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VP ☆ 2009-06-25 16:09 (6212 d 13:03 ago) Posting: # 3905 Views: 4,846 |
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Dear all In Project sample analysis, we got ISTD area in predose sample though it is predose sample without ISTD. In that case we have repeated predose sample analysis. Is it correct? If yes, What reason we should mention for that? Regards VP |
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Helmut ★★★   Vienna, Austria, 2009-07-06 20:41 (6201 d 08:32 ago) @ VP Posting: # 3932 Views: 4,176 |
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Dear VP! ❝ In Project sample analysis, we got ISTD area in predose sample though it ❝ is predose sample without ISTD. Interesting approach. To my knowledge nobody asks for a predose sample without IS - only one sample without IS in the calibration curve. ❝ In that case we have repeated predose sample analysis. Is it correct? I think so. ❝ If yes, What reason we should mention for that? The same reason you would give for any other repeated analysis. If you 'see' no more response at the retention time of the IS, most likely it was an error in the sample preparation.
In case (2) probably you should check your procedures: Watch for a potential contamination in the sample preparation, flush the injector with a solution of more organic modifier than the mobile phase, inject a blank/mobile phase after samples with high concentrations. — Dif-tor heh smusma 🖖🏼 Довге життя Україна! ![[image]](https://static.bebac.at/pics/Blue_and_yellow_ribbon_UA.png) Helmut Schütz ![[image]](https://static.bebac.at/img/CC by.png) The quality of responses received is directly proportional to the quality of the question asked. 🚮 Science Quotes |
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VP ☆ 2009-07-21 14:53 (6186 d 14:19 ago) @ Helmut Posting: # 3974 Views: 3,839 |
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Dear all Thanks for ur reply. Actually we are processing predose sample with and without IS. Response we got is very less, so as u said definately I will recheck the processing for next samples. regards VP |
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ElMaestro ★★★ Denmark, 2009-07-06 22:11 (6201 d 07:02 ago) @ VP Posting: # 3935 Views: 4,344 |
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Hi VP, ❝ In Project sample analysis, we got ISTD area in predose sample though it ❝ is predose sample without ISTD. I don't follow you here. Are you processing your pre-dose samples in a different way (without IStd) than your post-dose samples (with IStd)? That would in my opinion be clearly wrong and it would not allow you any conclusions about pre-dose concentrations. Best regards, EM. |
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Geokad ☆ Canada, 2009-07-07 20:35 (6200 d 08:38 ago) @ ElMaestro Posting: # 3942 Views: 4,022 |
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Hi ElMaestro, We do the same thing. Actually, we process the predose sample with and without IS. The one with IS is to have an idea about the predose concentration and the one without IS is to see if we have any supression or interference coming from this particular subject at the IS retention time. — Regards, Geokad |
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santosh kumar Manthri ● 2009-07-17 14:30 (6190 d 14:42 ago) @ VP Posting: # 3964 Views: 3,897 |
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Dear VP You did the right thing by repeating the predose sample. You can give the reason for repeat as "Improper sample processing". Regards Santosh kumar -- Edit: Full quote removed. Please delete anything from the text of the original poster which is not necessary in understanding your answer; see also this post! [Helmut] |
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Helmut ★★★ Vienna, Austria, 2009-07-17 15:26 (6190 d 13:47 ago) @ santosh kumar Manthri Posting: # 3965 Views: 3,989 |
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Dear Santosh! ❝ You can give the reason for repeat as "Improper sample processing". Everybody can claim anything. But how do know that the reason was "Improper sample processing"? Referring to my previous post essentially you opt for case (1), ignoring the possibility of case (2). — Dif-tor heh smusma 🖖🏼 Довге життя Україна! Helmut Schütz The quality of responses received is directly proportional to the quality of the question asked. 🚮 Science Quotes |
Ing. Helmut Schütz