A method for impregnating nylon transfer membranes with leucocrystal violet for enhancing and lifting bloody impressions.

The objective of this research project was to demonstrate a quick and easy method for impregnating nylon transfer membranes with leucocrystal violet (LCV) for the purpose of lifting and enhancing impressions made in blood. A stamp that would simulate fine detail found in fingerprints or footwear was used to create impressions on a variety of substrates. Four different LCV formulations were tested to determine the effectiveness of the prepared membranes in lifting and enhancing the impressions. Further investigation involved the feasibility of using the LCV membranes in the field by studying the shelf life and storage of the impregnated membranes and the longevity of the lifted impressions. One of the formations studied demonstrated superior lifting and enhancing capabilities, as well as a prolonged shelf life and a resilience of the lifted impressions, thus proving LCV to be an extremely valuable technique.

Spectral enhancement of leucocrystal violet treated footwear impression evidence in blood.

The results presented demonstrate the capacity for spectral enhancement to substantially improve the forensic examination of footwear impressions in blood treated with leucocrystal violet (LCV). The UV-Vis absorption spectra were generated of (i) an aqueous solution of leucocrystal violet, (ii) leucocrystal violet in 3% H(2)O(2), (iii) LCV working solution and (iv) whole blood added to LCV working solution. The resultant fluorescence emission spectra were subsequently generated (lambda(ex)=630nm, lambda(em)=661-900nm). The results indicate that the UV-Vis absorption spectra of an unbuffered solution of whole blood with LCV working solution produces a strong absorbance curve with a maxima at 630nm. Subsequent excitation at this wavelength and generation of the emission spectrum in the fluorescence mode indicates that a solution of whole blood added to LCV working solution is an extremely weak fluorophore. Therefore, to enable an adequate and timely enhancement of blood impression evidence treated with LCV utilising either visible fluorescence or infrared luminescence requires (i) selection of the most appropriate excitation wavelength (lambda(ex)) and emission wavelength (lambda(em)) with extremely narrow band pass filters, which in the absence of substrate matrix interference is excitation at 630nm producing the emission maxima at 665nm and (ii) a visual enhancement system such as a CCD colour IR video camera with image integration.

Determination of leucogentian violet in chicken fat by liquid chromatography with electrochemical and ultraviolet detection: interlaboratory study.

A laboratory trial was completed for a liquid chromatographic method that can quantitate leucogentian violet (LGV) in chicken fat at 10 ppb. With this method, LGV is isolated from the fat matrix by a series of liquid-liquid extractions. This trial evaluated 2 detection systems: electrochemical (EC) and ultraviolet (UV). The participating laboratories determined incurred residues at 2 levels as well as fat samples fortified at 5, 10, and 20 ppb. Using UV detection, the 3 laboratories reported the following range of recoveries: 71.0-89.6% at 5 ppb, 74.7-83.9% at 10 ppb, and 77.2-79.0% at 20 ppb. When these same samples were chromatographed with EC detection, the 2 reporting laboratories obtained the following average recoveries: 79.0 and 92.5% at 5 ppb, 75.9 and 85.4% at 10 ppb, and 77.3 and 79.8% at 20 ppb. The average concentrations found for the first level of incurred sample were 6.3, 6.3, and 5.4 ppb with coefficients of variation (CVs) of 2.4, 7.6, and 33.7%, respectively, when UV detection was used. Samples chromatographed with EC detection averaged 6.3 and 6.4 ppb with CVs of 4.0 and 8.2%, respectively. The second level of incurred sample gave average concentrations of 27.6, 29.0, and 10.9 ppb with CVs of 11.0, 5.0, and 42.8%, respectively, when the UV detection system was used. With the EC detector, the concentrations averaged 27.2 and 30.7 ppb with CVs of 15.7 and 3.5%, respectively.

Confirmation of leucogentian violet in chicken fat by gas chromatography/mass spectrometry.

A gas chromatographic/mass spectrometric (GC/MS) procedure for confirming the identity of leucogentian violet (LGV) in chicken fat was developed for regulatory application. The unused portion of the extract remaining from a determinative procedure was back-extracted into an organic phase, concentrated, and analyzed by GC/MS. Confirmation of the identity of LGV was based on matching the retention times and relative abundances of 6 ions in the extract to corresponding values obtained for the LGV standard. The procedure was validated by replicate analyses of negative control, fortified control, and residue-incurred chicken fat. The presence of LGV was confirmed by the GC/MS procedure in all samples found to contain LGV by prior liquid chromatographic analyses. There were no interferences in the control samples.

High-performance liquid chromatography of gentian violet, its demethylated metabolites, leucogentian violet and methylene blue with electrochemical detection.

High-performance liquid chromatographic conditions are reported for the electrochemical detection (ED) of Gentian Violet, its demethylated metabolites, Leucogentian Violet and Methylene Blue. Gentian Violet, its demethylated metabolites and Leucogentian Violet were separated within 14 min on a cyano column eluted isocratically with methanol-buffer (60:40) as the mobile phase. ED responses for Gentian Violet, Leucogentian Violet and Methylene Blue were linear over the ranges 0.54-6.75, 0.50-25.2, and 5.7-285 ng, respectively. Under these conditions, the compounds were eluted in the following order: Leucogentian Violet, N"-2-tetra-methylparaosaniline chloride, N'-1-tetramethylpararosaniline chloride, pentamethylpararosaniline chloride and Gentian Violet. Methylene Blue and Gentian Violet had essentially the same retention time under these parameters. The detection limit for Gentian Violet, its demethylated metabolites and Leucogentian Violet was determined to be 0.1 pmol. A detection limit of 3 pmol was established for Methylene Blue. Detector response, elution, separation, linearity and sensitivity of detection are discussed.

Biotransformation of gentian violet to leucogentian violet by human, rat, and chicken intestinal microflora.

Cellular suspensions of microflora isolated from human feces and from intestinal contents of rat and chicken transformed the triphenylmethane dye gentian violet under anaerobic conditions. Pure cultures of nine genera of strict and facultative anaerobes were also active. All pure cultures and mixed intestinal microflora were found to convert the dye to leucogentian violet. Leucogentian violet was identified by HPLC retention time in a reverse phase system, and by mass spectral comparison with authentic compound. Leucogentian violet was extracted from the supernatants of the microfloral cultures, but the major portion of the metabolite was often bound to the cells (up to 87% of the metabolite produced by human microflora). Metabolites were quantitatively extracted from cell-free supernatants with 1-butanol/hexane, and from cellular pellets with trichloracetic acid. Leucogentian violet, amounting to 11% of the total radioactivity, was also detected by HPLC in ether extracts of feces collected from a female Fischer 344 rat dosed orally for 4 days with 14C-labeled gentian violet.