what does it mean by sampling in ISO:IEC 17025. does it means something very difficult or something diffferent from our definition? or
it has very specific/ stringent requirements that most of the labs find difficult to follow?
any specific requirement for Chemical labs that someone can share.

Not difficult at all really.....since you are in Canada, appear to be a test lab, and therefore would have SCC as your accrediting body, always double-check with them.....

Test labs may or may not sample, depending on the lab.....a chemical lab will generally sample, meaning you have some smaller portion that is tested to represent the whole quantity. Under ISO/IEC 17025, you must have a procedure to define how the smaller quantity (the sample) is selected, and how you care for it (e.g., unique storage requirements or environment).

A calibration lab as a contrast almost never samples.

Hope this helps.

Hershal