Demonstrating Successful Method Migration of USP Organic Impurities Methods from an Agilent 1100 Legacy System to the Alliance iS HPLC System

Importance of the topic

Modernization of chromatographic hardware is a priority for pharmaceutical and regulated laboratories that rely on established compendial HPLC methods. Replacing aging legacy systems reduces lifecycle risk from parts obsolescence, downtime and limited serviceability while preserving validated analytical performance required for regulatory compliance. Demonstrating reliable method migration ensures continuity of impurity profiling, quantitative accuracy, and data integrity during instrument refresh cycles.

Objectives and study overview

This study evaluated migration of three USP organic impurity procedures (fluconazole, ibuprofen tablets, and quetiapine drug substance) from an Agilent 1100 legacy HPLC platform to the Waters Alliance iS HPLC System. Both isocratic and gradient methods were examined. The primary goal was to confirm that the Alliance iS could meet applicable USP system suitability criteria and produce impurity quantitation comparable to the Agilent 1100 without substantive method changes.

Methodology

Key method elements from published USP procedures were preserved where possible and included standard and system suitability solutions, sample preparations, and mobile phase compositions appropriate to each monograph. Assessments covered resolution, peak area precision (%RSD), retention time precision (%RSD), tailing, and sensitivity when required by the USP method. Comparative experiments used the same chromatographic columns and nominal method conditions (flow, temperature, injection volume) to isolate instrument-related differences (detector type, dwell volume, sampling rate, gradient formation). Data were processed using Empower chromatography data systems on both platforms.

Instrumentation used

• HPLC systems: Waters Alliance iS HPLC System versus Agilent 1100 Series Quaternary System.
• Detectors: Alliance iS Tunable UV (TUV); Agilent 1100 Variable Wavelength Detector (VWD) or Diode Array Detector (DAD) depending on method.
• Columns: XSelect HSS T3 (3.5 µm, 4.6 × 150 mm) for fluconazole; XBridge C18 (5 µm, 4.6 × 250 mm) for ibuprofen and quetiapine.
• Typical chromatographic conditions summarized: fluconazole (isocratic, 0.5 mL/min, 40 °C, 20 µL inj., 260 nm); ibuprofen (isocratic, 2.0 mL/min, 25 °C, 10 µL inj., 254 nm); quetiapine (gradient, 1.5 mL/min, 45 °C, 20 µL inj., 250 nm).
• Notable instrument variables: sampling rates differed (e.g., 2.5 Hz on Agilent DAD vs 2.0 Hz on Alliance TUV for ibuprofen), and gradient/dwell volumes differ between platforms.

Main results and discussion

All three USP impurity procedures met their applicable system suitability criteria on the Alliance iS and produced results comparable to the Agilent 1100.

Fluconazole (isocratic): Resolution between related compounds exceeded USP acceptance on both systems and peak area and retention time precision were well within USP limits (area and RT %RSD substantially below 5% acceptance). Some absolute retention time shifts were observed between systems, but relative retention times (RRTs) of impurities remained consistent. Elevated column temperature and differences in temperature control likely contributed to retention time offsets.

Ibuprofen (isocratic): Both systems met sensitivity and precision criteria. Chromatograms showed the same impurities (two unspecified and two related compounds) with comparable retention behavior. Quantitation matched closely: unspecified impurity #1 measured 0.10% on both systems; unspecified impurity #2 measured 1.10% (Alliance) vs 1.00% (Agilent). Total impurity levels were similar (1.20% vs 1.10%), differences consistent with normal analytical variability.

Quetiapine (gradient): Despite inherent differences in gradient delay between platforms, the method’s gradient design (late gradient start and 1.5 mL/min flow) minimized transfer impact. System suitability parameters, injection precision and retention time reproducibility were excellent on both systems (area %RSD ~0.1–0.3%; RT %RSD ~0.0–0.2%). Individual impurity measurements were nearly identical (e.g., quetiapine desethoxy 0.10% vs 0.11%); total impurities 0.17% vs 0.18; assay purity 99.83% vs 99.82.

Across methods, detector differences and sampling rate variations required only minor attention (not method re-design). The study demonstrates that careful matching of method parameters and targeted verification of system suitability are sufficient for successful migration in these cases.

Benefits and practical applications

• Enables laboratories to modernize HPLC instrumentation while preserving validated compendial method performance and regulatory compliance.
• Reduces operational risk from legacy hardware (downtime, parts obsolescence) without sacrificing impurity quantitation or sensitivity.
• Minimizes rework: when method parameters are maintained and system suitability is demonstrated, full revalidation may not be required beyond defined transfer verification steps.
• Provides an operational template for transferring both isocratic and gradient USP impurity methods between dissimilar platforms.

Future trends and potential applications

Laboratory modernization will continue to emphasize robust method transferability, automation, and data integrity. Anticipated trends include broader adoption of systems with improved diagnostics and remote maintenance, tighter integration of CDS/LIMS for traceability, increased use of mass-spectrometric detection for impurity identification, and model-based assessments to predict impact of instrument parameters (dwell volume, mixer efficiency) on transfer outcomes. Standardized transfer workflows and acceptance criteria tailored to impurity-level assays will further streamline migrations.

Conclusion

The Alliance iS HPLC System reproduced USP organic impurity methods for fluconazole, ibuprofen tablets, and quetiapine with chromatographic performance and quantitative results comparable to the Agilent 1100 legacy platform. System suitability criteria were met across isocratic and gradient procedures, supporting Alliance iS as a practical modernization option for regulated impurity testing when transfers are executed with careful matching of method conditions and verification of critical performance attributes.

References

1. Hong P.; McConville P.R. Transfer of an HPLC Method from an Agilent 1100 Series LC to an Alliance iS HPLC System. Waters Application Note, 2015.
2. USP Fluconazole Impurities Method, GUID-F961B739-9D37-4719-8E8A-1E7474DFE57D_3_en-US.
3. USP Ibuprofen Tablets Impurities Method, GUID-B108D32E-F28B-41A3-84C7-62D1C4F37646_1_en-US.
4. Reed C.E.; Hong P. Method Migration of the USP Ibuprofen Assay and Organic Impurities Method to an Alliance iS HPLC System. Waters Application Note, 2023.
5. Dlugasch A.B.; Gauthier L.; Hong P. Successful Method Migration of the USP Quetiapine Fumarate Impurities Method to an Alliance iS HPLC System. Waters Application Note, 2024.
6. USP Quetiapine Impurities Method, GUID-DBEED03E-7C75-4167-BD21-4E30BA2EFF2B_2_en-US.