Bioequivalence and Bioavailability Forum

Dear V. Pardhasaradhi!

❝ Is there any guideline specifying "Which class weights (Class E1, E2 or

❝ F1) need to be used for calibration of micro balance used in bioanalytical

❝ studies".

At least I don't know any (this one from the FDA refers to cGMP)...

❝ If not, can any one give some recommendation from experience?

❝ What can be the tolerances in the balance qualification test?

We obtained our first GLP-certificate in 1992, and never got any problems ever since by the following procedure:

1. The balance is daily calibrated by the internal 100 g weight (after >15 min of warm-up).
   
2. If the displayed result is 100.0000 g, proceed with Step 3. If not, Step 2 may be repeated once - if the result is 100.0000 g, proceed with Step 3 - or Step 6 otherwise.
   
3. External weights are also used daily; at least one of two certified weights (10 g and 50 g - class E2) is used.
   
4. If the displayed weight differs <0.0001 g from theoretical, the result is documented in a form (date, weight used, displayed weight, signature of analyst) and the balance is released for use.
   
5. If the displayed weight differs >0.0001 g from theoretical, both internal (Step 1) and external calibration (Step 2 and followings) have to be repeated once.
   
6. If the balance fails internal calibration (Step 2) or external calibration (Step 5), results are documented as in Step 4, but the balance is not released for use; service has to be initiated.

Furthermore both balance and weights are officially verfied by the national standards institute on a yearly basis.

For a controversial discussion have a look at this thread at the Chromatography Forum, and a nice article by C. Burgess and RD. McDowall in LCGC-Europe (2004).