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BEAZ ★ India, 2008-11-12 07:47 (6439 d 23:24 ago) Posting: # 2658 Views: 4,461 |
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Hai, If a predose (without IS) shows a very high concentaration, as per the bioanalysit it is due to back calculation of analyte area, the analyte area is less than 20% compared to the Standard A. the IS area also very less compared to normal IS area. This is observed with few number of subjects Pk data. Is this data acceptable or have to perform reanalysis? Analysts states that this is not a peak and observed because of the noise Kindly provide your views Thanks in advance Alhas — Alhas |
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kaushal09 ☆ India, 2008-11-12 12:31 (6439 d 18:40 ago) @ BEAZ Posting: # 2659 Views: 3,659 |
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hi, Please check pre dose sample with IS. if analyte area in this sample showing significant area as compare to standard 1 than pre dose sample can be repeated other wise not required to repeat samples. by kaushal -- Edit: Full quote removed. Please see this post! [Ohlbe] |
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Ohlbe ★★★ France, 2008-11-12 13:00 (6439 d 18:10 ago) @ BEAZ Posting: # 2660 Views: 3,674 |
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Dear Alhas, ❝ If a predose (without IS) shows a very high concentaration You can't calculate a concentration in a sample without IS, by comparison to a standard curve with IS ! Of course if you have a slight carry-over, or something your chromatographic software identifies as an IS peak, the software will calculate a concentration. But it is meaningless and it should be disregarded. All you can do with this sample is check that you have no interference at the retention time of your IS, and compare the analyte peak area to that of the first calibration sample. Regards Ohlbe |
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Geokad ☆ Canada, 2008-11-12 17:51 (6439 d 13:20 ago) @ BEAZ Posting: # 2662 Views: 3,704 |
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Hi, I agree with kaushal that you have to check the same pre-dose with IS. If the peak area is similar than it can tells you if it's coming from the sample itself. This can mainly happen in pre-doses of period 2 if the wash out period is not enough. — Regards, Geokad |
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srithan ● 2008-12-06 12:49 (6415 d 18:21 ago) @ BEAZ Posting: # 2887 Views: 3,503 |
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❝ If a predose (without IS) shows a very high concentaration, as per the ❝ bioanalysit it is due to back calculation of analyte area, the analyte area ❝ is less than 20% compared to the Standard A. Dear Alhas, What ever your analysts said seems to be absolutely correct. How come one can estimate the concentration of the drug in a blank (predose sample) with out Internal standard.  Check the area at the RT of analyte and IS and it should meet your SOP criteria, If it meets then you can accept the data and no need to perform reanalysis. |
Ing. Helmut Schütz