A method for enrichment of nucleic acids, comprising: (a) loading into a fluidic device (i) a sample comprising nucleic acids, (ii) a trailing electrolyte buffer, said trailing electrolyte buffer comprising trailing electrolyte ions with a first effective mobility, wherein said first effective mobility has a magnitude lower than a magnitude of an effective mobility of said nucleic acids, (iii) a first leading electrolyte buffer in a first leading electrolyte reservoir, said first leading electrolyte buffer comprising first leading electrolyte ions with a second effective mobility, wherein said second effective mobility has a magnitude greater than said magnitude of said effective mobility of said nucleic acids, and (iv) a second leading electrolyte buffer in a second leading electrolyte reservoir, said second leading electrolyte buffer comprising second leading electrolyte ions with a third effective mobility, wherein said third effective mobility has a magnitude greater than said magnitude of said effective mobility of said nucleic acids, wherein said first leading electrolyte buffer is different from said second leading electrolyte buffer, and said first leading electrolyte buffer has a higher ionic strength than an ionic strength of said second leading electrolyte buffer; (b) first conducting isotachophoresis with said trailing electrolyte ions, said nucleic acids, and said first leading electrolyte ions by applying a first electric field within said fluidic device with a first electric circuit, thereby enriching said nucleic acids from contaminants in said sample; and (c) second conducting isotachophoresis with said trailing electrolyte ions, said nucleic acids, and said second leading electrolyte ions, by applying a second electric field within said fluidic device with a second electric circuit, wherein said first electric circuit is different from said second electric circuit. (a) loading into a fluidic device (i) a sample comprising nucleic acids, (ii) a trailing electrolyte buffer, said trailing electrolyte buffer comprising trailing electrolyte ions with a first effective mobility, wherein said first effective mobility has a magnitude lower than a magnitude of an effective mobility of said nucleic acids, (iii) a first leading electrolyte buffer in a first leading electrolyte reservoir, said first leading electrolyte buffer comprising first leading electrolyte ions with a second effective mobility, wherein said second effective mobility has a magnitude greater than said magnitude of said effective mobility of said nucleic acids, and (iv) a second leading electrolyte buffer in a second leading electrolyte reservoir, said second leading electrolyte buffer comprising second leading electrolyte ions with a third effective mobility, wherein said third effective mobility has a magnitude greater than said magnitude of said effective mobility of said nucleic acids, wherein said first leading electrolyte buffer is different from said second leading electrolyte buffer, and said first leading electrolyte buffer has a higher ionic strength than an ionic strength of said second leading electrolyte buffer; (i) a sample comprising nucleic acids, (ii) a trailing electrolyte buffer, said trailing electrolyte buffer comprising trailing electrolyte ions with a first effective mobility, wherein said first effective mobility has a magnitude lower than a magnitude of an effective mobility of said nucleic acids, (iii) a first leading electrolyte buffer in a first leading electrolyte reservoir, said first leading electrolyte buffer comprising first leading electrolyte ions with a second effective mobility, wherein said second effective mobility has a magnitude greater than said magnitude of said effective mobility of said nucleic acids, and (iv) a second leading electrolyte buffer in a second leading electrolyte reservoir, said second leading electrolyte buffer comprising second leading electrolyte ions with a third effective mobility, wherein said third effective mobility has a magnitude greater than said magnitude of said effective mobility of said nucleic acids, (b) first conducting isotachophoresis with said trailing electrolyte ions, said nucleic acids, and said first leading electrolyte ions by applying a first electric field within said fluidic device with a first electric circuit, thereby enriching said nucleic acids from contaminants in said sample; and (c) second conducting isotachophoresis with said trailing electrolyte ions, said nucleic acids, and said second leading electrolyte ions, by applying a second electric field within said fluidic device with a second electric circuit,