Fig. 3

Pairwise overlap coverage of plasma vs. serum according to different extraction methods. Samples are analyzed using (i) + ESI HILIC, (ii) − ESI HILIC, (iii) + ESI RP C18 and, (iv) − ESI RP C18. The boxes with dark color and bolded numbers along the diagonal indicate the total count of potential metabolites detected using that extraction method on either plasma or serum. The gradient colors indicate high (99.9–80%), medium (79.9–50.0%), or low (50.0–0%) similarity of the potential metabolite populations seen by the two extraction methods specified. Thus, the methods indicated by the light-colored boxes are the extraction methods with the greatest overlap among all five extraction methods evaluated. (According to [6]). Each panel represents the results from a particular LC technology combined to a particular electrospray polarity setting: A: HILIC Column with ESI+, B: HILIC Column with ESI-, C: C18 column with ESI+, D: C18 column with ESI-. MeOH methanol, MeOH:ACN methanol combined with acetonitrile, ACN acetonitrile, SPE solid preparation extraction