Sodium citrate buffer pH 7.0 is an aqueous solution consisting mainly of di-sodium hydrogen phosphate (Na2HPO4) and a small amount of citric acid. The chemical reaction between these two substances leads to the formation of a buffer system that is able to keep the pH of the solution stable. This is particularly important in medical diagnostics and scientific laboratories, where pH-stable environments are often critical to the success of experiments and analyses.

In histology, sodium citrate buffer is commonly used for antigen unmasking in immunohistochemistry. Heating tissue sections in this buffer modifies the protein structure, allowing better binding of antibodies to their target antigens. This improves the quality of the staining and increases the sensitivity of the method.

Based on the given components, the molarity is 1.0 M for di-sodium hydrogen phosphate and 0.02 M for citric acid. The osmolarity is about 2.02 Osm/L and the buffer capacity is in the range of 0.02 M.