Improvements in Sensitivity for Quantification of Steroid Phosphate Drugs Using ACQUITY PREMIER and MaxPeak HPS Columns

Significance of the Topic

Quantitative bioanalysis of metal-sensitive drugs such as phosphate steroids is essential for accurate pharmacokinetic profiling, particularly at low concentrations encountered in clinical and preclinical studies. Traditional LC surfaces can adsorb these analytes, leading to poor peak shape, low sensitivity and variable results. Chemically inert high performance surfaces offer a solution to preserve analyte integrity and improve assay robustness.

Aims and Study Overview

This application study evaluated the performance gains achieved when quantifying hydrocortisone phosphate and dexamethasone phosphate in human plasma extracts using an ACQUITY PREMIER UPLC system equipped with MaxPeak High Performance Surface (HPS) columns, compared to a standard ACQUITY LC platform.

Methodology and Used Instrumentation

Sample Preparation:

• Stock solutions of each corticosteroid phosphate were made in DMSO and diluted in 5% methanol–water.
• Spiked human plasma calibration samples ranged from 5–1,000 ng/mL (hydrocortisone) and 1–1,000 ng/mL (dexamethasone).
• Protein precipitation with methanol, centrifugation, and transfer of supernatant into LC-MS vials.

Chromatography and Detection:

• System: ACQUITY PREMIER UPLC I-Class or ACQUITY UPLC I-Class.
• Columns: 2.1 × 50 mm ACQUITY MaxPeak HSS T3 1.8 μm (HPS) versus standard ACQUITY HSS T3 1.8 μm.
• Mobile phases: 0.1% formic acid in water (A) and acetonitrile (B); 5–75% B over 2.5 min.
• Flow rate: 600 µL/min; column temperature: 60 °C; injection volume: 10 µL.

Mass Spectrometry:

• Instrument: Xevo TQ-XS triple quadrupole.
• Ionization: positive ESI; acquisition in MRM mode.
• Transitions: 443.19 > 327.15 (hydrocortisone phosphate); 473.32 > 435.16 (dexamethasone phosphate).
• Data processed using MassLynx v4.2 and TargetLynx XS.

Main Results and Discussion

Comparison of the HPS-coated system and standard hardware showed:

• A 10-fold lower limit of quantification (LLOQ) for hydrocortisone phosphate (5 ng/mL vs >50 ng/mL).
• A 7.5-fold lower LLOQ for dexamethasone phosphate (1 ng/mL vs >7.5 ng/mL).
• Enhanced signal-to-noise ratios (>15 and >10 at LLOQ for the HPS system vs <3–4 for standard hardware).
• More symmetrical and narrower peaks, facilitating reproducible integration at low concentrations.
• Linear calibration curves across the studied range (r2 > 0.993 for hydrocortisone phosphate; r2 > 0.992 for dexamethasone phosphate) with minimal bias.
• Accuracy and precision within bioanalytical acceptance criteria (<11% precision for hydrocortisone phosphate; <8% for dexamethasone phosphate).

Benefits and Practical Applications

Use of the ACQUITY PREMIER system with MaxPeak HPS columns delivers:

• Significantly improved sensitivity and lower quantification limits, enabling detection of trace analyte levels.
• Robust and reproducible peak shapes and areas, reducing variability in bioanalytical workflows.
• Simplified method development without the need for mobile phase chelating additives or system passivation.

Future Trends and Applications

Advances in surface chemistry will continue to address adsorption issues for a broader range of polar and labile compounds. Integration of inert flow path materials and hybrid surfaces is expected to expand bioanalytical capabilities for other challenging analyte classes, including phosphorylated metabolites, sugars and acid-containing molecules. Further improvements in ultra-sensitive mass spectrometers coupled with high performance surfaces will support lower sample volumes, pediatric studies, and more detailed pharmacokinetic and metabolomic investigations.

Conclusion

The study demonstrates that chemically inert MaxPeak HPS surfaces in the ACQUITY PREMIER system substantially enhance quantitative performance for metal-sensitive steroids. By reducing analyte loss to system hardware, the approach achieves lower quantification limits, improved peak quality and dependable results, streamlining bioanalytical workflows and extending assay capabilities.

References

1. Hassan ME et al. Dexamethasone in Severe COVID-19 Infection: A Case Series. Respir Med Case Rep. 2020;31:101205.
2. Cevc G, Blume G. Hydrocortisone and Dexamethasone in Deformable Drug Carriers. BBA-Biomembranes. 2004;1663(1-2):61-73.
3. Lauber M et al. Low Adsorption HPLC Columns Based on MaxPeak High Performance Surfaces. Waters Corp. 2020.