Derivatization agents

Analyte functional group Derivatizing agent Product Examples of derivatizing agents... 

Derivatization with Optically Active Reagents and Separation on Achiral Columns. This method has been reviewed (65) a great number of homochiral derivatizing agents (HD A) are described together with many appHcations. An important group is the chloroformate HD As. The reaction of chloroformate HD As with racemic, amino-containing compounds yields carbamates, which are easily separated on conventional hplc columns, eg (66),... 

Treatment with HBF4 in CHCI3 liberates the thiol and returns the derivatizing agent, [(T7- C6H7)Fe(CO)3] BF4 [tricarbonyl[l,2,3,4,5-77]-2,4-cyclohexadien-l-yl-iron(]+) tetrafluoroborate] as a precipitate. ... 

Type Eduet Derivatizing Agent number type Stationary phase type of binding or reaetion... 

Type I Covalent Derivatization with a Unichiral Derivatizing Agent... 

This strategy is the one most commonly used for the analytical determination of ena-tiopurity. A given racemate is reacted with a unichiral derivatizing agent, and the resulting pair of diastereomers is separated on an achiral stationary phase, in most of the cases on a reversed-phase type (Fig. 7-2). 

Let us assume that a given compound has a purity of 98 % ee, and that this compound is reacted with a derivatizing agent which has also a purity of 98 % ee. The two major compounds plus the minor impurities in the compound to be analyzed and the derivatizing agent will create a set of four diastereomers. Two pairs of diastereomers (-i-)-A(-i-)B and (-)-A(-)-B as well as (- )-A(-i-)-B and (-i-)-A(-)-B are enantiomeric pairs, and thus elute together on an achiral column. Therefore, a peak area of 98.011 % will be detected for (-i-)-A(-i-)-B, which leads to a purity of 96.03 % ee for (-i-)-A. This is a quite significant deviation from the true value for (-i-)-A. 

Most of the reactions applied to amines can also be transferred to alcohols (Eig. 7-5). One large group of chiral alcohols are the (i-adrenoreceptor blockers, for which a variety of derivatization agents was developed. One highly versatile reagent for the separation of (i-blockers is A-[(2-isothiocyanato)cyclohexyl]3,5-dinitrobenzoyl-amide (DDITC) [11]. Alternatively, unichiral drugs such as (3-blockers or (S)-naproxen [12] may be used in a reciprocal approach to derivatize racemic amine compounds. 

It is important not only that a multiplicity of compounds in the sample mixture may be selectively derivatized - as was shown for Type III reactions - but also that one racemate may be derivatized with a multiplicity of derivatizing agents (Fig. 7-17). Although this approach can be used to optimize the analogues of a compound [28, 29], it is of special interest when a compound is required to be separated on a preparative scale. 

Pierce Handbook and General Catalog Derivatizing Agents for GC/MS. Pierce, P.O. Box 117, Rockford, IL 61105. 

At first glance, the HRC scheme appears simple the polymer is activated, dissolved, and then submitted to derivatization. hi a few cases, polymer activation and dissolution is achieved in a single step. This simplicity, however, is deceptive as can be deduced from the following experimental observations In many cases, provided that the ratio of derivatizing agent/AGU employed is stoichiometric, the targeted DS is not achieved the reaction conditions required (especially reaction temperature and time) depend on the structural characteristics of cellulose, especially its DP, purity (in terms of a-cellulose content), and Ic. Therefore, it is relevant to discuss the above-mentioned steps separately in order to understand their relative importance to ester formation, as well as the reasons for dependence of reaction conditions on cellulose structural features. 

Fig. 9 Scheme for explaining the relationship between chain-length of the derivatizing agent and DS obtained, from [180]... 

Fluorescence analysis has been extended to many nonfluorescent species by the development of a wide range of derivatizing agents that form a fluorescent product. This approach has been especially useful with biochemical molecules, many of which are not natural fluorophores. 

Carlo Erba, Company literature Derivatizing Agents, p. 79. 

At this point, the anaiyte may not be amenabie to UV, FL, or EC detection. In this case, the best course of action may be to choose LC/MS (see Section 4.2). However, one other option is to use a pre- " or post-coiumn derivatization step to increase the detectabiiity of the anaiyte with respect to FL or UV. Fluorescent or UV labels are available for carboxylic acids," amines, phenols, and thiols. The decision to use pre- or post-column derivatization is predicated upon the functionality of the analyte available for derivatization and the rate and extent of the reaction between each derivatizing agent and the analyte. 

Pyridine and BF3 in methanol are hazardous and must be used only in a well-ventilated hood. A solvent partition after acylation helps remove residual pyridine from the sample. Material Safety Data Sheets for the derivatizing agents should be reviewed and kept readily available. 

---