Counterfeiting is a significant problem for most major currencies and has high social and economic costs.
Chemical and physical identifiers that are unique to counterfeit currency are critical to forensic analysis.
The 100-yuan Chinese note is mostly red. Here, we analyzed the red ink used in 100-yuan Chinese notes
and developed a method to extract and analyze these dyes via high performance liquid chromatography
(HPLC) and HPLC/mass spectrometry (MS).