Cyclic Voltammetry (CV) baseline

Running cyclic voltammetry with a glassy carbon working electrode, Pt counter electrode, and an Ag/Ag+ reference electrode. Purge with Argon bubbling for 15 min. The solvent and electrolyte are MeCN (anhydrous sigma) and 0.1 M NBu4PF6. Running a scan starting at 0V to +2.5 to -2.5V at 250mV/s, observing high (ie. -20 uA) negative current across the scan and more so on the return (ie. -40 uA). The baseline has no discernable peaks.

Is this likely due to electroactive impurities? Is it worth going for further drying of the solvent and recrystallization of the supporting electrolyte?