This invention provides methods and devices for spatially separating at least first and second components in a sample which in one exemplary embodiment comprises introducing the first and second components into a first microfluidic channel of a microfluidic device in a carrier fluid comprising a spacer electrolyte solution and stacking the first and second components by isotachophoresis between a leading electrolyte solution and a trailing electrolyte solution, wherein the spacer electrolyte solution comprises ions which have an intermediate mobility in an electric field between the mobility of the ions present in the leading and trailing electrolyte solutions and wherein the spacer electrolyte solution comprises at least one of the following spacer ions MOPS, MES, Nonanoic acid, D-Glucuronic acid, Acetylsalicyclic acid, 4-Ethoxybenzoic acid, Glutaric acid, 3-Phenylpropionic acid, Phenoxyacetic acid, Cysteine, hippuric acid, p-hydroxyphenylacetic acid, isopropylmalonic acid, itaconic acid, citraconic acid, 3,5-dimethylbenzoic acid, 2,3-dimethylbenzoic acid, p-hydroxycinnamic acid, and 5-br-2,4-dihydroxybenzoic acid, and wherein the first component comprises a DNA-antibody conjugate and the second component comprises a complex of the DNA-antibody conjugate and an analyte.