[Latent fingerprint detection on porous surfaces by DFO--a practice-orientated approach]

The sensitivity of DFO (1,8-diazafluoren-9-one), a substance known since 1989, is clearly superior to that of ninhydrin for the visualization of latent fingerprints. Nevertheless DFO has not replaced ninhydrin in Germany up to now. One reason is its unreliability. The DFO working solutions commonly used in Germany tend to become cloudy very fast during application or to form second phases. According to some reports, these DFO solutions often produce unsatisfactory results in the detection of latent fingerprints, and additional prints may become visible after an extra treatment with ninhydrin. This means that these DFO applications are susceptible to failure and do not possess enough robustness. Now a new, more robust application of DFO is presented, which is also better adapted to the requirements of industrial safety. Moreover, the working solution is prepared from a stock solution that has a stability of more than six months, so that the required quantity is always available.