Determination of sarin, soman and their hydrolysis products in soil by packed capillary liquid chromatography-electrospray mass spectrometry.

An analytical method based on aqueous ultrasonic extraction and packed capillary liquid chromatography-electrospray mass spectrometry (LC-ESI-MS) analysis was developed and compared to an existing gas chromatography(GC)-MS based method for the determination of sarin, soman and their hydrolysis products in contaminated soil. Three soils, a red clay, a tan sandy clay and a brown sandy clay loam, were spiked with sarin and soman and their initial hydrolysis products, isopropyl methylphosphonic acid and pinacolyl methylphosphonic acid, at the 10 microg/g level to assess recovery efficiency. Recovery of sarin and soman from the aqueous soil extracts was comparable to the existing analytical method, with a significant improvement in recovery being demonstrated for the chemical warfare agent hydrolysis products. Sarin and soman were recovered in the 20-90% range from the three soil types with aqueous extraction, while the hydrolysis products of these chemical warfare agents were extracted with recoveries in excess of 80%. The developed soil extraction and analysis method appears to be an attractive alternative to the GC-MS based method, since aqueous extracts containing chemical warfare agent hydrolysis products may be analysed directly, eliminating the need for additional sample handling and derivatization steps.

Packed capillary liquid chromatography-electrospray mass spectrometry analysis of organophosphorus chemical warfare agents.

Packed capillary column liquid chromatography (LC)-electrospray mass spectrometry (ESI-MS) was used for the first time to detect and identify four common organophosphorus chemical warfare agents in aqueous samples. Aqueous samples containing the organophosphorus chemical warfare agents in the 0.01 to 0.1 mg/ml range were analyzed directly by packed capillary LC-ESI-MS with the chemical warfare agents and several minor related impurities being well resolved under acetonitrile-water gradient elution conditions. The ESI-MS data for isopropyl methylphosphonofluoridate (sarin or GB), O-ethyl N,N-dimethylphosphoramidocyanidate (tabun or GA), cyclohexyl methylphosphonofluoridate (GF) and pinacolyl methylphosphonofluoridate (soman or GD) were acquired with a sampling cone voltage setting that promoted collisionally activated dissociation, and resulted in the acquisition of informative mass spectra containing both molecular and product ion information. The developed method appears to be an attractive alternative to GC-MS for the analysis of aqueous samples containing organophosphorus chemical warfare agents and their hydrolysis products, since they may be analyzed directly without the need for additional sample handling.

Analysis of O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX) and its degradation products by packed capillary liquid chromatography-electrospray mass spectrometry.

Packed capillary column liquid chromatography (LC)-electrospray mass spectrometry (ESI-MS) was used for the first time to detect and identify O-ethyl, S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX) and its degradation products, including compounds containing a P-CH3 bond, bis(diisopropylamino)thioalkanes and ureas commonly employed as VX stabilizers. The reported ESI-MS data were generally acquired with a higher sampling cone voltage, a setting that promoted collisionally activated dissociation, and resulted in the acquisition in informative mass spectra containing both molecular and product ion information. The developed method appears to be an attractive alternative to GC-MS for the analysis of aqueous sample containing the degradation products of VX, since they may be analysed directly with little risk of thermal decomposition and without the need for additional sample handling or derivatization. Application of this method to a degraded VX sample resulted in the detection of a number of novel polar and higher-molecular-mass degradation products, not previously associated with VX during GC-MS analysis.

Liquid chromatographic-high-resolution mass spectrometric and tandem mass spectrometric identification of synthetic peptides using electrospray ionization.

Liquid chromatography-high-resolution electrospray mass spectrometry (LC-ESI-MS) was investigated for the identification of known and unknown synthetic peptides in a research effort designed to evaluate the applicability of this and complementary MS techniques for peptide characterization and identification. The monoisotopic molecular masses of five related peptides with molecular masses between 2000 and 2500 u were acquired with a resolution of 3000 (10% valley). Under narrow and wide mass range magnetic sector scanning conditions monoisotopic molecular mass errors were typically in the 10-20 and 30-40 ppm range, respectively. Tryptic maps were generated for each peptide following LC-ESI-MS analysis and collisionally activated dissociation (CAD) in the ESI interface resulted in the production of characteristic product ions that enabled amino acid sequencing of the tryptic fragments. Unknown identification was demonstrated during analysis of an incomplete synthetic peptide reaction mixture. The synthesis of an 18 amino acid peptide, LTTAVKKVLTTGLPALIS, was not successful. In its place were six unknown peptides that were identified on the basis of monoisotopic molecular mass and amino acid sequence data. The monoisotopic molecular masses of these unknowns were determined to within 10-20 ppm with a resolution of 3500 (10% valley). Amino acid sequences for the six peptides were generated during ESI-MS-MS analysis. Finally two synthetic peptides differing only by the incorporation of a 13C at leucine were analysed with a resolution of 6000 (10% valley) to confirm that the isotopic distributions were consistent with theoretical expectations.

Analysis of bioactive peptides by liquid chromatography-high-resolution electrospray mass spectrometry.

LC-high-resolution electrospray ionization (ESI)-MS data for a number of bioactive peptides, including substance P and bradykinins were acquired over a wide mass range by scanning the magnetic sector and calibrating externally with polyethylene glycol standards. Multiply charged ions were observed and errors between observed and theoretical monoisotopic molecular masses were typically in the 5 to 30 ppm range for the peptides during LC-ESI-MS and ESI-MS operation with magnetic sector resolutions between 2500 and 6000 (10% valley definition). Under collisionally activated dissociation conditions bn- and yn-series sequence ions were generally observed, enabling amino acid sequencing and the differentiation of lysine from glutamine, two amino acids differing in residue mass by only 0.0364 u. Mass accuracy was evaluated during an international round robin analytical exercise where the molecular masses of five unknown peptides were to be accurately determined. Isotopic clusters for charge states of up to +6 were fully resolved, facilitating the rapid and unambiguous assignment of charge states and calculation of monoisotopic molecular masses. Errors between theoretical and observed monoisotopic molecular masses were in the 2 to 18 ppm range for the five unknown peptides.

High resolution electrospray mass spectrometry with a magnetic sector instrument: accurate mass measurement and peptide sequencing.

The accurate molecular weights for a series of 37 unknown synthetic peptides, used in research studies involving synthetic vaccines, antibacterial peptides or the de novo design of helical peptides and proteins, were determined with a magnetic sector instrument. All data were obtained with external calibration over a wide mass range during magnetic scanning. Errors between observed and theoretical monoisotopic molecular weights were typically in the 5-60 ppm range for the unknowns at sector resolutions between 2500 and 9000 (10% valley). Isotopic clusters for charge states up to 10+ were resolved through the use of high resolution. Collisionally activated dissociation (CAD) in the electrospray interface resulted in product ions that enabled either full or partial sequencing of most unknown peptides of molecular weights below 2000 Da. The complete primary sequence for one peptide was determined and the importance of high resolution was demonstrated by the differentiation of lysine from glutamine, two amino acids differing in residue mass by only 0.0364 Da. Two other peptides, with identical monoisotopic masses, but different primary sequences, were differentiated based on CAD-MS data.

Bioassay of organophosphate nerve agents in soil using neuronal tissue cultures.

A soil sample originating from an area of suspected chemical warfare activity was subjected to chemical analysis and bioassay. Sarin and several related compounds were confirmed in the soil by capillary column gas chromatography-mass spectrometry (GC-MS); however, the binding of these compounds to the soil hindered quantitation. The chemical results were then compared to those obtained by bioassay in primary cultures of chick embryo forebrain neurons. By comparing the sample's anticholinesterase activity against those of purified standards in chick embryo neuron cultures, a reasonable agreement was found between the chemical and bioassay semi-quantitative estimates of sarin content in the soil extract. Furthermore, the in vitro system appears to offer a sensitive technique for the estimation of sarin remaining bound to the soil following solvent extraction as well as for an assessment of the potential toxicity of the contaminated soil in vivo.

Capillary column isobutane chemical ionization mass spectrometry of mustard and related compounds.

Capillary column isobutane chemical ionization was found to be an excellent method for the mass spectral characterization of mustard, other sulfur vesicants and related compounds. Interpretation of [M + H]+ and fragmentation ion information afforded by this technique enabled the identification of many previously unreported mustard impurities. The developed methodology was applied to the analysis of an Iran/Iraq soil sample suspected to have been contaminated with mustard. Mustard and 17 other mustard related impurities were identified and characterized in this sample under electron impact and isobutane chemical ionization conditions.

Gas chromatographic retention indices of sulfur vesicants and related compounds.

Temperature-programmed retention indices, relative to a n-alkane homologous series, were determined for 37 sulfur vesicant or vesicant-related compounds using DB-1, DB-5 and DB-1701 fused-silica capillary columns. Many of the compounds, including long chain dichloro, vinylchloro, vinylalcohol and macrocyclic compounds have either not been previously identified or have not been associated with sulfur vesicant analysis. Reproducibility of the retention indices, based on Van den Dool's equation, was excellent over the course of the study. In addition, changes in retention index (delta RI), which may enable the prediction of uncharacterized homologue chromatographic behaviour, were calculated for several homologous series.

Analysis of trichothecene mycotoxins in human blood by capillary column gas chromatography-ammonia chemical ionization mass spectrometry.

Capillary column gas chromatography-ammonia chemical ionization mass spectrometry was found to be an excellent technique for the trace detection and identification of underivatized trichothecene mycotoxins. Abundant (M + H)+ and/or (M + NH4)+ pseudo-molecular ions were observed for T-2 toxin, HT-2 toxin, T-2 triol, diacetoxyscirpenol, deoxynivalenol and verrucarol under the conditions developed. This method was successfully applied to the analysis of human blood samples spiked with mycotoxins in the 0-500 ng/g range during a recent interlaboratory exercise. T-2 toxin and diacetoxyscirpenol were detected in these samples in the 2-180 ng/g range. Detection limits of 0.7 and 3.6 ng/g for T-2 toxin and diacetoxyscirpenol, respectively, were possible owing to the specificity of the method.