Adductomics: a promising tool for the verification of chemical warfare agents’ exposures in biological samples

Glutathione conjugation of sesquimustard: in vitro investigation of potential biomarkers

Sesquimustard (Q) is a powerful blistering agent that contains additional sulfur atoms. Sulfur mustard causes covalent bonding by alkylating nucleophilic groups of biologically important macromolecules such as lipids, proteins, DNA, or RNA. Most cells maintain relatively high amounts of a unique tripeptide called glutathione (GSH) (γ-glutamyl-cysteinyl glycine), which possesses a free thiol group, to prevent unwanted reactions caused by reactive chemical entities. Moreover, these thiol groups on cysteines (Cys) are the main target for alkylation. Although Q is the most potent vesicant among sulfur mustards, research studies identifying biomarkers of Q are very limited. Therefore, here in this study, we aimed to identify the GSH and Cys conjugates of Q using mass spectrometric methods and to observe the formation of these conjugates in HaCat cell culture following exposure to different doses. We identified four different conjugates of Q, which are bis-glutathionyl ethylthioethylthioethyl conjugate (GSH-ETETE-GSH), hydroxyethylthioethylthioethyl glutathione conjugate (HETETE-GSH), bis-cysteinyl ethylthioethylthioethyl conjugate (Cys-ETETE-Cys), and hydroxyethylthioethylthioethyl cysteine conjugate (HETETE-Cys). The identity of the conjugates was elucidated using liquid chromatography-high-resolution mass spectrometry (LC-HRMS). We also investigated changes in conjugate formation with exposure concentration and time elapsed after exposure in the cell culture. After exposure, GSH conjugates decreased until 1st hour, while Cys conjugates increased until 6th hour. We also observed that conjugate formation depended on the concentration of Q. This is the first study to elucidate the conjugates of Q dependent on GSH conjugation. As biomarkers are essential tools for evaluating exposure to Q, this study contributes to the limited number of studies identifying biomarkers for Q.

Study on phosphonylation and modification characteristics of organophosphorus nerve agents on multi-species and multi-source albumins

Protein adducts are vital targets for exploring organophosphorus nerve agents (OPNAs) exposure and identification, that can be used to characterize the chemical burden and initiate chemical safety measures. However, the use of protein adducts as biomarkers of OPNA exposure has developed slowly. To further promote the development of biomarkers in chemical forensics, it is crucial to expand the range of modified peptides and active sites, and describe the characteristics of OPNA adducts at specific reaction sites. This study utilized multi-species and multi-source albumins as the protein targets. We identified 56 peptides in albumins from various species (including human, horse, rat and pig), that were modified by at least two OPNAs. Diverse modification characteristics were observed in response to certain agents: including (1) multiple sites on the same peptide modified by one or more agents, (2) different reactivities at the same site in homologous albumins, and (3) different preferences at the same active sites associated with differences in the biological matrix during exposure. Our studies provided an empirical reference with rationalized underpinnings supported by estimated conformation energetics through molecular modeling. We employed different peptide markers for detection of protein adducts, as (one would do) in forensic screening for identification and quantification of chemical damage. Three characteristic peptides were screened and analyzed in human albumin, including Y287ICENQDSISSK, K438VPQVS443TPTLVEVSR, and Y162LY164EIAR. Stable fragment ions with neutral loss were found from their tandem MS/MS spectra, which were used as characteristic ions for identification and extraction of modified peptides in enzymatic digestion mixtures. Coupling these observations with computer simulations, we found that the structural stability of albumin and albumin-adduct complexes (as well as the effective force that promotes stability of different adducts) changes in the interval before and after adduct formation. In pig albumin, five active peptides existed stably in vivo and in vitro. Most of them can be detected within 30 min after OPNA exposure, and the detection window can persist about half a month. These early findings provided the foundation and rationale for utilizing pig albumin as a sampling target for rapid analysis in future forensic work.

Progressive expansion of albumin adducts for organophosphorus nerve agent traceability based on single and group adduct collection

Protein adducts are important biological targets for traceability of organophosphorus nerve agents (OPNAs). Currently, the recognized biomarkers that can be used in actual samples in the field of chemical forensics only include Y411 in albumin and the active nonapeptide in butyrylcholinesterase (BChE). To explore stable and reliable protein adducts and increase the accuracy of OPNAs traceability further, we gradually expanded OPNAs-albumin adducts based on single and group adduct collection. Several stable peptides were found via LC-MS/MS analysis in human serum albumin (HSA) exposed to OPNAs in a large exposure range. These adducts were present in HSA samples exposed to OPNAs of each concentration, which provided data support for the reliability and stability of using adducts to trace OPNAs. Meanwhile, the formation mechanism of OPNAs-cysteine adduct was clarified via computer simulations. Then, these active sites found and modified peptides were used as raw materials for progressive expansion of albumin adducts. We constructed an OPNAs-HSA adducts group, in which a specific agent is the exposure source, and three or more active peptides constitute data sets for OPNAs traceability. Compared with single or scattered protein adducts, the OPNAs-HSA adduct group improves OPNAs identification by mutual verification using active peptides or by narrowing the identity range of the exposure source. We also determined the minimum detectable concentration of OPNAs for the adduct group. Two or more peptides can be detected when there is an exposure of 50 times the molar excess of OPNAs in relation to HSA. This improved the accuracy of OPNAs exposure and identity confirmation. A collection of OPNAs-albumin adducts was also examined. The collection was established by collecting, classifying, and integrating the existing albumin adducts according to the species to which each albumin belongs, the types of agents, and protease. This method can serve as a reference for discovering new albumin adducts, characteristic phosphonylated peptides, and potential biomarkers. In addition, to avoid a false negative for OPNAs traceability using albumin adducts, we explored OPNAs-cholinesterase adducts because cholinesterase is more reactive with OPNAs than albumin. Seven active peptides in red blood cell acetylcholinesterase (RBC AChE) and serum BChE can assist in OPNAs exposure and identity confirmation.

Monitoring Exposure to Five Chemical Warfare Agents Using the Dried Urine Spot Technique and Liquid Chromatography-Mass Spectrometry/Mass Spectrometry-In Vivo Determination of Sarin Metabolite in Mice

Dried urine spot (DUS) is a micro-sample collection technique, known for its advantages in handling, storage and shipping. It also uses only a small volume of urine, an essential consideration in working with small animals, or in acute medical situations. Alkyl-phosphonic acids are the direct and indicative metabolites of organophosphorus chemical warfare agents (OP-CWAs) and are present in blood and urine shortly after exposure. They are therefore crucially important for monitoring casualties in war and terror scenarios. We report here a new approach for the determination of the metabolites of five CWAs in urine using DUS. The method is based on a simple and rapid sample preparation, using only 50 µL of urine, spotted and dried on DBS paper, extracted using 300 µL methanol/water and analyzed via targeted LC-MS/MS. The detection limits for the five CWAs, sarin (GB), soman (GD), cyclosarin (GF), VX and RVX in human urine were from 0.5 to 5 ng/mL. Recoveries of (40-80%) were obtained in the range of 10-300 ng/mL, with a linear response (R2 > 0.964, R > 0.982). The method is highly stable, even with DUS samples stored up to 5 months at room temperature before analysis. It was implemented in a sarin in vivo exposure experiment on mice, applied for the time course determination of isopropyl methylphosphonic acid (IMPA, sarin hydrolysis product) in mice urine. IMPA was detectable even with samples drawn 60 h after the mice's (IN) exposure to 1 LD50 sarin. This method was also evaluated in a non-targeted screening for multiple potential CWA analogs (LC-Orbitrap HRMS analysis followed by automatic peak detection and library searches). The method developed here is applicable for rapid CWA casualty monitoring.

What do we currently know about Novichoks? The state of the art

Novichok is the name given to the group of nerve agents created stealthily in the later phases of the Cold War by the Soviet Union. Constitute the fourth generation of chemical warfare agents; like other nerve agents, they are organophosphorus compounds designed to be incurable and undetectable. The mechanism of action is based on the non-competitive and irreversible inhibition of acetylcholinesterase. Due to their enormous toxicity, Novichoks have become attractive targets for terrorists. However, little information is known about the identity of nerve agents. Furthermore, these compounds have never been submitted to the Chemical Weapons Convention. Our article aspires to provide a general overview of Novichoks knowledge. As part of this, we reviewed the available literature data to answer the question, what are Novichoks? In addition to the physical and chemical properties of A-agents, synthesis, mechanism of action, and toxicity of nerve agents were also reviewed. We hope that this review will highlight the tremendous threat posed by nerve agents and will inspire further studies on the interdisciplinary aspects of these compounds.

Current Progress for Retrospective Identification of Nerve Agent Biomarkers in Biological Samples after Exposure

Organophosphorus neurotoxic agents (OPNAs) seriously damage the nervous system, inhibiting AChE activity and threatening human health and life. Timely and accurate detection of biomarkers in biomedical samples is an important means for identifying OPNA exposure, helping to recognize and clarify its characteristics and providing unambiguous forensic evidence for retrospective research. It is therefore necessary to summarize the varieties of biomarkers, recognize their various characteristics, and understand the principal research methods for these biomarkers in the retrospective detection of OPNA exposure. Common biomarkers include mainly intact agents, degradation products and protein adducts. Direct agent identification in basic experimental research was successfully applied to the detection of free OPNAs, however, this method is not applicable to actual biomedical samples because the high reactivity of OPNAs promotes rapid metabolism. Stepwise degradation products are important targets for retrospective research and are usually analyzed using a GC–MS, or an LC–MS system after derivatization. The smaller window of detection time requires that sampling be accomplished within 48 h, increasing the obstacles to determining OPNA exposure. For this reason, the focus of retrospective identification of OPNA exposure has shifted to protein adducts with a longer lifetime. Compared to the fluoride-induced reactivation method, which cannot be used for aged adducts, digestive peptide analysis is the more elegant method for detecting various adducts, identifying more active sites, exploring potential biomarkers and excavating characteristic ions. Retrospective identification of biomarkers after OPNA poisoning is of primary importance, providing unambiguous evidence for forensic analysis in actual cases and judgment of chemical accidents. At present, degradation products, the nonapeptide from BChE adducts and Y411 from human serum adducts are used successfully in actual cases of OPNA exposure. However, more potential biomarkers are still in the discovery stage, which may prove inconclusive. Therefore, there is an urgent need for research that screens biomarker candidates with high reactivity and good reliability from the potential candidates. In addition, mass spectrometry detection with high resolution and reactivity and an accurate data processing system in the scanning mode must also be further improved for the retrospective identification of unknown agents.

Retrospective detection for V-type OPNAs exposure via phosphonylation and disulfide adducts in albumin

Organophosphorus nerve agents (OPNAs) that damage the central nervous system by inhibiting acetylcholinesterase activity, pose severe threats to human health and life security. Reliable biomarkers that quickly and accurately detect OPNAs exposure are urgently needed to help diagnose quickly and treat in time. Albumins that covalently bind to OPNAs could serve as important targets for retrospective verification of OPNAs exposure. The goal of this study is to explore the potential biomarkers in albumins with high reactivity and good stability and expand the group of potential biomarkers in different species for detecting the exposure of V-type OPNAs including O-ethyl S-(2-(diisopropylamino)ethyl) methylphosphonothioate (VX), O-isobutyl S-(2(diethylamino)ethyl) methylphosphonothioate (VR), and O-butyl S-(2-(diethylamino)ethyl) methylphosphonothioate (Vs). Taking human serum albumin (HSA), bovine serum albumin (BSA) and rabbit serum albumin (RSA) as the research objectives, multiple active sites including phosphonylation and disulfide adduct sites were observed in albumins from different species. Numerous phosphonylation sites labeled by all agents in one type of albumin were found. Among the different species, four shared phosphonylation sites with high reactivity include K499, K549, K249, and Y108. In addition, Y108 on ETY*GEMADCCAK, Y287 on Y*ICENQDSISSK, Y377 on TY*ETTLEK and Y164 on YLY*EIAR in HSA were stably phosphonylated by all agents in gradient concentration, making them stable and suitable potential biomarkers for V-type OPNAs exposure. Notably, Y108 on ETY*GEMADCCAK in HSA, on DTY*GDVADCCEK in RSA, and on ETY*GDMADCCEK in BSA were highly reactive to all V-type agents, regardless of species. It was also successfully labeled in HSA exposed to class V agents in gradient concentration. Y108 is expected to be used to screen and identify the exposure of V-type agents in the retrospective research. Disulfide adducts sites, consisted of four sites in HSA and two sites in BSA were also successfully labeled by V-type agents, and characteristic ion fragments from these disulfide adducts were also identified by secondary mass spectrometry. Molecular simulation of the stably modified sites were conducted to discover the promoting factors of covalent adduct formation, which help further clarify formation mechanism of albumin adducts at active sites.

Chemical forensic profiling and attribution signature determination of sarin nerve agent using GC-MS, LC-MS and NMR

Sarin is a highly toxic nerve agent classified by the Chemical Weapon Convention as a Schedule 1 chemical with no use other than to kill or injure. Moreover, in recent times, chemical warfare agents have been deployed against both military and civilian populations. Chemical warfare agents always contain minor impurities that can provide important chemical attribution signatures (CAS) that can aid in forensic investigations. In order to understand the trace molecular composition of sarin, various analytical approaches including GC-MS, LC-MS and NMR were used to determine the chemical markers of a set of sarin samples. Precursor materials were studied and the full characterisation of a synthetic process was undertaken in order to provide new insights into potential chemical attribution signatures for this agent. Several compounds that were identified in the precursor were also found in the sarin samples linking it to its method of preparation. The identification of these CAS contributes critical information about a synthetic route to sarin, and has potential for translation to related nerve agents.

Unambiguous identification and determination of A234-Novichok nerve agent biomarkers in biological fluids using GC-MS/MS and LC-MS/MS

The present study was intended to develop suitable methods for unambiguous identification and determination of ethyl (1-(diethylamino)ethylidene) phosphoramidofluoridate (known as A234-Novichok) biomarkers in urine and plasma samples. Multiple biomarkers were investigated for the first time, to verify intoxication by the A234-Novichok agent, using sensitive and accurate techniques including gas and liquid chromatography-tandem mass spectrometry (GC-MS/MS and LC-MS/MS). Like other nerve agents, in biological matrices, the A234-Novichok agent reacts with several proteins to form related adducts. Considering this, two different protein adduct biomarkers in blood samples were analyzed, and the regenerated A234 was determined. Two-dimensional chromatography and solid-phase extraction techniques were employed for blood sample preparation. Limits of detection for butyrylcholinesterase (BChE) adduct, the regenerated A234, and albumin covalent adduct were determined and reported as 1, 1, and 10 ng mL^-1, while the related calibration curves were linear within the range of 2-100, 2-100, and 15-100 ng mL^-1, respectively. The detection limit and linear range for the intact agent in the urine sample were determined as 0.1 and 1-100 ng mL^-1, respectively. Since A234 and some other Novichok chemicals have been added to the Schedule 1 of the Chemical Weapons Convention (CWC), Annex on Chemicals, after UK incidents, the analytical methods developed in this work might be used for verification purposes, as well as OPCW Biomedical Proficiency Tests.

Quo vadis blood protein adductomics?

Chemicals are measured regularly in air, food, the environment, and the workplace. Biomonitoring of chemicals in biological fluids is a tool to determine the individual exposure. Blood protein adducts of xenobiotics are a marker of both exposure and the biologically effective dose. Urinary metabolites and blood metabolites are short term exposure markers. Stable hemoglobin adducts are exposure markers of up to 120 days. Blood protein adducts are formed with many xenobiotics at different sites of the blood proteins. Newer methods apply the techniques developed in the field of proteomics. Larger adducted peptides with 20 amino acids are used for quantitation. Unfortunately, at present the methods do not reach the limits of detection obtained with the methods looking at single amino acid adducts or at chemically cleaved adducts. Therefore, to progress in the field new approaches are needed.

Scopes of Bioanalytical Chromatography–Mass Spectrometry

The areas of application of modern bioanalytical chromatography–mass spectrometry are so extensive that any attempt to systematize them becomes subjective. It would be more correct to say that there is no such area of biology and medicine where chromatography–mass spectrometry would not find application. This article focuses on the areas of application of this technique that are either relatively new or insufficiently covered in recent reviews. State-of-the-art bioanalytical techniques have become multitargeted in terms of analytes and standardized in terms of matrices. The ability to detect trace concentrations of analytes in the presence of a huge number of biomatrix macrocomponents using chromatography–mass spectrometry is especially important for bioanalytical chemistry. In the target-oriented determination of persistent organic pollutants by chromatography–mass spectrometry, the main problem is the expansion of the list of analytes, including isomers. In the detection of exposures to unstable toxicants, the fragmented adducts of xenobiotics with biomolecules become target biomarkers along with hydrolytic metabolites. The exposome reflects the general exposure of a human being to total xenobiotics and the metabolic status reflects the physiological state of the body. Chromatography–mass spectrometry is a key technique in metabolomics. Metabolomics is currently used to solve the problems of clinical diagnostics and anti-doping control. Biological sample preparation procedures for instrumental analysis are being simplified and developed toward increasing versatility. Proteomic technologies with the use of various versions of mass spectrometry have found application in the development of new methods for diagnosing coronavirus infections.

Applications of Adductomics in Chemically Induced Adverse Outcomes and Major Emphasis on DNA Adductomics: A Pathbreaking Tool in Biomedical Research

Adductomics novel and emerging discipline in the toxicological research emphasizes on adducts formed by reactive chemical agents with biological molecules in living organisms. Development in analytical methods propelled the application and utility of adductomics in interdisciplinary sciences. This review endeavors to add a new dimension where comprehensive insights into diverse applications of adductomics in addressing some of society's pressing challenges are provided. Also focuses on diverse applications of adductomics include: forecasting risk of chronic diseases triggered by reactive agents and predicting carcinogenesis induced by tobacco smoking; assessing chemical agents' toxicity and supplementing genotoxicity studies; designing personalized medication and precision treatment in cancer chemotherapy; appraising environmental quality or extent of pollution using biological systems; crafting tools and techniques for diagnosis of diseases and detecting food contaminants; furnishing exposure profile of the individual to electrophiles; and assisting regulatory agencies in risk assessment of reactive chemical agents. Characterizing adducts that are present in extremely low concentrations is an exigent task and more over absence of dedicated database to identify adducts is further exacerbating the problem of adduct diagnosis. In addition, there is scope of improvement in sample preparation methods and data processing software and algorithms for accurate assessment of adducts.

Advances in sulfur mustard-induced DNA adducts: Characterization and detection

Sulfur mustard (SM) is a blister chemical warfare agent with severe cytotoxicity and genotoxicity. It can extensively alkylate important macromolecules in organisms, such as proteins, DNA, and lipids, and produce a series of metabolites, among which the characteristic ones can be used as biomarkers. The exact toxicological mechanisms of SM remain unclear but mainly involve the DNA lesions induced by alkylation and oxidative stress caused by glutathione depletion. Various methods have been used to analyze DNA damage caused by SM. Among these methods, liquid chromatography-tandem mass spectrometry (LC-MS/MS) technology stands out and makes it possible to observe damage in view of biomarkers induced by SM. Sample preparation is critical for detection by LC-MS/MS and mainly includes DNA isolation, adduct hydrolysis, and adduct purification. Moreover, optimization of chromatographic conditions, selection of MS transitions, and quantitative strategies are also essential. SM-DNA adducts are generally considered to be N⁷-HETEG, O⁶-HETEG, N⁷-BisG, and N³-HETEA. This article proposes some other possibilities of SM-DNA adducts for the identification of SM genotoxicity.

Gas chromatography-tandem mass spectrometry-based detection of half nitrogen mustards in plasma as a new biomarker of nitrogen mustard exposure

The development and optimization of an analytical method for the detection and identification of reactive metabolite of organochlorine chemical warfare agent nitrogen mustards (NMs), 2-[(2-chloroethyl)(alkyl)amino]ethanol (CEAAE), known as half nitrogen mustard, in blood samples is presented, herein. In this study, half nitrogen mustards in plasma are presented as a new and unambiguous biomarker of NM exposure since the fully hydrolyzed product, i.e., amino alcohols, are common industrial chemicals that can be present as such without getting exposed to NMs. Thus, the detection of half nitrogen mustard as a biomarker holds great significance for verification by the Chemical Weapon Convention (CWC) and will also be helpful in understanding the pharmacokinetics of NM-based chemotherapeutic pro-drugs. To the best of our knowledge, this is the first report on the detection of half nitrogen mustards in any matrice, including plasma. A very simple sample preparation protocol was developed for its extraction from plasma samples. Heptafluorobutyrylation and gas chromatography-tandem mass spectrometry in the positive chemical ionization mode were developed for the detection and identification of halfNMs. The developed method has shown excellent analytical figures of merits such as a wide range of linearity (1.0-50 ng mL^-1), low limit of detection (0.3-0.5 ng mL^-1), and low limit of quantification (1.0 ng mL^-1). The interday and intraday reproducibilities were also less than 15%. The developed method was successfully applied to real-world samples; in vitro human plasma was spiked with ∼1 ng mL^-1 of all the NMs and in vivo studies were done with rats intravenously exposed to 1 × LD₅₀ of bis(2-chloroethyl)methylamine (HN2).

Quantitative Proteomic Changes after Organophosphorous Nerve Agent Exposure in the Rat Hippocampus

The widespread use of organophosphorous (OP) compounds and recent misuse of nerve agents on civilians requires an urgent need to decode their complex biological response to develop effective drugs. Proteomic profiling of biological target tissues helps in identification of molecular toxicity mechanisms. Quantitative proteomics profiling of the rat hippocampus was studied in this study. Liquid chromatography mass spectrometry (LC-MS) analysis of tandem mass tag (TMT)-labeled lysates identified 6356 proteins. A total of 69, 61, and 77 proteins were upregulated, and 66, 35, and 70 proteins were downregulated at 30 min, 1 day, and 7 days after soman exposure. This is the first report on the soman-induced proteomic changes to the best of our knowledge. Bioinformatics analysis revealed soman-induced broad-range proteomic changes in key pathways related to glutamate, acetylcholine, GABA, 5-hydroxytryptamine, and adrenergic receptors, G-protein signaling, chemokine and cytokine-mediated inflammation, cytoskeleton, neurodegeneration (Parkinson's and Alzheimer's), Wnt signaling, synaptic vesicle trafficking, MAP kinases, proteosome degradation, metabolism, and cell death. Selected protein changes were verified by immunoblotting, and neuropathological findings indicated significant brain damage. Results demonstrate that persistent proteomic changes in the brain can cause multiple neurological effects through cholinergic and non-cholinergic pathways, and these mechanistic insights are useful in the development of novel drugs.

Mass spectral fragmentation of perfluoroacyl derivatives of half nitrogen mustards for their detection by gas chromatography/mass spectrometry

RATIONALE

Analytical methods for the detection and identification of half nitrogen mustards (halfNMs), i.e., partially hydrolyzed products of nitrogen mustards (pHpNMs), using silyl derivatives are often associated with low sensitivity and selectivity. In order to overcome these limitations, the derivatization of halfNMs was performed using perfluoroacylation.

METHODS

Two efficient derivatization techniques using trifluoroacetyl (TFA) and heptafluorobutyryl (HFB) groups were developed for the unambiguous identification of halfNMs. A mass spectral database was generated by performing gas chromatography/electron ionization mass spectrometry (GC/EI-MS) and gas chromatography/positive chemical ionization mass spectrometry (GC/PCI-MS). The fragmentation pathways were studied by tandem mass spectrometry (MS/MS) in both EI and PCI mode.

RESULTS

The EI-MS spectra of the TFA and HFB derivatives of halfNMs contain intense molecular ions and fragment ions, thus making perfluoroacylation preferable to silylation. In addition, the background-free chromatogram obtained using these derivatives provides unambiguous identification of these compounds in blind samples. The structures of the fragment ions were postulated, and the sources of significant ions were traced by performing MS/MS precursor ion scans. In the PCI-MS spectra, along with the protonated molecule, significant peaks due to neutral losses of HF, HCl, CH₃ Cl and CF₃ COOH were observed.

CONCLUSIONS

This is the first report of the elucidation of the fragmentation pathways of perfluoroacyl derivatives of halfNMs. The complementary GC/PCI-MS and GC/PCI-MS/MS data will be helpful in the identification of unknown metabolites in a fast and reliable fashion.

Mass spectral studies of silyl derivatives of partially hydrolyzed products of nitrogen mustards: Important markers of nitrogen mustard exposure

RATIONALE

Nitrogen mustards (NMs) are vesicant class of chemical warfare agents. From the viewpoint of the Chemical Weapons Convention partially hydrolyzed products of nitrogen mustards (pHpNMs) are considered as important markers of nitrogen mustard exposure. The detection of pHpNMs from biological or environmental samples is highly useful for obtaining forensic evidence of exposure to NMs.

METHODS

Gas chromatography interfaced with tandem mass spectrometry (GC/MS/MS) is a widely used tool for the identification and sensitive detection of metabolites of NMs in complex matrices. The pHpNMs were derivatized using silylating agents as they are highly polar and non-amenable to GC. The mass spectral studies of these silyl derivatives of pHpNMs were performed using GC/MS/MS in both electron ionization (EI) and chemical ionization (CI) mode.

RESULTS

Various approaches have been proposed to assess the fragmentation pathways of the trimethylsilyl (TMS) and tert-butyldimethylsilyl (TBDMS) derivatives of pHpNMs. All the proposed fragmentation pathways were based on the product and/or precursor ion scanning of corresponding ions in both EI and CI mode. In the case of EI, most of the fragmentation pathways involved either α-cleavage or inductive cleavage.

CONCLUSIONS

This is the first report on the MS study of the silyl derivatives of pHpNMs. The study of the two different derivatives of pHpNMs using both EI- and CI-MS provides a reliable, unambiguous identification of pHpNMs in complex environmental and biomedical matrices (such as plasma and urine) during any verification activities.