Figure 5From: Polar non-hydrocarbon contaminants in reservoir core extractsMass spectra of (a) C27-cholesterol (labelled peak 1 in Fig. [4]), (b) C28-sterol (labelled peak 2 in Fig. [4]) and (c) C29-sterol (labelled peak 3 in Fig. [4]) isolated during C18 NEC SPE of core extract petroleum.Back to article page