主题：【My Topic--One】If I am an intelligent column

茅茅, too difficile

Just a little difficult. No problem, I'll go on. I——not column, but 茅茅 did do an interesting dream last night.

You know, chromatography is often compared to race. But I dreamed 跨栏（hurdle）.What catch our eyes is not who is the best one(刘翔）but all the players in the game.
The ideal mode is like this: stand hand in hand in a vertical
row. stand side by side（并列）should be avoided.

原文由 mhq111111 发表:
(to be continued...)

We columns differ in shape,materials of origins and functions. In gc family, we are made of glass or stainless steel. However, majority of us are of capliary types. If you feed us samples eviporized in the sample inlet through split or non split liners, then our functions can be different.

感谢ruojun大侠的参与。事实上，writing in English or thinking in English is perfectly difficult to me.记得上次ruojun说起不知道“顶空”是怎么回事，今天我在这里讲一个大概。
顶空进样和溶液直接进样都是针对GC来说的，以前只有溶液直接进样的方式，顾名思义，打进衬管的样品是液体，一般是0.2-1微升，在进样口瞬间汽化，进柱（起始柱温通常为40度）时的状态是一层液膜。
顶空进样进入衬管的是气体，一般是1到3ml，在仪器外部配了一个自动顶空进样器，有10或20ml规格的顶空玻璃瓶，液体样品加1到5ml，或者直接放入固体样品，“顶空”的意思就是液体或固体“顶上的空气”，在残留溶剂测定中，甲醇等挥发性成分在80度保温30min后达到气液平衡，在气体中的比例显然高于液体中，利用这个特性直接抽取上层的气体进样，样品本身不进入柱子，大大地降低了对柱子的污染。顶空进样法特别适合分析那些沸点低的挥发性成分。

谢谢茅茅姐，终于知道什么是顶空进样了。如此说来，顶空进样在药品检验里就是用来测溶剂的?如果同时有好几种残留溶剂存在，气液平衡时间怎么控制呢？如果没有达到气液平衡，是不是测得的结果会比实际值偏低？这种方法不适用于对热敏感的药物吧？

顶空还分动态顶空和静态顶空吧

原文由 happyjyl 发表:
如此说来，顶空进样在药品检验里就是用来测溶剂的?如果同时有好几种残留溶剂存在，气液平衡时间怎么控制呢？如果没有达到气液平衡，是不是测得的结果会比实际值偏低？这种方法不适用于对热敏感的药物吧？

是的，暂时只用于残留溶剂测定方面。好几种残留溶剂可以一起测定，时间一般都在30到60分钟，最常用45分钟。
第三问，clever girl!的确，没有达到平衡测量值会偏低。
第四问，加热后会分解，尤其是产生挥发性气体的药物，最好避免使用该方法。其实你提的这个问题相当好，我想要做一个方法学验证才可以的。
感谢参与！

原文由 christe 发表:
顶空还分动态顶空和静态顶空吧

是的，在残留溶剂测定中，用到的全是静态，上次我的帖子里已经说明了动态顶空我没有用过，也没有见过，水中月给了我答复。

下面的链接里有吹扫-捕集的方式的讲解 http://www.instrument.com.cn/bbs/shtml/20061106/617686/
低温吹扫捕集技术 http://www.instrument.com.cn/bbs/shtml/20060714/483817/
热解析 http://www.instrument.com.cn/bbs/shtml/20061029/607591/

我想这个帖子就这样讨论下去，前面几楼都作为铺垫，最后一楼我会回应主题。弄个故事连载的形式。

看到这样一篇短文，对柱子的选择有帮助
http://www.discoverysciences.com/product_Vials.aspx

Assistance in Choosing the Right HPLC Column
Alltech Packing Material Specifications
Alltech Packing Material Specifications HPLC Packing Material Specifications  Packing Base Material Particle Shape Particle Size (µm) Carbon Load (%) Pore Size (Å) Surface Area (m2/g) Phase Type Endcapped? USP L-Code Adsorbosphere® C18 Silica Spherical 3, 5, 10 12% 80 20

Alltech’s Key Column Families
Alltech’s Key Column Families Alltech manufactures our HPLC media and packs our columns to the highest standards of quality and reproducibility. Rely on our technical expertise for the best columns, the best applications, and the best technical support. Descriptions of our newest and most important column families fol

Choosing the Right HPLC Column Formats
Choosing the Right HPLC Column Formats Column dimensions and styles affect resolution, run time, solvent usage, and more Column Length For the same packing material, shorter columns provide faster run times, while longer columns provide better resolution. Consider the complexity of your sample and your desir

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Chromatographic Performance Since chromatography is a volume dependent technique, volume is the most accurate way to measure a separation. At constant flow rate, retention time or distance can be substituted for volume. Regardless of what terms are used, remember to be consistent. Definition of a Chromatogram Peak V

Choosing the Right HPLC Column
1. Set Your Separation Goals. Determine if your application requires high resolution, short analysis time, maximum sensitivity, long column life, low operating cost, or other important factors. 2. Choose Your Packing Material. Read below for an explanation of different specifications and how they affect your separation. 3. Choose Your Column Format. Make sure the column format that you choose has the appropriate affect on your separation.

Packing Materials
Understanding the specifications of HPLC packing materials and how they affect a separation will help you narrow your column choices. You will find all of these specifications for Alltech’s HPLC packings on pages 129-130.

Base Material
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Silica-based reversed-phase packings have free silanol groups that will interact with polar compounds. Endcapping the bonded phase minimizes these secondary interactions. Choose endcapped phases if you do not want interactions with polar compounds. Choose nonendcapped phases if you want enhanced polar selectivity, for stronger retention of polar organic compounds.