Improving Performance and Throughput of the USP Organic Impurities Analysis of Tioconazole on an Alliance HPLC System

Importance of the topic

The accurate and efficient determination of organic impurities in generic drug products is essential for ensuring product quality, safety, and regulatory compliance. Conventional USP methods can be lengthy and consume large volumes of solvents, driving the need for modernized chromatographic approaches that increase throughput and reduce operating costs while maintaining compendial standards.

Objectives and study overview

This application study aimed to update the USP organic impurities assay for tioconazole by transferring the method onto eXtended Performance (XP) 2.5 μm columns on a Waters Alliance HPLC System. The goals were to shorten analysis times, reduce solvent consumption, and preserve required resolution metrics specified in USP Chapter <621>.

Methodology

The original USP method used a 4.6 × 250 mm, 5 μm LiChrosorb RP-18 column under isocratic conditions (44:40:28 acetonitrile/methanol/water with 2 mL ammonium hydroxide) at 1.0 mL/min and 25 °C, detecting at 219 nm with a PDA detector. Tioconazole and related impurity standards were prepared in methanol and injected in volumes scaled to column dimensions. Method transfers applied ±70 % column length change, –50 % particle size change, and ±50 % flow rate limits per USP <621>.

Used Instrumentation

• Waters Alliance HPLC System with integrated fluidic design and solvent management
• XSelect CSH C18 stationary phase (4.6×250 mm, 5 μm; 4.6×150 mm and 4.6×100 mm, 2.5 μm XP columns)
• 2998 photodiode array detector (PDA)
• Empower 3 software for data management
• TruView LCMS certified vials for sample recovery

Main results and discussion

Method transfers to XP 4.6 × 150 mm, 2.5 μm and 4.6 × 100 mm, 2.5 μm columns achieved run time reductions of 43 % (17 min) and 57 % (13 min) versus the original 30 min, while maintaining resolution between impurity peaks above the USP requirement of ≥1.5. The 150 mm column improved resolving power (L/dp from 50 000 to 60 000), increasing resolution from 1.9 to 2.0. The shorter 100 mm column reduced L/dp to 40 000, yielding a resolution of 1.6—still acceptable for many impurity separations. Switching to XP columns increased potential sample throughput from 16 to 80 analyses per 8 h shift and halved solvent use from 480 mL to 240 mL per shift.

Benefits and practical applications

Updating compendial organic impurity assays with sub-3 μm XP columns on existing HPLC platforms allows pharmaceutical laboratories to:

• Significantly shorten analysis time and increase sample throughput
• Reduce solvent consumption and lower operating expenses
• Maintain compliance with USP <621> resolution and flow rate guidelines
• Leverage a single column technology across HPLC and UPLC systems

Future trends and applications

Emerging trends in impurity analysis include broader adoption of sub-2 μm and core–shell particles for even faster separations, integration with mass spectrometry for improved sensitivity, and method translation tools to automate scale changes. Continuous advances in column chemistry and HPLC instrumentation are expected to further optimize speed, resolution, and green chemistry initiatives in pharmaceutical quality control.

Conclusion

The method transfer of the USP tioconazole organic impurities assay onto XP 2.5 μm columns on an Alliance HPLC System successfully reduced run times by up to 57 % and solvent usage by at least 50 % without compromising critical resolution criteria. This modernization offers substantial time and cost savings for routine impurity testing while adhering to compendial requirements.

References

1. United States Pharmacopeial Convention. USP General Chapter <621> Chromatography. USP 35–NF 30, August 1, 2012.
2. United States Pharmacopeial Convention. Tioconazole Monograph. USP 35–NF 30 §4875, August 1, 2012.
3. Jones MD, Alden P, Fountain KJ, Aubin A. Implementation of Methods Translation between Liquid Chromatography Instrumentation. Waters Application Note 720003721en, September 2010.