Phenols extractive pentafluorobenzylation

In the last few years a number of reports have appeared on an extractive pentafluorobenzylation procedure for phenols and carboxylic acids to enhance their electron-capturing properties. 

Fogelgvist, E., Josefsson, B., and Roos, C., Determination of carboxylic acids and phenols in water by extractive alkylation using pentafluorobenzylation, glass capillary g.c. and electron capture detection, HRC CC, J. High Resolut. Chromatogr. Chromatogr. Commun., 3, 568, 1980. 

Another method is extraction with methylene chloride followed by derivatization with pentafluorobenzyl bromide or diazomethane and snbseqnent GC/ECD or GC/FID analysis . The extraction solvent has to be changed before analysis. More than 50 substituted phenols have been derivatized successfully with Af-(f-butyldimethylsilyl)-Af-methyltrifluoroacetamide by forming the corresponding f-bntyldimethylsilyl derivatives. This study includes 21 chlorinated phenols, 13 nitrophenols, 3 aminophenols, 4 alkylphenols, o-phenylphenol, some other substitnted phenols inclnding 6 phenolic pesticides and the nonsnbstitnted phenol. Using SPE with polymeric adsorbents and GC/MS, phenols with very different substituents can be detected in environmental samples with high matrix content at the ppt level . 

Rractically the same list of phenols can be determined by analysis of municipal and industrial wastewater detailed in ERA Method 604 (GC/FID or GC/ECD) and 625 (GC/MS) . Method 8041 for determination of phenols in wastewater, presented by the ERA Office of Waste Water, describes the determination of ca 40 phenols specifying extraction and cleanup conditions, derivatization with diazomethane or pentafluorobenzyl bromide and analytical determination by GC/FID, GC/ECD or GC/MS . ... 

Individual phenols may be analyzed by GC, GC/MS, and HPLC techniques. GC analyses require the use of FID or BCD. If BCD is used, phenols should be converted to their haloderivatives. Although GC-BCD analysis is more cumbersome, the deriva-tizations of phenols eliminate interference effects. Phenols in wastewaters may be analyzed by BPA Method 604 based on GC-FID (or GC-BCD) techniques (U.S. BPA 1984). Pentafluorobenzyl bromide is used for derivatization of phenols in the extracts. The chromatographic columns suitable for the purpose are 1% SP-1240 DA on Supelco-port (GC-FID) or 5% OV-17 on Chromosorb W-AW (GC-BCD). 

In a series of papers, Lee and coworkers described the use of pentafluorobenzyl bromide as derivatization agent for the determination of 22 phenols in water samples [83,84]. Before derivatization, the phenols were extracted from the water sample into dichloromethane. In the first paper, six different columns were tested, and the OV-101 fused silica capillary column with Carbowax-deactivated surface was found to give the most efficient separation [83]. Detection was carried out using both the BCD and MS. A similar approach, using derivatization with pentafluorobenzyl chloride and BCD, was described for the analysis of monochlorinated and brominated phenols in aqueous samples [85]. 

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