Differential pulse stripping voltammetry preceded by a
non-faradaic preconcentration step is a very powerful technique
for the direct determination of metal complexes, drug compounds
and proteins. Small molecules like the amino acids can play a very
important role in the biochemistry of living organisms. Despite
their importance, these substances (except for cystine and
cysteine) are generally not strongly adsorbed on mercury and /or
do not possess any electroactive group in their molecular structure making
their determination by direct electroanalytical techniques
difficult or even impossible. These difficulties can be overcome
by reacting these compounds with derivatising reagents [1).
Initially here, derivatisation techniques for the
determination of amino acids were studied. Methods are presented
for the determination of tyrosine and histidine after coupling
with diazotised sulphanilic acid (chapter 3) and for amino acids
in general, and glycine in particular, as methyl or
phenylthiohydantoin derivatives (chapter 5). Nanomolar levels of
histidine were determined by accumulating the amino acid in the
presence of an excess of copper(II) using the reduction peak of its
copper(II) complex (chapter 4) for detection.
The uses of polyamino acids as electrode modifiers were
also studied and a method for the determination of copper(II) based on its accumulation at a hanging mercury electrode
modified by adsorption of a polyhistidine film (chapter 6) and of
hexacyanoferrate(III) after preconcentration on a copper modified
polylysine film electrode (chapter 7) are proposed.
As an offshoot of the diazo coupling derivatization of
tyrosine and histidine, a method for the determination of
copper(ll) by reaction with diazo-1 H-tetrazole (DHT) and
accumulation of its complex on the HMDE (chapter 8) is presented.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.