Comparing betaine aldehyde derivaWzaWon and the NEDC matrix, we claim that the NEDC matrix has several drawbacks. It has to be used in the negaWve ionizaWon mode -usually posiWve ionizaWon mode is more "user friendly". There is a problem with calibraWon -mass spectra are usually recalibrated internally using a list of theoreWcal masses of detected metabolites . It seems that to preform proper analysis -internal standard calibraWon has to be done. This is not obvious -it was proposed only in work of Zahraei et al. awer careful study. It means that, without proper awareness of the issue, glucose analysis with NEDC matrix may lead to false posiWve results. The matrix generates some addiWonal peaks around chlorinated glucose ion, which means that obtaining the right separaWon window for MS/MS experiments is difficult. Moreover, slightly different methods of normalizaWon give completely different images.