24小时热门版块排行榜

返回列表

当前主题已经存档。

当前只显示满足指定条件的回帖，点击这里查看本话题的所有回帖

cyh2010

铁虫 (正式写手)

应助: 0 (幼儿园)
金币: 11.8
散金: 388
红花: 3
帖子: 633
在线: 108.1小时
虫号: 291126
注册: 2006-10-28
性别: GG
专业: 食品加工技术

[交流] 【求助】凝胶形成了，如何保持反应体系pH恒定？

最近看了些英文文献：凝胶在几分钟内形成，形成的凝胶还要不断搅拌几个小时，这期间用HCl控制pH，保持在4.75。
总觉得这个工艺有问题
   （1）既然形成凝胶了，转子可能就转不动了，不能搅拌了，如果还能搅拌的话，得需要较大的转速，转速过大，剪切力过大，就会使凝胶解体。
   （2）凝胶不像液体那样容易混匀，而是胶体，加入的盐酸怎样才能均匀分布到各个部位呢。
   (3)既然是凝胶，不是溶液，pH计都不能插到凝胶中去，充分接触凝胶，又怎样测得pH是否是 4.75呢？
不知大家有何高见，怎样理解这个操作过程。

[ Last edited by cyh2010 on 2009-4-28 at 21:22 ]

回复此楼

» 猜你喜欢

1楼 2009-04-28 21:03:37

已阅回复此楼关注TA 给TA发消息送TA红花 TA的回帖

cyh2010

铁虫 (正式写手)

应助: 0 (幼儿园)
金币: 11.8
散金: 388
红花: 3
帖子: 633
在线: 108.1小时
虫号: 291126
注册: 2006-10-28
性别: GG
专业: 食品加工技术

原文如下： 100 mg of HA were dissolved in 20 ml of double distilled water, then PAHy (64 mg) was added to this solution. The reaction mixture was maintained in a thermostatic bath at 37 C and the pH was adjusted to
4.75 by adding HCl 0.1 N solution.
Then activating agent EDC was added to the mixture.
After EDC addition, gelation occurred in few sec. The obtained gels were stirred at 37 C for 4 h and during this time the value of pH wascontinuously controlled and maintained at 4.75 by using HCl 0.1 N solution. After 4 h, each gel was puriﬁed by several washes with double distilled water, centrifuging, from time to time, at 12000 rpm at 4 C for 15 min, then recovered after lyophilization.

[ Last edited by cyh2010 on 2009-4-30 at 08:32 ]