquid handling robots (e.g., Gilson SPE 215, TomTec Quadra, Zymark RapidTrace) to HPLC and GC-MS systems. Method development employs load breakthrough tests and wash/elution profiling at varying pH and organic strength.

Main Results and Discussion

Systematic SPE development yields higher selectivity and reproducibility than generic protocols. In one case, tricyclic antidepressants from sheep serum achieved recoveries >90 % with low background using optimized wash with 40 % MeOH in basic buffer on C18 96-well plates, outperforming a polymeric competitor. Furosemide extraction from horse serum reached quantitative recovery down to 0.5 µg/mL using a weaker 60 % MeOH eluent. Urinary corticosteroids were cleanly fractionated on cyanopropyl SPE, avoiding column fouling observed with C18. Multi-residue pesticide cleanup in food employed QuEChERS dispersive SPE and dual-layer mixed-mode cartridges for efficient cleanup.

Benefits and Practical Applications

SPE offers high selectivity, low solvent consumption and compatibility with automation. It is versatile across aqueous and organic matrices, delivering high recoveries, improved sensitivity and minimal matrix effects for bioanalysis, environmental testing and food safety. Fractionation and mixed-mode strategies enable targeted isolation of neutral, acidic or basic analytes.

Future Trends and Applications

Emerging SPE technologies include molecularly imprinted polymers (MIPs) for ultra-selective extraction of trace analytes, supported liquid extraction devices, SPE disks for large-volume samples and online SPE interfaced with LC systems. Microextraction techniques such as solid-phase microextraction (SPME), stir-bar sorptive extraction (SBSE) and dispersive formats (QuEChERS) continue to expand adaptability and throughput.

Conclusion

A systematic approach to SPE method development, grounded in understanding retention mechanisms and controlled pH/organic strength experiments, ensures robust, reproducible protocols. Advances in sorbent chemistries and extraction formats enhance selectivity and ease of use, supporting high-throughput applications in analytical chemistry.

Used Instrumentation

• Solid phase extraction cartridges and 96-well plates (reversed-phase, ion-exchange, mixed-mode)
• Vacuum manifolds and Visiprep dispensers
• Automated SPE systems (Zymark RapidTrace, Gilson SPE 215, TomTec Quadra)
• Hybrid SPE formats (MIPs, SPE disks)
• HPLC systems with Discovery C18, C8, CN and F5 columns
• GC-MS analyzers

References

• Majors RE. New Sample Prep Technologies for the Sample Prep Industry. GMP Training Systems; 2006.
• Wells DA. High Throughput Bioanalytical Sample Preparation. Elsevier; 2003.
• Simpson NJK, editor. Solid-Phase Extraction: Principles, Techniques, Applications. Marcel Dekker; 2000.
• Fritz JS. Analytical Solid-Phase Extraction. John Wiley & Sons; 1999.
• Wiltshire H. In: Venn RF, editor. Principles and Practice of Bioanalysis. Taylor & Francis; 2000.