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navin ☆ 2008-11-21 10:15 (6425 d 02:26 ago) Posting: # 2760 Views: 5,560 |
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Dear all, If we got the monohydrated version of the drug ex. Doxycycline Monohydrate and we have to prepare stock solution of Doxycycline 1000 micrograms/ml. according to COA we got the assay as is basis for the monohydrated version. Then how we have to proceed for the calculation? The formula is weigh/volume*assay*molecular weight of analyte/mol.weight of drug*10=1000 mic gram/ml In the above case we have to take mol.weigh of monohydrate divided by mol.weight of analyte? or both monohydrated versions? we are quantifying only the doxycycline not doxycycline monohydrate. |
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vpardhasaradhi ☆ 2008-11-22 15:23 (6423 d 21:18 ago) @ navin Posting: # 2775 Views: 4,668 |
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Dear Navin, The following formula should work for you: Solution concentration (microgram/mL) = [weight(g)/Volume(mL)] x [1/1000]x[1/1000]x[purity (%)/100]x[Molecular weight of Doxycycline/Molecular weight of Doxycycline monohydrate] With best regards, V.Pardhasaradhi |
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Debbie ★ India, 2009-07-22 20:21 (6181 d 17:20 ago) @ vpardhasaradhi Posting: # 3978 Views: 4,348 |
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Hi, regarding the calculation of concentration of the stock solution, we have esomeprazole magnesium dihydrate, the potncy on as is basis is 99.2%, when the potency, is given on as is basis, do we need to take in to consideration for the dihydrate during the follwoing calculation? the standard formula used is: [weight(g)/Volume(mL)] x [purity (%)/100]x[Molecular weight of free form /Molecular weight of salt form) in this case, what do we need to consider as the salt form: 1. esomeprazole magnesium dihydrate or 2. esomeprazole magnesium only? if the answer is the first one, my question is why do we need to consider the dihydrate, since the potency is on "as is basis" means it would have been calculated by cosnidering the water content. please share your valuable thoughts. regards, |
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Ohlbe ★★★ France, 2009-07-23 01:06 (6181 d 12:35 ago) @ Debbie Posting: # 3979 Views: 4,339 |
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Dear Debbie, ❝ in this case, what do we need to consider as the salt form: ❝ ❝ 1. esomeprazole magnesium dihydrate Yes. ❝ if the answer is the first one, my question is why do we need to consider ❝ the dihydrate, since the potency is on "as is basis" means it would have ❝ been calculated by considering the water content. The free water is taken into consideration, not the dihydrate. Otherwise you would not get a purity of over 99%. Regards Ohlbe |
Ing. Helmut Schütz