Bio-rad Laboratories, Inc.

Edward T Liang

Michael I Watkins

Clifford R Bartlett

Mark A Staples

John M Pocekay

Denaturing agents used to pretreat test samples for immunoassays are neutralized and deactivated by the addition of a treatment agent which is a combination of a buffering agent in acid form and an agent for converting the sulfhydryl groups of the denaturing agents to a non-active form such as disulfides or alkylthio groups. The treatment agent serves this function without having sufficient denaturing activity by itself to interfere with subsequent steps of the assay procedure. Also disclosed is a protocol for a vitamin B.sub.12 assay which involves a sequential rather than competitive binding of the B.sub.12 with excess intrinsic factor followed by the binding of excess enzyme-labeled B.sub.12 to any remaining intrinsic and immobilizing such intrinsic factor on a solid phase. Various problems associated with B.sub.12 assays are avoided by this technique.

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Hercules, CA, United States of America

Edward T Liang