Internal standardization could not correct for non-spectral interferences in external calibration.

Both internal and external calibration plots approached 45 degrees.

Internal and external calibration curves fitted well.

First, methodological developments were implemented including external calibration, and corrections of phased-array coil sensitivity and cerebrospinal fluid volume contribution.

The levels of sinigrin and gluconasturtiin in the vegetables and Chinese herbs were determined by using an external calibration method.

Comparison of solvent and matrix-matched calibration curves demonstrated the absence of significant matrix effects and the feasibility of using external calibration.

The emphasis is given on the elemental composition determination of individual metabolites based on accurate masses typically better than 5ppm even with the external calibration.