A colorimetric immunoassay based on an enzyme inhibitor method.

A competitive binding immunoassay was developed using an enzyme inhibitor for labeling the analyte. Thyroxine was labeled by covalent coupling of the alpha-amino group to the gamma-carboxyl of the glutamyl residue of methotrexate. This thyroxine-methotrexate conjugate was a potent inhibitor of dihydrofolate reductase.

Dialkylnitrosamines in elastomers.

Accelerators and stabilizers used in natural rubber and many types of synthetic rubber are often derived from dialkylamines. It has been found that raw polymers, compounded uncured elastomers, and cured rubber parts containing these dialkylamino compounds emit low concentrations of the corresponding dialkylnitrosamine (R2N-N = O) when they are heated. Exposure of operators working with these materials can be reduced below a level of 50 parts per trillion by volume in air by use of ventilation velocities of about 50 ft/min.

Immunoassay for serum thyroxine monitored by chemiluminescence.

An immunoassay for thyroxine (T4) monitored by chemiluminescence was evaluated with clinical serums. A thyroxine-label conjugate (T4-L) and serum samples were applied sequentially to alkaline Sephadex G-25 columns which adsorbed the thyroxine species. Other serum components and potential interferents were washed from the column with barbital buffer.