Apparatus for the analysis and/or isolation and/or enrichment of target structures in a fluid sample, the apparatus comprising a lateral arrangement of a plurality of magnetic elements (11a, 11b), wherein the plurality of magnetic elements (11a, 11b) comprises at least four magnetic elements (11a, 11b), and wherein the magnetic elements (11a, 11b) are arranged adjacent to each other in an array of magnetic elements (11a, 11b) with lines and columns, a flow-through tube, wherein the magnetic axes of the magnetic elements (11a, 11b) in the array of the arrangement are almost or fully parallel to each other and the magnetic axes of the magnetic elements (11a, 11b) in the array of the arrangement are almost or fully perpendicular to the plane of the arrangement spanned by the direction of the lines and the columns, and a driving means to move the flow-through tube or the arrangement of magnetic elements or the flow-through tube and the arrangement of the magnetic elements, wherein neighbouring magnetic elements (11a, 11b) of each line adjoin each other with magnetic poles of different polarities, and wherein the arrangement and the flow-through tube are movable relative to each other such, that the arrangement on the one hand and the flow-through tube on the other hand can be approached to each other and/or detached from each other, wherein, when the flow-through tube is in a position, where it is approached to the arrangement, the flow-through tube is arranged i) in parallel to columns of said magnetic elements (11a, 11b) and along the area where neighbouring columns of magnetic elements face each other, with turning points at or between the ends of neighbouring columns of magnetic elements (11a, 11b), or ii) in parallel to lines of said magnetic elements (11a, 11b) and along the area where neighbouring lines of magnetic elements face each other, with turning points at or between the ends of neighbouring lines of magnetic elements (11a, 11b), wherein neighbouring magnetic elements (11a, 11b) of each column adjoin each other with magnetic poles of different polarities, and wherein neighbouring magnetic elements (11a, 11b) of each column and/or each line adjoin each other with a maximum gap between the neighbouring magnetic elements (11a, 11b) of ≤ 1 mm, wherein the magnetic elements (11a, 11b) are arranged in a rectangular, chessboard-like arrangement, wherein the edges of individual magnetic elements (11a, 11b) define bordering lines between different lines and columns of magnetic elements (11a, 11b). a lateral arrangement of a plurality of magnetic elements (11a, 11b), wherein the plurality of magnetic elements (11a, 11b) comprises at least four magnetic elements (11a, 11b), and wherein the magnetic elements (11a, 11b) are arranged adjacent to each other in an array of magnetic elements (11a, 11b) with lines and columns, a flow-through tube, wherein the magnetic axes of the magnetic elements (11a, 11b) in the array of the arrangement are almost or fully parallel to each other and the magnetic axes of the magnetic elements (11a, 11b) in the array of the arrangement are almost or fully perpendicular to the plane of the arrangement spanned by the direction of the lines and the columns, and a driving means to move the flow-through tube or the arrangement of magnetic elements or the flow-through tube and the arrangement of the magnetic elements, wherein neighbouring magnetic elements (11a, 11b) of each line adjoin each other with magnetic poles of different polarities, and wherein the arrangement and the flow-through tube are movable relative to each other such, that the arrangement on the one hand and the flow-through tube on the other hand can be approached to each other and/or detached from each other, wherein, when the flow-through tube is in a position, where it is approached to the arrangement, the flow-through tube is arranged i) in parallel to columns of said magnetic elements (11a, 11b) and along the area where neighbouring columns of magnetic elements face each other, with turning points at or between the ends of neighbouring columns of magnetic elements (11a, 11b), or ii) in parallel to lines of said magnetic elements (11a, 11b) and along the area where neighbouring lines of magnetic elements face each other, with turning points at or between the ends of neighbouring lines of magnetic elements (11a, 11b), i) in parallel to columns of said magnetic elements (11a, 11b) and along the area where neighbouring columns of magnetic elements face each other, with turning points at or between the ends of neighbouring columns of magnetic elements (11a, 11b), or ii) in parallel to lines of said magnetic elements (11a, 11b) and along the area where neighbouring lines of magnetic elements face each other, with turning points at or between the ends of neighbouring lines of magnetic elements (11a, 11b), wherein neighbouring magnetic elements (11a, 11b) of each column adjoin each other with magnetic poles of different polarities, and wherein neighbouring magnetic elements (11a, 11b) of each column and/or each line adjoin each other with a maximum gap between the neighbouring magnetic elements (11a, 11b) of ≤ 1 mm, wherein the magnetic elements (11a, 11b) are arranged in a rectangular, chessboard-like arrangement, wherein the edges of individual magnetic elements (11a, 11b) define bordering lines between different lines and columns of magnetic elements (11a, 11b).