FAQ

NMR: Nuclear magnetic resonance has the advantage of detecting non-damaged samples without complicated sample pre-processing, and thus, the sample is as close to their physiological condition as possible. However, it suffers from lower sensitivity, especially a low abundance of metabolites.

LC-MS: The combined technology of liquid chromatography and mass spectrometry has a relatively high resolution, and high sensitivity, and allows the detection of a wide range of metabolites. This is typically used to detect non-volatile polar compounds that are less than 1000 Da.

GC-MS: Gas chromatography and mass spectrometry are mainly used for identifying volatile substances or metabolites with low polarity. Typically detects molecules with lower molecular weight (< 300Da). 

Mass specs need regular maintenance and calibration, thus quantifications from Widely-Targeted Metabolomics between different batches typically cannot be compared directly. In the mass spec, the degree of ionization of compounds is different and thus you cannot compare different compounds from the same samples.

Screening criteria for differential metabolites: select metabolites with fold change ≥ 2 and fold change ≤ 0.5. If the difference in metabolites between the control group and the experimental group is more than 2 times or less than 0.5, the difference is considered significant. If there is biological duplication in the sample grouping, on the basis of the above, select the metabolites with VIP≥1. The VIP value represents the influence of the difference between the corresponding metabolites in the classification and discrimination of the samples in each group in the model. It is generally considered that the metabolites with VIP≥1 are significantly different.

Mass specs need regular maintenance and calibration, thus quantifications from Widely-Targeted Metabolomics between different batches typically cannot be compared directly.

In the mass spec, the degree of ionization of compounds is different and thus you cannot compare different compounds from the same samples.

The detection range of liquid-phase mass spectrometry should be less than 1000Da,  and the molecular weight of frequently encountered macromolecular substances such as glycans, peptides, starch, pectin, and lignin are not within the detection range.