A composition, method and device for the preparation of biological samples for subsequent LC-MS analysis using a combined and concurrent protein precipitation and solid phase extraction (SPE) process is described. Through an integrated combination of protein precipitation, filtration, and SPE using a novel zirconia-coated chromatographic media, interfering compounds, such as proteins and phosphate-containing compounds, are eliminated from the biological samples, affording a higher degree of analyte response during LC-MS analysis.