Analysis of the Sulfur Mustard Metabolite 1,1′-Sulfonylbis[2-S-(N-acetylcysteinyl)ethane] in Urine by Negative Ion Electrospray Liquid Chromatography-Tandem Mass Spectrometry

Novel analytical approaches to determination of chemical warfare agents and related compounds for verification of nonproliferation of chemical weapons

In this paper a summary of the author’s approaches for investigation of the mass spectral behavior of some chemical warfare agents (CWAs), their degradation products and metabolites, as well as the results of development of analytical methods for confirmation of nerve and blister agents application are presented. Hydrolysis and oxidation metabolites of nerve agents, sulfur mustard and lewisite were used as biomarkers of the exposure. Sensitive analytical methods have been developed for their detection, based mainly on tandem mass spectrometry coupled with liquid chromatography. Several techniques for fast screening of CWAs degradation products based on capillary electrophoresis were also proposed. Some of developed approaches were successfully applied in the frame of the proficiency testing system of the Organization for the Prohibition of Chemical Weapons.

Solid-Phase Extraction of Sulfur Mustard Metabolites Using an Activated Carbon Fiber Sorbent

A novel solid-phase extraction method using activated carbon fiber (ACF) was developed and validated. ACF has a vast network of pores of varying sizes and microporous structures that result in rapid adsorption and selective extraction of sulfur mustard metabolites according to the pH of eluting solvents. ACF could not only selectively extract thiodiglycol and 1-methylsulfinyl-2-[2-(methylthio)-ethylsulfonyl]ethane eluting a 9:1 ratio of dichloromethane to acetone, and 1,1'-sulfonylbis[2-(methylsulfinyl)ethane] and 1,1'-sulfonylbis- [2-S-(N-acetylcysteinyl)ethane] eluting 3% hydrogen chloride in methanol, but could also eliminate most interference without loss of analytes during the loading and washing steps. A sample preparation method has been optimized for the extraction of sulfur mustard metabolites from human urine using an ACF sorbent. The newly developed extraction method was applied to the trace analysis of metabolites of sulfur mustard in human urine matrices in a confidence-building exercise for the analysis of biomedical samples provided by the Organisation for the Prohibition of Chemical Weapons.

Applying human and pig hepatic in vitro experiments for sulfur mustard study: screening and identification of metabolites by liquid chromatography/tandem mass spectrometry

RATIONALE

Sulfur mustard is a chemical warfare agent (CWA) with high toxicity and complex metabolism. This study aimed at identification of new metabolic biomarkers for sulfur mustard using in in vitro exposures and various mass spectrometric techniques.

METHODS

Human and pig liver subcellular fractions were used as biocatalysts. Metabolites were screened by liquid chromatography and tandem mass spectrometry (LC/MS/MS) using positive electrospray ionization (ESI). For structural identification, product ion scans (MS/MS, MS(3) ) and accurate mass measurements using liquid chromatography/time-of-flight mass spectrometry (LC/TOFMS) were acquired.

RESULTS

Sulfur mustard is metabolized in vitro by S-oxidation and glutathione (GSH) conjugations. One S-oxidized metabolite, bis(2-chloroethyl) sulfoxide (m/z 175), was formed in both species only when liver microsomes were present in incubations, and it was the main metabolite if GSH was not added into the reaction mixture. However, conjugation with GSH was found to be a spontaneous reaction in physiological pH and buffered solution. Three GSH conjugates of sulfur mustard were detected and identified, among which two were novel; 2-((2-(S-glutathionyl)ethyl)thio)ethanol (m/z 412) and 2-((2-(S-glutathionyl)ethyl)thio)ethyl phosphate (m/z 492).

CONCLUSIONS

To our knowledge, this was the first time that S-oxidized metabolites and GSH conjugates of sulfur mustard have been detected and identified from human samples in vitro by LC/MS/MS. The usefulness of the GSH conjugates to serve as biomarkers for sulfur mustard exposure in human samples requires further studies.

Detection and identification of alkylphosphonic acids by positive electrospray ionization tandem mass spectrometry using a tricationic reagent

The retrospective detection and identification of degradation products of chemical warfare agents are of immense importance in order to prove their spillage and use. A highly sensitive liquid chromatography/electrospray ionization tandem mass spectrometric (LC/ESI-MS/MS) method--using an imidazolium-based tricationic reagent--was developed for the detection and identification of the anionic degradation products of nerve agents. A commercially available solution of 1,3-imidazolium-bis-(1-hexylbenzylimidazolium) trifluoride (IBHBI) formed adducts with alkylphosphonic acids (APAs), allowing detection of the APAs by positive mode ESI-MS. Tandem mass spectrometry was used for the unambiguous identification of the APAs. Parameters influencing the formation and stability of these adduct during mass spectrometric analysis, such as solvent composition, concentration of IBHBI, effect of pH and interferences by salts, were optimized. The absolute limits of detection (0.1 ng) for achieved for the APAs were better than those previously reported, and linear dynamic ranges of 10-2000 ng mL(-1) were achieved. The method was repeatable with a relative standard deviation ≤7.3%. APAs present in aqueous samples provided by the Organization for the Prohibition of Chemical Weapons during the 22(nd) and 24(th) Official Proficiency tests were detected and identified as IBHBI adducts. The added advantage of this method is that low-mass analytes are detected at higher mass, thus obviating the problem with background noise at low mass.

Analysis of Chemical Warfare Agents in Food Products by Atmospheric Pressure Ionization-High Field Asymmetric Waveform Ion Mobility Spectrometry-Mass Spectrometry

Flow injection high field asymmetric waveform ion mobility spectrometry (FAIMS)-mass spectrometry (MS) methodology was developed for the detection and identification of chemical warfare (CW) agents in spiked food products. The CW agents, soman (GD), sarin (GB), tabun (GA), cyclohexyl sarin (GF), and four hydrolysis products, ethylphosphonic acid (EPA), methylphosphonic acid (MPA), pinacolyl methylphosphonic acid (Pin MPA), and isopropyl methylphosphonic acid (IMPA) were separated and detected by positive ion and negative ion atmospheric pressure ionization-FAIMS-MS. Under optimized conditions, the compensation voltages were 7.2 V for GD, 8.0 V for GA, 7.2 V for GF, 7.6 V for GB, 18.2 V for EPA, 25.9 V for MPA, -1.9 V for PinMPA, and +6.8 V for IMPA. Sample preparation was kept to a minimum, resulting in analysis times of 3 min or less per sample. The developed methodology was evaluated by spiking bottled water, canola oil, cornmeal, and honey samples at low microgram per gram (or microg/mL) levels with the CW agents or CW agent hydrolysis products. The detection limits observed for the CW agents in the spiked food samples ranged from 3 to 15 ng/mL in bottled water, 1-33 ng/mL in canola oil, 1-34 ng/g in cornmeal, and 13-18 ng/g in honey. Detection limits were much higher for the CW agent hydrolysis products, with only MPA being detected in spiked honey samples.

Detection of sulfur mustard adducts in human callus by phage antibodies

As part of a research program to develop novel methods for diagnosis of sulfur mustard exposure in the human skin the suitability of phage display was explored. Phage display is a relative new method that enables researchers to quickly evaluate a huge range of potentially useful antibodies, thereby bypassing the more costly and time-consuming hybridoma technique. The Tomlinson I and J phage libraries were used to select phage antibodies exhibiting affinity for sulfur mustard adducts on keratins, isolated from human callus. Two kinds of phage antibodies were obtained: antibodies recognizing keratin and antibodies recognizing keratin which was exposed to sulfur mustard. These phage antibodies retained activity after repeated culturing and culturing in larger volumes. For the first time antibody phage display was successfully applied for immunodiagnostics of a chemical warfare agent.

Modern instrumental methods in forensic toxicology

This article reviews modern analytical instrumentation in forensic toxicology for identification and quantification of drugs and toxins in biological fluids and tissues. A brief description of the theory and inherent strengths and limitations of each methodology is included. The focus is on new technologies that address current analytical limitations. A goal of this review is to encourage innovations to improve our technological capabilities and to encourage use of these analytical techniques in forensic toxicology practice.

A sensitive method for quantitation of β-lyase metabolites of sulfur mustard as 1,1′-sulfonylbis[2-(methylthio)ethane] (SBMTE) in human urine by isotope dilution liquid chromatography–positive ion-electrospray-tandem mass spectrometry

A method for measurement of an important biological marker, 1,1'-sulfonylbis[2-(methylthio)ethane] (SBMTE) of sulfur mustard agent HD [bis-(2-chloroethyl)sulfide] in human urine, to quantify HD exposure, is presented. It employs TiCl3 reduction of beta-lyase metabolites to SBMTE, and automated solid-phase extraction sample preparation, followed by isotope dilution liquid chromatography-positive ion-electrospray ionization-tandem mass spectrometry with 7.5 min/sample cycle time, to achieve SBMTE quantitation of up to 200 samples/24h a day. Percent relative standard deviations over the calibration range varied from 12.0% at 0.1 ng/mL to 0.9% at 100 ng/mL, and the limit of detection from a 0.5 mL sample was below the lowest level calibration standard of 0.1 ng/mL.

Analysis of the sulphur mustard metabolites thiodiglycol and thiodiglycol sulphoxide in urine using isotope-dilution gas chromatography–ion trap tandem mass spectrometry

A sensitive method has been developed for the trace analysis of the sulphur mustard metabolite thiodiglycol (TDG) in urine, and its oxidation product thiodiglycol sulphoxide (TDGO) after reduction to thiodiglycol. Thiodiglycol was extracted from urine by solid phase extraction onto a polymeric cartridge and, after isolation, converted to its bis-heptafluorobutyryl derivative with heptafluorobutyryl imidazole. An ion trap mass spectrometer in selected reaction monitoring mode detected spiked concentrations down to 0.2 ng/ml with a signal to noise ratio>3:1. Urine, from human volunteers with no known exposure to sulphur mustard, contained detectable but very low concentrations (<0.2 ng/ml) of thiodiglycol, consistent with previous observations using different methodologies. Combined concentrations of thiodiglycol and thiodiglycol sulphoxide were determined after reduction of the latter with titanium trichloride. In this case higher background levels (up to 3 ng/ml) were observed, consistent with the sulphoxide being the major excretion product of the two metabolites. The method was applied to urine samples, stored frozen for 13 years, from two casualties of accidental mustard poisoning. Levels of thiodiglycol were 1 and 3 ng/ml, which increased to 78 and 104 ng/ml after treatment of the urine with titanium trichloride.

Exposure to a First World War blistering agent

Sulfur mustards act as vesicants and alkylating agents. They have been used as chemical warfare since 1917 during the first world war. This brief report illustrates the progression of injury on a primary exposed patient to a first world war blistering agent. This case documents the rapid timeline and progression of symptoms. It emphasises the importance of appropriate personal protective equipment and immediate medical response plan with rapid decontamination and proper action from military and civilian medical treatment facilities. This case reports the first US active duty military exposure to a blistering agent in the age of global terrorism.

Survey of albumin purification methods for the analysis of albumin-organic toxicant adducts by liquid chromatography-electrospray ionization-tandem mass spectrometry

HSA has been shown to react with many organic toxicants to form adducts that are useful biomarkers for exposure. Albumin isolation is an important first step for the analysis of these protein-toxicant adducts. We tested several approaches to isolate albumin from serum treated with an electrophilic organic toxicant known to form adducts with albumin, i.e., sulfur mustard agent (HD) (2,2'-dichloroethyl sulfide), in order to evaluate these techniques as purification methods. To select the most efficient isolation strategy, methods were evaluated using gel electrophoresis, total protein quantitation, and peptide-adduct identification by MS. Results suggest that the albumin-rich fractions obtained can be used to identify exposure by quantitating the albumin adducts to electrophilic organic toxicants such as HD. The HiTrap Blue HP albumin isolation system appears to display the most promising results for purifying albumin to detect HD-adducts, exhibiting high purification efficiency, satisfactory albumin recovery, promising specificity, and a higher loading capacity for serum.