Optimal hapten design criteria are based on various factors such as the location of the conjugation, length of handles, composition, type of spacer arm and the size of haptens. These offer a variety of modifications and largely influence design systems of haptens in order to generate the compound- or class-specific antibodies. Therefore, the hapten design, hapten modification and the synthesis of hapten selection of carrier and coupling of hapten to a carrier and artificial antigen preparation purification and identification are essential processes for the development of the small molecular compounds.