What is derivatization? Derivatization experiment classification?

Derivatization is the use of chemical transformations to convert compounds into substances with similar chemical structures. In general, compounds with a specific function are involved in derivatization reactions, and solubility, boiling point, melting point, aggregate state, or chemical composition will deviate. The resulting new chemistries can be used for quantification or separation.

The derivatization of samples is mainly used to convert difficult-to-analyze substances into substances that are similar to their chemical structure but easy to analyze, which is convenient for quantification and separation.

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Derivatization is to chemically react the sample with a certain chemical reagent before chromatographic separation, prepare the target compound in the sample into appropriate derivatives, and then use chromatography for separation and detection.

Purpose: Converts compounds that are not suitable for analysis by a chromatographic technique into derivatives that can be analyzed by that chromatographic technique. For example, some compounds with high boiling point, non-vaporization or thermal instability cannot be analyzed by gas chromatography, and are converted into vaporized or thermally stable derivatives by derivatization, and then analyzed by gas chromatography.

The derivatization reaction used for pre-column derivatization in chromatography should meet the following conditions:

The reaction can be carried out quickly and quantitatively, the reaction repeatability is good, the reaction conditions are not harsh, and it is easy to operate.

The selectivity of the reaction is high, and it is best to react only with the target compound, that is, the reaction should be specific.

There is only one derivatization reaction product, and the by-products of the reaction and excess derivatization reagents should not interfere with the separation and detection of the target compound.

Derivatization reagents should be easily available and versatile.

Commonly used reactions in derivatization include esterification, acylation, alkylation, silanization, boralkation, cyclization, and ionization. Although there are many derivatization methods for gas chromatography, it has the fatal disadvantage that it cannot be used for thermally labile compounds. In addition, for some actual samples with complex matrices, in addition to the difficulty of separation, it is easy to contaminate the injector and damage the column.

Derivatization reactions can be divided into two types in terms of whether covalent bonds are formed or not: labeled and unlabeled. The labeling reaction is the formation of a covalent bond between the analyte and the labeling reagent during the reaction; All other types of reactions, such as ion pairing, photolysis, redox, electrochemical reactions, etc., are label-free.

Another differentiation of derivatization reactions is based on the site of derivatization reactions, which are pre-columnderivatization, on-columnderivatization and post-columnderivatization. From the perspective of whether it is connected to the instrument, there are three types: ** (on-line), offline (off-1ine) and at-line (automated).

At present, the offline pre-column derivatization method (referred to as the pre-column derivatization method) and the ** post-column derivatization method (referred to as the post-column derivatization method) are mostly used in HPLC, and the by-line derivatization method is the development direction.

Both the pre-column derivation method and the post-column derivation method have their own advantages and disadvantages. The advantages of the pre-derivatization method are: relatively free selection of reaction conditions; There are no limitations on reaction kinetics; Derivatization by-products can be pre-treated to reduce or eliminate their interference; It is easy to allow multi-step reactions; There are more derivatization reagents to choose from; No complicated instrumentation is required.

The disadvantages are: the by-products formed may cause greater difficulty in chromatographic separation; During derivatization, it is easy to introduce impurities or interfering peaks, or to lose samples. The advantages of the post-column derivation method are:

1) The formation of by-products is not important, the reaction does not need to be complete, and the products do not need to have high stability, only need to have good repeatability; (2) The analyte can be separated in its original form, and it is easy to use the existing analysis method. The disadvantages are: (1) for a certain solvent and limited reaction time, there are only a limited number of reactions to choose from; (2) Additional equipment is required for the reactor to cause peak broadening and hold reduced resolution.

A derivative product is a financial instrument, which is generally represented by an agreement between two subjects, which is determined by the other underlying products. In addition, there are corresponding spot assets as the subject matter, which do not need to be delivered immediately when the transaction is completed, but can be delivered at a future point in time. Typical derivatives include forwards,**, options, and swaps.

Life is the embryonic stage of things.

Length is the stage when things are formed.

Transformation is the stage of mutation of things.

Transformation is the transformation of things from one form to another. For example, a plant grows in the form of a plant before it is transformed into a seed, and once it reaches a certain period of time, the plant generates power from the inside and becomes a seed form.

This is the connotation of the first kind of life and transformation in Chinese medicine.

The second kind of biochemistry is that traditional Chinese medicine borrows the theory of the five elements to explain the law of the movement of qi, blood and fluid in the five internal organs of the human body, which is summarized into four words: birth, restraint, system, and transformation.

The gram here refers to the restrictive nature relationship between the two organs, Chinese medicine is the middle medicine, balanced medicine, harmonious medicine, Chinese medicine people believe that the spirit of yin and yang is the cure. Therefore, the ecosystem of the five organs not only has life, but also grams, such as lung gold and liver wood, liver wood and spleen soil, spleen soil and kidney water, kidney water and heart fire and lung gold. This kind of restraint and release of life is like the left and right hands of people, ensuring the smooth balance and harmony of the human organs, and will not monopolize one family, which is a manifestation of the health of the internal ecological environment.