Fig. 1.

Analytic results of liquid chromatography (left) and mass spectrometry (right). Genuine raw material used to manufacture indigo carmine (top) shows a single peak at 1.24 minutes in liquid chromatography and this peak shows three mass peaks representing mass fragment of indigo carmine in mass spectrometry. The raw material for the indigo carmine that caused the hypotensive episodes (bottom) shows bimodal curve on liquid chromatography. The peak at 1.24 minutes in liquid chromatography shows the same three mass peaks as genuine raw material (not shown). A second liquid chromatography peak, at 1.33 minutes, shows abnormal relative abundance value, m/z = 340, by mass spectrometry. This peak is likely due to a chain of SO₃Na that came off one side of the indigo carmine structure.