Sampling of precious metal materials

[Eric1285]

I am trying to figure out the most specific, scientific way to properly sample materials which contain precious metals. I would like to know what % of the material must be sampled, given at least 95% confidence. I understand that there's no 100% method for sampling; I am looking for maybe a formula I can use, while weighing what I want my confidence level/interval to be.

I work at a plant that recycles materials containing precious metal, so there is a long list of stuff we take on. Sometimes, a customer shipment to us may have 3 or 4 different materials in it, so I want to make sure the sample is representative. I'm trying to tighten up the sampling as part of some initial Six Sigma steps...

 

[Jmoore1]

Any stats textbook can give you procedures for determining sample sizes to acheive a certain confidence and standard deviation.

 

[TVP]

Eric,

Are you familiar with ASTM standards for specific materials (gold, platinum, etc.) and the methods for determination of their chemical composition? An example is ASTM B562 for gold, which references E1446 for chemical analysis. Take a look at the abstract as well as the references which discuss some of these issues:

http://www.astm.org/Standards/E1446.htm

 

[blacksmith37]

Having worked at a secondary copper smelter : I think you can expect different compositions from the same customer from load to load, and even within truckload quantities if it is anything like the copper business.