Derivatization with benzoyl chloride

Powdered samples of Radix astragali were extracted and analyzed for astragalo-side IV concentration [398]. The analyte was derivatized with benzoyl chloride and quantitated on a Cig (A = 230 nm) column using a 90/4/6/0.2 methanol/THF/ water/triethylamine mobile phase. Elution occurred at 25 min and a linear range of 4-80 pg/mL was reported along with a detection limit of 2 pg/mL. 

Gao, S. Wilson, D.M. Edinboro, L.E. McGuire, G.M. Williams, S.G.P. Karnes, H.T. Improvement of sensitivity for the determination of propylene glycol in rat plasma and limg tissue using HPLC/tandem MS and derivatization with benzoyl chloride, J.Liq.Chromatogr.Rel.Technol., 2003,26, 3413 3431. 

In analytical LC there are two primary reasons why chemical derivatization of the sample constituents would be necessary, and they are 1) to enhance the separation and 2) to increase the sensitivity of detection. Under certain circumstances, derivatization can also be used to reduce peak asymmetry, i.e. to reduce tailing, or to improve the stability of labile components so that they do not re-arrange or decompose during the chromatographic process. However, sensitivity enhancement is the most common goal of derivatization. For example, aliphatic alcohols that contain no UV chromaphore can be reacted with benzoyl chloride to form a benzoic ester. 

Hwang et al. developed a rapid and sensitive HPLC-UV method for the analysis of nine derivatized BAs, with benzoyl chloride as the derivatization agent. The reaction is faster than with tosyl chloride and leads to stable products with shorter elution times than do dansyl derivatives. The amines were previously extracted after acidification with TCA. The method was applied to detect BAs in fried marlin fillet, implicated in a food poisoning incident (in Taipei City in 1996) and indicated that a high level of His (84.1 mg/100 g) was present in the sample (80). 

A quantitative HPLC method for the analysis of sphingolipids as their perbenzoyl derivatives was first developed for ceramides (5). Ceramides can be conveniently derivatized with benzoic anhydride in pyridine (3 hrs at 110°C) and the products formed have been utilized for the quantitative analysis of NFA and HFA ceramides in normal and Farber s disease tissue. Iwamori and Moser also utilized this procedure for the analysis of ceramides in Farber s disease urine (6). More recently Iwamori and Moser (7) established that the ceramide derivatives formed by reaction with benzoyl chloride or benzoic anhydride are analogous to those formed with cerebrosides. They also characterized the behavior... 

Creasy (68) investigated postcolumn derivatization of A-ethyldiethanolamine and triethanolamine with benzoyl chloride in combination with APCI. Derivatization of one hydroxyl group occurred after mixing the reagent with LC eluent, and sensitivity was not affected by derivatization. A possible advantage of this method is to increase the molecular mass to remove the analyte from interferences. 

Recently Street et al. acylated diatomaceous earth with benzoyl chloride in pyridine as a pretreatment for coating. They reported that a marked reduction in adsorption could be obtained, enabling polar compounds, such as morphine, to be gas chromatographed in nanogram amounts without derivatization. A 1000-fold improvement in chromatographic capability could be obtained, compared to the best conventional conmercial packing. 

A number of various derivatization reactions have been used, as shown in Table 14.25. The derivatization has been carried out as off-column or on-column derivatization, mostly in order to give morphine and related alkaloids with phenolic or alcoholic hydroxyl groups better gas chromatographic properties. Especially for quantitative determination of morphine in opium or biological material such derivatization was necessary. Street et al. found, however, that the problem of adsorption of a phenolic alkaloid, such as morphine, because of "active sites" on the solid support could be solved by deactivation of the solid support by treatment of it (diatomaceous earth) with benzoyl chloride in pyridine before coating it with the stationary phase. 

Parameters such as solvent, basic medium and reaction time, affecting the derivatization of alcohols and phenols with benzoyl chloride, were investigated. End analysis was by GC with UVD . a sensitive method proposed for trace determination of phenols in water consists of preconcentration by SPE with a commercial styrene-divinylbenzene copolymer, acylation with pentafluorobenzoyl chloride in the presence of tetrabutylammonium bromide and end analysis by GC with either ECD or ITD-MS. LOD was 3 to 20 ngL for ECD and 10 to 60 ngL for ITD-MS, with 500 mL samples . Acylation with the fluorinated glutaric acid derivative 43 was proposed for determination of urinary phenols, as indicative of exposure to benzene and other aromatic hydrocarbons. End analysis by GC-MS shows strong molecular ions of the derivatives by electron ionization. The proto-nated ions are the base peaks obtained by chemical ionization. LOD was 0.5 mgL and the linearity range 0-100 mg L for phenol . 

A simultaneous way of determining ammonia including aliphatic amines, aromatic amines, and phenols in environmental samples by GC-MS method using a single derivatization reagent has been reported recently by Mishra et al. The method consisted in precolumn formation of benzoate esters and benzamides under the conditions of the Schotten-Baumann procedure with benzoyl chloride and SPE of the derivatives. The limit of detection of ammonia was 20 /rg/l when 80 ml of sample was preconcentrated, after derivatization, on a styrene divinyl benzene copolymer sorbent. 

Among the derivatization methods for hydroxyl groups, esterification with benzoyl chloride and its analogues... 

Chemical derivatization has become a very popular technique for increasing the sensitivity of a specific type of detector to compounds for which it normally exhibits little or no response. An examples of this procedure would be the reaction of an aliphatic alcohol, which contains no UV chromophore, with benzoyl chloride to form the benzyl ester which could then be detected by the UV detector. Derivatization can also be used to permit the use of an alternative type of detector to increase sensitivity. For example an amino acid may exhibit only weak absorption in the UV, but when reacted with a suitable fluorescing reagent, could be detected by means of the fluorescence detector at concentration levels one or two orders of magnitude lower than with the UV detector. It is clear that derivatization procedures can increase significantly the versatility of many detectors. 

Recently, Song et al. utilized a derivatization strategy to measure the broadest range of small molecule neurotransmitters reported to date, which included several amino acids, four monoamines, ACh, adenosine, and their major metabolites [54]. Due to the inherent chemical diversity and polar nature of these compounds, all the analytes, with the exception of ACh, were derivatized with benzyl chloride to achieve efficient separation in 8-minute run times by RPLC. Derivatization also improved the sensitivity of ESI—MS/MS analysis and provided a convenient way to generate isotope-labeled internal standards for quantification with commercially available C benzoyl chloride. The LC—MS method described in this study was suitable for the simultaneous detection of all analytes of interest in low-volume dialysis samples with sufficient sensitivity and high-throughput capability to permit fast sampling rates. 

M. Zheng, C. Fu and H. Xu, High-performance liquid chromatographic detection of trace N-nitrosoamines by precolumn derivatization with 4-(2-phthalimidyl)benzoyl chloride. Analyst, 1993,118(3), 269-271. 

We initially demonstrated that brain cerebrosides, galactosyl-ceramides containing hydroxy fatty acids (HFA) and nonhydroxy fatty acids (NFA), could be completely derivatized by reaction with 10% benzoyl chloride at 60°C for 1 hour (2). After removal of excess reagents by partition between hexane and alkaline aqueous methanol, the perbenzoyl derivatives were seen to separate into two completely resolved components (HFA and NFA... 

Polysaccharide-based CSPs also exhibit a chiral recognition for alcohols and a large number of resolutions have been reported. Chiral alcohols can usually be directly resolved with hexane containing a small amount of an alcohol as the eluent. For aliphatic alcohols, which cannot be directly resolved, their resolution is often efficiently attained as phenylcarbamate or benzoate derivatives on OD (Figure 17).85 For example, 2-butanol and 2-pentanol are completely resolved with a very high selectivity on OD as their phenylcarbamates. The derivatization of alcohols to phenylcarbamates and benzoates can be easily achieved by the reaction with phenyl isocyanates and benzoyl chlorides, respectively. In most cases, the phenylcarbamates are better resolved than the benzoates. For chiral compounds bearing phenolic hydroxy groups, the addition of a small amount of an acid to an eluent is recommended to depress its dissociation. 

Direct tri-0-alkylation of calix[4]arenes has been reported to lead to the syn/syn isomer using bases such as BaO, BaO/Ba(OH)2 or CaH2 in DMF " . The tribenzoate of the p-unsubstituted calix[4]arene, one of the first examples of selectively derivatized calix[4]arenes, was obtained as the anti-syn isomer (benzoyl chloride/pyridine) , while the tribenzoate of 2a obtained in toluene with iV-methylimidazole as base (70% yield) was described as the syn-syn isomer, assuming a partial cone conformation with an inverted phenol ring . Both tris(3,5-dinitrobenzoates) of 2a were obtained by acylation with 3,5-dinitrobenzoyl chloride/l-methylimidazole. While 95% of the syn-syn isomer was formed in acetonitrile, 70% of the anti-syn isomer was obtained in chloroform . 

Pyridine has also been used as the basic catalyst and chloride acceptor for benzoylation reactions. In one procedure, amines, volatile alcohols or thiols isolated by benzene extraction, are benzoylated with pyridine (1 ml) and benzoyl chloride (0.5 ml) by shaking intermittently at room temperature for several hours. The pyridine phase is extracted with 2 M HCl and the excess benzoyl chloride is hydrolysed with water for 12 hours. After shaking with 2 M sodium carbonate to remove benzoic acid, the benzene solution is dried and concentrated for analysis [144]. Aminoglycoside antibiotics are derivatized to the benzoyl derivatives in a similar reaction using 90 fi of pyridine and 10 /il of benzoyl chloride at 80 °C for 30 minutes. The pyridine is evaporated in a stream of nitrogen and excess benzoyl chloride is converted to methyl benzoate with methanol, again at 80°C, for 10 minutes. The product is cleaned up for analysis by a rather involved solvent extraction procedure [145]. 

Benzoyl chloride is the preferred derivatizing agent for polyamines, as it reacts with most of the naturally occurring diamines and polyamines. Redmond and Tseng [13] described a procedure involving the addition of benzoyl chloride to the sample suspended in an alkaline solvent. Fumiss et at. [14] recommended that following the reaction the mixture should be washed with alcohol to remove excess benzoyl chloride. Benzoylated poly-... 

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