Phenolic compounds alternative separation techniques

Another major problem in this work concerned the gas chromatographic overlap of several compounds. The use of alternate columns was insufficient for complete resolution of all the phenols. An alumina column cleanup and separation technique was devised which overcame most of the problem. 

GC separation of the isolated phenolic compounds occurs prior to identification and quantification using ECD- and MS-coupled detectors (Sect. 4.3). However, phenolic compounds are polar, and derivatization gives better GC peak shapes in the most commonly used types of GC columns. Hitherto the standard method of derivatization of OH-PCBs retained in blood has been methylation by diazomethane to form the corresponding methoxy-PCB (MeO-PCB) [39,43, 135]. OH-PCB methylation by ion-pair alkylation with methyl iodide is an alternative to the diazomethane technique [43,140]. Acetylation has been shown to give comparable recoveries of OH-PCB derivatization as the methyl iodide and diazomethane approaches to OH-PCB methylation [139]. Silylation reactions have also been applied for the derivatization of various OH-PCBs [137]. 

Capillary electrophoresis (CE) is a good alternative to GC and LC techniques for profile determination of OL derivatives. CE requires minimal sample preparatiOTi and represents a good compromise between analysis time and satisfactory characterization. The most efficient operative mode to separate phenolic compounds is the borate-based CE, which makes use of a borate run buffer at alkaline pH [52], To date, the most widely used detector in CE is based on UV absorption [53, 54], although the coupling to MS analyzers such as QqQ, IT, TOF has revalorized the potential of this technique [55]. 

---