High-performance liquid chromatographic measurement of exogenous thiosulfate in urine and plasma

Hydrogen sulfide poisoning in forensic pathology and toxicology: mechanism and metabolites quantification analysis

Historically, hydrogen sulfide (H₂S) poisoning has extremely high and irreparable mortality. Currently, the identification of H₂S poisoning needs to combine with the case scene analysis in forensic medicine. The anatomy of the deceased seldom had obvious features. There are also a few reports about H₂S poisoning in detail. As a result, we give a comprehensive analysis of the related knowledge on the forensic aspect of H₂S poisoning. Furthermore, we provide the analytical methods of H₂S and its metabolite-which may assist in H₂S poisoning identification.

Sample preparation method with ultrafiltration for whole blood thiosulfate measurement

Quantitative analysis of thiosulfate is useful for diagnosing hydrogen sulfide poisoning. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) enables more rapid and sensitive measurements than previous methodologies. As simple measurements of blood thiosulfate concentration are affected by the blood matrix, blood is used as the solvent to prepare the standard solution for calibration curve generation. Thus, a large amount of blood devoid of thiosulfate is required. We developed a preparation method by incorporating an ultrafiltration step to overcome this limitation and generate a calibration curve using a standard solution prepared with pure water. We used this improved method to investigate the stability of thiosulfate in refrigerated samples. To compare the effects of refrigeration, blood samples were prepared using the following two methods: one sample was treated with a 50-kDa exclusion ultrafiltration membrane and the other was not treated. The samples were stored at 4 °C, and then measured at 0, 3, 6, 24, 48, and 96 h. The incorporation of the ultrafiltration step in the measurement procedure enabled the quantification of thiosulfate, by plotting a calibration curve using a standard of pure water; it did not require a blood standard. Additionally, the reduction in whole blood thiosulfate concentration was within 10% during 2 days of refrigeration. Thus, the need for a large amount of blood to prepare the standard solution was resolved by the ultrafiltration step in test sample preparation. This method is useful to measure thiosulfate concentration and is not hindered by sample refrigeration for a few days.

An optical material for the detection of trace S2O32- in milk based on a copper complex

A novel S₂O₃^2- luminescent sensor (Cu²⁺-p-CPIP) was developed and the presence of S₂O₃^2- caused an obvious fluorescence enhancement at 420 nm upon excitation at 330 nm, which could be distinguished with the naked eye under a UV lamp. Remarkably, the compound exhibited excellent selective and sensitive response to S₂O₃^2- over other common anions with a micromolar limit of detection (0.442 μM) in DMSO/H₂O (v/v, 1:1) buffer. The absorbance intensity and the color of Cu²⁺-p -CPIP solution changed gradually with the increase of S₂O₃^2- concentration. The proposed method was applied to the determination of S₂O₃^2- in milk samples and the recoveries were 97.5-105%. The preparation of Cu²⁺-p -CPIP exhibited the quick, simple and facile advantages. The results showed that Cu²⁺-p -CPIP can be a good candidate for simple, rapid and sensitive colorimetric detection of S₂O₃^2- in aqueous solution.

Liquid chromatography-tandem mass spectrometry method for the determination of thiosulfate in human blood and urine as an indicator of hydrogen sulfide poisoning

Being a stable metabolite of hydrogen sulfide, thiosulfate has been utilized as an index for hydrogen sulfide poisoning (HSP). Thiosulfate analysis is mainly performed using gas chromatography/mass spectrometry (GC-MS) due to its high sensitivity and specificity. The GC-MS analysis requires two-step derivatizations of thiosulfate, and the derivative is not stable in solution as it has a disulfide moiety. To resolve this stability issue, we developed a novel analytical method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) for monitoring the pentafluorobenzyl derivative of thiosulfate (the first reaction product of the GC-MS method) in this study. The established method exhibited high reproducibility despite being a more simplified and rapid procedure compare to the GC-MS method. Phenyl 4-hydroxybenzoate was used as an internal standard because 1,3,5-tribromobenzene which had been used in the GC-MS method was not suitable compound for LC-MS/MS with Electrospray ionization (ESI) negative detection. The linear regression of the peak area ratios versus concentrations was fitted over the concentration ranges of 0.5-250μM and 0.25-250μM in blood and urine, respectively. The validation results satisfied the acceptance criteria for intra- and inter-day accuracy and precision. Blood and urine samples from 12 suspected HSP cases were tested using this method. The thiosulfate concentration detected in the sample coincided well with that determined at the scene of each HSP accident.

Development for the measurement of serum thiosulfate using LC-MS/MS in forensic diagnosis of H2S poisoning

Thiosulfate measurement is crucial to diagnosis of hydrogen sulfide (H2S) poisoning in forensic toxicology. Although GC-MS method is currently regarded as a standard thiosulfate measurement, it requires complicated sample preparation prior to analysis. This study presents a simple, rapid, and highly sensitive method for the quantitative analysis of serum thiosulfate by using liquid chromatography-tandem mass spectrometry (LC-MS/MS). This method is based on selected reaction monitoring and has high sensitivity with a lower quantification limit of 0.5μM. Precision and accuracy of this method meet the basic requirements for quantitative analysis (intra- and inter-day tests have a relative standard deviation of ⩽10.4%; range of analytical recovery is 94.3-102.6%). On the measurements of serum thiosulfate by our developed method, a thiosulfate concentration as 57.5μM was detected clearly in the H2S poisoning case comparing to the non poisoning case in which only a trace amount of thiosulfate was observed.

Redox status expressed as GSH:GSSG ratio as a marker for oxidative stress in paediatric tumour patients

Oxidative stress causes profound alterations of various biological structures, including cellular membranes, lipids, proteins and nucleic acids, and it is involved in numerous malignancies. Reduced glutathione (GSH) is considered to be one of the most important scavengers of reactive oxygen species (ROS), and its ratio with oxidised glutathione (GSSG) may be used as a marker of oxidative stress. The main aim of this study was to determine GSH:GSSG ratio in the blood serum of paediatric cancer patients to use this ratio as a potential marker of oxidative stress. The whole procedure was optimised and the recoveries for both substances were greater than 80% under the optimised conditions. We analysed a group of paediatric patients (n=116) with various types of cancer, including neuroblastoma, anaplastic ependymoma, germ cell tumour, genital tract tumour, lymphadenopathy, rhabdomyosarcoma, nephroblastoma, Ewing's sarcoma, osteosarcoma, Hodgkin's lymphoma, medulloblastoma and retinoblastoma. We simultaneously determined the levels of reduced and oxidised glutathione, and thus, its ratio in the blood serum of the patients. The highest ratio was observed in retinoblastoma patients and the lowest in anaplastic ependymoma. We were able to distinguish between the diagnoses based on the results of the obtained GSH:GSSG ratio.

Chromatographic and mass spectrometric analysis of glutathione in biological samples

Biological thiol compounds are classified into high-molecular-mass protein thiols and low-molecular-mass free thiols. Endogenous low-molecular-mass thiol compounds, namely, reduced glutathione (GSH) and its corresponding disulfide, glutathione disulfide (GSSG), are very important molecules that participate in a variety of physiological and pathological processes. GSH plays an essential role in protecting cells from oxidative and nitrosative stress and GSSG can be converted into the reduced form by action of glutathione reductase. Measurement of GSH and GSSG is a useful indicator of oxidative stress and disease risk. Many publications have reported successful determination of GSH and GSSG in biological samples. In this article, we review newly developed techniques, such as liquid chromatography coupled with mass spectrometry and tandem mass spectrometry, for identifying GSH bound to proteins, or for localizing GSH in bound or free forms at specific sites in organs and in cellular locations.

[Development of assay methods for endogenous inorganic sulfur compounds and sulfurtransferases and evaluation of the physiological functions of bound sulfur]

Inorganic sulfur compounds, such as S(2-), SO(3)(2-) and S(2)O(3)(2-), are produced from sulfur- containing amino acids as intermediary metabolites in mammalian tissues through complex pathways and are ultimately incorporated into sulfate. Reduced sulfur is also produced via the desulfuration of cysteine by several sulfurtransferases present in mammalian tissues; these enzymes include gamma-cystathionase (gamma-CST), and 3-mercaptopyruvate sulfurtransferase (3-MST). This reduced sulfur is then incorporated into pools of active reduced sulfur (sulfane sulfur; polysulfides, polythionates, thiosulfate, thiosulfonates and elemental sulfur) that are involved in the detoxication of cyanide and in the biosynthesis of iron-sulfur cluster. Sulfane sulfur is labile and is reduced to H(2)S by reducing agents. The physiological function of these sulfur species is less clear. We have found that a reduced sulfur species is commonly present in mammalian sera and tissues as a high molecular weight material and as both a high and a low molecular weight material, respectively; we designated this sulfur species as "bound sulfur." Bound sulfur can be easily liberated as sulfide by reduction with DTT. This review describes sensitive and specific assay method for determining the presence of inorganic sulfur compounds as well as bound sulfur and related sulfurtransferases in biological samples. The physiological functions of bound sulfur in rat tissues were also evaluated using these assay methods. Bound sulfur was found to be located primarily in the rat liver cytosolic fraction in the form of high molecular weight components. The capacity of bound sulfur production was enriched in the cytosol fraction and depended on gamma-CST. Bound sulfur also affected redox regulation by modifying active thiol residues in some liver cytosol enzymes and effectively inhibited cytochrome P-450-dependent lipid peroxidation induced by CCl(4) and t-BuOOH.

Occupational fatality and persistent neurological sequelae after mass exposure to hydrogen sulfide

Exposure to hydrogen sulfide (H2S) has been associated with death as well as survival following coma with or without hypoxic brain damage. The release of H2S at a beachfront construction site led to the emergency evaluation and treatment of 37 people, with six admissions and one death. At least one victim, who underwent extensive therapy with hyperbaric oxygen, developed persistent neurological sequelae. Despite increased awareness of the potentially life-threatening consequences of exposure to H2S, significant poisoning continues to occur, even in workplaces where the hazards are well-known and can be avoided. Recommended therapy includes nitrites, hyperbaric oxygen, and supportive care, but documentation of efficacy is lacking. Because patients with chronic neurological sequelae after acute H2S exposure continue to be reported, we suggest that any survivor of H2S poisoning who presents in coma or who manifests objectively verifiable evidence of neurotoxicity on physical examination or lab testing should undergo baseline and annual neurological and neuropsychological testing for at least five years. This approach could standardize and enhance our knowledge of, and ability to detect, the subtle but permanent alterations of central nervous system function that follow H2S exposure.