Biotin is an essential micronutrient for all livingmammals becauseof its role as a cofactor of
carboxylation and decarboxylation enzymes. Human cells have four biotin-dependent
carboxylases that catalyse key reactions ingluconeogenesis, amino acid catabolism and
fatty acid synthesis (2).
The first biotin tests for foods relied on microbiological principles. Microbiological
determination of biotin is based on the principle that growth of specific microorganisms is
dependent on the presence of limiting amounts of biotin in the culture media (3). This
method is cost effective but is sensitive tomany factors that can compromise the results and
is highlymanipulative and time-consuming (2).
In physiochemical analysis, toobtain suitable sensitivity and selectivity, biotinmust first be
derivatized. In purematerials, biotin can bedetermined using alkaline titration but in complex
matrices, biotin is best chromatographically separated fromother compounds toallow
practical determination (3). Highperformance liquid chromatography uses derivatization of
biotin to a suitable fluorophore for quantification. Post-column derivatization of biotinwith
avidin labelled fluorescein isothiocyanate has become the simplest HPLCmethod for biotin
(4, 5). An interesting feature of the reaction is itsnon-linearitywhich can confuse analysts,
but aquadratic fit usingmultiple calibration points can beused; thismethod becomes a
EuropeanNorm (6). Streptavidin-FTIC can replace avidin-FTICand exhibits enhanced
reagent stability and better linearity although at greater cost. HPLC coupledwithmass
spectrometers arenowbeing deployed for water-soluble vitamin determinations in dietary
supplementswith electrospray ionization interface (7).
Many biospecific ligand-binding assay variants have been applied to thedetermination of
biotin in biological matrices, including foods (8). Suchmethods include protein-binding
assays and immunoassayswhere protein-binding assay uses biotin specific protein and
immunoassay uses antibody.
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