HPLC and HPLC/MS analysis of red ink on counterfeit 100-yuan notes

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). We used this approach to analyze the chemical structures of the adulterated colorants from 46 counterfeit 100-yuan notes seized from different locations. The results showed that a variety of inks were found among the seized counterfeit notes from different sources. The chromatographic data signature could be used to clearly discriminate authentic from counterfeit notes, but could also potentially be used to trace the notes to the counterfeiter. To the best of our knowledge, this is the first report to use HPLC/MS to profile red dyes in Chinese currency with important implications for the forensics and law enforcement communities.