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moblak ☆ 2010-04-21 18:06 (5909 d 13:25 ago) Posting: # 5180 Views: 3,581 |
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Hi everyone, in the past, we have validated (FDA, EMA) an LC-MS/MS method for simultaneous determination of parent compound and its three metabolites in human plasma. For internal standard a mixture of all four corresponding deuterated standards was used. Now, we would like to use this method for determination of parent compound only. We intend to prepare the CCs and QCs only for the parent compound (no metabolites in the plasma samples), while for the internal standard only corresponding deuterated standard of the parent compound would be used. Is there any additional cross-validation needed in such case? Any other suggestions? Many thanks Marko |
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Geokad ☆ Canada, 2010-04-23 19:50 (5907 d 11:41 ago) @ moblak Posting: # 5206 Views: 2,911 |
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Hi Marko, ❝ We intend to prepare the CCs and QCs only for the parent compound (no ❝ metabolites in the plasma samples), Personally, I do not recommend that. All your evaluations were done in the presence of 4 analytes. Your method performance might be different if you don't have all of them in there (e.g. competition). — Regards, Geokad |
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moblak ☆ 2010-04-28 13:49 (5902 d 17:43 ago) @ Geokad Posting: # 5255 Views: 2,865 |
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Hi Geokad, since I usually take a rather conservative approach, I sort of agree with you.  But on the other hand, if this would be true: "Your method performance might be different if you don't have all of them in there ..."...then I would have a BIG problem with any method that is used for the measurement of parent compound only (while other (in)active metabolites are also present in the matrix). The way I (could) see the situation is as follows: Method 1: validated method for parent compound only (selectivity and (no) matrix effect demonstrated for the presence of three (in)active metabolites) Method 2: validated method for parent compound and three (in)active metabolites. The same chromatographic conditions as in method 1 and nearly the "same" sample preparation as in method 1 (QC and CC samples contain parent compound and all three metabolites, while IS solution is a mix of all four deuterated analogs) Method 1 can be used to quantify only parent compound in the presence of metabolites, whereas method 2 can be used to quantify parent compound AND metabolites. IMHO method 2 has added value compared to method 1 and could be "reduced" to quantify parent compound only. Would one A/P experiment with parent compound only and IS (mix, no mix?) be sufficient for cross validation. Any other suggestions/opinions are welcome... Regards Marko |
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Debbie ★ India, 2010-04-28 19:53 (5902 d 11:39 ago) @ moblak Posting: # 5260 Views: 2,815 |
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Hi, i think you can use your combination method(parent and metabolites) to quantify only parent compound. as you said establishing one precison and accuracy batch with only parent compund and its internal standard would suffice the requirement to test the method performance. Regards, |
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Ohlbe ★★★ France, 2010-04-29 02:38 (5902 d 04:54 ago) @ Debbie Posting: # 5264 Views: 2,837 |
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Dear all, I would agree with Debbie, at least if you have demonstrated that you have no selectivity issue and no ion suppression / enhancement from any of the 3 metabolites and corresponding 3 SIL IS on the parent and corresponding IS. (If you did have selectivity or matrix effects issues, your combined method would be flawed anyway as you will never have a fixed proportion of the 4 analytes in your study samples). Regards Ohlbe — Regards Ohlbe |
Ing. Helmut Schütz