A biosensor based on surface plasmon resonance (SPR) measurement was develo
ped for use in an immunoassay for detection of sulfamethazine (SMZ) in milk
, The biospecific surface was a carboxymethyl dextran-modified gold-surface
sensor chip to which SMZ was covalently bound. The assay was based on inhi
bition of the binding of polyclonal antibodies to immobilized SMZ by SMZ in
the sample. The SPR response changed inversely in relation to the antibiot
ic concentration in the sample. Calibration curves were constructed for SMZ
in buffer and in milk at a concentration which included the maximum residu
e limit (0 to 200 mu g/kg). The analysis time per sample varied from 8 to 3
0 min. Different flow rates and antibodies were modified alternatively duri
ng the study to assess their influence on the performance of the assay. The
active antibody concentration was calculated at approximately 1880 and 180
nM for the antibody anti-SMZ 1 and the antibody anti-SMZ 2, respectively.
No cross-reactivity of antibodies with other antibiotics was found. Under o
ptimal conditions, the detection limits in milk for SMZ were 8 and 1.7 mu g
/kg, respectively, for antibody 1 and antibody 2, at a flow rate of 20 mu L
/min.