The present invention relates to an apparatus comprising a substrate having at least one assay station. The at least one assay station has at least a first assay station channel and at least a second assay station channel and the first and second assay station channels each separately being in communication with the at least one assay station. The apparatus has an arrangement of at least first and second multipurpose channels in communication with the first and second assay station channels, respectively. The first multipurpose channel and first assay station channel have internal surface characteristics conducive to conduction of a sample solution therethrough. There is at least one sample fluid inlet in communication with the at least first multipurpose channel, and at least one isolation-medium inlet in communication with the at least first and second multipurpose channels. The at least one second multipurpose channel has an internal surface portion non-conducive to conduction of said sample solution.