Hi, you better give the retest date because these chemicals are oxidising easily and based on the purity also. based on the inhouse procedure,sometimes these chemicals will be use after retesting which indicates purity level.

thank you.

This probably depends somewhat on your customers needs and usage of the materials you sell and then also on your own stock levels (ie how much stock you still carry and want to be able to sell to customers a year after you manufacture it.

Expiry or retest dates are both valid ways to advise customers of material shelf life but the stated shelf life should be accompanied by storage condition instructions. (e.g. keep dry and store below 25oC)

If your purpose in retesting after two years is to be able to sell more material from an older manufacture lot to customers who are happy with a 1 year shelf life then what you describe is an applicable procedure.

Chemical suppliers that we deal with will not offer us, the customer, a new CoA for the material upon retest in their factory probably because they cannot be sure we have correctly stored the material.  Customers may be able to conduct their own material retest if they want to extend the shelf life of the material in their own business use.

If you accumulate data over time that justifies reissuing another 2 year expiry I would suggest that is probably something you should consider doing.  However, if 1 year shelf life is acceptable to most of your clients then a 1 year expiry or retest date would be acceptable.

Hope these thoughts help.

Kind regards, Colin

Thank  you very much  Colin. Your opinions is seems meaningful.

Thank you very much Sachidanandam. Sometimes giving an retest date is more correct.