The absolute amount of LysoGb1 in the vial was determined using quantitative NMR to have the stated value on the vial. The vial may have additional components, but none are isobaric with LysoGb1, d7-LysoGb1, Psychosine, or d5-Psychosine, and these additional components have no effect on the ability to quantify the LysoGb1 or Psychosine.