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IK ☆ India, 2010-05-27 12:11 (5873 d 11:12 ago) Posting: # 5383 Views: 4,326 |
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Dear All, In a Method Validation - Plasma Preparation has been done by adding 30ml of 25% Ascorbic acid solution in 100ml plasma (i.e. 30% buffer solution in plasma). All QC & CC standards prepared as mentioned above. Whereas during sample collection (clinical phase) 50µL of 25% Ascorbic Acid has been added to vial containing approx. 1.5ml plasma. From the above it is evident that the % buffer added to plasma during validation and sample collection do not mimic (more variation in % buffer). With Reference to the above:
Best Regards IK |
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Ohlbe ★★★ France, 2010-05-27 13:35 (5873 d 09:48 ago) @ IK Posting: # 5384 Views: 3,768 |
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Dear IK, I would recommend a full revalidation of the method using the same conditions as for the subject samples, and to use for the study phase calibration and QC samples containing the same proportion of ascorbic acid as the subject samples. Tons of reasons for this. There was a huge dilution of your samples during validation. This reduces the protein contents (which can influence recovery), the amount of matrix components (which can influence matrix effects), changes the pH due to ascorbic acid (recovery again), etc. Just look at the difference in response you can get between CPD plasma (approximately 20 % dilution due to the CPD buffer) and EDTA plasma ! In addition I would certainly repeat the long-term stability as you have a different amount of stabiliser (and a different pH). Regards Ohlbe — Regards Ohlbe |
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Helmut ★★★   Vienna, Austria, 2010-05-27 16:22 (5873 d 07:01 ago) @ IK Posting: # 5385 Views: 3,662 |
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Dear IK, I agree with Ohlbe's post. What was the rationale to 'validate' the method in a matrix different from the study's? Such a procedure is against all guidelines (FDA, EMA, ANVISA, ...). — 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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IK ☆ India, 2010-05-28 10:01 (5872 d 13:22 ago) @ Helmut Posting: # 5391 Views: 3,553 |
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Helmut ★★★ Vienna, Austria, 2010-05-28 13:15 (5872 d 10:08 ago) @ IK Posting: # 5392 Views: 3,563 |
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Dear IK, THX for not answering my question. — 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