Transfer of USP Methods for Impurities Analysis of Ziprasidone HCl between HPLC Systems and to UPLC

Transferring compendial HPLC methods between systems can be challenging. Many of the USP monographs utilize diluents with a high concentration of organic solvents for the preparation of standard and sample solutions. While strong solvent diluents are common for HPLC applications, they often prove unsatisfactory for analyses performed on modern systems that feature minimized dispersion.

In this study, the transfer of two USP compendial methods for impurities analysis of ziprasidone HCl from HPLC to UPLC is demonstrated with a straightforward way to address this potential issue.

Benefits

• Method transferability between different systems and different sites 
• 63% reduction in run time when using UPLC
• 93% savings in mobile phase consumption when using UPLC
• Reduced cost for solvent and waste disposal

U.S. Pharmacopeia (USP) compendial methods are routinely adopted by pharmaceutical companies for testing raw materials and finished products. Successful implementation of the USP methods and transferability between instruments are key steps to enhance throughput for routine analysis. Effective method transfer generates identical results for the same analysis independent of the laboratory, instrument, and the resources for a specific method.

By ensuring successful lab-to-lab method transferability, companies can replicate methods at additional sites or with partners such as contract research or manufacturing organizations (CROs and CMOs). Transferring an HPLC-based USP method to UPLC Technology offers such organizations the additional opportunity to achieve productivity goals by reducing analysis time while ensuring reliable, high-quality chromatographic separations that are the basis for decisions about product quality. UPLC Technology offers QC and manufacturing facilities significant advantages in terms of increased throughput, improved quality, and reduced costs.

Transferring compendial HPLC methods between systems can be challenging. Many of the USP monographs utilize diluents with a high concentration of organic solvents for the preparation of standard and sample solutions. While strong solvent diluents are common for HPLC applications, they often prove unsatisfactory for analyses performed on modern systems that feature minimized dispersion.

In this study, the transfer of two USP compendial methods for impurities analysis of ziprasidone HCl¹ from HPLC to UPLC is demonstrated. The use of strong solvent as a sample diluent can be a barrier when transitioning a method to a low-volume system, depending on the injection volume. Presented here is a straightforward way to address this potential issue.

The success of the method transfer between different HPLC systems and conversion to UPLC was measured by evaluating the system suitability requirements listed in the USP monograph for ziprasidone HCl. Success of the transfer was further demonstrated by running the methods on the same instrument configurations in a laboratory located in a different country, where identical results were achieved.

Sample description

All solutions (Table 1) were prepared in methanol/water/ concentrated HCl at a composition of 20:5:0.01 to comply with the impurities methods defined in the USP monograph for ziprasidone HCl. Since the USP does not list a sample preparation protocol for the ziprasidone HCl capsules, the drug substance sample preparation was used with one modification. Sample solutions were filtered through 0.2-μm PTFE syringe filters to remove any particulates.

System control, data acquisition, and analysis

Empower 3 Software

USP system suitability criteria for early-eluting method:

For five replicate injections of system suitability solution

• Resolution between ziprasidone and ziprasidone related compound B: Not less than (NLT) 1.5
• Relative standard deviation (RSD) for ziprasidone related compound B: Not more than (NMT) 10%

USP system suitability criteria for late-eluting method:

For five replicate injections of system suitability solution

• Resolution between ziprasidone and ziprasidone related compound C: NLT 6.0 
• RSD for ziprasidone related compound C: NMT 10%

Managing system volume differences

One of the challenges of migrating a USP monograph from legacy to modern LC technologies is the impact of technology improvements in managing system volume and dispersion that may cause distorted peaks. The volume of an LC system in front of the injector will impact the time required to equilibrate the method to the initial conditions. The system volume after the injector is related to the system dispersion, which mixes sample with the mobile phase. In this work, we investigate these relationships and determine an effective way to adjust for different volumes.

As an example, injecting sample dissolved in a strong organic diluent onto systems with a small post-injector volume can yield a less focused injecton, often evidenced by fronting. Peaks with lower retention factor (k') eluting isocratically are typically observed to be more distorted compared to the later eluting peaks with larger k'. Methods with a gradient elution are also susceptible but less affected by the strong organic diluents, due to peak focusing at the head of the column.

Method transfer of USP HPLC method

The USP monograph designates using an L7 column for the ziprasidone HCl early and late impurities methods and suggests using a Zorbax RX-C₈ Column. Using the Waters Reversed-Phase Column Selectivity Chart (www.waters.com/selectivitychart), a Waters XBridge C₈ Column was chosen. The standard and sample solutions were prepared in diluent containing 80% methanol. The compendial method for the early eluting impurities was run as described on the Alliance HPLC System (Figure 1A), and on the ACQUITY UPLC H-Class System (Figure 1B) using the same XBridge C₈ Column and the same mobile phase. Distortion of the peaks was observed when the system suitability solution was injected on the ACQUITY UPLC H-Class System.

Several experiments were designed to investigate and solve the issue of observed peak distortion. It was hypothesized that the peak distortion was due to a high concentration of organic solvent. These experiments included the following:

1. Reducing the injection volume.
2. Reducing the concentration of organic solvent in sample diluent.
3. Increasing the post-injector volume of the UPLC system.

The USP allows reduction of the injection volume as long as the precision and the detection limits are acceptable.² While reducing the injection volume improved peak symmetry and resolution, it decreased sensitivity (Figure 2). For this reason, injection volume could not be decreased to mitigate the distorted peaks.

Reducing the composition of methanol in the diluent to 70% enhanced the chromatographic separation (Figure 3). However, modification of the sample diluent is not recommended by the USP.

Increasing system volume between the injector and the column inlet with 50-μL tubing significantly improved peak shape and resolution between all the peaks, conforming to allowable modifications documented by the USP (Figure 4).

Finally, increasing the volume of the UPLC system after the injector allows the diluent to mix with the mobile phase before it enters the column, improving peak symmetry and resolution.

By increasing the post-injector volume, the compendial HPLC methods for the early- and late-eluting impurities could be successfully run on the ACQUITY UPLC H-Class System. Overall, transferability of the compendial methods between LC systems with different extra-column volume, specifically the Alliance HPLC and ACQUITY UPLC H-Class systems, was successful (Figures 5 and 6).

Finally, the system suitability results for the five replicate injections of the system suitability solution met the requirements listed in the USP monograph for ziprasidone HCl (Tables 2 and 3).

Lab-to-lab method transfer

Finally, a lab-to-lab method transfer study was conducted using the compendial HPLC method for the earlyeluting impurities on the ACQUITY UPLC H Class System. Two different laboratories performed the test,including Waters laboratories in Milford, MA, USA and Guyancourt, Yvelines, France.

Reproducibility of the HPLC method acquired by both labor atories was demonstrated by comparing the system suitability results (Table 4). System suitability results acquired by both laboratories were comparable and met the requirements defined in the USP monograph for ziprasidone HCl.

Two compendial HPLC methods for impurities of ziprasidone HCl were tested on two different HPLC systems and successfully transferred to UPLC. Increasing post-injector volume of the ACQUITY UPLC H-Class System was required to duplicate the chromatographic separation and meet the USP requirements for system suitability.

The ACQUITY UPLC H-Class System successfully replicated the analytical quality of the HPLC compendial methods. Excellent performance of both the HPLC and the UPLC methods demonstrate that the ACQUITY UPLC H-Class System is suitable for HPLC and UPLC applications.

•  Implementing the ACQUITY UPLC H-Class System within quality control laboratories can reduce the costs of operation and maintenance by maximizing asset utilization and eliminating the need for multiple systems to perform HPLC and UPLC analyses.
• Conversion to UPLC technology can decrease overall costs and improve laboratory throughput and productivity for release testing of finished products.
• The UPLC methods for the required early- and late-eluting impurities tests provided a 67% and 58% reduction in run times over the corresponding HPLC methodologies.
• In addition to reduced analysis time, UPLC technology provides cost savings related to solvent and waste disposal. Consumption of mobile phase per UPLC injection, for the early and late impurities methods, is reduced by 93% compared to the HPLC injection.

The reproducibility of the compendial HPLC method on the ACQUITY UPLC H-Class System during the lab-to-lab study was excellent, which is the final key to successful method transferability between sites.

1. USP Monograph, Ziprasidone HCl, USP35-NF29, The United States Pharmacopeia Convention, official May 1, 2012.
2. USP General Chapter, <621> Chromatography, USP35-NF30, The United States Pharmacopeia Convention, official December 1, 2012.
   
3. Jones MD, Alden P, Fountain KJ, Aubin A. Implementation of Methods Translation between Liquid Chromatography Instrumentation. Waters Application Note 720003721en. 2010 Sept.