Water diffusion permeability of human erythrocytes studied by a pulsed gradient NMR technique.

Water diffusion permeability of human erythrocytes has been measured by NMR using a pulsed magnetic field gradient technique. The measurement of exchange rates was based on restricted diffusion of water molecules within red blood cells. This method avoids addition of paramagnetic ions, such as Mn2+, and is used in vivo. The mean lifetime of water insed human erythrocytes was found to be 17 ms at 24 degrees C. A sulfhydryl reagent, known to inhibit water osmotic permeability, reduced significantly water diffusion across the red cell membrane.

Identification of compounds and specific functional groups in the wavelength region 168-330 nm using gas chromatography with UV detection.

A GC-UV instrumental set up with two different GC units has been used for determination of specific functional groups and compounds in complex mixtures. Separations have been made using a micro gas chromatograph built into a gas flow cell and by means of an external capillary gas chromatograph linked to the same gas flow cell. Four various applications (cigarette smoke, petroleum, dust, flavour) have been performed in order to demonstrate the potential of the GC-UV method. Gas phase UV spectra have been recorded in the region of 168-330 nm. Based on a gas phase spectrum reference library the identification of unknowns as well as the determination of specific functional groups have been achieved. A table showing the spectral shapes and positions of the absorption bands for 50 specific functional groups is presented. The advantage of using derivative spectra in order to amplify spectral details and improve selectivity is discussed. Regarding sensitivity, it has been found that identifications can be made in the mid-pg range and limit of detection for naphthalenes are at a level of 0.5-3 pg/s.

Stable storage conditions of Immobiline chemicals for isoelectric focusing.

Most of the problems connected with the use of the Immobiline chemicals (a set of six, non-amphoteric, acrylamido buffers having pK values in the pH 3.5-9.5 interval) can be attributed to the alkaline species (with pK values 6.2, 7.0, 8.5 and 9.3). These compounds, to varying degrees are subjected to two degradation pathways: (a) hydrolysis of the amido bond, producing free acrylic acid and a diamine, the latter unable to be incorporated into the polyacrylamide matrix; (b) spontaneous auto-polymerization, producing a number of oligomers up to n-mers, able to aggregate and precipitate large proteins. Storage of their water solutions as frozen aliquots, a method widely employed, only partially alleviates the problem. Addition of trace-amounts of inhibitors, as lately adopted by the manufacturer, could only reduce the problem of auto-polymerization, but not block the hydrolysis of the amido bond. A new solution has been found, which abolishes both phenomena: storage in n-propanol. As demonstrated by gas chromatography, HPLC analyses and two-dimensional separations of complex samples, storage in organic solvent completely abolishes both hydrolysis and auto-polymerization and allows production of highly reproducible focusing patterns.

The estimation of age of bloodstains by HPLC analysis.

A new HPLC system is described for estimating the age of bloodstains deposited on clothing. In addition to the decomposition peak designated as "X" and reported earlier in the literature, several other ageing processes were studied and found suitable for estimation of age of the stains. The various processes can be used independently of each other for estimation of bloodstain age when the storing temperature is known. Moreover, the ratio between the different peaks formed by ageing is practically independent of temperature between 0 degree C and 37 degrees C.

HPLC analysis of ballpoint pen inks stored at different light conditions.

A method for comparison of ink entries on documents stored in different light conditions is presented. Various blue inks were exposed to light, both daylight and artificial light from fluorescent tubes. Inks were then extracted from the document and analyzed by HPLC (high performance liquid chromatography). Significant changes in composition were noted on exposure to light. These changes were followed by using ternary diagrams constructed for dyes generally present in blue-colored inks--Crystal Violet, Methyl Violet, and Tetramethyl Para Rosaniline. Also, the amount of the various compounds formed by decomposition of these dyes on exposure to light was measured and employed for comparison of inks. An example of the use of the proposed method in casework is given.

Time since discharge of pistols and revolvers.

The estimation of time since the latest discharge of pistols and revolvers has been achieved by the Solid Phase Microextraction (SPME) sampling technique and the GC/TEA analytical system. The TEA2 compound, which in our previous work (1) was observed in barrels of shotguns and rifles as well as inside spent cartridges, was also detected in pistols and revolvers. The amount of this compound was very low in short-barreled small arms and its escape from the barrel could generally be measured for only a few days or up to two weeks after the latest discharge. To improve the detection of TEA2 compound, the SPME sampling time was prolonged and fibers coated by Carboxen/polydimethylsiloxane were used. The decrease of the TEA2 peak with time after shooting from pistols is nonexponential but the curve-fitting procedure proposed for the estimation of time since discharge of shotguns and rifles is difficult to apply as the decay is very rapid. Therefore, the detection of TEA2 compounds in small arms should be interpreted that the firearm had been used very recently. The amount of volatile decomposition products of smokeless powder increased significantly with the length of the barrel when firearms of the same caliber, but with different barrel lengths were investigated.

Sensitive identification of hemoglobin in bloodstains from different species by high performance liquid chromatography with combined UV and fluorescence detection.

HPLC with reversed phase large pore columns (5 microns particle size, C4-phase, 300A pore size) has been used to analyze extracts from bloodstains. Bloodstains from humans as well as various animals often encountered in forensic casework have been investigated. Bloodstains from common wild animals as well as domestic animals could be distinguished by this technique with one exception--dog and wolf. The use of fluorescence detection increased the sensitivity of the method. For human bloodstains, the detection limit was about 1 to 2 nanoliter blood. The method has the advantage of simplicity, speed and sensitivity for use in forensic practice.

Shampoo residue profiles in human head hair.

Washing hair with shampoo results in an accumulation of shampoo components in the hair. Hair of individuals using different shampoos can be distinguished by analysis of shampoo residues. A method for extraction and analysis of such residues is presented. The hair is extracted using a methanol/water mixture, and the extract is analyzed by reverse-phase high-pressure liquid chromatography (HPLC). The detector system consists of two ultraviolet (UV) detectors connected in series. The method is nondestructive to hair and is sensitive enough to be applied to a single hair 5 to 10 cm in length. Residues from hair balsams are analyzed by this technique as well. The use of this method in forensic science examination of human head hair is demonstrated.

Time since discharge of rifles.

The estimation of time since the latest discharge of rifles has been achieved by the SPME sampling technique and the GC-TEA analytical system. An unidentified compound, designated as the TEA2 compound, was detected in all the rifles investigated. The same compound was observed in shotguns and spent cartridges in our previous work. This compound escapes rapidly from the inside of rifle barrels, but can still be detected there one to two months after the shooting. The decrease of the TEA2 peak with time after shooting is non-exponential, and the curve-fitting procedure proposed for the estimation of time since discharge of shotguns can be applied also for rifles.

ENFSI proficiency test program on identification of GSR by SEM/EDX.

Within the framework of the ENFSI Expert Working Group "Firearms," a proficiency test on the detection and identification of GSR by SEM/EDX was organized and performed. The test material was designed by the Bundeskriminalamt and manufactured to order by an external company for SEM accessories. The participating laboratories were requested to determine the total number of PbSbBa-containing particles on the test samples following their own laboratory specific methods of automated GSR particle search and detection by SEM/EDX. Two similar samples with synthetic GSR particles were dispatched to all participants in order to gain additional information on systematic errors within the obtained results (split-level study), whereas one sample was supplied only with PbSbBa particles, and the second one was additionally contaminated with some environmental particles. This report summarizes the results of the study as well as a statistical evaluation and comparison with previous studies.

Water in agarose gels studied by nuclear magnetic resonance relaxation in the rotating frame.

The dependence of the spin-lattice relaxation time in the rotating frame (T1rho) on radio frequency (RF) field strength and temperature has been studied for agarose gels in order to investigate molecular motion. The results indicate the presence of slow motions with a correlation time of ca. 5-10(-6) s at room temperature. This interaction is responsible for the short spin-spin relaxation times (T2) for water protons in agarose gels and is ascribed to firmly bound water. The fraction of bound water is estimated to about 0.003 for a 7.3% agarose gel. The motion of the more mobile protons in agarose-water systems can not be characterized by single correlation time. This fraction is presumably composed of water in different motional states and some of the agarose hydroxyl protons. Higher mobilities are the most common.

A simple method for collection of gunshot residues from clothing.

Simple equipment for the sampling of gunshot residue particles from clothing, inside of bags, pockets, etc, is described. Collection was achieved by vacuuming through a double filtration system constructed from a Nucleopore aerosol holder connected to an ordinary vacuum cleaner. The collected particles were examined by scanning electron microscopy. Good results were observed in functional tests of this equipment and the method has been introduced into casework in our laboratory. Various experiments on possible contamination of clothing by GSR particles were performed. The usefulness of clothing as evidence material in searching for GSR particles is discussed.

The Use of Gas-Phase UV Spectra in the 168-330-nm Wavelength Region for Analytical Purposes. 1. Qualitative Measurements.

A novel instrument, which combines gas chromatographic separation with ultraviolet detection, has been employed in the qualitative study of molecular UV absorption spectra in the gas phase. The wavelength range available with the current instrument made studies in the region of 168-330 nm possible. The absorption spectra between 168 and 330 nm for ∼1000 organic compounds and a number of inorganic gases were registered. For all the spectra recorded, 69% showed absorption maxima shorter than 190 nm, and as much as 87% shorter than 200 nm. This indicates the importance of the short UV wavelength region for analytical purposes. The results showed that each compound studied gave rise to unique absorption spectra. The influence of temperature on the shape of the spectra was studied in the range of 15-205 °C. A slight broadening effect on spectral absorption bands (0.3 nm) and the vibrational structure (maximally 1.4 nm) with increased temperature was observed. However, this effect was shown to have no influence on the analytical results. In the vast majority of cases, where structural isomers were investigated, there were clear differences between the recorded spectra. Compounds with the same functional group showed pronounced similarities. The influence of conjugation and various substituents could be demonstrated. A commercial computer program was used for a computer search of unknowns against the recorded reference spectra. This showed that the gas-phase UV spectra are very well defined and that a search always resulted in a very close agreement, even if concentrations and chromatographic conditions were different between the recording of reference and unknown. When a search was performed on a compound not present in the library, the result pointed out the correct class of compounds.