A. Sternesjo et al., DETERMINATION OF SULFAMETHAZINE RESIDUES IN MILK BY A SURFACE-PLASMONRESONANCE-BASED BIOSENSOR ASSAY, Analytical biochemistry, 226(1), 1995, pp. 175-181
The use of antibiotics and chemotherapeutics in animal husbandry has l
ed to the occurrence of veterinary drug residues in all types of food
of animal origin. Due to the specification of toxicologically based ma
ximum residue levels for a large number of substances, existing contro
l strategies need even faster acid more sensitive methods to meet new
and more rigorous regulations. The applicability of an immunosensor de
vice for biospecific interaction analysis was investigated and the dev
elopment of an assay for analysis of sulfamethazine (SMZ) in milk is d
escribed. SMZ was covalently immobilized to a carboxymethyldextran-mod
ified gold film. Spiked samples with known concentrations of SMZ were
prepared in HBS buffer and skim and raw milk for construction of stand
ard curves. Polyclonal antibodies against SMZ were added to the sample
and the immobilized surface was used to determine the amount of free
antibodies by surface plasmon resonance detection. After each measurem
ent the surface was regenerated by NaOH and HCl. In milk, the mean rel
ative standard deviation of the assay was approximately 2% and the lim
it of detection less than 1 ppb. By introduction of a secondary sheep
anti-rabbit antibody, the use of specific antibody could be reduced. M
ilk samples from the individual cow, herd, and tanker levels were anal
yzed and the relative standard deviations within each sample category
were 4.4, 2.4, and 2.2%, respectively. The effect of some potential in
terferences, e.g., high somatic cells, bacterial contamination, and pr
eservatives, was investigated. The results were not influenced in such
a way that the risk for so-called false-positive findings was obvious
. (C) 1995 Academic Press, Inc.