How purchaser can be protected if goods (raw materials) received do not coplies with samples received, in case either of advanced or LC payment?

Quoting from [vincenzo01]:

How purchaser can be protected if goods (raw materials) received do not coplies with samples received, in case either of advanced or LC payment?

That would be a terrrible problem, and I think you can do nothing on that. it is lucky that this has not happened to you and you just asking a case.

If by advanced payment, be sure to have a pre-shipment inspection for your goods, this does not cost you so much.

If by LC payment, you can stated to have a inspection report which issued by a third party, before shipment which is the doc. need for negotiation, this is a usually way that most people from Europe used.

And if you import a big qty each month, maybe you can hire a helper to work for you and give just a month salary.