Weight: Traceability to NIST or local standard?

[Terry]

Hello all,

This thread kind of strays from LC. But I will appreciate it if you shed some light on this issue.

We are building a pharmaceutical plant in China, the drug product is supposed to be marketed in the US. At this point, we come across a tricky problem: traceability of weights used for balance performance check.

The higher-up of our company indicated that we shall buy weights that are traceable to NIST, rather than Chinese National Standard. But we found it really difficult to get NIST weights in China.

Does the US FDA or USP have any requirements on the traceability of weights? Will the inspectors consider this as an observation when they come to our site to inspect?

Many thanks,

Terry

[Peter Apps]

Ultimately all weights (more formally mass pieces) are traceable to the International Kilogram at the BIPM in Paris. Each country in the international metrology community has its own national kilogram, that is compared directly to the International Kilogram, and is then used in comparisons with local mass pieces. The bottom end of this chain of comparisons are the weights that are used to check balance performance in working laboratories.

The statement "traceable to NIST" actually means "traceable through NIST to the International Kilogram". Many labs use NIST traceable references just because a lot of laboratory hardware etc is made in the US. They could just as well use references that are traceable to other national references. Some of these others might have larger uncertainties in their certified values than the NIST references, but these differences are extremely unlikely to have any impact at laboratory level.

Check out http://www.bipm.org/en/home/

Peter

[Terry]

Peter,

Sounds reasonable. I will check the BIPM out.

Thanks,

Terry

[DR]

Whatever weights you buy, you will need to send them out periodically for recertification. They company (usually the weight vendor) will check them, make any needed adjustment and recertify them to be within whatever tolerance range they were purchased as. Depending on the frequency of use, you may be able to do this annually - more often for weights that are used a lot.