Attempts were made to select an internal standard that could be
taken through the entire analytical process but none was identified
that fulfilled the necessary criteria of (i) absence inmilk powders and
infant formulae, (ii) stability to acid and high temperatures, (iii)
elution near inositol and (iv) commercially available and economic.
Fig. 2 indicates the chromatographic positions of scyllo-inositol, Lchiro-
inositol and allo-inositol that are naturally-occurring isomers of
myo-inositol. Scyllo-inositol (scyllitol), found in various plant species,
fulfilled the requirements of an internal standard but its high cost
excluded it fromeveryday use, although de Koning (1994) and March
et al. (1996) have reported its use in fish products and urine respectively.
The other isomers of myo-inositol (allo-, epi-, muco-, D-chiro-,
neo- and cis-inositol) were not available in this study. Fig. 2 also illustrates
the positions of a few selected polyhydric alcohols. Unfortunately,
the open-chain sugar alcohols, D-sorbitol and D-mannitol did
not survive the digestion intact so made poor surrogates to act as
internal standards for inositol throughout the entire procedure