Abstract
The zinc sulfate turbidity test (ZTT) is a convenient assay procedure to follow qualitative and quantitative changes in serum proteins, and it has been used clinically as an important di-agnostic test. The standard procedure of ZTT uses a Kunkel reagent which is a solution of zinc sulfate in 2.6mM barbiturate buffer. However, it is difficult for this buffer to maintain its pH in solution which is important for the test. The pH in the solution decreases due to absorption of carbon dioxide from the air when the vial is opened and due to instability of barbiturate even when the vial is capped. As a result, the sensitivity increases with use leading to variation between assays and between laboratories. For these reasons, we developed a new Kunkel reagent using a Bis-Tris buffer which has a low dissociation constant and is chemically stable. The results using the new Kunkel reagent correlated with those using the standard Kunkel reagent, and the former showed good stability even when the vial was opened to the air. This new reagent may contribute to renewed interest in the clinical significance of ZTT.
