[Stepan]

I am sure you will be able to find enough methods in library or even on Google

[m-khalili]

Can I use xylenol orange (as a ligand) for determining concentration
of Pb2+  in a solution which following material are in :HCl, NaOH,
acetic acid,  sodium tripolyphosphate, NO3-
how about Hg(II) ?

[Stepan]

Dear m-khalili, your questions require intensive literature research and lab experimenting. Your problem cannot be resolved through forum - your questions are very broad. The answer depends on: you industry, your legal requirements, range of concentrations you need to cover, your matrix, composition of the sample, your resources, your background,.

You need either develop appropriate analytical method yourself or hire somebody who can do it for you.