Provided is a meandering correction apparatus for an electrode assembly. The pivot mechanism includes a lower ring mounted on a pressure plate, an upper ring mounted on a housing upper plate and ball transfer units disposed on the lower ring. The inner cannula is driven by both a rotary motor and a reciprocating motor. A method for characterizing crude oil fractions includes providing a maltene sample, eluting saturates, aromatics, and resins of the maltene sample, determining an optical density of each, and determining a concentration of each of the saturates, aromatics, and resins based upon optical densities over time for each. The safety cover has a plurality of through-holes for as removal.