Development of a LC-UV Method for Separating 12 Steroids using a Waters Acquity™ Biphenyl RP Column with MaxPeak™ Technology

Importance of the topic

Reliable separation and quantification of steroid mixtures is critical in clinical diagnostics, pharmaceutical quality control, and research because many steroids are structurally similar and several are isobaric. Robust chromatographic methods that achieve baseline resolution of closely related steroids—including phosphorylated or acidic derivatives that interact with metal surfaces—improve accuracy, reproducibility, and sensitivity for routine assays and impurity profiling.

Study objectives and overview

This application study aimed to develop a fast, reliable LC-UV method to separate a panel of 12 steroids (including a steroid phosphate) using a systematic column- and solvent-screening approach. Six reversed-phase chemistries were screened with formic-acid–modified mobile phases and either acetonitrile or methanol as the organic strong solvent. After scouting, the Waters ACQUITY BEH Biphenyl stationary phase in MaxPeak Premier (HPS) hardware provided the best overall separation. Method optimization focused on cycle-time reduction and resolving a co-eluting impurity. A direct comparison of the BEH Biphenyl packing in inert MaxPeak Premier hardware versus conventional stainless-steel hardware demonstrated the advantage of inert flow-paths for recovering and detecting the phosphate-containing steroid.

Methodology

Key experimental parameters and procedures used in method development are summarized below:

• Sample: stock standards at 1 mg/mL; combined mixture at 50 µg/mL per compound, final sample solvent ~31:69 v/v acetonitrile:water.
• Detection: UV at 275 nm (PDA).
• Scouting gradient: maintained 5% of 2% formic acid aqueous modifier (providing ~0.1% formic acid); initial organic 5% ramp to 95% acetonitrile in 6.86 min, 1.14 min hold, return and 2.28 min re-equilibration; total run 10.3 min.
• Optimization strategy: compare methanol vs acetonitrile as the strong solvent; screen six stationary phases in parallel; adjust column temperature and gradient start/end points and slope (%B per column volume) to resolve critical pairs and shorten runtime.

Used instrumentation

The study employed the following chromatography instrumentation and columns:

• System: ACQUITY Premier QSM System (with CM and auxiliary modules) and PDA detector.
• Data system: Empower chromatography software.
• Columns screened (2.1 x 50 mm scale): BEH C18 (1.7 µm), CSH Phenyl‑Hexyl (1.7 µm), HSS PFP (1.8 µm), BEH Biphenyl (1.7 µm), BEH Phenyl (1.7 µm), CORTECS C8 (1.6 µm). All columns evaluated using MaxPeak Premier hardware; a direct packing into stainless-steel hardware was used for the hardware comparison.
• Chromatographic conditions: column temperature nominally 30 °C (varied to 35–40 °C during optimization), sample temp 10 °C, injection 5 µL, flow 0.4 mL/min, mobile phases water (A), acetonitrile (B), methanol (C), 2% formic acid in water (D).

Results and discussion

Screening findings and method optimization outcomes are summarized below:

• Solvent effect: methanol produced greater retention (analytes eluting after ~4 min) and generally poorer selectivity for the panel. Acetonitrile delivered reduced retention, lower backpressure, and improved resolution overall.
• Stationary phase selectivity: with acetonitrile the HSS PFP and BEH Biphenyl columns separated all 12 steroids; BEH Biphenyl provided the best separation for critical analyte groups (notably components 7–10) and for three isobaric pairs (2 & 10, 7 & 8, 11 & 12).
• Impurity co-elution: an unexpected impurity co-eluted with component 11 under initial conditions. Elevating column temperature from 30 °C to 35 °C resolved this impurity from component 11; 40 °C improved resolution slightly but offered marginal benefit compared to 35 °C.
• Gradient optimization: increasing the initial organic content reduced retention and enabled shorter cycle time. Starting the gradient at 30% organic (instead of 5%) was optimum to avoid elution at the void while enabling a truncated gradient that ended at ~60% acetonitrile. A shallower slope (%B per column volume) across the truncated gradient preserved separation of critical pairs.
• Hardware comparison: packing the BEH Biphenyl stationary phase into traditional stainless-steel hardware resulted in nondetection of betamethasone phosphate and altered retention of the impurity (causing re‑coelution with component 11). In contrast, MaxPeak Premier hardware with High Performance Surface (HPS) technology recovered betamethasone phosphate and maintained the resolved separation. These results confirm that ionic/acidic analytes such as phosphorylated steroids can adsorb to metal surfaces, and inert column hardware mitigates analyte loss and selectivity artifacts.

Key results and implications

Major outcomes of the work:

• Baseline resolution of all 12 steroids, including three isobaric pairs, was achieved using a BEH Biphenyl stationary phase with acetonitrile and formic-acid modifier.
• Cycle time was reduced by adjusting the gradient start and end points and by using a shallower gradient slope while retaining critical separations.
• Use of MaxPeak Premier (HPS) column hardware was essential to detect and quantify the steroid phosphate (betamethasone phosphate) and to avoid metal-induced retention shifts for an impurity—demonstrating the importance of inert flow-paths for acidic/phosphorylated analytes.

Benefits and practical applications

The developed method and workflow provide practical advantages:

• Robust LC-UV assay suitable for routine steroid profiling in clinical, pharmaceutical QC, and research laboratories where MS may not distinguish isobars or where UV detection is preferred.
• Faster throughput through gradient truncation while maintaining baseline separation, improving laboratory efficiency.
• Reduced method development risk by combining systematic column screening and inert hardware to prevent analyte losses and misleading selectivity artifacts.

Future trends and potential applications

Anticipated developments and opportunities building on this work include:

• Broader adoption of inert flow-path and column hardware (HPS-type surfaces) for acidic, phosphorylated, or metal-adsorptive analytes in both LC-UV and LC-MS workflows.
• Integration of automated, high-throughput column and solvent screening with algorithmic or machine‑learning guidance to accelerate method selection for complex mixtures.
• Extension of the approach to tandem MS and HRMS workflows to combine separation of isobars with mass-selective detection for enhanced specificity and quantitation in complex matrices.
• Further stationary-phase innovation (e.g., tuned π-π selectors, polar-embedded phases) and greener solvent strategies to optimize selectivity, robustness, and sustainability.

Conclusion

A structured scouting and optimization protocol enabled development of a fast, baseline-resolving LC-UV method for 12 steroids. The BEH Biphenyl stationary phase with acetonitrile provided the best selectivity, and method refinement (temperature and gradient tuning) resolved a co-eluting impurity and shortened cycle time. Crucially, MaxPeak Premier inert column hardware prevented loss of the steroid phosphate and avoided metal-induced retention artifacts—highlighting the importance of inert surfaces when analyzing acidic or phosphorylated analytes. The workflow offers a reproducible path for analysts developing steroid panels and similar complex separations.

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