柱色谱中理论板的概念

As a chromatographer you would be interested in getting the maximum return from your column in terms of performance efficiency.Useful tips on care of HPLC columnshave been suggested earlier to preserve the performance features and improve useful life of your column. Now the question arises as to how do you quantify efficiency and decide if you can still use your column to get reliable separations. The answer lies in keeping a track on theoretical plates over the lifespan of a column.

The setup of chromatography consists of two phases: the mobile phase and stationary phase. The prior one is a fluid in which the mixture that has to be separated gets dissolved. After this, the mixture containing fluid is passed through the stationary phase where the separation happens. This is where a column comes into the role.

It contains the stationary phase and lets the mobile one pass through it. That brings us to the concept of理论板材在柱色谱。让我们了解它之前的重要性。

什么是理论板在HPLC？

A chromatographic column does not consist of any physical plates which can be measured from time to time to rate a column’s performance efficiency. It is only a theoretical concept drawinga与使用的巨大分数蒸馏柱的相似性the精炼粗石油。

Such distillation column actually包含separator plates which help separation and isolation of different petroleum fractions which are collected as separate streams.Now, let’s see from where this concept came into existence.

HPLC理论板的历史

之前，分数蒸馏过程用于具有不同的长度和柱设计。因此，需要分离效率会计，从而带来了概念理论板材。这个的基础plate theory of chromatography假设蒸馏程序在沿着二手柱的长度发生了各个阶段。

然而，这里要注意的点是分数蒸馏不属于色谱过程的类别。

为什么这些板块重要?

Theoretical plates在列chromatography are directly related to the efficiency of its column. Therefore, it can assist in improving the resolution, which is directly proportional to the square root of理论板材’ number when all other variables are kept constant. This means the resolution will increase by a factor of two each time the number of plates is raised by four.

从所有这些东西中，很明显理论板材暗示更好的分离质量，因为在静止和移动阶段之间可以获得更多的平衡。

You can understand this with a simple example of stairs. As the number of stairs reduces, the length of each stair increases. So you need to stretch your legs more to climb every stair. On the other hand, shorter stairs will definitely increase their number but they will reduce your efforts of climbing each one of them. The same thing goes with理论板材。更多的板使整体分离过程更简单。

这些因素显示,理论板材对于提高柱的效率并使色谱过程更加简单，这是重要的。

色谱中的理论板数量现在必须清楚它no such plates exist在reality在色谱柱中。您只需想象您的专栏分为许多部分或板块。如前所述，样品组件在每个板上花费有限时间，因为它移动柱长，这是在固定相和移动相之间在其浓度之间建立平衡所需的时间。

In simple terms, it can be stated that a theoretical plate represents the distance that is needed for every adsorption-desorption step.作为一系列平衡的流动相插塞，从板上假设分析物的运动。换一种说法,越大的板块数量越大,the more efficient is the separation power of the column.

柱长（L）上的板（n）的数量取决于板高度（h）

N = L/H

Smaller plate height implies large number of plates in the column and higher is the column efficiency. H is also referred to as height equivalent to a theoretical plate (HETP) and smaller the value of HETP the greater is the column efficiency.

We can also notice that the column length directly affects the number of plates. It means the longer the column, the more plates can be incorporated in it. Therefore, you can achieve better efficiency by opting for columns that are lengthier.

计算数量（n）

从p N计算eak of the injected standard under prescribed operational conditions

N = 16\((\frac{t_r}{W_b})^2\)

where TR is the retention time of the peak and Wb is the peak width. In case peak width is measured at half height or W1/2 then the relation is expressed as

N = 5.54\((\frac{t_r}{W_1_/_2})^2\)

In above calculations retention time and width should be expressed in the same units

现今的色谱软件提供Number N，无需手动计算，但基本假设是峰值形状应该是高斯。

The number of theoretical plates is dependent on several operational parameters such as flow rate, analyte characteristics, temperature and sample size. Overloading a column rapidly deteriorates its performance.

The Height of Theoretical Plates in Chromatography

可用于测量柱效率的另一个因素是等于理论板（HETP）的高度。马丁和联邦队也提到了这款因素作为板块的厚度。

这是在板数的公式中使用的相同的高度。它通常以毫米计算。从楼梯示例中，我们可以看出每个板的高度决定了柱的数量和柱的效率。您还可以查看以下公式：

HETP = L/N, where L is the column’s length and N is the number of plates.

因此，较短的我们保持高度，由于静止阶段的深度减小，可以获得更好的效率。

对板号的影响

以下是对中等影响的一些因素理论板材:

• Size of the particle (very strong impact)
• Inter-connecting tubing’s dead volume (very strong impact)
• 梯度概况（强烈影响）
• Temperature of column (strong impact)
• 柱长（强烈影响）
• 固定阶段的组成（中等冲击）
• 流动相的组成（中等冲击）
• 颗粒的形状（中等冲击）
• 颗粒形状的均匀性（中等冲击）

希望所有这些东西都制作了plate theory of chromatography清楚给你。