Citrate buffer is used in Heat Induced Epitope Retrieval (HIER) methods. HIER is used to reverse the loss of antigenicity that occurs with some epitopes in formalin-fixed paraffin embedded tissues. During epitope retrieval, tissue slides are immersed in a solution and heated (>95° C) by hot plate or other appropriate heat source such as a pressure cooker or steamer. Citrate buffer is the preferred solution for most antibodies.