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liuxx1683木蟲 (小有名氣)
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[交流]
不溶于水物質(zhì)要怎么測pH值 已有3人參與
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請問各位,在測不溶于水藥物的pH值時,是怎么操作的? 比如說克拉霉素,在水中幾乎不溶,按藥典的方法,得到是一個懸濁液,那這種情況測pH值,要怎么辦呢? |
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美國藥典規(guī)定克拉霉素的pH為8.0 到10.0,用水:甲醇(19:1)混合溶劑配制2mg/mL的懸浮溶液,然后測pH值(at 25+-2攝氏度)。 pH < 791 >: between 8.0 and 10.0, determined in a 1 in 500 suspension of it in a mixture of water and methanol. pH 測定儀準(zhǔn)確到0.02 pH unit即可。( capable of reproducing pH values to 0.02 pH unit ),應(yīng)該是邊攪拌(用磁力攪拌子不停地攪拌)邊測定pH。 如果pH讀數(shù)不穩(wěn)定,換一臺pH計再測定試試看。 pH < 791 >: Prepare a slurry by weighing 20.0 g +- 100 mg of Topical Starch, transferring to a suitable nonmetallic container, and adding 100 mL of water. Agitate continuously at a moderate rate for 5 minutes, then stop agitation, and immediately determine the pH to the nearest 0.1 unit: the pH, determined potentiometrically, is between 4.5 and 7.0. 淀粉是不能完全溶解于水中的,可以制成混懸液,美國藥典USP規(guī)定是攪拌5分鐘后停止攪拌,立即測定pH,pH準(zhǔn)確到0.1 pH unit。 [ Last edited by penn007 on 2013-1-11 at 01:18 ] |
木蟲 (小有名氣)
銀蟲 (初入文壇)

木蟲 (小有名氣)
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