Development of a Solid-phase microextraction (SPME) Fiber protector and its application in flammable liquid residues analysis.

Solid-phase microextraction (SPME) has been established as a very powerful alternative to traditional extraction methods since its introduction in the early 1990s. The heart of the SPME device is an expensive thin and very delicate fused-silica fiber, coated with a thin polymer film. When extracted, the fiber may bend and break. Due to the fragility of the SPME fiber, a fiber protector device is proposed. The protector is easily assembled on the SPME device and can easily be removed by unscrewing for sampling to the injector. The SPME with the fiber protector was tested by headspace-SPME (HS-SPME) gasoline and diesel fuel vapor analyses. The results of the extractions with the SPME protector were compared with the results of the extractions by SPME without the protector. An enhancement to the lighter hydrocarbons was observed in the results with the protector but the method sensitivity was not altered. The SPME protector was easily cleaned from contaminant residues by ethyl acetate washings. The protector can be used for years and the fibers remain intact for hundreds of samplings.

An analytical method to identify traces of white phosphorus on burned victim clothes.

We report for the first time, the chemical identification of phosphorus on the remains of burned clothes taken from an injured woman. The woman was accidentally burned as a result of spontaneous combustion of a "stone" pebble-like material her daughter picked up innocently on a beach. The remains of the woman's clothes were analyzed by gas chromatograph mass spectrometer (GCMS) after headspace adsorption using solid phase microextraction (SPME). The results of this test showed that the injuries were due to phosphorus, leading to the understanding that the "stone" was actually white phosphorus. This method can help both forensic investigators in a crime scene investigation and physicians that need this information in order to give the correct treatment to their patient.

Detection of gasoline on arson suspects' hands.

An arson suspect's contact with an ignitable liquid container can leave small traces of the substance on his hands, but detecting these traces is difficult. This research paper presents a method to obtain clear gasoline detection even 3h after hands have been moistened with 50 µL of gasoline using activated charcoal strips to adsorb the ignitable liquid traces directly from the suspect's hands. Light heating of the hands to 45 °C significantly increases the ability to detect gasoline traces. This methodology is part of a system to sample a suspect's hands at the scene of crime or in a police station. Samples are taken by investigators then analyzed in a laboratory. The suggested method provides an important improvement in detection sensitivity for ignitable liquids on suspect's hands.

Chemical contamination of soft drinks in sealed plastic bottles by environmental stress cracking.

A contamination of soft drinks in sealed bottles by organic solvents is reported: closed bottles full of soft drinks were accidentally placed on a cardboard soaked with thinner and the organic fluid subsequently fissured the bottom of the bottles and penetrated into the soft drinks without any apparent leakage of the soft drinks. Experiments were carried out to simulate the process: the penetration of different organic solvents into soft drinks through the bottom of closed bottles was tested. The penetration occurred only when the closed bottles contained carbonated soft drinks (CSD), indicating that inner pressure is a necessary condition for the fissuring of the bottles. This paper discusses environmental stress cracking of polyethylene terephthalate (PET) bottles by organic solvents and migration of chemicals to CSD. Experiments were conducted to determine the conditions in which PET can be permeable to poisoning organic products.

A novel method for the analysis of discharged smokeless powder residues.

A novel method for the estimation of intermediate-long firing distance range is proposed. The method is based on the characterization and chemical analysis of the smokeless powder particles on the target. An adhesive lifter is applied to collect the suspected gunshot residues (GSRs) from the surface of an object, and a Modified Griess Test (MGT) is carried out after alkaline hydrolysis on the adhesive lifter. Visualized particles are removed from the adhesive lifter under a microscope. Two systems are used for the analysis of organic discharge residues from the smokeless powder: (1) gas chromatography/thermal energy analysis (GC/TEA) for the analysis of nitroglycerine (NG) and 2,4-dinitrotoluene (2,4-DNT), (2) gas chromatography/mass spectrometry (GC/MS) for the identification of organic components such as DNT, NG, and some stabilizers. By using this procedure and confirming that the suspected particles are indeed GSR, one can estimate the intermediate-long firing distance of c. 0.75-3 m in the presence of very few particles and provide information for the classification of ammunition type in casework.

Vacuum collection of gunpowder residues from clothing worn by shooting suspects, and their analysis by GC/TEA, IMS, and GC/MS.

Experiments were conducted to collect gunpowder (propellant) residues from shooters' clothing by vacuum and to analyze them by gas chromatography/thermal energy analyzer (GC/TEA), ion mobility spectrometry (IMS), and gas chromatography/mass spectrometry (GC/MS). The residues were collected on fiberglass and Teflon filters using the portable vacuum sampler, all supplied with the IMS instrument. Several solvents were examined for the extraction of the propellant components from the filters. The extracts were centrifuged and/or filtered, concentrated by evaporation, and analyzed without any additional clean-up procedure. Based on the results of the study, an operational method for analysis of gunpowder residues was introduced into casework without changing the present operational technique for gunshot (primer) residue (GSR) analysis on clothing implemented by the Israel Police. In the modified method, the clothing is first sampled by double-side adhesive-coated aluminum stubs (the tape-lift method) for GSR analysis (the existing method), followed by vacuum collection for propellant residue examination. The issue of interpretation of the analytical results is discussed.

Building Units for N-Backbone Cyclic Peptides. 3. Synthesis of Protected N(alpha)-(omega-Aminoalkyl)amino Acids and N(alpha)-(omega-Carboxyalkyl)amino Acids.

An improved synthesis of a family of amino acids that contain omega-aminoalkyl groups and of a new family containing omega-carboxyalkyl groups linked to the alpha-amine is described. The synthesis was performed by alkylation of suitably monoprotected alkylenediamines and protected omega-amino acids with triflates of alpha-hydroxy acid esters. The reaction proceeded with inversion of configuration yielding optically pure products. The N(alpha)-(omega-aminoalkyl)amino acids and N(alpha)-(omega-carboxyalkyl)amino acids were orthogonally protected to allow their incorporation into peptides by solid-phase peptide synthesis (SPPS) methodology.