Abstract
The sources of iron blanks in liquid chromatography and interactions of these blanks with injected samples were investigated. The main sources of the blanks are the chemicals used and the chromatographic equipment. Even so-called “metal-free” systems contain iron blanks in the low-ng range, which can be a source or error in speciation analysis of iron. The effects induced by iron blanks include the formation of additional peaks (positive and negative) and changes in the recovery of injected species. Especially free ligands, which are present in the sample, interact strongly with blanks. The mechanism of interaction of blanks with injected species was investigated in some detail using organic acids as complexing agents for Fe(II), Fe(III) or both. The experimental results were compared with computer-simulated chromatograms. It is shown that the observed effects can be explained by using a model based on chemical equilibria in the stationary and mobile phases.
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