SOLAμ for pre-analysis sample concentration

Significance of the Topic

The accurate quantification of trace analytes in biofluids is essential for pharmacokinetics, toxicology and clinical studies. Efficient pre-concentration improves analytical sensitivity and sample throughput by minimizing evaporation steps and stabilizing labile compounds.

Objectives and Study Overview

This study evaluates Thermo Scientific™ SOLAμ™ Solid Phase Extraction (SPE) for twenty-fold pre-concentration of niflumic acid in human plasma. The goal is to achieve lower limits of quantitation and high recovery without traditional dry-down and reconstitution.

Methodology

Plasma samples were diluted 1:1 with 4% phosphoric acid. Each 500 µL aliquot was loaded onto a SOLAμ WAX 96-well plate, washed with 25 mM ammonium acetate (pH 4) and 70% methanol (pH 4), then eluted in two 12.5 µL fractions of methanol/acetonitrile with ammonia. Direct injection followed without evaporation.

Used Instrumentation

• Thermo Scientific™ Dionex™ UltiMate™ 3000 RSLC system with Accucore RP-MS (50 × 2.1 mm, 2.6 µm) column and Defender guard cartridge.
• Thermo Scientific™ TSQ Vantage™ triple-stage quadrupole mass spectrometer with HESI source (positive mode, 3000 V spray voltage, 475 °C vaporizer temperature).

Main Results and Discussion

The SPE protocol concentrated analyte twenty-fold, achieving a linear dynamic range of 40–40000 pg/mL with r² = 0.998. The 40 pg/mL limit of quantitation exhibited clear chromatographic peaks at acceptable signal-to-noise. Intra-assay precision (%RSD) was ≤ 1.31% at low QC and ≤ 1.06% at high QC; accuracy deviations were within ± 5%. Recovery exceeded 89.9% and matrix effects were below 9% at both low and high QC levels.

Benefits and Practical Applications

• Enhanced sensitivity through minimal elution volumes and high reproducibility.
• Time savings by eliminating evaporation and reconstitution steps.
• Improved analyte stability and recovery due to reduced non-specific binding and adsorption.

Future Trends and Potential Applications

Automation of micro-elution SPE formats for high-throughput workflows, integration with ultra-high-pressure LC systems and expansion to a wider range of analytes are anticipated. Applications include therapeutic drug monitoring, biomarker quantitation and trace-level environmental analysis.

Conclusion

Thermo Scientific SOLAμ SPE provides a streamlined, robust pre-concentration method delivering twenty-fold analyte enrichment with excellent accuracy, precision and cleanliness. The approach supports sensitive, high-throughput bioanalysis without complex sample handling.