60% is quite good actually! The yield depends on your resin loading, secondary structure formation during the synthesis, and the peptide sequence.

there are also different methods on how to improve yield..for example the use of pseudoproline dipeptides.

60% is very good. If the synthesis is very clean you might try to concentrate the cleavage cocktail under an Ar/N2 current instead of precipitating the peptide. Shorter peptides sometimes do not precipitate as well as longer ones. However, in our experience, HPLC purification is where the yields really go down. Try perhaps using a shorter column. Anyawy, I'd kill for a 60%.

Dear Saraniya Baharathi,

You just do first amino acid loading to the resin as efficient and concentrate on each and every coupling, if one amino acid in first or middle yields some less coupling means your total yield should be affected,

after 6aminoacid the peptide get aggregate know, it also affect yield, so try to use pesudoproline or other method to remote this, and solvation, use NMP as solvent for coupling.

see my articles will help you to improve quality of the peptides.

Regards

R.Selva...

It is accepted yield in solid phase synthesis 20 amino acids.

For loading of amino acid to your resin is importatnt step. You can check the swelling power of your resin in different solvents. Available in literature.

Swelling decides the surface area available for the bonding.

Change in solvent system for subsequent reaction will also affect the swelling property of your resin thereby affecting your yield.

60% is really good . i had never seen more than 50 % in my case

 What kind of chemistry you are using. What is the quality of your reagents and solvents (for e.g. water content). Take care about coupling methods, efficiency and  synthesis protocols. I have synthesised several peptides of length >30AA in >90% yield (using HBTU coupling) with very good purity