. . . "For example, the loading wells 20 in FIG. 10 are arranged in a two-tier arrangement, thus providing an effective pitch of 1.125 mm. [0061] The loading bar should be made from a material that allows fabrication of the loading wells 20 and fluid passages 165, is chemically compatible with the samples and other materials to which the loading bar will be exposed, e.g., D.I. water, aqueous polymer solu" .