Quantitative metabolomics is a crucial ingredient for systems biology of microorganism.

Measurement protocols for intracellular metabolite quantification are highly complex and error-prone.

Thorough analyses of systematic and random errors are essential to increase both, accuracy and precision, of in vivo measurement data.

At current state of the art many sources of systematic errors are known and can be corrected.

However, establishing a gold standard fails due to fundamental limitations.