C18 column and 琛C18 column selection technique

琛航 C18 column and C18 column column selection technique

In the liquid chromatography, the reversed-phase chromatography using the C18 column is used to analyze the organism-related substances, which can meet the needs of the main research fields, and use the 钗惴骸U饫锝 饫锝 ∩掀 ∩掀 lt lt; SPAN> C18 column and our C18 column for a brief introduction, as well as some tips for column selection.

As shown in the figure below, this is the overall bonding idea for the C18 column. The silylating agent having an alkyl chain is reacted with a silanol group on the surface of the silica gel, and since the alkyl chain is tightly immobilized on the surface of the silica gel using a covalent bond, the alkyl chain is not washed away by the mobile phase. It plays a role as a stable chromatographic stationary phase.

Introduction of C18 groups using a silane coupling agent ( Silane Coupler )

The synthesis of the C18 filler described in this figure appears to be simple, but in fact the reaction between the solid phase and the liquid phase is more difficult to control than the reaction between the liquid phases. The reproducibility of chromatographic media is much higher than that of general chemicals. If the actual materials used and the reaction conditions are slightly different, the separation characteristics of the final product will vary greatly. Such changes, depending on the purpose or become a disadvantage, may also be an advantage. However, if it does not have good reproducibility, it cannot be used in practical applications. Thus, hundreds of C18 columns with different separation options have appeared on the market .

The following figure is a detailed description of the synthesis of the filler, and the products on the market are mostly divided into the following two steps for synthesis.

Synthesis of filler  

First, as just described, the C18 group was introduced onto the surface of the silica gel. Next, a second step of the reaction is carried out to introduce the small molecule reagent onto the silanol group remaining in the first step, which is called tailing. By sealing, the effect of the raw material silica gel is reduced as much as possible, and the separation effect of the compound having a strong interaction with the surface of the silica gel is ensured. In addition, by this step, it is possible to relatively easily ensure the reproducibility of product performance. It is an eternal issue for manufacturers to provide products with stable performance without being affected by the properties of the raw material silica gel. In addition, recently, as a substitute for silica gel, raw materials containing organic materials are also commercially available and sold. However, such raw materials have not exceeded silica gel, and most of the products are still made of silica gel.

Here we can simply guess the main reasons for the differentiation of C18 bonded fillers:

1, a silica gel starting material not only differences in the geometric properties of the pore size, particle size, surface area, but which have different chemical properties.

2, the reaction with the silanol group has a functional, difunctional and trifunctional points. Moreover, depending on the reaction conditions, the final properties of the product will also be significantly different, as follows:

Types and properties of residual silanol groups  

3 , the difference in the column tailing reaction of each company is also a major factor causing the difference in column performance, and the sealing method is also the existence of confidentiality of each company.

The performance results of the column caused by these three reasons can be summarized as the following seven points:

a. The number of theoretical plates of the column, the service life;

b. Reproducibility of the same batch of columns;

c. column bleed observed using LC-MS ;

d. retention ability of the compound;

e. the peak shape of the acid neutral compound;

f. a peak shape for a polar (basic) compound;

g. Peak shape of the coordination compound.

Combined with more than 7:00, and here I make a simple evaluation (to a general e 5:00 This is our basic requirements column, constitute the basic problem) Sum of several major aircraft company C18 column.

Comasil C18

The ultra-high carbon loading and ultra-low metal ion content are outstanding advantages. The former guarantees the strong retention and separation ability of the column, while the latter guarantees a good peak shape for the coordination compound and low metal ion content. It also makes the residual silicon hydroxyl group p H larger than the general column and thus has better inertness. Its derivative product, Comasil BDS C18 , is the first choice for detecting polar (alkaline) compounds.

Comatex C18

Similar to Comasil 's separation and analysis capabilities, but its low column pressure and long service life are its outstanding advantages. Its derivative Comatex C18-AQ has good retention and special selectivity for hydrophilic compounds.

Inertex C18

Compared with Comasil , Comatex has only a slightly lower carbon loading, but it greatly reduces the retention time of the compound. It is very suitable for the analysis of strongly retained compounds, such as ginsenosides, astragaloside and other very good Chinese herbal medicines. At the same time, the size of silica gel used by Inertex is very small, so it has a lower column pressure than the general column, which greatly guarantees its service life, which is its outstanding advantage.

The company's main three columns are introduced to this, in one sentence, there is no column on the market that can cover all applications, specific applications have to be specifically analyzed, and seeking truth from facts is the basic requirement of chemical analysis.

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