Robust peptide quantitation using the TSQ Certis triple quadrupole mass spectrometer and OptiSpray ion source and cartridges

Significance of the topic

Precise, reproducible quantitation of targeted peptides is essential for biomarker verification, translational proteomics, and therapeutic development. As studies scale to large cohorts and demand higher throughput, platforms must combine sensitivity, speed, and operational robustness. The TSQ Certis triple quadrupole mass spectrometer paired with the OptiSpray ion source and cartridge workflow addresses these requirements by delivering high duty-cycle SRM performance optimized for capillary-flow proteomics, simplifying routine operation while maintaining sub-femtomole sensitivity and stringent quantitative metrics.

Goals and overview of the study

The work aimed to evaluate quantitative performance and operability of the TSQ Certis MS with OptiSpray cartridges for a multiplexed targeted peptide assay. Key objectives were to assess sensitivity, linearity, reproducibility, retention time stability, and suitability for high-throughput operation. The evaluation used an 82-peptide Health Surveillance Panel (HSP) representing 57 plasma proteins (including >20 established biomarkers) across an 11-point stable isotope-labeled (SIL) dilution series and extended replicate injections to mimic real-world, high-throughput runs (100 samples per day; 13 min per run).

Methodology

• Assay composition: 82 SIL-spiked peptides from 57 plasma proteins; background matrix: 50 ng digested human plasma; PRTC (Pierce Peptide Retention Time Calibration Mixture) included for retention time control.
• Calibration: 11-point SIL dilution curve (0 to 120 fmol on-column) with six replicates per point to evaluate linearity and limits of detection/quantification.
• LC configuration: trap-and-elute at capillary flow (1.8 μL/min) using PepMap Neo trap (300 μm × 5 mm) and PepMap Neo cartridge (150 μm × 15 cm); total run time = 13 min (100 SPD).
• MS acquisition: scheduled SRM method covering 1,080 transitions (including PRTC) with 2-min retention windows; TSQ Certis architecture enabling up to 900 SRM/s, short dwell times (~1.3–2 ms) and cycle times ~0.4–0.6 s.
• Data processing: Skyline for peak detection and AUC; Thermo TraceFinder for automated review and quantitative reporting.

Used instrumentation

• Thermo Scientific TSQ Certis triple quadrupole mass spectrometer with OptiSpray ion source and PepMap Neo 150 μm × 15 cm cartridge (tapered emitter).
• Thermo Scientific Vanquish Neo UHPLC System (capillary-flow configuration).
• PepMap Neo trap cartridge (300 μm × 5 mm) for preconcentration/desalting.
• Software: Xcalibur for acquisition, Skyline-daily for processing, TraceFinder for automated quantification and review.
• Representative source settings reported: positive ion voltage 1,800 V; sheath gas ~10 (arb); ion transfer tube temperature 250 °C; cartridge temperature 45 °C.

Main results and discussion

• Sensitivity and linearity: median lower limit of detection (LLOD) ~0.019 fmol on-column and median lower limit of quantification (LLOQ) ~0.164 fmol. More than 99% of peptides showed excellent linearity (R² > 0.99) across the 0–120 fmol range.
• Throughput and sampling density: Scheduled acquisition of 1,080 transitions yielded median ~16 data points across chromatographic peaks and >96% of transitions had >8 points across the peak, meeting recommended sampling for accurate quantitation in highly multiplexed methods.
• Duty cycle performance: Short dwell times (~1.3–2 ms) with adaptive dwell scheduling produced cycle times of ~0.4–0.6 s, enabling robust signal collection even at high transition loads.
• Reproducibility: For an 11-point calibration at 100 SPD, six replicate injections produced an average peak-area %RSD of 3.2% (range 0.77–12.9%); >98% of peptides exhibited RSD <10% in that experiment. Across 71 consecutive injections of 50 ng plasma digest, median peptide peak-area RSD was 3.2% with ~89% of native peptides showing RSD <10% and ~95% <20% when considering low-abundance outliers.
• Retention time stability: Retention times for 35 peptides representing 24 key protein biomarkers ranged from ~3.09 to 10.42 min with RSDs typically <0.5% (average ~0.3%), supporting tight scheduling windows for high multiplexing.
• PRTC performance: The 14 PRTC peptides showed highly stable intensity and retention time across 71 injections with most peptides having intensity RSD <10% and retention time RSD <0.5%.

Benefits and practical applications

• High-throughput targeted quantitation: The combination of TSQ Certis scan architecture and OptiSpray cartridges supports 100 SPD workflows without sacrificing quantitative performance, suitable for large-cohort studies and verification workflows.
• Operational robustness and ease-of-use: Cartridge-based OptiSpray simplifies emitter positioning and reproducible ionization, reducing operator-dependent variability and downtime in capillary-flow setups.
• Preclinical and translational research: Sub-femtomole sensitivity, excellent linearity, and robust retention-time control make the platform appropriate for biomarker verification, targeted proteomics studies, and multiplexed clinical-research assays (non-diagnostic use).

Future trends and opportunities

• Higher multiplexing at maintained quantitative fidelity: Continued improvements in scan speed and dynamic scheduling will permit even larger SRM panels while preserving points-per-peak and sensitivity.
• Integration with automated sample prep and lab information systems: Combining robust MS hardware with fully automated sample workflows will further increase throughput and reproducibility for clinical research cohorts.
• Standardized cartridge-based interfaces: Wider adoption of cartridge emitters and standardized capillary-flow hardware could reduce inter-laboratory variability and accelerate method transfer for multi-site studies.
• Hybrid workflows: Pairing high-throughput SRM with complementary discovery or PRM assays will streamline biomarker pipelines from discovery through verification.

Conclusion

The TSQ Certis triple quadrupole MS with the OptiSpray source and PepMap Neo cartridges demonstrated high sensitivity (sub-femtomole), outstanding linearity for nearly all targets, tight retention-time reproducibility (<0.6% RSD for most peptides), and excellent quantitative precision at 100 samples/day throughput. These characteristics, together with simplified cartridge-based operation, make the platform well suited for translational proteomics and high-throughput targeted peptide quantification in research and preclinical biomarker studies.

References

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2. Fu Q, Johnson C, Inker LA, Van Eyk JE. A targeted LC MS/MS assay of a health surveillance panel and its application to chronic kidney disease. bioRxiv [Preprint]. 2025 Mar 16. doi:10.1101/2025.03.14.643399. PMID:40161722; PMCID:PMC11952516.