Ben L. M. van Baar

Identification of chemicals related to the chemical weapons convention during an interlaboratory proficiency test

In order to test the ability of laboratories to detect and identify chemicals related to the Chemical Weapons Convention (CWC), which prohibits the development, production, stockpiling and use of chemical weapons, and to designate laboratories for this task, the Technical Secretariat of the Organisation for the Prohibition of Chemical Weapons organises proficiency tests. This paper describes the conduct of such a test at the TNO-Prins Maurits Laboratory in Rijswijk, The Netherlands. The analytical strategies and procedures that resulted in the unambiguous identification in the test samples of chemicals relevant to the CWC are discussed.

Characterisation of botulinum toxins type A and B, by matrix-assisted laser desorption ionisation and electrospray mass spectrometry

A method earlier developed for the mass spectrometric (MS) identification of tetanus toxin (TTx) was applied to botulinum toxins type A and B (BTxA and BTxB). Botulinum toxins are extremely neurotoxic bacterial toxins, likely to be used as biological warfare agent. Biologically active BTxA and BTxB are comprised of a protein complex of the respective neurotoxins with specific haemagglutinins (HAs) and non-toxic non-haemagglutinins (NTNHs). These protein complexes are also observed in mass spectrometric identification. The particular BTxA complex, from Clostridium botulinum strain 62A, almost completely matched database data derived from genetic sequences known for this strain. Although no such database information was available for BTxB, from C. botulinum strain okra, all protein sequences from the complex except that of HA-70 were found to match proteins known from other type B strains. It was found that matrix-assisted laser desorption ionisation MS provides provisional identification from trypsin digest peptide maps and that liquid chromatography electrospray (tandem) mass spectrometry affords unequivocal identification from amino acid sequence information of digest peptides obtained in trypsin or pepsin digestion.

Development of an automated on-line pepsin digestion-liquid chromatography-tandem mass spectrometry configuration for the rapid analysis of protein adducts of chemical warfare agents

Rapid monitoring and retrospective verification are key issues in protection against and non-proliferation of chemical warfare agents (CWA). Such monitoring and verification are adequately accomplished by the analysis of persistent protein adducts of these agents. Liquid chromatography-mass spectrometry (LC-MS) is the tool of choice in the analysis of such protein adducts, but the overall experimental procedure is quite elaborate. Therefore, an automated on-line pepsin digestion-LC-MS configuration has been developed for the rapid determination of CWA protein adducts. The utility of this configuration is demonstrated by the analysis of specific adducts of sarin and sulfur mustard to human butyryl cholinesterase and human serum albumin, respectively.

On the structure of the C2H4O2 neutrals (acetic acid versus 1,1-dihydroxyethene) generated from ionized n-hexanoic acid and n-butyl acetate in the gas phase. Implications for the mechanism of the McLafferty rearrangement

Abstract Results are reported of CIDI and NRMS experiments which show that the C 2 H 4 O 2 neutral co-generated with C 4 H + 8 from the metastable n -hexanoic acid ion and the n -butyl acetate molecular ion is acetic acid and not its stable enol, CH 2 C(OH) 2 . This is in marked contrast to the structure of the C 2 H 4 O + 2 ion, co-generated with C 4 H 8 from the metastable n -hexanoic acid ion, which was earlier shown to be exclusively the enol form of acetic acid. The implication of this and earlier findings for the mechanism of McLafferty-type processes is discussed and it is suggested that this ubiquitous reaction is more complex than hitherto expected. The reaction may well proceed via long-lived ion/dipole or hydrogen-bridged intermediates.

Identification of the C3H7 moiety of isopropyl‐ and propylphosphonates by electrospray tandem mass spectrometry

Structure analysis of phosphorus compounds within the framework of the Chemical Weapons Convention requires the specific identification of alkyl substituents on phosphorus. In this work the distinction of the P-propyl substituent in propylphosphonic acid derivatives by electrospray tandem mass spectrometry was investigated. P-Isopropyl and P-n-propyl groups were readily distinguished and a mechanistic proposal was given, based on labelling experiments. The findings were applied to the identification of the P-propyl moiety of two V-agents, O-ethyl S-[2-(dialkylamino)ethyl/propylphosphonothiolates, and to a degradation product of a G-agent, propyl propylphosphonate.

Identification of carbamates by particle beam/mass spectrometry.

The possibility of analysing 33 carbamate pesticides and 14 of their transformation products was investigated utilizing flow injection particle beam/mass spectrometry (PBMS) with electron impact (EI) ionization and ammonia and methane positive and negative chemical ionization (CI). Optimum operating conditions of the interface and mass spectrometer in each mode were determined, with special attention given to spectrum quality; variables investigated included ion source temperature and ion source pressure in CI experiments. Ammonia, as a reagent gas, provided less fragmentation and better quantitative results than methane. The CI response was generally higher with positive ion detection (PCI) than with negative ion detection (NCI), but NCI was found to be highly selective for compounds such as aminocarb, asulam and thiophanate-methyl. As regards analyte detectability, EI performed best for most compounds, with the spectra providing relevant structure information. The response of more polar degradation products is generally larger by 2–3 orders of magnitude compared with the parent compounds. When analysing real samples, the combined use of CI for molecular mass determination and EI for structure elucidation is required. The spectral information from this study and additional chromatographic data were used for the determination of low- and sub-μg l-1levels of the test carbamates in surface water.

Adduct ion formation by aromatic amines in thermospray mass spectrometry.

The formation of solvent adduct ions in thermospray and ionspray mass spectrometry was studied for twelve aromatic amines : aniline, N-methylaniline, N,N-dimethylaniline, 3-aminophenol, 3-methylaminophenol, 3-dimethylaminophenol, 2-aminopyridine, 2-methylaminopyridine and 2-dimethylaminopyridine, 2-amino-5,6-dimethyl-4-hydroxypyrimidine, 2-methylamino-5,6-dimethyl-4- hydroxypyrimidine and 2-dimethyl-amino-5,6-dimethyl-4-hydroxypyrimidine. For all compounds, adduct ions, [M + H + A n ] + , with A being methanol or acetonitrile, were observed in the thermospray mass spectra ; water adduct ions were observed for a few compounds. No adduct ions with ammonia were formed when ammonium acetate was added to the liquid chromatographic carrier stream. These observations cannot be explained on the basis of gas-phase ion-molecule reactions of the neutral analyte and protonated solvent or solvent additive molecules. Comparative experiments, changing the pH of the carrier stream in both thermospray and ionspray ionization, showed that the solvent adduct ions present in the thermospray mass spectra are not likely to be formed by ion evaporation processes. Incomplete evaporation of droplets or cluster ions is proposed to be responsible for the observations. With this hypothesis, both the absence of ammonium adduct ions and the dependence of the adduct ion abundances on the N-methylation can be related to the adduct-analyte bond strengths.

Recent Advances in Real-time Mass Spectrometry Detection of Bacteria

The analysis of bio-aerosols poses a technology challenge, particularly when sampling and analysis are done in situ. Mass spectrometry laboratory technology has been modified to achieve quick bacteria typing of aerosols in the field. Initially, aerosol material was collected and subjected off-line to minimum sample treatment and mass spectrometry analysis. More recently, sampling and analysis were combined in a single process for the real-time analysis of bio-aerosols in the field. This chapter discusses the development of technology for the mass spectrometry of bio-aerosols, with a focus on bacteria aerosols. Merits and drawbacks of the various technologies and their typing signatures are discussed. The chapter concludes with a brief view of future developments in bio-aerosol mass spectrometry.The analysis of bio-aerosols poses a technology challenge, particularly when sampling and analysis are done in situ. Mass spectrometry laboratory technology has been modified to achieve quick bacteria typing of aerosols in the field. Initially, aerosol material was collected and subjected off-line to minimum sample treatment and mass spectrometry analysis. More recently, sampling and analysis were combined in a single process for the real-time analysis of bio-aerosols in the field. This chapter discusses the development of technology for the mass spectrometry of bio-aerosols, with a focus on bacteria aerosols. Merits and drawbacks of the various technologies and their typing signatures are discussed. The chapter concludes with a brief view of future developments in bio-aerosol mass spectrometry.

Remarkable rearrangement–dissociation processes of gaseous protonated methyl formate involving ion–dipole complexes

Collision induced decarbonylation of 13C, 18O-labelled protonated methyl formate, HC(OH)O*C*H3, involves the loss of both CO (40%) and CO*; the intermediacy of proton-bound dimers and ion–dipole complexes is invoked to explain the mechanisms.

CH3OC+: a long-sought molecule, predicted to exist by theory, identified

The oxygen-methylated carbon monoxide cation, CH3OC+(2), has been generated and identified in the gas phase as a stable species ( lifetimet < 10–5 s) using mass spectrometry based experiments.