evaluating its performance in sequence with DFO and ninhydrin (227).About the physical developer, quality control procedures were proposed(228, 229), an extended shelf-life has been measured for the newformulation of physical developer (230), and its robustness has beentested (231). The interest of introducing physical developer in a sequenceafter amino acid reagents has also been confirmed (232). Finally,TECTOPO has been applied on paper (233) and Nile red proposed as anew lipid stain (234).Used acronyms: DFO (1,8-diaza-9-fluorenone), EDTA (ethylenediamine-tetraacetic acid), IND (1,2-indanedione), NIN (ninhydrin), ORO (oil red O),PD (physical developer), R6G (rhodamine 6G).Oil Red O - An alternative to the original formulation of ORO (see: (226)) isproposed, in which the methanol-based solution is replaced by propylene-glycol(224). This new formulation was proved to be as efficient as the original one, but issafer, quicker, and requires fewer reagents. It however suffers from the samelimitations as the original formulation, especially on some kinds of substrates and onaged fingermarks. A sequence of treatment for porous substrates is further proposed:"IND (/HFE-7100) – ORO (/propylene-glycol) – PD" (225). The authors recommendedreducing the immersion time in the IND solution to less than 5 seconds, to avoid adetrimental effect on the lipid fraction of the secretion (which could impact thesubsequent ORO treatment). Another research aimed at studying the sensitivity ofDFO, NIN, and ORO over time, as well as the contrast of the resulting marks, fordifferent kinds of porous substrates (227). It has been shown that ORO could beapplied subsequently to the "DFO (/HFE-7100) – NIN (/HFE-7100)" sequence, whichcould result in an enhancement of the already-detected marks and detection oflatent-remaining ones (especially on kraft paper, cardboard and thermal paper). Onwhite and recycled papers, no additional marks were detected by ORO when appliedafter DFO and NIN. Finally, a luminescent alternative to the original ORO formulationhas been proposed, which could be used on wetted and dark porous substrates(226). Substrates of interest are first processed with the original ORO, andimmediately followed by the spraying of a R6G staining solution. The marks obtainedusing this procedure appear as dark ridges on a luminescent background.Physical developer - In order to test the reliability of a prepared PD workingsolution, two procedures were proposed: (a) printed standardized test strips using amodified inkjet printer (228), and (b) EDTA spot tests on Whatman #2 filter paper(229). The pattern developed by Kupferschmid et al. contains geometric shapesmade of ascorbic acid and oleic acid aqueous solutions (used as inks by the printer).The correlation between the number of detected shapes on the test strip and thequality of fingermark development was shown to be high. The EDTA spot testprocedure represents an inexpensive, reliable, stable, and rapid alternative to aprinted pattern as well as to gold chloride spot tests on filter paper. The shelf-life ofthe last PD formulation (in which Synperonic N has been replaced by Tween 20) hasbeen thoroughly studied (230). As a result, it has been shown that the shelf-life of thePD working solution was of 10-15 days for the Synperonic N formulation, but rises upto 2 1/2 months when using Tween 20. The robustness of the PD formulation wastested by comparing the efficiency of different working solutions, among whichvoluntary alterations and modifications were introduced (231). It has been shown that