Abstract:
A method for rapid analysis of stamp seals using hydrogen flame desorption ionization mass spectrometry (HFDI-MS) was developed. HFDI-MS combined with multivariate statistical analysis provides an analysis strategy for the identification and traceability of stamp seals. First, HFDI-MS was used to quickly analyze different types of stamp ink (mud) samples, and it was found that the captured mass spectra were significantly different. The characteristic ion signals on the mass spectra of different types of stamp inks were different, indicating that HFDI-MS has the potential of analyzing stamp seals. It was also found that the reproducibility of HFDI-MS was good. Subsequently, the mass spectra of two different types of probes (smooth surface probe and sand surface probe) for HFDI-MS analysis were compared after sampling. The experimental results showed that more abundant mass spectrometry information could be captured with the combination of sand probe sampling and HFDI-MS analysis. Therefore, the sand surface probe was used for sampling in HFDI-MS analysis of the stamp seals. At last, the feasibility of HFDI-MS to directly analyze the stamp seals was examined. Photosensitive ink, atomic ink and ink pad (for engraving seal) were used to make stamp seals. The seal stamp was placed in the air for 4 h before being analyzed by HFDI-MS. A sand surface probe was used to collect samples of the simulated stamp seal. Then, HFDI-MS was used to quickly analyze the stamp seals. The mass spectra captured by HFDI-MS were significantly different in the number and intensity of ion signals. So cluster analysis was used to identify stamp seals. The results showed that the three types of stamp seals from different sources were clearly distinguished. Finally, the signals of 26 characteristic ions of the three types of stamp seals were screened out by combining the mass spectra. According to the reference, the characteristic ion signals of pigment 21 and polyacrylic alcohol compounds have been found. HFDI-MS has the advantages of no voltage, easy operation, and the method is rapid and direct. The combustion product of hydrogen will not introduce impurity interference and cause pollution to the mass spectrometer. In addition, there is no memory effect for HFDI-MS. HFDI-MS can provide a new analysis strategy for the rapid identification and traceability of stamp seals in forensic science, cultural relic identification or other fields. It was worth noting that HFDI-MS cannot be considered as an absolute non-destructive analysis, and it was not suitable for scenarios that require non-destructive analysis of materials. However, it could be considered as minimally invasive sampling to ensure that the original file was not damaged.