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raghavendra_s ★ 2010-02-03 17:33 (5983 d 22:17 ago) Posting: # 4702 Views: 3,240 |
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Dear friends, One of our submitted LS-MS method of Clarithromycin using Alprazolam to a journal posed some peer review comments. Can you please help us in finding the best answers. Discuss rationale for choice of alprazolam as the internal standard. Thanks in advance, |
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Ohlbe ★★★ France, 2010-02-03 18:59 (5983 d 20:51 ago) @ raghavendra_s Posting: # 4703 Views: 2,510 |
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Dear Raghavendra, For LC-MS/MS methods the choice of IS is usually, in order of preference: 1. stable isotope labelled analyte 2. structural analogue (for instance in your case, azithromycin could have been an option) 3. any other compound which you expect will have the same behaviour as your analyte during sample preparation, HPLC, ionisation, detection etc. You opted for option 3. So what made you expect that it would have the same behaviour as your analyte ? I'm afraid I fail to see the rationale when looking at the respective structures of clarithromycin and alprazolam. Regards Ohlbe — Regards Ohlbe |
Ing. Helmut Schütz