Achieve higher bioanalytical sensitivity with SOLAμ SPE for analytes susceptible to issues during pre-concentration dry down

Importance of the Topic

In bioanalysis, achieving low-level detection of labile or volatile analytes often requires pre-concentration. Traditional SPE methods use high elution volumes necessitating evaporation and reconstitution steps, which can cause analyte loss and variability. Thermo Scientific SOLAµ SPE eliminates drying by enabling direct micro-elution, improving sensitivity and reproducibility.

Objectives and Study Overview

The study aims to evaluate SOLAµ SPE coupled with micro-elution for extraction of analytes prone to loss during concentration. Ibuprofen and ketoprofen in rat plasma served as model compounds. The performance was compared to conventional SPE with dry-down steps using metrics of accuracy, precision, recovery, matrix effects, and linearity.

Methodology and Instrumentation

The sample workflow involved:

• Plasma diluted 1:1 with 4% H₃PO₄; loading 200 µL on SOLAµ SAX 96-well plate
• Sequential conditioning, sample loading, washing, and elution in two 25 µL aliquots of 50:50 MeOH/ACN with 2% HCOOH
• No evaporation; final volume of 50 µL achieves fourfold concentration

Chromatographic separation was performed on an Accucore RP-MS column with a 4-minute gradient at 1.2 mL/min on a Dionex UltiMate 3000 RSLC. MS/MS detection used a TSQ Vantage with HESI source in positive/negative polarity switching.

Used Instrumentation

• Dionex UltiMate 3000 RSLC system
• Accucore RP-MS HPLC column (50 × 2.1 mm, 2.6 µm) with Defender guard cartridge
• Thermo Scientific SOLAµ SAX 96-well SPE plate (2 mg/1 mL)
• TSQ Vantage triple quadrupole mass spectrometer
• HyperSep 96 vacuum manifold and associated 96-well plates and mats

Key Results and Discussion

The SOLAµ SPE method delivered a linear dynamic range of 10–1000 ng/mL for both ibuprofen (R²=0.997) and ketoprofen (R²=0.999). Accuracy across calibration was within ±5%, and QC levels (25, 500, 750 ng/mL) showed precision RSD<4% for ibuprofen and <2% for ketoprofen. Recovery exceeded 90% for both analytes. Matrix effects were below 7% except for 15% at low QC for ibuprofen. Chromatograms at LOQ displayed acceptable signal-to-noise ratios.

Practical Benefits and Applications

• Fourfold pre-concentration without evaporation steps
• Reduced sample handling time and risk of analyte loss
• Improved sensitivity benefiting bioanalytical assays in pharmacokinetics, toxicology, and drug metabolism studies
• Compatibility with high-throughput 96-well workflows

Future Trends and Opportunities

Micro-elution SPE formats like SOLAµ are poised to expand in bioanalysis due to demands for higher throughput and lower detection limits. Integration with automated liquid handlers, miniaturized chromatographic systems, and novel sorbent chemistries targeting polar biomarkers will further enhance analytical performance. Coupling with high-resolution MS and multiplex assays can broaden applications in proteomics and untargeted metabolomics.

Conclusion

The SOLAµ SPE micro-elution approach offers a robust alternative to conventional SPE with dry down, providing significant gains in sensitivity, reproducibility, and sample integrity. It streamlines bioanalytical workflows while meeting stringent industry requirements for accuracy and precision.