Chemical species which lack a convenient chromophore such as an aromatic group for spectrophotometric detection can be challenging to detect selectively, particularly in a complex sample matrix.  Recently, in our research group, such carboxylate, phosphate, and sulfhydryl compounds have been detected using flow injection by measuring the loss of absorbance of the Fe(III)-salicylate complex due to preferential ligand interaction with ferric ion.  Targeted compounds included polycarboxylates such as citrate, oxalate, and ethylenediaminetetracetic acid (EDTA), phosphate compounds such as monofluorophosphate, trimetaphosphate, and hexametaphosphate, and the sulfhydryl compound cysteine.  However, incorporation of this quite selective detection approach with a separation method has not been done. Capillary electrophoresis (CE) offers a high separation capability for charged compounds.  We are studying in particular the  interaction of ferric ion as well as Fe(III)-salicylate with phosphate and polyphosphates in order to permit detection of this class of UV transparent compounds. Addition of  Fe(III)-salicylate in the CE run buffer has permitted the detection of an injected phosphate sample. In addition, it has been reported that the detection of the important anticoagulant pharmaceutical heparin has been accentuated by the use of Cu(II) in the run buffer. However, CE resolution of various glycoaminoglycans (GAGs) such as dermatan sulfate from heparin when complexed with Cu(II) has been modest. We are comparing the use of Fe(III) and Cu(II) as GAG detection reagents with a high ionic strength run buffer which will promote sample injection stacking and maintain peak resolution. Spectrophotometric results definitely show an enhanced absorbance for such heparin-metal complexes. Other transition metals such as Fe(II) and Ni(II) may also be considered as detection candidates.

Transition metals as detection reagents for capillary electrophoresis

246th National Meeting (2013)

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