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Biospecific methods of analysis for selected vitamins of the B group can be broadly classified as immunoassays and protein-binding assays [1]. Immunoassays are based on the specific interaction of an antibody with its antigen, and are represented by the radioimmunoassay (RIA) and the enzyme-linked immunosorbent assay (ELISA). Protein-binding assays utilize naturally occurring vitamin-binding proteins with either radiolabels (as in the radiolabeled protein-binding assay, RPBA) or enzyme labels (as in the enzyme-labeled protein-binding assay, EPBA). A more recent innovation is the optical biosensor-based immunoassay/ protein-binding assay. Biospecific assays can be performed on complex biological matrices, so they require minimal sample cleanup. The analytical stages can be automated using equipment that is commercially available, but the methods can only be described as semiautomated, as it is necessary to liberate the vitamins from their bound forms using manual extraction procedures.