Paul E. Pigou

New Developments in SPME Part 2: Analysis of Ammonium Nitrate-based Explosives

Solid-phase microextraction (SPME) followed by gas chromatography-mass spectrometry (GC-MS) is a simple, reliable technique for the recovery and analysis of many organic explosives. However, this technique is impractical for the analysis of ammonium nitrate-type explosives due to the extreme polarity, low molecular weight, and high volatility of the amine moiety. This article describes an initial investigation of a derivatization process utilizing alkylchloroformates that converts ammonium nitrate and methylammonium nitrate into a form suitable for recovery by SPME and analysis by GC-MS.

Surface-assisted laser desorption ionization mass spectrometry techniques for application in forensics

Matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS) is an excellent analytical technique for the rapid and sensitive analysis of macromolecules (>700 Da), such as peptides, proteins, nucleic acids, and synthetic polymers. However, the detection of smaller organic molecules with masses below 700 Da using MALDI-MS is challenging due to the appearance of matrix adducts and matrix fragment peaks in the same spectral range. Recently, nanostructured substrates have been developed that facilitate matrix-free laser desorption ionization (LDI), contributing to an emerging analytical paradigm referred to as surface-assisted laser desorption ionization (SALDI) MS. Since SALDI enables the detection of small organic molecules, it is rapidly growing in popularity, including in the field of forensics. At the same time, SALDI also holds significant potential as a high throughput analytical tool in roadside, work place and athlete drug testing. In this review, we discuss recent advances in SALDI techniques such as desorption ionization on porous silicon (DIOS), nano-initiator mass spectrometry (NIMS) and nano assisted laser desorption ionization (NALDI™) and compare their strengths and weaknesses with particular focus on forensic applications. These include the detection of illicit drug molecules and their metabolites in biological matrices and small molecule detection from forensic samples including banknotes and fingerprints. Finally, the review highlights recent advances in mass spectrometry imaging (MSI) using SALDI techniques.

Application of solid-phase microextraction to the recovery of organic explosives.

The application of solid-phase microextraction to the recovery of residues of organic explosives by headspace sampling is discussed. It was found that the technique was rapid and simple. Polydimethylsiloxane and polyacrylate resin were examined as adsorption phases and the latter was found to be more effective. It was found that non-volatile explosives (PETN, RDX, and TNT) should be extracted at about 100 degrees. Acceptable limits of detection were achieved using bench top quadrupole mass spectrometry and short extraction times (about 30 min). Increasing the extraction times to many hours resulted in significantly enhanced detection. Desorption of PETN from the solid phase was found to induce some decomposition of the explosive, but the technique was still valuable for the analysis of this compound.

The analysis of dyes in ball point pen inks on single paper fibres using laser desorption ionisation time of flight mass spectrometry (LDI-TOFMS)

An important requisite for the forensic analysis of inks on documents is that damage to the document is avoided or minimised. This paper describes a technique for dye identification in ballpoint pen inks using LDI-TOFMS on single ink bearing paper fibres and its application to a case. A single ink bearing paper fibre can be prised from the surface of the document under a stereo microscope and presented to the instrument for analysis without further treatment. This sampling process causes imperceptible damage to the surface of the document. Clear mass spectrometric identification of the ink dyes is obtained. A case example is provided to illustrate the practical application of the technique.

Development of millimeter- and submillimeterwave spectroscopy and its application to isotopically-substituted nonpolar molecules, deuterated cubane and deuterated cyclobutanes

Abstract A spectroscopic method has been developed to observe rotational spectra of molecules in the millimeter- and submillimeter-wave regions. Advantages and disadvantages of the method are discussed and compared to those of Stark-modulation and Fourier-transform spectroscopy in the centimeter-wave region. As examples of the methods applicability, the results for cubane-d and cis and trans cyclobutane-1,2-d 2 are presented. The transitions of J = 14 ← 13 up to 26 ← 25 are observed for cubane-d, yielding the rotational and centrifugal distortion constants B 0 = 3220.720 08 (85) and D JO = 0.000 180 99 (93) MHz; values in parentheses represent three standard deviations. Trans cyclobutane-1,2-d 2 is found to exist in an equatorial-equatorial and an axial-axial conformation, with only the b-dipole component being nonvanishing, as expected from previous results on the structure of cyclobutane. The observed spectra lead to the rotational constants A = 9 794.3831 (58), B = 9 758.3272(56), and C = 5 782.6540(73) and A = 9 738.242 (15), B = 9 693.452(14), and C = 6 048.564 (14) MHz, for the two forms, respectively; values in parentheses again represent three standard deviations. Cis cyclobutane-1,2-d 2 is expected to exist in two equivalent forms, axial-equatorial and equatorial-axial. The observed spectrum exhibits the effect of puckering. Preliminary values of the rotational constants are A = 9 938.757 (47), B = 9 577.008(47), and C = 5 913.212(41) MHz.

Evaluation of Some Oxygen, Sulfur, and Selenium Substituted Ninhydrin Analogues, Nitrophenylninhydrin and Benzo[f]furoninhydrin

Six ninhydrin analogues containing oxygen, sulfur, and selenium substituents at the C-5 position, 5-(4-nitrophenyl)ninhydrin, and benzo[f]furoninhydrin were evaluated as fingerprint development reagents. The analogues all showed good fingerprint color development but were not superior to ninhydrin in this respect. The benzo[f]furoninhydrin complex was strongly luminescent at room temperature following zinc complexation, while the remaining analogues required cooling to -196 degrees C to produce optimum luminescence. The benzo[f]furo, nitrophenyl, and methyl selenide analogues showed the best potential as fingerprint reagents with the benzo[f]furo analogue comparing favorably with DFO.

Natural-abundance studies of 13C13C coupling constants. Substituent dependencies of directly bonded and vicinal 13C13C coupling constants in 1-substituted bicycloalkanes

Abstract A series of 1-substituted-bicyclo[2.2.2]octanes and bicycloalkane-l-carboxylic acids were synthesized and the 13 C 13 C coupling constants were measured in natural abundance by 13 C satellite and/or double-quantum coherence methods. Experimental data for vicinal/geminal coupling between the bridgehead carbon atoms are in good agreement with calculated molecular orbital results, which are based on the INDO-FPT method for the Fermi contact contributions. Although the numerical agreement for the directly bonded 13 C 13 C coupling constants is not as good, the substituent trends are well reproduced. Moreover, a linear least squares fit of the calculated and experimental data for the bicyclo [2.2.2]octanes provides a good correlation of most of the directly bonded coupling constant data. This is discussed in terms of the approximations which are implicit in the INDO-FPT method.

The photoelectron spectrum and molecular geometry of bicyclo[2.1.1]hexane

Abstract The He(I) photoelectron spectrum of bicyclo[2.1.1]hexane shows excellent correlation with a theoretical spectrum based on the eigenvalues obtained in an ab initio calculation at the theoretical molecular geometry. By contrast, a calculation performed at the experimental geometry exhibits an effect of enhanced ring strain in showing a first ionization energy which is considerably lower than the experimental value. This observation offers experimental support for the recent claim that the published structure for bicyclo [2.1.1]hexane based on electron-diffraction measurements is incorrect. It also accounts for inconsistencies observed in the calculated values of some spin—spin coupling constants for substituted bicyclo[2.1.1]hexanes.

Detailed investigations into the Akabori–Momotani reaction for the synthesis of amphetamine type stimulants: Part 2

The Akabori-Momotani reaction can be used to synthesise pseudoephedrine in 50% yield from N-methylalanine and benzaldehyde. This paper investigates electronic effects of substituted benzaldehydes on the reaction to synthesise amphetamine type stimulants and identifies several new Akabori-Momotani by-products, 1-[(4-methoxybenzyl)(methyl)amino]ethanol (11c), 2-(4-methoxyphenyl)-3,4-dimethyl-1,3-oxazolidine (12c), 1,2,3,4-tetramethyl-5,6-di-(4-methoxyphenyl)piperazine (13c) and 1,2,4,5-tetramethyl-3,6-di-(4-methoxyphenyl)piperazine (14c). This paper also investigates pseudoephedrine and methamphetamine isomeric distribution from the Akabori-Momotani reaction with the aid of molecular modelling to understand why more pseudoephedrine than ephedrine is produced.

An investigation into artefacts formed during gas chromatography/mass spectrometry analysis of firearms propellant that contains diphenylamine as the stabiliser

In the course of providing assistance to legal counsel in a matter that involved the analysis of firearms propellant by gas chromatography/mass spectrometry it was noticed that phenoxazine was reported as a component of 0.22 calibre propellant that contained diphenylamine as the stabiliser. The research was conducted to find how phenoxazine was formed. The results showed that the compound was not phenoxazine but a diphenylamine derivative 4-(phenylimino) cyclohexa-2,5-dien-1-one that formed in the injection port of the gas chromatograph. In addition a second artefact was found to form in the ion source of the mass spectrometer. While the presence of the artefacts does not affect the ability to identify particles as propellant they may impact on comparison with source ammunition.