Fuel Oil Degradation/Retention Time Mix C17-C20 4 Analytes, each 2,0mg/mL in CS2:CH2Cl2 (1:1); unit: 1x4.5mL in Certan® Use this standard for the quantification of C17/Pristane and C18/Phytane ratios. Heptadecane C17 Octadecane C18 Pristane (2,6,10,