Optimized method for analysis of ethanolamines, hydrolysis products of nitrogen mustards, from urine samples using LC-MS/MS

Highly polar ethanolamines (EAs), excreted in urine, are hydrolysis products of nitrogen mustards (NMs), which are prohibited by the Chemical Weapons Convention (CWC). The methods established for biological matrices are essential for verification analysis of the CWC related chemicals. This paper describes a new liquid chromatography-tandem mass spectrometry (LC-MS/MS) method developed for qualitative and quantitative analysis of EAs, N-ethyldiethanolamine (EDEA), N-methyldiethanolamine (MDEA) and triethanolamine (TEAOH) from urine samples. After optimization of sample preparation and chromatographic conditions, the method was fully validated. Silica solid-phase extraction (SPE) cartridges and a porous graphite carbon (PGC) column were selected for validation studies. The method is linear from 5 to 500, 0.5 to 250, and 0.5 to 500 ng/mL for TEAOH, EDEA, and MDEA, respectively. It is also precise and accurate. A minimum sample amount of 0.5 mL urine was used. The limit of quantification using this approach was 0.4, 5.5, and 6.3 ng/mL for MDEA, EDEA and TEAOH, respectively. The combination of the PGC column and high pH eluents in analysis retained and separated the studied EAs. Retention times were 2.11, 2.56 and 2.98 min for MDEA, EDEA and TEAOH, respectively. The method is applicable for verification analysis of the CWC.

Gold nanoparticles-enhanced ion-transmission mass spectrometry for highly sensitive detection of chemical warfare agent simulants

Gold nanoparticles (AuNPs)-embedded paper was coupled with ion-transmission mass spectrometry (MS) to enable the highly sensitive detection of chemical warfare agent (CWA) simulants in solutions. With the assistance of a low-temperature plasma (LTP) probe, we found that AuNPs were capable to enhance the ionization efficiencies of target analytes, with MS signal intensities surprisingly undergone an 800-fold increase under optimized conditions. The interaction between AuNPs and the radiofrequency electromagnetic field was believed to promote the desorption/ionization process, resulting in the unusual signal enhancement phenomenon. Based on this finding, we established a method for the rapid analysis of two simulants of nerve agents, dimethyl methylphosphonate (DMMP) and diisopropyl methylphosphonate (DIMP), with a dynamic range from 0.5 ng/mL to 100 ng/mL and detection limits of 0.1 ng/mL and 0.3 ng/mL, respectively. As sample pretreatments have been eliminated, the developed strategy is particularly promising for the on-site detection of CWAs considering its simple and rapid analytical workflow.

Use of 1,5-diaminonaphthalene to combine matrix-assisted laser desorption/ionization in-source decay fragmentation with hydrogen/deuterium exchange

RATIONALE

In-Source Decay (ISD) in Matrix-Assisted Laser Desorption/Ionization (MALDI) mass spectrometry is a fast and easy top-down activation method. Our objective is to find a suitable matrix to locate the deuterons following in-solution hydrogen/deuterium exchange (HDX). This matrix must circumvent the commonly encountered undesired back-exchange reactions, in order to preserve the regioselective deuteration pattern.

METHODS

The 1,5-diaminonaphthalene (1,5-DAN) matrix is known to be suitable for MALDI-ISD fragmentation. MALDI Mass Spectrometry Imaging (MSI) was employed to compare 1,5-DAN and other commonly used MALDI matrices with respect to the extent of back-exchange and the uniformity of the H/D exchange profiles within the MALDI spots. We tested the back-exchange on the highly sensitive amyloid-beta peptide (1-40), and proved the regioselectivity on ubiquitin and β-endorphin.

RESULTS

MALDI-MSI results show that 1,5-DAN leads to the least back-exchange over all the spot. MALDI-ISD fragmentation combined with H/D exchange using 1,5-DAN matrix was validated by localizing deuterons in native ubiquitin. Results agree with previous data obtained by Nuclear Magnetic Resonance (NMR) and Electron Transfer Dissociation (ETD). Moreover, 1,5-DAN matrix was used to study the H/D exchange profile of the methanol-induced helical structure of β-endorphin, and the relative protection can be explained by the polarity of residues involved in hydrogen bond formation.

CONCLUSIONS

We found that controlling crystallization is the most important parameter when combining H/D exchange with MALDI. The 1,5-DAN matrix is characterized by a fast crystallization kinetics, and therefore gives robust and reliable H/D exchange profiles using MALDI-ISD.

Determination of nitrogen mustard degradation products in water samples using a portable capillary electrophoresis instrument

In this work, a new purpose-made portable CE instrument with a contactless conductivity detector was used for the determination of degradation products of nitrogen mustards in different water samples. The capillary was coated with poly(1-vinylpyrrolidone-co-2-dimethylaminoethyl methacrylate) to avoid analyte-wall interactions. The coating procedure was studied to obtain the best repeatability of the migration time of the analytes. Four different coating procedures were compared; flushing the capillary with the copolymer at 100 psi for 2 min at 60°C provided the best RSD values (<4%). The analytical method was also optimized. The use of 20 mM of MES adjusted to pH 6.0 with His as running buffer allowed a good baseline separation of the three analytes in different water samples without matrix interferences. The method permitted the detection of the three degradation products down to 5 μM.