Analysis of Immunosupressant Drugs in Whole Blood Using a High-Efficiency Method on an Affordable High-Resolution Mass Spectrometer

Significance of the Topic

Precise quantification of immunosuppressant drugs in whole blood is crucial for therapeutic drug monitoring in transplant patients and for research in autoimmune conditions. High selectivity and throughput are required to support clinical decision making and large-scale studies.

Objectives and Study Overview

This study aimed to assess the performance of the Thermo Scientific Q Exactive Focus hybrid quadrupole-Orbitrap mass spectrometer coupled with a rapid HPLC method for quantitative analysis of four immunosuppressants. The method was compared to a conventional triple quadrupole approach and evaluated for accuracy, precision, linearity and matrix effects.

Methodology

Sample preparation involved protein precipitation of 100 µL whole blood with zinc sulfate and methanol containing internal standards. Calibration standards and quality control samples were sourced from a commercial kit covering relevant concentration ranges. Method performance was assessed over multiple days with replicate measurements for inter- and intra-day precision and accuracy. Matrix effects were evaluated using spiked donor samples and the method was cross-validated against a collaborator triple quadrupole method.

Instrumentation

• Liquid chromatograph: Thermo Scientific Dionex UltiMate 3000RS with OAS autosampler
• Mass spectrometer: Thermo Scientific Q Exactive Focus Orbitrap with Ion Max source and HESI-II probe
• Data system: Thermo Scientific TraceFinder software in parallel-reaction monitoring mode

Main Results and Discussion

Limits of quantitation were equivalent to the lowest calibration levels (2.27–26.1 ng/mL). All analytes demonstrated linear calibration curves with R2 > 0.97. Intra- and inter-assay precision was better than 7% RSD and accuracy within ±17% at the lowest QC and ±10% at higher levels. Matrix recoveries ranged from 82% to 112%, indicating minimal matrix interference. Comparison with the triple quadrupole method showed excellent agreement (slope ~1, R2 > 0.97).

Benefits and Practical Applications

Compared to traditional triple quadrupole methods, this high-resolution approach offers improved selectivity by using high-accuracy mass measurements, reduces analysis time with a two-minute gradient, and can be scaled to high throughput with multi-channel LC systems for clinical research laboratories.

Future Trends and Applications

Advances may include integration of multiplexed microflow or nanoLC systems, application to additional drug classes, automated sample preparation workflows and use of data-driven algorithms for enhanced quantitation and quality control in clinical environments.

Conclusion

The Q Exactive Focus Orbitrap mass spectrometer, combined with rapid HPLC and targeted PRM acquisition, provides a robust, high-throughput solution for quantitative analysis of immunosuppressant drugs in whole blood, meeting the stringent requirements of clinical research.

References

• Gao M, Kozak M. Analysis of Immunosuppressant Drugs in Whole Blood Using a High-Efficiency Method on an Affordable High-Resolution Mass Spectrometer. Thermo Fisher Scientific Application Note 632; 2015.