Mass spectrometry imaging of latent fingerprints using titanium oxide development powder as an existing matrix.

Recent research has focused on increasing the evidentiary value of latent fingerprints through chemical analysis. Although researchers have optimized the use of organic and metal matrices for matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) of latent fingerprints, the use of development powders as matrices has not been fully investigated. Carbon forensic powder (CFP), a common nonporous development technique, was shown to be an efficient one-step matrix; however, a high-resolution mass spectrometer was required in the low mass range due to carbon clusters. Titanium oxide (TiO2 ) is another commonly used development powder, especially for dark nonporous surfaces. Here, forensic TiO2 powder is utilized as a single-step development and matrix technique for chemical imaging of latent fingerprints without the requirement of a high-resolution mass spectrometer. All studied compounds were successfully detected when TiO2 was used as the matrix in positive mode, although, generally, the overall ion signals were lower than the previously studied CFP. TiO2 provided quality mass spectrometry (MS) images of endogenous and exogenous latent fingerprint compounds. The subsequent addition of traditional matrices on top of the TiO2 powder was ineffective for universal detection of latent fingerprint compounds. Forensic TiO2 development powder works as an efficient single-step development and matrix technique for MALDI-MSI analysis of latent fingerprints in positive mode and does not require a high-resolution mass spectrometer for analysis.