QC samples help ensure the reliability and reproducibility of your results by

In general, quality control is essential for producing reliable metabolic data, facilitating better scientific conclusions and applications in fields such as medicine, environmental science, and nutrition. On the other hand, quality control helps confirm that the metabolic changes observed are of biological significance and not merely a product of the experimental process, which enhances the credibility of the results.

Briefly, QC work-up is mainly for showing the robustness, i.e. stability and repeatability, of your LC-MS system.

This usually be reflected in two results: 1) the good overlap of total ion curves, especially on the tail. 2) the good overlap of QC samples' points on the PCA plot.