On the use of 3-methyl-2-benzothiazolinone hydrazone to determine cell surface sialic acid: A simplified procedure and a caution

Membrane-bound sialic acid may be quantitated by colorimetric determination of formaldehyde released upon mild periodate oxidation. In the presence of washed erythrocyte membranes at 20% suspension the colorimetry based on 3-methyl-2-benzothiazolinone hydrazone has an extinction coefficient of 68.5 mM^?1 cm^?1. With intact erythrocytes large losses in color yield are experienced with suspensions in excess of 2% (2 × 10⁸ cells/ ml).