Very interesting... I have been involved in natural gas for many years and I have honestly never heard of a Tin Sulphide problem in natural gas. Its not to say that this isn't the problem, it is just something I have never heard of.
I look up Tin Sulphide in two reference manuals (one being Merck Index) and their is no record of this chemical.
Is it possible that tin and sulphide (as seperate molecules, not necessarily as a compound) are in your sample?
I'd like to know more about this, as this is very interesting.
I am looking forward to your reply.