Samples, force-degraded

Where the specific impnrity is unavailable or is too costly, the use of composite or degraded samples is possible. This approach involves the nse of a dirty sample of a drug substance or the creation of a mixture of impurities through the in situ forced degradation method. Both of these approaches are best nsed for qualitative uses. In each of these mixtures, the impurities are present in unknown quantities. The real benefit of this type of impnrity standard is the low cost and the ability to unequivocally identify the peak loci of the impurities. When these mixtures are used in conjunction with a compendial standard and a well-developed set of relative response factors the resnlts will meet most analytical needs. 

FIGURE I I Capillary zone electrophoresis of forced degraded rMAb sample. Experimental conditions as in Figure 9. 

Screening several different types of stationary phases during method development for a particular separation is often useful because different columns usually have different selectivity for components in a sample, as can be seen for a forced degradation sample analyzed on three different types of reversed-... 

Step 5 Gradient scouting studies (shallow/steep x 2 temperatures) with the optimized pH of the aqueous phase use crude and forced degraded samples... 

Some approaches/examples for conducting forced degradation studies are given below For a forced degradation acid study for a particular API the API is exposed to acidic conditions. The API (at a known concentration) is usually prepared in the sample preparation solvent, which gives 0.1 M HCl concentration in the final solution. Once this solution is prepared, it is injected every half hour or hour to determine the loss of API over time. If the API is susceptible to degradation under acidic conditions, then peak(s) of degradation products would increase over time and the API should decrease over time... 

I. Case Study B.l Identification Using a Combination of Enriched Forced Degradation Samples and Normal-Phase HPLC... 

A bulk lot sample of drug substance contained an unknown process-related impurity at 0.4% in case study B.7. To meet project time lines, it was necessary to identify the impurity. Mass spectral data indicated that the impurity had a molecular weight of M+12 (compared to the parent). LC/MS/ MS data indicated that the change was located in the sugar portion of the molecule. Isolation and NMR analysis was required to provide more structural information on the impurity. This again was a process-related impurity not observed in forced degradation studies therefore, effort was placed on finding an enriched mother liquor sample. 

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