10 Similarities between High Performance Liquid Chromatography (HPLC) and Gas Chromatography (GC)

在早期的文章中讨论了HPLC和GC之间的异化 -How are Gas chromatography (GC) and High Performance liquid chromatography (HPLC) different?. The present article discusses 10 key features which are common to both the techniques. On going through these features you will recollect your basic understanding of chromatography and appreciate the commonality between the two most popular separation techniques.

1.公共基础

Separation of components of a mixture, their identification and quantification is the common underlying objective of both the techniques. This is achieved through a choice of columns, mobile phases, stationary phases, detectors and operating conditions.

2. Role of Mobile Phase

The移动阶段以顺序方式在将样品及其分离的组件运送到分离柱和其分离的组分来发挥重要作用。虽然HPLC和GC功能在相同的原理上，但唯一的区别是HPLC使用液体流动相，而GC使用气体作为载体。

3.样本介绍

GC和HPLC are capable of analysis of liquids and dissolved solid mixtures though gaseous mixtures are also routinely analyzed using GC. Sample introduction techniques are common generally common.A gas tight syringe is sufficient for introduction of liquid samples. For gases Teddler bags or auto sampler (manual or automated operation) are used.In HPLC systems the mobile phase is moving under higher pressure so direct syringe injection is not possible. A syringe is used to fill a fixed volume loop in the manual sample introduction valve and with the change of the valve position the entire sample inside the loop is carried by the mobile phase into the column. Auto samplers are a great help for unattended operation when the number of samples is large.

4. Stationary Phases

Separation of the sample components inside the columns takes place on the basis of distribution of sample components between the stationary phase and the moving carrier mobile phase. The distribution is influenced by physico – chemical interactions between the sample components and the stationary phase materials. An exception is Gel Permeation chromatography where separation takes place due to difference in size of the eluting molecules.

5. Band Broadening

乐队扩展是对解决损失的主要贡献，因为它导致重叠和合并否则分开的峰值。范认为方程描述了GC或HPLC柱的整体效率，并考虑了移动相的扩散，传质和速度等因素。这种关系有助于理解GC和HPLC分离的频带扩大和优化操作条件。

6.峰值响应

GC和HPLC chromatogramslook similar. The response is peak shaped in both cases and the concentration of the eluting compound is proportional to the peak height or peak area.
主要是HPLC和GC中的四种方法用于定量估计：

• Normalization of Peak areas
• Internal standard method
• External standard Method
• Standard additions method

7. Reference standards

The basis of quantitative analysis is comparison of the sample response with that of a pure reference compound. Such reference working standards need to be validated from time to time by comparison of their specified parameters against standards traceable to certified materials available from internationally recognized standardization bodies. In routine analysis you need to verify the retention time of injected standards on GC or HPLC systems under specified operating conditions.

8. Common Application Softwares

大多数制造商提供普通的HPLC和GC应用软件，因为峰值分析和数据处理很常见。如果系统是从相同的制造商采购的系统，并且获得多用户许可证，这是一个很大的好处。这种软件还有助于建立操作参数和方法排序。

Examples of software provided by reputed suppliers are:

1. Perkin Elmer-总兼容
2. Agilent- ChemStation，EZ Chrom Elite
3. Thermo Scientific- Chromleon 7.1

9.与其他技术连字符

GC和HPLC均已成功地用质谱连字，以实现优异的分辨率和高敏感性。这两种技术也已成功耦合FT-IR.在分离的混合物组分上到达结构确认。

10. Expression of Column Efficiency

The efficiency of both HPLC and GC columns is expressed in terms of Height equivalent to theoretical plate(HETP). This value is used in deciding the useful life of both GC and HPLC columns over their usage.

GC和HPLC都是色谱分析实验室的柱状石头，虽然了解它们之间的差异非常重要，但了解相似性同样重要的是，以便在手中确定特定应用的正确方法。