Hemendra K. Gupta

On-line high-performance liquid chromatography–ultraviolet–nuclear magnetic resonance method of the markers of nerve agents for verification of the Chemical Weapons Convention

This paper details an on-flow liquid chromatography-ultraviolet-nuclear magnetic resonance (LC-UV-NMR) method for the retrospective detection and identification of alkyl alkylphosphonic acids (AAPAs) and alkylphosphonic acids (APAs), the markers of the toxic nerve agents for verification of the Chemical Weapons Convention (CWC). Initially, the LC-UV-NMR parameters were optimized for benzyl derivatives of the APAs and AAPAs. The optimized parameters include stationary phase C(18), mobile phase methanol:water 78:22 (v/v), UV detection at 268nm and (1)H NMR acquisition conditions. The protocol described herein allowed the detection of analytes through acquisition of high quality NMR spectra from the aqueous solution of the APAs and AAPAs with high concentrations of interfering background chemicals which have been removed by preceding sample preparation. The reported standard deviation for the quantification is related to the UV detector which showed relative standard deviations (RSDs) for quantification within +/-1.1%, while lower limit of detection upto 16mug (in mug absolute) for the NMR detector. Finally the developed LC-UV-NMR method was applied to identify the APAs and AAPAs in real water samples, consequent to solid phase extraction and derivatization. The method is fast (total experiment time approximately 2h), sensitive, rugged and efficient.

Microsynthesis and gas chromatography/electron ionization mass spectrometric and tandem mass spectrometric analysis of cyclic alkylphosphonates for verification of the Chemical Weapons Convention.

We describe the microsynthesis and gas chromatography/mass spectrometric (GC/MS) analysis of cyclic alkylphosphonates (CAPs), which are included in schedule 2B4 chemicals in the Chemical Weapons Convention (CWC). The reported microsynthesis is efficient in comparison with traditional synthesis. GC/MS and GC/tandem mass spectrometric (MS/MS) analysis of a variety of CAPs revealed that their fragmentations were dominated by alpha-cleavages, alkene eliminations and hydrogen rearrangements. Based on the obtained mass spectra and precursor and product ion analysis of five-, six- and seven-membered cyclic alkylphosphonates, the proposed fragmentation routes rationalize most of the characteristic ions.

Rapid Synthesis of O,O-Dialkyl Alkylphosphonates on TLC with Analytical Purity for the Verification Analysis of Chemical Weapons Convention

Reaction parameters for the rapid synthesis of O,O′-dialkyl alkylphosphonates and O-alkyl hydrogen alkylphosphonates were optimized using thin-layer chromatographic plates as a solid-supported platform under microwave irradiation. Immediate synthesis of these compounds with analytical purity is of paramount importance for the verification analysis of the Chemical Weapons Convention.

N,N′-Dichlorobis(2,4,6-trichlorophenyl)urea (CC-2): an Efficient Reagent for the Synthesis of Chemical Weapons Convention-Related Dialkyl-N,N-dialkylphosphoramidates from Dialkylphosphites

The present paper describes the one-pot synthesis of dialkyl N,N-dialkylphosphoramidates (DADAP) from dialkylphosphites and dialkylamines using N,N′-dichlorobis(2,4,6-trichlorophenyl)urea (CC-2) as chlorinating reagent. DADAP belong to the schedule 2.B.6 category of the Chemical Weapons Convention (CWC), as they are the important markers of the chemical warfare agent tabun and its analogues. The study was undertaken to develop the spectral database of DADAP for verification of CWC. The reported synthetic strategy can be adopted to rapidly synthesize several analogues of DADAP during official proficiency tests.