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Ramesh ☆ India, 2007-10-24 10:56 (6821 d 08:18 ago) Posting: # 1246 Views: 5,009 |
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Dear group members, I have two queries regarding the calculation of the % stability. Query1 % stability calculation: one by calculating the % accuracy. i.e 85-115% of nominal conc. second by calculation of response ratio of test/reference. (area response ratio) in both of them which is the correct method for the calculation of the stability. Query 2: Precision and Accuracy: For the determination of the stability, fresh CC and QC samples are prepared, in such case is it necessary to prove the precision and accuracy of the freshly prepared QC samples. i mean to say whether it is necessary a to analysis the P& A batch along with the stability samples. with regards, Ramesh.V — with regards, Ramesh |
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sudeshnamandal1 ☆ India, 2008-03-17 14:01 (6676 d 04:13 ago) @ Ramesh Posting: # 1704 Views: 3,774 |
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❝ Query1 ❝ % stability calculation: ❝ one by calculating the % accuracy. i.e 85-115% of nominal conc. ❝ Percent Stability [%]Stability = 100 x Mean Conc. of Stability Samples / Mean Conc. of Comparison Samples ❝ Query 2: ❝ Precision and Accuracy: ❝ ❝ For the determination of the stability, fresh CC and QC samples are ❝ prepared, in such case is it necessary to prove the precision and accuracy ❝ of the freshly prepared QC samples. i mean to say whether it is necessary a ❝ to analysis the P& A batch along with the stability samples. No need to prepare freshly prepared QC samples along with fresh CC. Compare the stability QC samples with first day P&A batch QC samples. -- Edit: Full quote removed. Please see this post! [HS] — Sudeshna |
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Ohlbe ★★★ France, 2008-03-17 19:33 (6675 d 22:41 ago) @ sudeshnamandal1 Posting: # 1706 Views: 3,769 |
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Dear Sudeshna, ❝ [%]Stability = 100 x Mean Conc. of Stability Samples / ❝ Mean Conc. of Comparison Samples True. But for post-preparative stability, keeping an eye on peak areas is a good idea too. If you have a decreased signal for both your analyte and your IS you may still have an acceptable accuracy, but you may end with LLOQ problems. ❝ No need to prepare freshly prepared QC samples along with fresh CC. There are some discussions there. Some people say you should also prepare fresh QCs along with your fresh CCs. As your stability samples are in fact unknown samples (you don't know if the stability is OK, so you don't really have a nominal concentration any more), they say you should have fresh QC samples to validate your run (3 levels in duplicate, with the usual acceptance rules). ❝ Compare the stability QC samples with first day P&A batch QC samples. That's what the FDA guideline says. But have a look at the 2007 Crystal City paper: they now recommend to compare to the nominal concentration. Day 0 or day 1 concentrations are rather used to make sure the stability samples were preprared correctly. Regards Ohlbe |
Ing. Helmut Schütz