ther are two routes for synthesising peptides: solid phase and solution phase. they each have operational advantages and disadvantages, they involve different quality controls and can lead to different types of impurities and contaminants in the final product, aggregate formation, variations in secondary structure etc. the engineer who is performing the synthesis should be able to give a straight forward answer to this question and a justification for his choice. the information would be useful in carrying out more precise testing, because we'd know what kind of issues to look for.