For any kind of substance, preparation methods are well known to everybody. And it is not the preparation methods which trouble the people. Even if you prepare the substance, it will not be useful with so much impurities contained in it. You will have to purify the substance to the greatest possible extent. Purifying the substance to even 99 % is being a difficult process. Such is the difficulty associated with the purification process. In the field of organic chemistry, if the products, especially peptides are not purified, the impurities present in the substance, react with the reagent and other reactants thereby spoiling the entire chemical reaction. If you are expecting a useful product to come out of it, it might as well turn to be a disastrous and dangerous product as well. The main problem is that you will not even know that something like this happened and you might assume you have got the right product and keep going in the same way.
Insight on purification of the peptides:
You will have to purify the substance after preparation, no matter what, before you put it to proper use as such. Purification of a substance is the one of the most costliest process in the entire procedure of preparation of the substance. You cannot even afford to take the alternative methods to this process which are cost efficient because of the reason that, if you take up something cheaper and less efficient, you will not get a product with the highest amount of purity and there will be some part of the impurity still left, if not on a major scale at least on a minor note. Only if you adopt the right method of purification, you will be able to acquire the product with the greatest possible extent and due to this and this will cost you even more than the preparation cost sometimes. The pros and cons of the procedures that are being used in the industry have been stated properly in the peptide guide.
But, it is totally worth it, if you are spending so much money on the purification process. This is because of the fact that; a pure peptide will give a better result. All these details have been clearly discussed in the peptide guide where the procedure are also mentioned in a clear manner.