Flow injection determination of sialic acid based on amperometric detection

In the present paper, we continue to utilize the sequential action of sialic acid aldolase and pyruvate oxidase to construct improved sialic acid (SA) amperometric biosensors and immobilized enzyme reactors (IERs). The enzymes were co-immobilized using glutaraldehyde crosslinking at the surface of a platinum disc electrode and by covalent attachment to the modified controlled pore glass beads packed in stainless steel columns to prepare the SA biosensors and IERs, respectively. Two different configurations were adapted in the present work to produce the first report on flow-injection amperometric determination of SA. In the first configuration, the SA biosensor was used as a detector in a flow injection setup. In the second configuration, an IER was used in conjunction with a flow-through amperometric cell equipped with a Pt disc electrode polarized at 0.7 V vs Ag/AgCl for the anodic detection of the produced hydrogen peroxide. We also report a simple way to control the temperature in the flow injection setups. The FI determination of SA based on IER was found to be more superior and showed linear dependence of the FI peak heights on SA concentration in the range of 0.002-5.0 mM (r² = 0.9997), RSD of 1.1% at 250 μM SA and a sample throughput of 35 sample h^-1.