Correct selection of raw materials is crucial in controlling possible alterations in the final extender. The different raw materials should present a high degree of water solubility, a specific density, a pH that meets the spermatic conservation ranges of the extender, high purity, and a specific rotation.
Raw materials that meet the technical specifications should be tested, especially about the levels of heavy metals. Excess of some of them could change the biological and physicochemical qualities of the extender or even be harmful to spermatozoa.
For example, an excess of calcium may lead to an increase in this molecule in the final product and could produce premature sperm capacitation, just the opposite effect we intend to achieve with the conservation of spermatozoa in the extenders. An excess of iron can also alter the extender’s physicochemical properties, reducing the useful life of the product.
*Raquel Ausejo, Noelia Mendoza and Joaquín Miguel