I don't know what acids you have used, but I would run a conventional elemental analysis, this should anyway be done to make sure which "doping" degree you have, it should not be more than 0.5:1 (acid:monomer unit)

I don't know what acids you have used, but I would run a conventional elemental analysis, this should anyway be done to make sure which "doping" degree you have, it should not be more than 0.5:1 (acid:monomer unit)

Thank you for your  valuable answer.

I am using acetic acid and HCl for doping.

Even if I get 0.5:1 ratio , I guess it will not differentiate between physical mixture of these two PANI (individually prepared pani hcl and pani Acetic acid and mixed together) Vs condition said above i.e. simultaneous doping of both dopants on same emeraldine base chain.

first, please don't assume before you analyze; just analyze and draw your conclusions later; second, as you were using 2 acids which have a different acid strength, so that HCl will be the preferred dopant; how did you rinse after polymerisation / after doping?

you can tell us the elemental analysis results as well after you get them, then we can discuss them here.

I individually dissolved acids and monomer .. like first I neutralized aniline with acetic acid in a vial then in second vial I neutralized aniline with HCl and in third I dissolved APS in water. Finally mixed them.  So the question of preference does not hold. By this step I made sure that there will not be any competition between these two that who will dope first and all. The acid strength effect will be zero.

I rinse with water and methanol.

with my understanding of acid strength and effects onto doping and after having seen your short description, I would strongly assume that HCl is the preferred dopant. It is necessary to confirm by elemental analysis.

It does not matter what you or I believe, analysis should tell. Only analysis can tell you whether or not the question of preference is relevant.

Again from experience, rinsing is very critical for removing excess acids; by the way, during first filtration and rinsing you have another objects for analysis:

you carefully collect all the liquids (first filtrate, then the rinsing liquids), then you can titrate the amount of acids and also differentiate between how much acetic and hydrochloric acid youhave collected, and by comparing with what you used to begin with, you know how much is left together with the PAni for doping it.

I concur with Wessling - I expect near quantitative doping by Cl. What solution are you using to "wash" the salt?

just one more comment to avoid misunderstanding:

The "doping" does not occur by the anions (Cl-, Acetate- or else-minus), "doping" (wrong term, but widely used) is effected by H+. Then the charged chain requires counterions, that will mainly be Cl-. 

Why? because Acetic acid has the weaker dissociation constant, that means that the acetate ion likes to be more "together" with H+ and form HAc, rather than H+Ac-, while HCl is preferably dissociated, so the Cl- ion does not care that the H+ is sitting close to the N on the chain, but Ac- cares and wants to get the H+ back.

Therefore, HAc is the weaker doping acid and usually results in lower conductivity for the ES salt doped with HAc compared to HCl.

one more comment, this one about doping with HCl:

it is not preferred as HCl (besides doing the doping job) also forms some undefined chlorinated PAni compounds, that means: doping with HCl leads to side products which contain covalently boud Cl. This one does not like.

Therefore other acids are preferred, the best is para-toluene sulfonic acid.

Thanks Bernard , for your enlightening comments. 

I use water and some methanol for washing.