The performance of an extractant is determined by its structure; to function effectively, an organic extractant must meet two criteria:

The extractant molecule must contain at least one functional group capable of binding with metal ions to form an extraction complex. Common functional groups involve atoms such as O, N, P, and S. These atoms possess lone pair electrons and act as electron donors-referred to as coordinating atoms. Oxygen atoms are the most frequently encountered functional groups in extractants;

The extractant molecule must contain a sufficiently long carbon chain or a benzene ring. These structural features ensure that both the extractant and the resulting extraction complex are readily soluble in the organic phase while remaining sparingly soluble in the aqueous phase. However, excessively long carbon chains can increase the extractant's viscosity or cause it to solidify, rendering it unsuitable for use. Typically, the relative molecular mass of an extractant falls within the range of 350 to 500.