Abstract: A method for detecting the presence of antibiotics in milk which comprises the steps of: (a) contacting a solid matrix having attached thereto a purified immobilized antibody with a volume of milk and an enzyme-labeled antibiotic, said antibody being specific to said antibiotic; (b) separating the matrix from the milk and rinsing the matrix with water to remove excess milk and enzyme-labeled antibiotic; (c) contacting the rinsed matrix with a substrate, said substrate in the presence of said enzyme-labeled antibiotic exhibiting a color change the amount of which is quantitatively related to the amount of enzyme-labeled antibiotic; and (d) measuring the amount of antibiotic present in said milk by comparing the color change in said substrate with a standard.

Abstract: A method for the reversible immobilization of proteins through covalent attachment to inorganic oxide surfaces, such as glass or silica, via thioester containing coupling chains. Resulting succinamidopropyl-surfaces are converted into the acyl derivative using anhydrous thionyl chloride, and then treated with either 3-mercaptopropionic acid or mercaptoacetic acid. Thus derivatized, the material is dried, and can be stored for extended periods of time without detectable loss of reactivity with proteins. Immobilization of proteins can be readily achieved simply by suspending the derivatized material in buffer (pH=5 to 8) and recycling the protein solution through the material. Following immobilization, protein molecules can be released from the surface by cleavage of the coupling chains at the thioester linkage through treatment with hydroxylamine.