*3.7.1 High performance liquid chromatography (HPLC)*

High performance liquid chromatography (HPLC) is a rapid separation and analysis technology developed on the basis of conventional column chromatography. Its separation principle is the same as regular column chromatography, including adsorption chromatography, gel chromatography, partition chromatography, ion exchange chromatography, and other methods. HPLC columns are produced

#### *Phytochemicals in Human Health*

with particle fillers (particle diameter 5–20 μm) and high pressure homogenate column loading technology. The eluents are pressed into the column by a high pressure infusion pump and equipped with high sensitive detectors and automatic recording and collection devices. As a result, it is far superior to conventional column chromatography in separation speed and efficiency. It has the characteristics of high efficiency, high speed, and automation. Preparative HPLC can be used to prepare a large amount of samples of high purity. HPLC has played an increasingly important role in the separation, qualitative identification, and quantitative analysis of plant chemical constituents. During the separation of many plant chemical constituents, it is necessary to separate trace constituents from a large amount of crude extracts. Usually, in the final stage of separation, samples with high purity are prepared by high or medium pressure liquid chromatography. Constant concentration eluents are mostly used in preparative HPLC. However, gradient elution is sometimes applied for samples that are difficult to be separated. Moreover, HPLC retains the advantages of liquid chromatography, such as a wide range of application and flexibility of mobile phase change. It can be applied to chemical constituents of difficult gasification, high molecular weight, or thermal instability.

The detectors commonly used in HPLC are ultraviolet detectors and differential refractive index detectors, but both have limitations. Differential refractive index detectors are sensitive to temperature change, the detection of a small amount of substances is often not ideal, and gradient elution cannot be used. As for ultraviolet detectors, they cannot detect samples without ultraviolet absorption. In recent years, a kind of mass detector, called evaporative light scattering detector (ELSD), has been applied in HPLC. It can not only detect samples without ultraviolet absorption, but also use gradient elution. It is suitable for most nonvolatile components [20].

#### *3.7.2 Droplet counter-current chromatography (DCCC)*

DCCC is an improved liquid-liquid partition chromatography based on the counter-current partition method. The formation of droplets is required when the mobile phase passes through a liquid stationary phase column. Droplets of mobile phase contact with stationary phase effectively, and form new surfaces in thin partition extraction tubes constantly, which promote the partition of solutes in two-phase solvents, and the chemical components of mixtures are isolated in immiscible two-phase droplets due to different partition coefficients. This method is suitable for the separation of phytochemicals with strong polarity. The separation effect is usually better than counter-current partition chromatography, and there is no emulsification phenomenon. Furthermore, nitrogen is used to drive the mobile phase, so the separated substance will not be oxidized by oxygen in the atmosphere. However, the solvent system which can generate droplets must be selected in this method, the amount of sample treated is small, and special equipment is needed.

DCCC possesses good reproducibility, and can handle crude extract samples of milligram to gram grade. It can be used in either acidic or basic conditions. Because no solid separation carriers are used, the phenomenon of irreversible adsorption and band broadening of chromatographic peaks can be avoided. Compared with preparative HPLC, DCCC consumes less solvent, but the separation time is longer and the resolution is lower. For example, see [21].

#### *3.7.3 High speed counter-current chromatography (HSCCC)*

HSCCC is also a liquid-liquid partition chromatography. It is another mild form of chromatography with no solid support and hence no chance of loss of substrate by binding to the column. The only media encountered by the sample are solvent

**57**

*Analytical Methods of Isolation and Identification DOI: http://dx.doi.org/10.5772/intechopen.88122*

phase are eluted later.

pressure or voltage.

example, see [23].

*3.7.5 Affinity chromatography (AC)*

technology in recent years. For example, see [24].

and Teflon tubing. The former is common to all forms of chromatography and the latter to most. The chemical constituents with higher partition coefficient in mobile phase are eluted first, whereas those with higher partition coefficient in stationary

HSCCC chromatography could avoid the shortcomings of irreversible adsorption and abnormal tailing of chromatographic peaks caused by solid carriers in liquid chromatography because it does not need solid carriers. The sample recovery is near 100% from a chromatography. It also has advantages of good reproducibility, high purity of separated compounds, and fast speed. It is suitable for the isolation and purification of wide kinds of phytochemicals, such as saponins, alkaloids, flavonoids, anthraquinoids,

It is an instrumental analysis method developed in the late 1980s combining classical electrophoresis with modern microcolumn separation technologies. In pharmaceutical analysis, the most commonly used separation modes are capillary zone electrophoresis, micellar electrokinetic capillary chromatography, and capillary gel electrophoresis. It is an efficient separation technology of large and small molecules in a hollow and thin inner diameter capillary (10–200 μm). The two ends of the capillary are immersed in a buffer solution and electrodes connected with a high voltage power supply are inserted separately. The voltage makes samples migrate along the capillary. According to the charge and volume of the separated substances, various molecules are separated under high voltage. In zone capillary electrophoresis, separation could be achieved by the movement of electrophoresis and electroosmotic flow. The strength of electroosmotic flow depends on the strength of electric field, PH value of electrolyte, composition of buffer solution, ionic strength, internal friction, and so on. Sample injection could be accomplished by pressing the sample into a capillary tube by atmospheric

HPCE has the advantages of high efficiency, microamount, economy, high automation, and wide application. However, it has the disadvantages of poor preparation ability, low sensitivity, and poor separation reproducibility. For

Affinity chromatography is a unique chromatographic separation method based on the principle of reversible combination of high affinity and specificity between molecules. By simulating the reversible and specific interaction between biological molecules, affinity chromatography uses the adsorption medium coupled with affinity ligands as the stationary phase to adsorb target compounds. It is a development of adsorption chromatography. This method can selectively separate and analyze specific chemical constituents from complex samples. Firstly, ligands that can specifically bind to the target compounds are fixed on the filler carrier to make the chromatographic column. Then the mixture containing the target compounds is passed through the column. Only the target compounds which show affinity with the ligands can bind to the ligands and remain in the column. Finally, the adsorbed target compounds are eluted by changing the composition of the mobile phase and are separated from other chemical constituents. AC is mainly used for the separation and purification of proteins, especially enzymes, antigens, and antibodies. Its application range has been expanding along with the continuous development of

lignans, triterpenes, proteins, and carbohydrates. For example, see [22].

*3.7.4 High performance capillary electrophoresis (HPCE)*

#### *Analytical Methods of Isolation and Identification DOI: http://dx.doi.org/10.5772/intechopen.88122*

*Phytochemicals in Human Health*

with particle fillers (particle diameter 5–20 μm) and high pressure homogenate column loading technology. The eluents are pressed into the column by a high pressure infusion pump and equipped with high sensitive detectors and automatic recording and collection devices. As a result, it is far superior to conventional column chromatography in separation speed and efficiency. It has the characteristics of high efficiency, high speed, and automation. Preparative HPLC can be used to prepare a large amount of samples of high purity. HPLC has played an increasingly important role in the separation, qualitative identification, and quantitative analysis of plant chemical constituents. During the separation of many plant chemical constituents, it is necessary to separate trace constituents from a large amount of crude extracts. Usually, in the final stage of separation, samples with high purity are prepared by high or medium pressure liquid chromatography. Constant concentration eluents are mostly used in preparative HPLC. However, gradient elution is sometimes applied for samples that are difficult to be separated. Moreover, HPLC retains the advantages of liquid chromatography, such as a wide range of application and flexibility of mobile phase change. It can be applied to chemical constituents of difficult

The detectors commonly used in HPLC are ultraviolet detectors and differential refractive index detectors, but both have limitations. Differential refractive index detectors are sensitive to temperature change, the detection of a small amount of substances is often not ideal, and gradient elution cannot be used. As for ultraviolet detectors, they cannot detect samples without ultraviolet absorption. In recent years, a kind of mass detector, called evaporative light scattering detector (ELSD), has been applied in HPLC. It can not only detect samples without ultraviolet absorption, but also use gradient elution. It is suitable for most nonvolatile components [20].

DCCC is an improved liquid-liquid partition chromatography based on the counter-current partition method. The formation of droplets is required when the mobile phase passes through a liquid stationary phase column. Droplets of mobile phase contact with stationary phase effectively, and form new surfaces in thin partition extraction tubes constantly, which promote the partition of solutes in two-phase solvents, and the chemical components of mixtures are isolated in immiscible two-phase droplets due to different partition coefficients. This method is suitable for the separation of phytochemicals with strong polarity. The separation effect is usually better than counter-current partition chromatography, and there is no emulsification phenomenon. Furthermore, nitrogen is used to drive the mobile phase, so the separated substance will not be oxidized by oxygen in the atmosphere. However, the solvent system which can generate droplets must be selected in this method, the amount of sample treated is small, and special equipment is needed. DCCC possesses good reproducibility, and can handle crude extract samples of milligram to gram grade. It can be used in either acidic or basic conditions. Because no solid separation carriers are used, the phenomenon of irreversible adsorption and band broadening of chromatographic peaks can be avoided. Compared with preparative HPLC, DCCC consumes less solvent, but the separation time is longer

HSCCC is also a liquid-liquid partition chromatography. It is another mild form of chromatography with no solid support and hence no chance of loss of substrate by binding to the column. The only media encountered by the sample are solvent

gasification, high molecular weight, or thermal instability.

*3.7.2 Droplet counter-current chromatography (DCCC)*

and the resolution is lower. For example, see [21].

*3.7.3 High speed counter-current chromatography (HSCCC)*

**56**

and Teflon tubing. The former is common to all forms of chromatography and the latter to most. The chemical constituents with higher partition coefficient in mobile phase are eluted first, whereas those with higher partition coefficient in stationary phase are eluted later.

HSCCC chromatography could avoid the shortcomings of irreversible adsorption and abnormal tailing of chromatographic peaks caused by solid carriers in liquid chromatography because it does not need solid carriers. The sample recovery is near 100% from a chromatography. It also has advantages of good reproducibility, high purity of separated compounds, and fast speed. It is suitable for the isolation and purification of wide kinds of phytochemicals, such as saponins, alkaloids, flavonoids, anthraquinoids, lignans, triterpenes, proteins, and carbohydrates. For example, see [22].
