The precision of the sorbent weight distribution and of the plasma sample profile were assessed (Experimental S4). For sorbent weight precision, the suspension was dispensed into three 96-well PCR tube racks. Each tube was weighed before and after the addition of the suspension, the difference calculated, and the %RSD reported. The precision of the LMWM profile of 288 replicates of the EDTA pooled plasma sample prepared using the optimized dSPE protocol and analyzed by C18 RPC+/-was assessed using principal component analysis (PCA) and %RSD calculated for the measured signal intensities of individual molecular species.