We have now demonstrated a dielectrophoretic (DEP) based approach that allows a full range of cfc-DNA biomarkers from chronic lymphocytic leukemia (CLL) patients to be isolated directly from a small volume of unprocessed whole blood. Using a DEP microarray device, cfc-DNA from 50 uls of patient blood is separated and concentrated into DEP high-field regions in about 10-15 minutes. Blood cells, serum proteins and low molecular biomolecules are quickly removed by a fluidic wash. The cfc-DNA concentrated on the DEP microelectrodes is first analyzed by fluorescence, and then eluted with a fluidic wash for subsequent PCR and sequencing analysis. In a majority of CLL samples, fluorescent stained cfc-DNA was clearly observed on the DEP microelectrodes, while little or no fluorescence was observed for the normal blood control samples. Eluted cfc-DNA (equivalent to 2ul-5ul of original blood sample) was then PCR amplified using VHL specific primers, which verified the CLL patient type for 29 of 35 CLL samples. The CLL patients amplified DNA was then sequenced and correlated with previous patient specific sequencing results from DNA originally isolated from white blood cells.