The main limitation associated
with ordinary stationary phase SPE columns is low selectivity.
Therefore, the selective SPE methods such as molecular imprinted
polymers (MIPs) and immunoaffinity have been developed [1].
Immunoaffinity is a powerful technique based on high affinity
between antigen–antibody interactions. The use of antibodies in
the analysis is associated with specificity, however there are some
limitations mainly attributed to the nature of these protein receptors.
Recently, antibodies are replaced by aptamers on solid support
with more advantages