Design and degradation in drug determination

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  • Published: Feb 1, 2018
  • Author: Ryan De Vooght-Johnson
  • Channels: HPLC
thumbnail image: Design and degradation in drug determination

Analytical quality by design applied to new sorafenib analysis method

Sorafenib is an important anticancer drug, used to treat kidney, thyroid and liver carcinomas. A generic version of the drug is produced in India. Existing HPLC methods use relatively high levels of buffer salts, which may eventually lead to column blockages. They are also not particularly suitable for the study of the compound’s degradation products. The Panjab University researchers used an analytical quality by design (AQbD) approach to develop a new buffer-free HPLC method for sorafenib and its degradation products. AQbD involves a systematic, risk-based approach to method development, and typically employs experimental designs, along with rigorous validation protocols.

New HPLC method developed for sorafenib using experimental designs

HPLC was carried out on a Waters Acquity HPLC system fitted with a Thermo Scientific Accucore C18 column, with DAD (diode-array detection) at 265 nm. The column was run under isocratic conditions, using acetonitrile and aqueous orthophosphoric acid (the relative amounts of these two solvents were varied as part of the experimental design).

Initially, critical analytical attributes (CAAs), such as peak area and retention time, were identified, along with critical method parameters (CMPs), such as flow rate, solvent ratio and run time. An Ishikawa fish bone diagram was used to determine the CMPs; this relates cause and effect, giving a formal method of identifying relevant parameters.

A Taguchi seven-factor, two-level design was then used to determine which CMPs were the most important. The seven factors investigated were the following CMPs: mobile phase ratio, flow rate, run time, column temperature, injection volume, column particle size (4 or 5 μm) and pH. Eight experimental runs were carried out. The results of the Taguchi design indicated that the column temperature should be set at 40 °C, not 25 °C, and the injection volume should be 10 μL, not 20 μL.

From the Taguchi design results, two parameters, flow rate and mobile phase ratio were found to be particularly important: they were further optimised using a face-centred cubic experimental design, where each of the two variables was set to three different levels. The results from this design were used to plot response surfaces for the different CAAs with respect to the flow rate and mobile phase ratio. An optimum solution, giving acceptable values for all the CAAs, was found. The optimised acetonitrile/aqueous ratio was set at 65:35 and the flow rate to 0.8 mL/min.

The method was successfully validated, giving good linearity, accuracy and precision. The method worked just as well on another instrument, demonstrating its ‘ruggedness’. It was also shown to work successfully using sorafenib in blood plasma, with matrix effects being small.

Forced degradation studies were carried out under a variety of conditions: dilute HCl, dilute NaOH, hydrogen peroxide, light and heat. Overall, sorafenib was found to be reasonably stable under all these conditions. The new HPLC method successfully separated the degradation products. They were identified by LC-MS, with formic acid replacing orthophosphoric in the HPLC aqueous phase.

New HPLC method suitable for sorafenib and its degradation products

Careful optimisation using experimental design methods allowed the development of a novel buffer-free HPLC method for Sorafenib and its degradation products. The method was shown to work effectively with blood plasma samples. It remains to be seen to what extent the new technique will replace existing methods since regulatory requirements mean that analytical techniques are slow to change once pharmaceuticals are on the market.

Related Links

Biomedical Chromatography, 2018, Early View article. Sharma et al.. Development of a validated liquid chromatographic method for quantification of sorafenib tosylate in the presence of stress-induced degradation products and in biological matrix employing analytical quality by design (AQbD) approach.

American Pharmaceutical Review, August 27, 2013. Reid et al.. Analytical quality by design (AQbD) in pharmaceutical development.

Wikipedia, Taguchi Methods.

Article by Ryan De Vooght-Johnson

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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