1/6/2024 0 Comments Timeworks fingerprint![]() When the working solution absorbs too much moisture (for example from the paper that is dipped in it), part of the solvents separate. Due to the presence of (toxic) methanol in the working solution, working in the fume hood is necessary anyway. That is why working with the DFO solutions should be done a fume hood (no open fire in the vicinity). The lower the temperature, the less the amount of a compound can stay dissolved in a solvent.Īll solutions of the DFO-set are flammable and the vapors when mixed with air can be explosive. Because the solubility of DFO is marginal, the working solution should not be stored in the refrigerator. The mixed working solution has a shelf life of at least several weeks. We advise to first add the solvent mixture to the petroleum ether/MTBE mixture and then add the DFO concentrated solution. Additionally, a 1 liter aluminium bottle with 830 ml of a petroleum ether 40-60°/ tert-butylmethylether (MTBE) mixture as the bulk solvent is included in the set. This solvent mixture contains xylene, acetone, and isopropanol. To keep the DFO (60 ml solution in methanol/acetic acid (B-79800) soluble in the working solution, a solvent mixture is needed (110 ml, in a 150 ml amber glass bottle). Spraying of the solution has been found to be a useful method (in a fume hood). The ink running is slightly stronger than with the frigen formulation. The solution is however less sensitive to moisture and therefore easier to use. ![]() ![]() The petroleum ether based formulation that we supply nowadays has a lower concentration of DFO than the one based on frigen (0.3 gram versus 0.5 gram per liter). Due to the ban on the use of frigen, this formulation can no longer be used. The formulation prescribed dissolving 0.5 gram DFO in 40 ml methanol and 20 ml acetic acid, to be diluted with frigen to 1 liter of working solution. The formulation used and published by Pounds was based on frigen (1,1,2-trichlorotrifluoroethane). Such spectacular results were never mentioned by later researchers so probably this number was not reproducable. When DFO was introduced it was reported by the Home Office that according to their research up to 2.5 times the amounts of identifiable prints were developed with DFO, compared to ninhydrin. A prerequisite for the advantageous use of DFO however, is the availability of a (preferably strong) light source that can deliver light in the blue-green region (for example a Polilight). However, when the fluorescence of the DFO treated prints is viewed, DFO develops fingerprints better. The consensus in the forensic community is that where DFO was used, 1,2-IND is the better alternative.įingerprints, developed with DFO are less visible (light red/purple) than if they would have been treated with ninhydrin. ![]() The introduction of the reagent was announced at the IAI conference in Pensacola (USA, July 1989 ) by C.A. Pounds of the Central Research and Support Establishment of the Home Office Forensic Service in Aldermanston. It is assumed that it reacts with the same components in the fingerprint as ninhydrin does.
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