Determination of dimethyl trisulfide in rabbit blood using stir bar sorptive extraction gas chromatography-mass spectrometry

[Determination of cyanogen chloride in organic and water matrices by gas chromatography-mass spectrometry based on thiol derivatization]

Cyanogen chloride (ClCN) has been widely used in industrial production. ClCN is also listed in the Schedule of the Chemical Weapons Convention (CWC). The use of traditional colorimetric analysis or gas chromatography for the detection of ClCN has been characterized by low efficiency and poor sensitivity. In this study, a method was established for the qualitative analysis and quantitative detection of ClCN in organic and water matrices by gas chromatography-mass spectrometry (GC-MS) based on thiol derivatization. 1-Butylthiol was selected as the optimal derivatization reagent. The optimal temperature for thiol derivatization in the organic matrices was 40 ℃ and the reaction time was 10 min. The pH for derivatization was approximately 9. The ClCN in the organic matrices was directly analyzed by GC-MS after derivatization. The conditions of ClCN derivatization in the water matrices were the same as those in the organic matrices. After the derivatization of ClCN, headspace-solid phase microextraction (HS-SPME) was employed during sample preparation for water matrices. Different temperatures for HS-SPME were explored, and the optimal temperature was found to be 55 ℃. The product of thiol derivatization was confirmed as butyl thiocyanate. The main fragmentation patterns and mass spectrometric cleavage pathway were investigated by GC-MS/MS. The quantitative determination of ClCN in organic and water matrices was conducted via the internal standard and external standard methods, respectively. ClCN showed good linearity in the corresponding ranges in the organic and water matrices. The correlation coefficients for both matrices were greater than 0.99. The linearities of ClCN in the organic and water matrices were in the range of 20-2000 μg/L and 20-1200 μg/L, respectively. An organic sample and water samples from different substrates were selected to verify the accuracy and precision of the method at three spiked levels. The average spiked recoveries of ClCN in the organic sample and water samples were 87.3%-98.8% and 97.6%-102.2%, respectively. The corresponding relative standard deviations (RSDs, n=6) were 2.1%-4.7% and 2.8%-4.2%. The derivatization method established in this study showed good reaction specificity. The method was successfully applied in the analysis of samples obtained from the Organisation for the Prohibition of Chemical Weapons (OPCW). The method established in this study for the detection of ClCN showed high sensitivity and precision, and could aid in the analysis and detection of ClCN in the environment.

Evaluation of aqueous dimethyl trisulfide as an antidote to a highly lethal cyanide poisoning in a large swine model

BACKGROUND

Cyanide is a rapid acting, lethal, metabolic poison and remains a significant threat. Current FDA-approved antidotes are not amenable or efficient enough for a mass casualty incident.

OBJECTIVE

The objective of this study is to evaluate short and long-term efficacy of intramuscular aqueous dimethyl trisulfide (DMTS) on survival and clinical outcomes in a swine model of cyanide exposure.

METHODS

Anesthetized swine were instrumented and acclimated until breathing spontaneously. Potassium cyanide infusion was initiated and continued until 5 min after the onset of apnea. Subsequently, animals were treated with intramuscular DMTS (n = 11) or saline control (n = 10). Laboratory values and DMTS blood concentrations were assessed at various time points and physiological parameters were monitored continuously until the end of the experiment unless death occurred. A subset of animals treated with DMTS (n = 5) were survived for 7 days to evaluate muscle integrity by repeat biopsy and neurobehavioral outcomes.

RESULTS

Physiological parameters and time to apnea were similar in both groups at baseline and at time of treatment. Survival in the DMTS-treated group was 90% and 30% in saline controls (p = 0.0034). DMTS-treated animals returned to breathing at 12.0 ± 10.4 min (mean ± SD) compared to 22.9 ± 7.0 min (mean ± SD) in the 3 surviving controls. Blood collected prior to euthanasia showed improved blood lactate concentrations in the DMTS treatment group; 5.47 ± 2.65 mmol/L vs. 9.39 ± 4.51 mmol/L (mean ± SD) in controls (p = 0.0310). Low concentrations of DMTS were detected in the blood, gradually increasing over time with no elimination phase observed. There was no mortality, histological evidence of muscle trauma, or observed adverse neurobehavioral outcomes, in DMTS-treated animals survived to 7 days.

CONCLUSION

Intramuscular administration of aqueous DMTS improves survival following cyanide poisoning with no observed long-term effects on muscle integrity at the injection site or adverse neurobehavioral outcomes.

Analysis of the Soil Fumigant, Dimethyl Disulfide, in Swine Blood by Dynamic Headspace Gas Chromatography-Mass Spectroscopy

Plant parasites and soilborne pathogens directly reduce the overall yield of crops, vegetables, and fruits, negatively impacting the market demand for these products and their net profitability. While preplant soil fumigation helps maintain the consistent production quality of high-value cash crops, most soil fumigants are toxic to off-target species, including humans. Dimethyl disulfide (DMDS) has recently been introduced as a relatively low toxicity soil fumigant. Although DMDS exhibits low toxicity compared to other soil fumigants, it is volatile and exposure can cause eye, nasal, and upper respiratory tract irritation, skin irritation, nausea, dizziness, headache, and fatigue. While there is one analysis method available for DMDS from biological matrices, it has significant disadvantages. Hence, in this study, a dynamic headspace gas chromatography-mass spectroscopy (DHS-GC-MS) method was developed for the analysis of DMDS in swine whole blood. This method is highly sensitive and requires only three steps: 1) acid denaturation, 2) addition of internal standard, and 3) DHS-GC-MS analysis. The method produced a wide linear range from 0.1 - 200 µM with an excellent limit of detection of 30 nM. Intra- and interassay accuracy (100±14% and 100±11%, respectively) and precision (<5% and <6% relative standard deviation, respectively) were also excellent. The method worked well to quantify the DMDS levels in the blood of dimethyl trisulfide (DMTS)-treated swine (i.e., DMDS is a byproduct of DMTS treatment) with no interfering substances at or around the retention time of DMDS (i.e., 2.7 min). This simple, rapid, and extremely sensitive method can be used for the quantification of DMDS levels in blood to verify exposure to DMDS or to monitor levels of DMDS following DMTS treatment (e.g., for cyanide poisoning).

Interpol review of toxicology 2016-2019

This review paper covers the forensic-relevant literature in toxicology from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20.Papers%202019.pdf.

Determination of free cyano-cobinamide in swine and rabbit plasma by liquid chromatography tandem mass spectrometry

In recent years, Cobinamide (Cbi) has shown promise as a therapeutic for cyanide poisoning. There are several forms of Cbi based on the identity of the ligands bound to the cobalt in Cbi and these different forms of Cbi have divergent behavior (e.g., the aquo and hydroxo forms of Cbi readily bind to proteins, limiting their distribution significantly, whereas [Cbi(CN)₂] does not). While current analysis techniques only measure total Cbi, methods to elucidate the behavior of 'available' Cbi versus cyanide-complexed Cbi would be valuable for biomedical and pharmacokinetic studies. Therefore, a method was developed for the analysis of cyanide-complexed Cbi in plasma via liquid chromatography tandem mass spectrometry (LC-MS-MS). Plasma samples were prepared by denaturing proteins with 10% ammonium hydroxide in acetonitrile. The resulting mixture was centrifuged, and the supernatant was removed, dried, and reconstituted. Cyanide-complexed Cbi was then analyzed via LC-MS-MS. The limit of detection was 0.2 μM, and the linear dynamic range was between 1 and 200 μM. The accuracy was 100 ± 17% and the precision, measured by relative standard deviation (%RSD), was ≤18.5%. Carryover, a severe problem when analyzing Cbi via liquid chromatography was eliminated using a polymeric-based stationary phase (PLRP-S) and a controlled washing protocol. The method allowed evaluation of the cyanide-bound and 'available' Cbi from treated animals and, when paired with a method for total Cbi analysis, allows for estimation of Cbi utilization when treating cyanide poisoning.

Intramuscular dimethyl trisulfide: efficacy in a large swine model of acute severe cyanide toxicity

BACKGROUND

Cyanide is a deadly compound used as a terrorist agent. Current FDA approved antidotes require intravenous administration, limiting their utility in a mass casualty scenario. Dimethyl trisulfide (DMTS), a sulfur-based molecule, binds cyanide converting it to the less toxic by-product thiocyanate. Studies evaluating efficacy in rodents have been performed, but a large, clinically relevant animal model has not been reported.

OBJECTIVE

This study evaluates the efficacy of intramuscular DMTS on survival and clinical outcomes in a swine model of acute, severe cyanide toxicity.

METHODS

Anesthetized swine were instrumented for continuous monitoring of hemodynamics. Prior to potassium cyanide infusion animals were acclimated and breathing spontaneously. At 5-minutes post-apnea animals were treated with DMTS or saline. Vital signs, hemodynamics, and laboratory values were evaluated at various time points.

RESULTS

Baseline values and time to apnea were similar in both groups. Survival in the DMTS treated group was 83.3% and 0% in saline controls (p = .005). The DMTS group returned to breathing at a mean time of 19.3 ± 10 min after antidote, control animals did not return to breathing (CI difference 8.8, 29.8). At the end of the experiment or time of death, mean lactate was 9.41 mmol/L vs. 4.35 mmol/L (CI difference -10.94,0.82) in the saline and DMTS groups, respectively and pH was 7.20 vs. 7.37 (CI difference -0.04, 0.38). No adverse effects were observed at the injection site.

CONCLUSION

Intramuscular administration of DMTS improves survival and clinical outcomes in our large animal swine model of acute cyanide toxicity.

Determination of methyl isopropyl hydantoin from rat erythrocytes by gas-chromatography mass-spectrometry to determine methyl isocyanate dose following inhalation exposure

Methyl isocyanate (MIC) is an important precursor for industrial synthesis, but it is highly toxic. MIC causes irritation and damage to the eyes, respiratory tract, and skin. While current treatment is limited to supportive care and counteracting symptoms, promising countermeasures are being evaluated. Our work focuses on understanding the inhalation toxicity of MIC to develop effective therapeutic interventions. However, in-vivo inhalation exposure studies are limited by challenges in estimating the actual respiratory dose, due to animal-to-animal variability in breathing rate, depth, etc. Therefore, a method was developed to estimate the inhaled MIC dose based on analysis of an N-terminal valine hemoglobin adduct. The method features a simple sample preparation scheme, including rapid isolation of hemoglobin, hydrolysis of the hemoglobin adduct with immediate conversion to methyl isopropyl hydantoin (MIH), rapid liquid-liquid extraction, and gas-chromatography mass-spectrometry analysis. The method produced a limit of detection of 0.05 mg MIH/kg RBC precipitate with a dynamic range from 0.05-25 mg MIH/kg. The precision, as measured by percent relative standard deviation, was <8.5%, and the accuracy was within 8% of the nominal concentration. The method was used to evaluate a potential correlation between MIH and MIC internal dose and proved promising. If successful, this method may be used to quantify the true internal dose of MIC from inhalation studies to help determine the effectiveness of MIC therapeutics.

Sealing Effects on the Storage Stability of the Cyanide Antidotal Candidate, Dimethyl Trisulfide

Background

Dimethyl trisulfide (DMTS) is a highly lipid-soluble cyanide (CN) antidote candidate molecule. In prior studies with various US FDA-approved co-solvents, surfactants, and their combinations, aqueous solutions containing 15% polysorbate 80 (Poly80) were found to effectively solubilize DMTS in formulations for intramuscular administration. However, DMTS formulated in 15% aqueous Poly80 solutions showed gradual losses over time when stored in vials with septum-based seals.

Objective

The present study tested whether storing DMTS formulations in hermetically sealed glass ampules could mitigate storage losses.

Methods

Samples consisted of 1-mL aliquots of a 50 mg/ml stock solution of DMTS in 15% aqueous Poly80. The control samples were stored using a vial-within-a-vial system—the inner and outer vials were sealed respectively, with a snap cap, and with a crimped septum. The hermetically sealed test samples were stored in fire-sealed glass ampules. The DMTS content was measured by HPLC–UV analysis at specific time points over a 100-day period.

Results

While the control samples exhibited systematic DMTS losses, no DMTS losses were observed from the test samples stored in hermetically sealed glass ampules over the 100-day testing period.

Conclusion

DMTS formulated in 15% aqueous Poly80 solution has excellent stability when stored in fire-sealed glass ampules and thus has the potential to be effectively stored as an intramuscular CN countermeasure for mass casualty scenarios.

Percent residual accuracy for quantifying goodness-of-fit of linear calibration curves

Linear models for calibration curves are overwhelmingly created based on minimization of least squares error, with their goodness-of-fit (GOF) quantified using the square of the correlation coefficient (R²). Yet, R² has well-known disadvantages when used to quantify GOF of calibration curves stemming from its calculation based on the absolute error of the signal (i.e., calculated vs. experimental). These disadvantages are exacerbated when using a geometric series of concentrations for calibration standards (e.g., 1, 2, 5, 10, etc.) and when calibration curves span 2-3 orders of magnitude, which is typical for modern analytical techniques. While there are multiple alternative GOF measures, R² overwhelmingly persists in the field of Analytical Chemistry as the most reported measure of GOF. We evaluated R², alternative GOF measures, and multiple quantitative bias parameters, along with residual analysis, for over 60 experimental calibration curves. R² did a poor job of consistently and accurately quantifying the GOF over the entire calibration curve. This was especially true for situations where the low concentration calibrators were not accurately described by the calibration equation. While other GOF parameters, including the sum of the absolute percent error, mean absolute percent error, and quality coefficient, did a better job of describing GOF of calibration curves, each had significant theoretical and/or practical disadvantages. Therefore, we introduce a descriptive GOF parameter called Percent Residual Accuracy (%RA or PRA) which equally weights the accuracy of all calibrators into a single value, generally falling between 0% and 100%, with 100% representing a perfect fit and a "good" fit for calibration data producing a %RA of 90-100%. The %RA much more effectively described the GOF for the entire calibration range than R², and it similarly quantified GOF as compared to the other GOF parameters tested. With the performance and practical advantages of %RA, we conclude that it is the most advantageous GOF parameter and that it should be reported as a standard GOF measure for calibration curves.

An Official American Thoracic Society Workshop Report: Chemical Inhalational Disasters. Biology of Lung Injury, Development of Novel Therapeutics, and Medical Preparedness

This report is based on the proceedings from the Inhalational Lung Injury Workshop jointly sponsored by the American Thoracic Society (ATS) and the National Institutes of Health (NIH) Countermeasures Against Chemical Threats (CounterACT) program on May 21, 2013, in Philadelphia, Pennsylvania. The CounterACT program facilitates research leading to the development of new and improved medical countermeasures for chemical threat agents. The workshop was initiated by the Terrorism and Inhalational Disasters Section of the Environmental, Occupational, and Population Health Assembly of the ATS. Participants included both domestic and international experts in the field, as well as representatives from U.S. governmental funding agencies. The meeting objectives were to (1) provide a forum to review the evidence supporting current standard medical therapies, (2) present updates on our understanding of the epidemiology and underlying pathophysiology of inhalational lung injuries, (3) discuss innovative investigative approaches to further delineating mechanisms of lung injury and identifying new specific therapeutic targets, (4) present promising novel medical countermeasures, (5) facilitate collaborative research efforts, and (6) identify challenges and future directions in the ongoing development, manufacture, and distribution of effective and specific medical countermeasures. Specific inhalational toxins discussed included irritants/pulmonary toxicants (chlorine gas, bromine, and phosgene), vesicants (sulfur mustard), chemical asphyxiants (cyanide), particulates (World Trade Center dust), and respirable nerve agents.

Method development for detecting the novel cyanide antidote dimethyl trisulfide from blood and brain, and its interaction with blood

The antidotal potency of dimethyl trisulfide (DMTS) against cyanide poisoning was discovered and investigated in our previous studies. Based on our results it has better efficacy than the Cyanokit and the Nithiodote therapies that are presently used against cyanide intoxication in the US. Because of their absence in the literature, the goal of this work was to develop analytical methods for determining DMTS from blood and brain that could be employed in future pharmacokinetic studies. An HPLC-UV method for detection of DMTS from blood, a GC-MS method for detection of DMTS from brain, and associated validation experiments are described here. These analytical methods were developed using in vitro spiking of brain and blood, and are suitable for determining the in vivo DMTS concentrations in blood and brain in future pharmacokinetic and distribution studies. An important phenomenon was observed in the process of developing these methods. Specifically, recoveries from fresh blood spiked with DMTS were found to be significantly lower than recoveries from aged blood spiked in the same manner with DMTS. This decreased DMTS recovery from fresh blood is important, both because of the role it may play in the antidotal action of DMTS in the presence of cyanide, and because it adds the requirement of sample stabilization to the method development process. Mitigation procedures for stabilizing DMTS samples in blood are reported.