Phenylalanine, tryptophan, a dipeptide (Phe-Trp) and pentapeptide
(Leu-Trp-Met-Arg-Phe) were dissolved in deionised water at a
concentration of 0.2 g/L. Blank microbeads (0.2 g) were placed in
solutions of each of the amino acids and peptides for 24 h under
magnetic stirring. The volume of amino acid or peptide solution
was varied (1–15 ml) to alter the volume ratio. The volume ratio
is the volume of microbeads ðVbeadÞ divided by the volume of solution
ðVaqÞ. Samples (100 ll) of each of the solutions were analysed
by HPLC as per Section 2.8 before and 24 h after microbead addition.
The E (%) of each of the compounds in the microbeads was calculated
using Eq. (1).