Selective enrichment of the degradation products of organophosphorus nerve agents by zirconia based solid-phase extraction

Parallel artificial liquid membrane extraction of organophosphorus nerve agent degradation products from environmental samples

An emerging miniaturized high-throughput microextraction technique named Parallel artificial liquid membrane extraction (PALME) was, for the first time, investigated for the extraction of polar alkyl methylphosphonic acids (AMPAs) that are the degradation products of organophosphorus nerve agents. The effect of the key-parameters of the extraction method (nature of the membrane, of the extraction solvent, of the pH values of both donor and acceptor phases, agitation speed, extraction time, temperature and ionic strength) on the extraction recoveries was studied in spiked pure water samples. This led to extraction recoveries in the range of 25-102% for the 5 targeted analytes from water with enrichment factors in the range of 4.50-42.75. The developed PALME-LC-MS/MS method was first evaluated with spiked pure water. LOQs (S/N ≥ 10) were in the range of 0.009-1.141 ng mL^-1, linearity above 0.9973 for all the AMPAs and with RSD values below 11%. This method was then applied on simulated waste water, river water and aqueous soil extracts. The achieved LOQs were in the range of 0.011-1.210, 0.013-1.196 and 0.016-6.810 ng mL^-1, respectively. A detailed comparison of the performances of this PALME method with those of a previously developed hollow fiber liquid-phase microextraction methods already applied to AMPAs was done thus allowing to demonstrate the easy transfer of methods from HF-LPME to PALME. Moreover, the high-throughput potential of PALME was revealed since 192 samples were processed in parallel during 120 min (37.5 s/sample).

Sample bottle coated with sorbent as a novel solid-phase extraction device for rapid on-site detection of BTEX in water

Solid-phase extraction (SPE) is a popular technique for environmental sample pretreatment. However, SPE usually requires complex sample pretreatment processes, which is time-consuming and inconvenient for real-time and on-site monitoring. Herein, a solvent-free, rapid, and user-friendly SPE device was developed by coating the polydimethylsiloxane (PDMS)/divinylbenzene (DVB) sorbent on the inner wall of a sample bottle. The extraction process and desorption process were both carried out in the bottle. The analytes trapped in the sorbent were thermally desorbed and simultaneously sucked out from the bottle by an air sampling tube equipped on field-portable GC-MS. Different to previous work, the sample pretreatment process didn't require any complicated and time-consuming steps, such as centrifugation or filtration. The total analysis time for each sample was less than 25 min, which was feasible for rapid on-site detection, and thus avoided the losses and contamination of samples in conventional sample storage and transportation processes. Under optimal conditions, the proposed SPE method exhibited wide linear ranges, low detection limits (0.010-0.036 μg L^-1, which were much lower than the maximum levels restricted by the US Environmental Protection Agency and the Chinese GB3838-2002 standard), good intra-bottle repeatability (6.13-7.17%, n = 3) and satisfactory inter-bottle reproducibility (4.73-6.47%, n = 3). Finally, the method was successfully applied to the rapid detection of BTEX in the field. The recoveries of BTEX in spiked water samples ranged from 89.1% to 116.2%. This work presents a novel SPE approach for rapid on-site monitoring in water samples.

Highly sensitive retrospective determination of organophosphorous nerve agent biomarkers in human urine implemented in vivo in rabbit

Highly toxic organophosphorous nerve agents (OPAs) have been used in several armed conflicts and terror attacks in the last few decades. A new method for retrospective determination of alkyl methylphosphonic acid (AMPA) metabolites in urine after exposure to VX, GB and GF nerve agents was developed. This method enables a rapid, sensitive and selective determination of trace levels of the nerve agent biomarkers ethyl methylphosphonic acid (EMPA), isopropyl methylphosphonic acid (IMPA) and cyclohexyl methylphosphonic acid (CMPA) in urine. The new technique involves a unique combination of two solid phase extraction (SPE) cartridges: a Ba/Ag/H cartridge for urine interference removal, and a ZrO₂ cartridge for selective reconstitution and enrichment of the AMPAs. Extraction of AMPAs from the ZrO₂ cartridge was accomplished with a 1% ammonium hydroxide (NH₄OH) solution and was followed by analysis via liquid chromatography-mass spectrometry (LC-MS). The limits of quantitation (LOQs) were in the range of 10-100 pg/mL with recoveries of 64-71% (± 5-19%) after fast sample preparation and a total LC-MS analysis cycle time of 15 min and 13 min, respectively. This method was successfully applied in vivo in a rabbit that was exposed to 0.5 LD₅₀ (7.5 µg/kg, i.v.) sarin for retrospective monitoring of the IMPA metabolite in urine. For the first time, IMPA was determined in rabbit urine samples for 15 days post-exposure, which is longer than any reported post-exposure method for AMPAs. To the best of our knowledge, this new method is the most sensitive and rapid for AMPA determination in urine by LC-MS/MS analysis.

Sampling and analyses of surfaces contaminated with chemical warfare agents by using a newly developed triple layered composite wipe

A three-layered composite wipe was fabricated by laminating individual layers of non-woven polypropylene, activated carbon fabric (ACF) and aramid fabric for the sampling and investigation of chemical warfare agents (CWA)-contaminated urban porous and non-porous surfaces. The material of main ACF layer was characterized to ascertain its suitability to act as an efficient adsorbent for the surface wipe sampling. The performance of ACF-based composite wipe was determined by evaluating its extraction efficiency, wiping efficacy and adsorption capacity for the sampling of blister and nerve agent class of CWA-contaminated surfaces using gas chromatography-mass spectrometry (GC-MS). Parameters like amount of wipe required, solvent selection, amount of solvent, time of extraction etc. were optimized to achieve the maximum recovery of contaminating analytes required for the forensic investigations. Overall recoveries of contaminating analytes after sampling and extraction were found to be in the range of 45-85% for all types of surfaces. No breakthrough in wiping process was noticed up to contamination density (CD) 1.6 mg/cm² for non-porous surface and 3.2 mg/cm² for porous surfaces. ACF-based wipe was found capable to significantly reduce the vapour hazards from liquid sulphur mustard (HD) and sarin (GB). Contamination from surfaces could be preserved within the wipe up to 15 days for the extended forensic investigation purposes. Limit of detections (LOD) of contaminants was determined in the range of 0.8-6.8 ng/cm² while limit of quantitation (LOQ) was achieved up to the range of 2.4-14.4 ng/cm² for wipe sampling of different surfaces. Graphical abstract.

Sensitive quantitative analysis of phosphorylated primary metabolites using selective metal oxide enrichment and GC- and IC- MS/MS

In this study, we present a novel selective cleanup/enrichment method based on metal oxide solid phase extraction combined with quantitative gas chromatography-tandem mass spectrometry and ion exchange chromatography-tandem mass spectrometry for the analysis of phosphorylated metabolites in yeast cell extracts relevant to biotechnological processes. Following screening of several commercially available metal oxide-based enrichment materials, all steps of the enrichment process (loading, washing and elution) were optimized for both the selective enrichment of 12 phosphorylated compounds from the glycolysis and pentose phosphate pathways, and the simultaneous removal of highly abundant matrix components such as organic acids and sugars. The full analytical workflow was then validated to meet the demands of accurate quantification of phosphorylated metabolites in yeast (Pichia pastoris) cell extracts using the best performing material and cleanup/enrichment method combined with quantification strategies based on internal standardization with isotopically labeled internal standards and external calibration. A good recovery (>70%) for 5 of the 12 targeted phosphorylated compounds with RSDs of less than 6.0% was obtained while many sugars, organic acids and amino acids were removed (>99% of glucose, and >95% of aspartate, succinate, glutamate, alanine, glycine, serine, threonine, proline, and valine). The use of isotopically labeled internal standards added to the samples prior to SPE, enables accurate quantification of the metabolites as it compensates for errors introduced during sample pretreatment and GC-MS or LC-MS analysis. To the best of our knowledge, this is the first time an effective and selective metal oxide-based affinity chromatography cleanup/enrichment method was designed and applied successfully for intracellular phosphorylated metabolites.

Single vial sample preparation of markers of nerve agents by dispersive solid-phase extraction using magnetic strong anion exchange resins

A sample preparation method involving extraction, enrichment and derivatization of acidic degradation products of nerve agents was developed using magnetic strong anion exchange resins (MSAX). The method was performed in a single vial involving magnetic dispersive solid phase extraction (MDSPE). Analytes were derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) in the presence of resins. MSAX were custom synthesized using Fe3O4 nanoparticles as core, 4-vinylpyridine-co-divinylbenzene as polymer shell and quaternary pyridinium function as anion-exchanger. Hydroxide ions were the counter-anions of MSAX to effectively capture the acidic alkyl alkylphosphonic acids (AAPAs) and alkylphosphonic acids (APAs). Quantitative measurements of analytes were performed in the selected ion monitoring mode of GC-MS. Full scan mode of analysis was followed for identifications. Under the optimized conditions analytes were recovered in the range of 39.7-98.8% (n=3, relative standard deviations (RSD) from 0.3 to 6.5%). Limits of detection (LODs) were in the range of 0.1-1.1ngmL(-1); and the linear dynamic range was 5-1000ngmL(-1) with r(2) of 0.9977-0.9769. Applicability of the method was tested with rain-, tap-, muddy-water and Organization for Prohibition of Chemical Weapons (OPCW) Proficiency Test samples.

Quantitation of five organophosphorus nerve agent metabolites in serum using hydrophilic interaction liquid chromatography and tandem mass spectrometry

Although nerve agent use is prohibited, concerns remain for human exposure to nerve agents during decommissioning, research, and warfare. Exposure can be detected through the analysis of hydrolysis products in urine as well as blood. An analytical method to detect exposure to five nerve agents, including VX, VR (Russian VX), GB (sarin), GD (soman), and GF (cyclosarin), through the analysis of the hydrolysis products, which are the primary metabolites, in serum has been developed and characterized. This method uses solid-phase extraction coupled with high-performance liquid chromatography for separation and isotopic dilution tandem mass spectrometry for detection. An uncommon buffer of ammonium fluoride was used to enhance ionization and improve sensitivity when coupled with hydrophilic interaction liquid chromatography resulting in detection limits from 0.3 to 0.5 ng/mL. The assessment of two quality control samples demonstrated high accuracy (101-105%) and high precision (5-8%) for the detection of these five nerve agent hydrolysis products in serum.

Exploration of interactions between membrane proteins embedded in supported lipid bilayers and their antibodies by reflectometric interference spectroscopy-based sensing

A microfluidic reflectometric interference spectroscopy (RIfS)-based sensor was fabricated to investigate the activity of multidrug resistance-associated protein 1 (MRP1), applied as a model membrane protein.

Recent advances in bioanalytical sample preparation for LC-MS analysis

Sample preparation has historically been, and continues to be, the most challenging part of the bioanalytical workflow. Several techniques have been developed over the years to deal with the problems of recovery and matrix effects in an effort to increase the reliability and robustness of the bioanalytical method. In recent years certain techniques have come into prominence and gained acceptance in routine sample preparation, and some have shown promise in their use in a discovery environment where speed is critical and method development time is often limited. The aim of this review is to examine several of these techniques and provide examples of their use from the literature, as well as comment on their utility in current workflows.