Modern Mass Spectrometry Research Articles

Identifying Process Differences with ToF-SIMS: An MVA Decomposition Strategy.

In time-of-flight secondary ion mass spectrometry (ToF-SIMS), multivariate analysis (MVA) methods such as principal component analysis (PCA) are routinely employed to differentiate spectra. However, additional insights can often be gained by comparing processes, where each process is characterized by its own start and end spectra, such as when identical samples undergo slightly different treatments or when slightly different samples receive the same treatment. This study proposes a strategy to compare such processes by decomposing the loading vectors associated with them, which highlights differences in the relative behavior of the peaks. This strategy identifies key information beyond what is captured by the loading vectors or the end spectra alone. While PCA is widely used, partial least-squares discriminant analysis (PLS-DA) serves as a supervised alternative and is the preferred method for deriving process-related loading vectors when classes are narrowly separated. The effectiveness of the decomposition strategy is demonstrated using artificial spectra and applied to a ToF-SIMS materials science case study on the photodegradation of N719 dye, a common dye in photovoltaics, on a mesoporous TiO2 anode. The study revealed that the photodegradation process varies over time, and the resulting fragments have been identified accordingly. The proposed methodology, applicable to both labeled (supervised) and unlabeled (unsupervised) spectral data, can be seamlessly integrated into most modern mass spectrometry data analysis workflows to automatically generate a list of peaks whose relative behavior varies between two processes, and is particularly effective in identifying subtle differences between highly similar physicochemical processes.

Quantification of Total Ketone Bodies in Biological Matrices Using Stable Isotope-Labeled Internal Standards and RP-UHPLC-MS/MS.

Acetoacetate (AcAc) and D-beta-hydroxybutyrate (D-βOHB), the two major ketone bodies found in circulation, are linked to multiple physiological and pathophysiological states. Therefore, analytical methodologies surrounding the quantification of total ketone body (TKB) concentrations in biological matrices are paramount. Traditional methods to quantify TKBs relied on indirect spectrophotometric assays with narrow dynamic ranges, which have been significantly improved upon by modern mass spectrometry (MS)-based approaches. However, the lack of stable isotope-labeled internal standards (ISs) for AcAc and the need to distinguish D-βOHB from its closely related structural and enantiomeric isomers pose significant obstacles. Here, we provide a protocol to synthesize and quantify a [13C] stable isotope-labeled IS for AcAc, which, in conjunction with a commercially available [2H] stable isotope-labeled IS for βOHB, allows TKBs to be measured across multiple biological matrices. This rapid (7min) analysis employs reverse phase ultra-high performance liquid chromatography (RP-UHPLC) coupled to tandem MS (MS/MS) to distinguish βOHB from three structural isomers using parallel reaction monitoring (PRM), providing excellent specificity and selectivity. Finally, a method is provided that distinguishes D-βOHB from L-βOHB using a simple one-step derivatization to produce the corresponding diastereomers, which can be chromatographically resolved using the same rapid RP-UHPLC separation with new PRM transitions. In summary, this method provides a rigorous analytical pipeline for the analysis of TKBs in biological matrices via leveraging two authentic stable isotope-labeled ISs and RP-UHPLC-MS/MS.

From Proteomics to the Analysis of Single Protein Molecules.

Limit of detection (LoD) is a term that is used to characterize the sensitivity of an analytical method. The existing limitation of the sensitivity of analysis using modern mass spectrometry methods has been experimentally shown to be a limiting factor in the application of proteomic technologies in medicine. This article proposes a concept of a new technology that will set a new vector of development in the development of systems for solving problems of medical diagnostics and deals with theoretical and practical aspects of creating a new technology for the detection of single biomacromolecules (in particular, proteins) in biological samples. Such technology should be based on the principle of signal registration similar to that used in a Geiger counter (also known as a Geiger-Müller counter or G-M counter), a device that automatically counts the number of ionizing particles that hit it. This counter is free from probabilistic components; it registers a signal if there is at least one target molecule in the analysis chamber. Predictive medical diagnostics require technology based on methods where sensitivity allows for the detection of single marker molecules in a biological sample volume of 1-10 µL, the smallest volume of biomaterial used in laboratory diagnostics. Creation of a detector with a sensitivity of 10-18 M would allow for the detection of one molecule in 1 µL of the sample, which fundamentally makes this approach analogous to a G-M counter for solutions. To date, bioanalytical methods are limited to a sensitivity of 10-12 M (which is approximately 1 million molecules per 1 μL), which is insufficient to capture the early stages of pathological processes.

Towards a universal method for middle-down analysis of antibodies via proton transfer charge reduction-Orbitrap mass spectrometry.

Modern mass spectrometry technology allows for extensive sequencing of the ~ 25kDa subunits of monoclonal antibodies (mAbs) produced by IdeS proteolysis followed by disulfide bond reduction, an approach known as middle-down mass spectrometry (MD MS). However, the spectral congestion of tandem mass spectra of large polypeptides dramatically complicates fragment ion assignment. Here, we report the development and benchmark of an MD MS strategy based on the combination of different ion fragmentation techniques with proton transfer charge reduction (PTCR) to simplify the gas-phase sequencing of mAb subunits. Applied on the liquid chromatography time scale using an Orbitrap Tribrid mass spectrometer, PTCR produces easy-to-interpret mass spectra with limited ion signal overlap. We demonstrate that the accurate estimation of the number of charges submitted to the Orbitrap mass analyzer after PTCR allows for the detection of charge-reduced product ions over a wide mass-over-charge (m/z) window with low parts per million m/z accuracy. Therefore, PTCR-based MD MS analysis increases not only sequence coverage, number of uniquely identified fragments, and number of assigned complementary ion pairs, but also the general confidence in the assignment of subunit fragments. This data acquisition method can be readily applied to any class of mAbs without an apparent need for optimization, and benefits from the high resolving power of the Orbitrap mass analyzer to return sequence coverage of individual subunits exceeding 80% in a single run, and > 90% when just two experiments are combined.

Children of Nature: Thoughts on Targeted and Untargeted Analytical Approaches to Decipher Polyphenol Reactivity in Food Processing and Metabolism.

Following 25 years of polyphenol research in our laboratory, the astonishing chemical and metabolic reactivity of polyphenols resulting in considerable chemical diversity has emerged as the most remarkable attribute of this class of natural products. To illustrate this concept, we will present selected data from black tea and coffee chemistry. In black tea chemistry, enzymatic fermentation converts six catechin derivatives into an estimated 30 000 different polyphenolic compounds via a process we have termed the oxidative cascade process. In coffee roasting, around 45 chlorogenic acids are converted into an estimated 250 novel derivatives following a series of diverse chemical transformations. Following ingestion by humans, these dietary polyphenols, whether genuine secondary metabolites or food processing products, encounter the microorganisms of the gut microbiota, converting them into a myriad of novel structures. In the case of coffee, only two out of 250 chlorogenic acids are absorbed intact, with most others being subject to gut microbial metabolism. Modern mass spectrometry (MS) has been key in unravelling the true complexity of polyphenols subjected to food processing and metabolism. We will accompany this assay with a short overview on analytical strategies developed, including ultrahigh-resolution MS, tandem MS, multivariate statistics, and molecular networking that allow an insight into the fascinating chemical processes surrounding dietary polyphenols. Finally, experimental results studying biological activity of polyphenols will be presented and discussed, highlighting a general promiscuity of this class of compounds associated with nonselective protein binding leading to loss of enzymatic function, another noteworthy general property of many dietary polyphenols frequently overlooked.

Observation of Large, Charged Droplet Signatures within the High-Vacuum Region of a Commercial Electrospray TOF-MS.

Electrospray ionization (ESI) is one of the most prominent atmospheric pressure ionization techniques in modern mass spectrometry. It generates charged droplets from an analyte-containing solution as an initial step in the ionization process. Textbooks and the majority of the articles assume the entire droplet evaporation and release of bare analyte ions within the ionization chamber. However, non-mass-spectrometry-related literature and recent reports demonstrate droplet observation in regions of the vacuum systems of a variety of mass spectrometers. In this work, we report on the observation of large droplet fragments within the orthogonal acceleration stage of a Bruker micrOTOF by connecting an oscilloscope to an auxiliary ion current detector downstream of the acceleration stage. Moreover, we detected fragment debris even with the MCP TOF detector by evaluating individual TOF spectra. Droplet fragments appear as pronounced and intensive pulses of the ion current. This observation is clearly connected to ESI, as other atmospheric pressure ionization methods do not show this behavior. The recorded droplet signatures show clear dependencies on the ion source and transfer stage parameters. The existence of large and highly charged droplets may adversely affect or at least impact the analytical performance of the instrument due to space charge or complex heterogeneous chemical reactions. Furthermore, the penetration of large charged aggregates into the vacuum system explains the reported surface contamination after multipole stages. This contamination of critical components leads to substantially higher maintenance efforts.

Formation Enthalpies of C3 and C4 Brominated Hydrocarbons: Bringing Together Classical Thermodynamics, Modern Mass Spectrometry, and High-Level Ab Initio Calculations.

The enthalpies of formation of brominated C3-C4 hydrocarbons were critically evaluated using experimental data sources ranging from classical thermodynamics methods to modern high-precision mass spectrometry and reported in a time span of a century. The experimental data were used in conjunction with the results of modern high-level ab initio calculations. To facilitate quantitative analysis, a recently developed local coupled cluster-based computational protocol was extended to organic compounds containing univalent Br. Several erroneous data sources were identified in a course of the study. Possible reasons for the inconsistency between the ΔfHm° values recommended by the Committee on Data of the International Science Council (CODATA) and Active Thermochemical Tables for HBr in the gas and aqueous solution were discussed. The most up-to-date recommendations based on the comprehensive analysis of collected information are provided for 23 brominated hydrocarbons. For several compounds under consideration, the recommended values were previously lacking, while improved values and uncertainties were obtained for those with existing recommendations.

12-Plex Isobaric Multiplex Labeling Reagents for Carbonyl-Containing Compound (SUGAR) Tag-Enabled High-Throughput Quantitative Glycomics.

Glycans, which are ubiquitously distributed on most proteins and cell surfaces, are a class of important biomolecules playing crucial roles in various biological processes such as molecular recognition and cellular communication. Modern mass spectrometry (MS) coupled with novel chemical probe labeling strategies has greatly advanced analysis of glycans. However, the requirement of high-throughput and robust quantitative analysis still calls for the development of more advanced tools. Recently, we devised isobaric multiplex reagents for carbonyl-containing compound (SUGAR) tags for 4-plex N-glycan analysis. To further improve the throughput, we utilized the mass-defect strategy and expanded the multiplexing capacity to 12 channels without changing the chemical structure of the SUGAR tag, achieving a threefold enhancement in throughput compared with the original design and managing to perform high-throughput N-glycan analysis in a single LC-MS/MS injection. Herein, we present detailed methods for the synthesis of 12-plex SUGAR isobaric tags, the procedure to release and label the N-glycans from proteins, and the analysis by high-resolution LC-MS/MS, as well as data processing to achieve multiplexed quantitative glycomics.

Diverse thermal desorption combined with self-aspirating corona discharge ionization for direct mass spectrometry analysis of complex samples.

The thermal desorption (TD) technique is widely employed in modern mass spectrometry to facilitate the detection of non-volatile analytes. In this study, we developed a compact TD device based on a small resistance wire and coupled it with a self-aspirating corona discharge ionization (CDI) source to conduct direct MS analysis of various liquid and solid samples. Due to its small size and low heat capacity, the temperature of the TD module can be flexibly and rapidly modulated by controlling the power sequence. Multiple heating modes, including pulse heating (PH), isothermal heating, and step heating (SH), are realized and characterized, and then applied for the detection of different real samples. In particular, the PH mode is suitable for the simultaneous detection of multiple components in samples with relatively simple matrices, while the SH mode is capable of component separation. In addition, the sensitivity and quantitative capability of the TD-CDI system for DEP solutions were tested, showing acceptable stability with a relative standard deviation of about 6.7% and a detection limit of 0.088 ng. Overall, the developed TD-CDI system provides a simple, convenient, and versatile tool for direct mass spectrometry analysis of real samples.

Copper isotope ratios in serum do not track cancerous tumor evolution, but organ failure.

Relative to healthy controls, lighter copper isotopic compositions have been observed in the serum of breast cancer and end-stage liver disease patients, raising the possibility that Cu isotope ratios could be used as a tracer for disease progression. Here, we assess the potential of natural Cu isotopic variations (expressed as δ65Cu) as diagnostic tools for cancer progression and/or liver failure by performing a first-order analysis of Cu isotopic cycling in the human body. Using a box model, we simulate the kinetics of Cu mass transfer throughout significant reservoirs in the body, allowing isotopic fractionation to occur during Cu uptake/release from these reservoirs. With this model, we determine under which conditions the serum δ65Cu values would reflect perturbation related to cancer growth and/or liver failure at a level resolvable with modern mass spectrometry. We find that tumor growth alone is unable to explain the light isotopic signature observed in serum. Instead, we find that metabolic changes to the liver function resulting in a ∼1‰ isotope fractionation during Cu uptake from the blood into the liver can readily explain the long-term serum isotopic shift of ∼0.2‰ observed in cancer patients. A similar fractionation (∼1.3‰) during Cu uptake into the liver also readily explains the -1.2‰ shift observed in the serum of cirrhosis patients with ascites, suggesting a potentially common driver of isotopic fractionation in both cases. Using this model, we then test hypotheses put forward by previous studies and begin to probe the mechanisms behind the measured isotopic compositions.

A Five-Year Update on Matrix Compounds for MALDI-MS Analysis of Lipids.

Matrix-assisted laser desorption and ionization (MALDI) is a widely used soft-ionization technique of modern mass spectrometry (MS). MALDI enables the analysis of nearly all chemical compounds-including polar and apolar (phospho)lipids-with a minimum extent of fragmentation. MALDI has some particular advantages (such as the possibility to acquire spatially-resolved spectra) and is competitive with the simultaneously developed ESI (electrospray ionization) MS. Although there are still some methodological aspects that need to be elucidated in more detail, it is obvious that the careful selection of an appropriate matrix plays the most important role in (lipid) analysis. Some lipid classes can be detected exclusively if the optimum matrix is used, and the matrix determines the sensitivity by which a particular lipid is detected within a mixture. Since the matrix is, thus, crucial for optimum results, we provide here an update on the progress in the field since our original review in this journal in 2018. Thus, only the development during the last five years is considered, and lipids are sorted according to increasing complexity, starting with free fatty acids and ending with cardiolipins and phosphoinositides.

A direct examination of microbial specialized metabolites associated with ocean sediments from Baffin Bay and the Gulf of Maine.

Specialized metabolites produced by microorganisms found in ocean sediments display a wide range of clinically relevant bioactivities, including antimicrobial, anticancer, antiviral, and anti-inflammatory. Due to limitations in our ability to culture many benthic microorganisms under laboratory conditions, their potential to produce bioactive compounds remains underexplored. However, the advent of modern mass spectrometry technologies and data analysis methods for chemical structure prediction has aided in the discovery of such metabolites from complex mixtures. In this study, ocean sediments were collected from Baffin Bay (Canadian Arctic) and the Gulf of Maine for untargeted metabolomics using mass spectrometry. A direct examination of prepared organic extracts identified 1468 spectra, of which ∼45% could be annotated using in silico analysis methods. A comparable number of spectral features were detected in sediments collected from both locations, but 16S rRNA gene sequencing revealed a significantly more diverse bacterial community in samples from Baffin Bay. Based on spectral abundance, 12 specialized metabolites known to be associated with bacteria were selected for discussion. The application of metabolomics directly on marine sediments provides an avenue for culture-independent detection of metabolites produced under natural settings. The strategy can help prioritize samples for novel bioactive metabolite discovery using traditional workflows.

Familiarizing Undergraduate Students with Advanced Mass Spectrometry Techniques: An Example of Detailed Lipid Structure Characterization

This study highlights the importance of incorporating modern mass spectrometry techniques into undergraduate education. By focusing on the structure-characterizing capability of MS, students are able to gain hands-on experience with cutting-edge techniques and better understand how MS can be used to solve real-world problems. The three-step lipid structure analysis strategy presented in the study is a great example of this, as it allows students to understand the process of lipid analysis from headgroup identification to the determination of fatty acyl chain composition and the location of C═C double bonds. The use of chemical derivatization to preactivate a structural moiety for MS/MS analysis is also emphasized in the study. This provides students with a deeper understanding of the limitations of MS/MS analysis and how chemical modifications can be used to overcome these limitations. The demonstration of a [2 + 2] photochemical reaction to locate a C═C in unsaturated lipids is a practical example of this concept. Overall, this study supports the idea that incorporating advanced research techniques into undergraduate education can not only enhance students' understanding of scientific instruments but also promote their interests in research and innovation.

Ultra-sensitive fluorescent and colorimetric probes for femtomolar detection of picric acid: Mechanochromic, latent fingerprinting, and pH responsive character with AIE properties

• Probes 1(a-c) were synthesized through one-pot multicomponent reaction. • This study offers design strategy to transform ACQ into AIE feature. • Probes showed mechanochromism, pH responsive, and identification of latent fingerprints. • Probes displayed ultrasensitive femtomolar level sensing of picric acid (PA) • Selective sensing of PA was achieved through the predominant involvement of ground state complexation. Multiple stimuli responsive easy to synthesize organic probes with remarkable structural properties are imminently essential. To this endeavor, 1,4-dihydropyridine (DHP) based three new probes 1(a-c) were successfully synthesized and characterized through modern spectroscopic and mass spectrometry techniques. Planar dihydropyridine was appended with multiple donor-acceptor and rotors to bring aggregation induced emission (AIE) character in probes 1(a-b) . Interestingly, probe 1c displayed aggregation caused quenching (ACQ) effect due to perpendicularly attached naphthyl ring. Therefore, this study presents extensive structure-property relationship to invoke AIE character. Moreover, probes 1(a-c) exhibited high photostability, reversible mechanochromism, pH responsive character, and adequate identification of latent fingerprints (LFPs). Importantly, multifunctional probes 1(a-c) served as highly selective fluorescent and colorimetric probes for picric acid (PA). In solution, highly sensitive femtomolar (fM) level (limit of detection (LOD); 12.3, 14.6, and 27.1 fM) detection of PA was attributed to combined effect of ground-state charge transfer complex formation and Forster resonance energy transfer (FRET). Favorable complexation between probes and PA was proved through UV-visible absorption, density functional theory (DFT), and dynamic light scattering (DLS) studies. Advantageously, probes were able to detect picric acid in vapor phase. In addition, probes were practically applicable for the contact mode detection of PA and sensing of PA in LFPs and industrial samples.

アスファルテン分子モデルの変遷

This paper reviews the average molecular models of asphaltene proposed in past years, and introduces recent results of individual molecular structure analyses. The understanding of the asphaltene molecular structure has evolved as analytical techniques advance. In around 2016, modern mass spectrometry ended the controversy over whether island-type or archipelago-type molecules are correct, and clarified the diversity in chemical composition. Atomic force microscopy techniques can now determine individual molecular structures. The historical changes in our understanding of asphaltene are summarized in five stages (Asphaltene 1.0∼5.0).

High-Throughput Quantitative Glycomics Enabled by 12-plex Isobaric Multiplex Labeling Reagents for Carbonyl-Containing Compound (SUGAR) Tags.

Glycans, which are widely distributed on most proteins and cell surfaces, are a class of important biomolecules playing crucial roles in various biological processes such as immune response and cellular communication. Modern mass spectrometry (MS) coupled with novel chemical probes greatly facilitates routine analysis of glycans. However, the requirement of high-throughput analysis still calls for advanced tools to be developed. Recently, we devised isobaric multiplex reagents for carbonyl-containing compound (SUGAR) tags for 4-plex N-glycan analysis. To further improve the throughput, we utilized the subtle mass differences among different isotopologues and expanded the multiplexing capacity to 12 channels, a 3-fold throughput improvement for the original SUGAR tag design and achieved high-throughput N-glycan analysis in a single LC-MS/MS injection. We then applied 12-plex SUGAR tags to profile the N-glycans in four subtypes of human Immunoglobulin G (IgG) and to investigate the N-glycan changes in the endometrial cancer cells (ECC1) treated with Atovaquone, a quinone antimicrobial medication, and a dihydroorotate dehydrogenase (DHODH) inhibitor. Data are available via ProteomeXchange with the identifier PXD038501.

Intact Transition Epitope Mapping-Force Differences between Original and Unusual Residues (ITEM-FOUR).

Antibody-based point-of-care diagnostics have become indispensable for modern medicine. In-depth analysis of antibody recognition mechanisms is the key to tailoring the accuracy and precision of test results, which themselves are crucial for targeted and personalized therapy. A rapid and robust method is desired by which binding strengths between antigens and antibodies of concern can be fine-mapped with amino acid residue resolution to examine the assumedly serious effects of single amino acid polymorphisms on insufficiencies of antibody-based detection capabilities of, e.g., life-threatening conditions such as myocardial infarction. The experimental ITEM-FOUR approach makes use of modern mass spectrometry instrumentation to investigate intact immune complexes in the gas phase. ITEM-FOUR together with molecular dynamics simulations, enables the determination of the influences of individually exchanged amino acid residues within a defined epitope on an immune complex's binding strength. Wild-type and mutated epitope peptides were ranked according to their experimentally determined dissociation enthalpies relative to each other, thereby revealing which single amino acid polymorphism caused weakened, impaired, and even abolished antibody binding. Investigating a diagnostically relevant human cardiac Troponin I epitope for which seven nonsynonymous single nucleotide polymorphisms are known to exist in the human population tackles a medically relevant but hitherto unsolved problem of current antibody-based point-of-care diagnostics.

Proteomics and AQP2 regulation.

The advent of modern quantitative protein mass spectrometry techniques around the turn of the 21st century has contributed to a revolution in biology referred to as 'systems biology'. These methods allow identification and quantification of thousands of proteins in a biological specimen, as well as detection and quantification of post-translational protein modifications including phosphorylation. Here, we discuss these methodologies and show how they can be applied to understand the effects of the peptide hormone vasopressin to regulate the molecular water channel aquaporin-2. The emerging picture provides a detailed framework for understanding the molecular mechanisms involved in water balance disorders.

The role of vitamin D and trace elements in premature newborns with congenital pneumonia

The objective of the research is to determine the levels of vitamin D and trace elements in the umbilical cord blood, as well as to evaluate the clinical and laboratory characteristics in premature newborns with congenital pneumonia. This single‑center case-control research included 228 premature newborns who were divided into the main group composed of 76 newborns with congenital pneumonia, and control group composed of 152 newborns without congenital pneumonia, who were born in the period from January 2021 to December 2021. An enzyme immunoassay of vitamin D determination was performed along with an assessment of clinical and laboratory characteristics. The modern mass spectrometry was performed to determine the trace element status of the blood of 46 premature newborns proven to have a severe vitamin D deficiency. The results of our research demonstrated that premature newborns with congenital pneumonia had a severe vitamin D deficiency, low Apgar scores, and severe respiratory disorder (assessed by means of modified Downes score). The analysis showed that the newborns with congenital pneumonia had a significantly worse pH, lactate, HCO3, and pCO2 as compared with the newborns without pneumonia (p<0.05). The analysis also revealed early biomarkers of congenital pneumonia in premature newborns, particularly thrombocytopenia, leukocytosis, high c-reactive protein (CRP) (p < 0.05).Stage 2 of the research was performed with the use of modern mass spectrometry to determine the trace element status (in the first stage, vitamin D was determined) in 46 premature newborns proven to have a severe vitamin D deficiency. The examination revealed that the levels of iron, calcium, manganese, sodium, strontium were decreased, whereas the levels of magnesium, copper, zinc, aluminum, and arsenic were increased. Only potassium, chromium, and lead turned out to be in normal range. According to the available data, in contrast to the most of micronutrients in the context of inflammatory response, the plasma concentrations of copper and zinc are reported to be increased as opposed to iron, the concentration of which is shown to be decreased. Our results demonstrated a high prevalence of 25 (OH) vitamin D deficiency in premature newborns. A significant relationship has been shown between the respiratory status of vitamin D and presence of congenital pneumonia in premature newborns. The analysis also showed that the content of trace elements in premature newborns plays an immunomodulatory role and affects the susceptibility and outcome of the infectious process. Thrombocytopenia in premature newborns may be an early biomarker for monitoring congenital pneumonia (Tab. 2, Ref. 28). Text in PDF www.elis.sk Keywords: congenital pneumonia, premature newborn, vitamin D, trace elements, mass spectrometry.

Detection of clobazam and its metabolites in urine during poisoning using HPLC-QqQ-MS/MS

BACKGROUND: Determining the incidence of acute and lethal poisoning with clobazam remains an urgent task of analytical toxicology. The medicinal substance clobazam belongs to the group of benzodiazepines, which is included in the list of psychoactive substances whose turnover is limited because of its high toxicity profile in overdose and abuse.&#x0D; AIM: To propose a simple, reliable, and sensitive technique for the identification of clobazam and its metabolite in the urine by the modern high-performance liquid chromatography-tandem mass spectrometry (HPLC-QqQ-MS/MS).&#x0D; MATERIALS AND METHODS: We have described a simple and sensitive HPLC-QqQ-MS/MS method for the qualitative determination of clobazam in the urine.&#x0D; RESULTS: The retention time in the selected chromatography conditions for clobazam was 5.17 min, and its metabolite (norclobazam) in urine was 4.56 min. The base peaks for clobazam and norclobazam were 259 m/z and 245 m/z, respectively.&#x0D; CONCLUSION: For the first time, this study provides a validated method of chemical-toxicological examination for poisoning with clobazam by HPLC-MS/MS, tested both on a model mixture and real biological matrix of the patients urine after taking clobazam. This technique can be a confirmatory research method in addition to the clinical picture in forensic medical examination.