More highlights from the JCA Special Issue CCC2008. When describing countercurrent chromatography to non-chemists we often describe the 2-phase solvent system as “oil and water.” This article – “Counter-current chromatography for oil analysis,” takes that analogy literally.  This paper shows off three unusual and useful characteristics of the countercurrent technique. First, consider the mobile phase. Can you image running straight crude oil through a chromatography column? Yes, its true, crude oil is the mobile phase of a CCC separation! Okay, there were some issues with viscosity: an increase in the difference between the viscosities of the mobile and stationary phases is proportional to a decrease in the stationary phase volume retention ratio. On the other hand, an increase in the density difference between the mobile and stationary phases is proportional to an increase in the stationary phase volume retention ratio. Second, let’s look at the stationary phase. Its nitric acid folks! To my knowledge, not too many chromatographic processes can be done with nitric acid as one of the phases. Of course, metal ions love nitric acid, which leads to my third point. Countercurrent chromatography can be practiced as an extractive process. In this case, metal ions are sucked out of an inhospitable oily environment into a cozy acidic aqueous broth. According to this article, it’s a highly efficient extractive process that can easily be seen by comparing CCC extraction to standard “static” extraction methods. Oh, and another thing: be sure to wash out the column with acetone, toluene, and iso-octane after each run. JCA Special Issue 1216 (2009) 4243-4236