Information-Dependent Acquisition-Mediated LC−MS/MS Screening Procedure with Semiquantitative Potential

Metabolite profiling of liquiritin in acute myocardial infarction model rat after intragastric administration using an information-dependent acquisition-mediated ultra-high-performance liquid chromatography-tandem mass spectrometry method

Liquiritin (LQ), a kind of flavonoid isolated from licorice, was proven to have great potential in treating heart failure. Pharmacokinetic evaluation is important for demonstrating clinical efficacy and mechanisms, and the prototype drug and its metabolite profiling are important for drug discovery and development. However, the metabolism of LQ in acute myocardial infarction (AMI) model rats still needs to be studied in depth. An information-dependent acquisition (IDA)-ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was applied to profile LQ metabolites in AMI model rat plasma. Protein precipitation and extraction were used for sample preparation. Chromatographic separation was achieved using an XSelect BEH C18 column (2.1 × 150 mm, 2.5 μm) using gradient elution method combining 0.1% formic acid and acetonitrile with a flow rate of 0.3 mL/min. Twelve metabolites were identified in IDA mode, sulfation, glucuronidation, methylation, methyl esterification, glutamine conjugation, and valine conjugation, and their composite reactions were presumed as the primary pathways of LQ metabolism. The variation in the peak areas showed that the time to reach the peak drug concentration of LQ and 12 metabolites was within 5 h. In summary, IDA-bridged UHPLC-MS/MS from characteristic fragment ions toward confidence-enhanced identification could effectively screen and profile metabolites.

Omics approaches for the assessment of biological responses to nanoparticles

Nanotechnology has enabled the development of innovative therapeutics, diagnostics, and drug delivery systems. Nanoparticles (NPs) can influence gene expression, protein synthesis, cell cycle, metabolism, and other subcellular processes. While conventional methods have limitations in characterizing responses to NPs, omics approaches can analyze complete sets of molecular entities that change upon exposure to NPs. This review discusses key omics approaches, namely transcriptomics, proteomics, metabolomics, lipidomics and multi-omics, applied to the assessment of biological responses to NPs. Fundamental concepts and analytical methods used for each approach are presented, as well as good practices for omics experiments. Bioinformatics tools are essential to analyze, interpret and visualize large omics data, and to correlate observations in different molecular layers. The authors envision that conducting interdisciplinary multi-omics analyses in future nanomedicine studies will reveal integrated cell responses to NPs at different omics levels, and the incorporation of omics into the evaluation of targeted delivery, efficacy, and safety will improve the development of nanomedicine therapies.

Characterization of the Structural Diversity and Structure-Specific Behavior of Oxidized Phospholipids by LC-MS/MS

Polyunsaturated fatty acids (PUFAs), esterified to phospholipids, are susceptible to oxidation. They form oxidized phospholipids (OxPLs) by oxygenases or reactive oxygen species (ROS), or both. These OxPLs are associated with various diseases, such as atherosclerosis, pulmonary injuries, neurodegenerative diseases, cancer, and diabetes. Since many types of OxPLs seem to be generated in vivo, precise determination of their structural diversity is required to understand their potential structure-specific functions. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is a powerful method to quantitatively measure the structural diversity of OxPLs present in biological samples. This review outlines recent advances in analytical methods for OxPLs and their physiological relevance in health and diseases.

Integration of mass spectral fingerprinting analysis with precursor ion (MS1) quantification for the characterisation of botanical extracts: application to extracts of Centella asiatica (L.) Urban

INTRODUCTION

The phytochemical composition of plant material governs the bioactivity and potential health benefits as well as the outcomes and reproducibility of laboratory studies and clinical trials.

OBJECTIVE

The objective of this work was to develop an efficient method for the in-depth characterisation of plant extracts and quantification of marker compounds that can be potentially used for subsequent product integrity studies. Centella asiatica (L.) Urb., an Ayurvedic herb with potential applications in enhancing mental health and cognitive function, was used as a case study.

METHODS

A quadrupole time-of-flight analyser in conjunction with an optimised high-performance liquid chromatography (HPLC) separation was used for in-depth untargeted fingerprinting and post-acquisition precursor ion quantification to determine levels of distinct phytochemicals in various C. asiatica extracts.

RESULTS

We demonstrate the utility of this workflow for the characterisation of extracts of C. asiatica. This integrated workflow allowed the identification or tentative identification of 117 compounds, chemically interconnected based on Tanimoto chemical similarity, and the accurate quantification of 24 phytochemicals commonly found in C. asiatica extracts.

CONCLUSION

We report a phytochemical analysis method combining liquid chromatography, high resolution mass spectral data acquisition, and post-acquisition interrogation that allows chemical fingerprints of botanicals to be obtained in conjunction with accurate quantification of distinct phytochemicals. The variability in the composition of specialised metabolites across different C. asiatica accessions was substantial, demonstrating that detailed characterisation of plant extracts is a prerequisite for reproducible use in laboratory studies, clinical trials and safe consumption. The methodological approach is generally applicable to other botanical products.

An LC-MS-based lipidomics pre-processing framework underpins rapid hypothesis generation towards CHO systems biotechnology

INTRODUCTION

Given a raw LC-MS dataset, it is often required to rapidly generate initial hypotheses, in conjunction with other 'omics' datasets, without time-consuming lipid verifications. Furthermore, for meta-analysis of many datasets, it may be impractical to conduct exhaustive confirmatory analyses. In other cases, samples for validation may be difficult to obtain, replicate or maintain. Thus, it is critical that the computational identification of lipids is of appropriate accuracy, coverage, and unbiased by a researcher's experience and prior knowledge.

OBJECTIVES

We aim to prescribe a systematic framework for lipid identifications, without usage of their characteristic retention-time by fully exploiting their underlying mass features.

RESULTS

Initially, a hybrid technique, for deducing both common and distinctive daughter ions, is used to infer parent lipids from deconvoluted spectra. This is followed by parent confirmation using basic knowledge of their preferred product ions. Using the framework, we could achieve an accuracy of ~ 80% by correctly identified 101 species from 18 classes in Chinese hamster ovary (CHO) cells. The resulting inferences could explain the recombinant-producing capability of CHO-SH87 cells, compared to non-producing CHO-K1 cells. For comparison, a XCMS-based study of the same dataset, guided by a user's ad-hoc knowledge, identified less than 60 species of 12 classes from thousands of possibilities.

CONCLUSION

We describe a systematic LC-MS-based framework that identifies lipids for rapid hypothesis generation.

Venomics-Accelerated Cone Snail Venom Peptide Discovery

Cone snail venoms are considered a treasure trove of bioactive peptides. Despite over 800 species of cone snails being known, each producing over 1000 venom peptides, only about 150 unique venom peptides are structurally and functionally characterized. To overcome the limitations of the traditional low-throughput bio-discovery approaches, multi-omics systems approaches have been introduced to accelerate venom peptide discovery and characterisation. This “venomic” approach is starting to unravel the full complexity of cone snail venoms and to provide new insights into their biology and evolution. The main challenge for venomics is the effective integration of transcriptomics, proteomics, and pharmacological data and the efficient analysis of big datasets. Novel database search tools and visualisation techniques are now being introduced that facilitate data exploration, with ongoing advances in related omics fields being expected to further enhance venomics studies. Despite these challenges and future opportunities, cone snail venomics has already exponentially expanded the number of novel venom peptide sequences identified from the species investigated, although most novel conotoxins remain to be pharmacologically characterised. Therefore, efficient high-throughput peptide production systems and/or banks of miniaturized discovery assays are required to overcome this bottleneck and thus enhance cone snail venom bioprospecting and accelerate the identification of novel drug leads.

Comprehensive analyses of oxidized phospholipids using a measured MS/MS spectra library

Oxidized phospholipids (OxPLs) are widely held to be associated with various diseases, such as arteriosclerosis, diabetes, and cancer. To characterize the structure-specific behavior of OxPLs and their physiological relevance, we developed a comprehensive analytical method by establishing a measured MS/MS spectra library of OxPLs. Biogenic OxPLs were prepared by the addition of specific oxidized fatty acids to cultured cells, where they were incorporated into cellular phospholipids, and untargeted lipidomics by LC-quadrupole/TOF-MS was applied to collect MS/MS spectra for the OxPLs. Based on the measured MS/MS spectra for about 400 molecular species of the biogenic OxPLs, we developed a broad-targeted lipidomics system using triple quadrupole MS. Separation precision of structural isomers was optimized by multiple reaction monitoring analysis and this system enabled us to detect OxPLs at levels as low as 10 fmol. When applied to biological samples, i.e., mouse peritoneal macrophages, this system enabled us to monitor a series of OxPLs endogenously produced in a 12/15-lipoxygenase-dependent manner. This advanced analytical method will be useful to elucidate the structure-specific behavior of OxPLs and their physiological relevance in vivo.

Wide-scope screening of pesticides in fruits and vegetables using information-dependent acquisition employing UHPLC-QTOF-MS and automated MS/MS library searching

This paper presents an application of ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS) for simultaneous screening and identification of 427 pesticides in fresh fruit and vegetable samples. Both full MS scan mode for quantification, and an artificial-intelligence-based product ion scan mode information-dependent acquisition (IDA) providing automatic MS to MS/MS switching of product ion spectra for identification, were conducted by one injection. A home-in collision-induced-dissociation all product ions accurate mass spectra library containing more than 1700 spectra was developed prior to actual application. Both qualitative and quantitative validations of the method were carried out. The result showed that 97.4 % of the pesticides had the screening detection limit (SDL) less than 50 μg kg^-1 and more than 86.7 % could be confirmed by accurate MS/MS spectra embodied in the home-made library. Meanwhile, calibration curves covering two orders of magnitude were performed, and they were linear over the concentration range studied for the selected matrices (from 5 to 500 μg kg^-1 for most of the pesticides). Recoveries between 80 and 110 % in four matrices (apple, orange, tomato, and spinach) at two spiked levels, 10 and 100 μg kg^-1, was 88.7 or 86.8 %. Furthermore, the overall relative standard deviation (RSD, n = 12) for 94.3 % of the pesticides in 10 μg kg^-1 and 98.1 % of the pesticides in 100 μg kg^-1 spiked levels was less than 20 %. In order to validate the suitability for routine analysis, the method was applied to 448 fruit and vegetable samples purchased in different local markets. The results show 83.3 % of the analyzed samples have positive findings (higher than the limits of identification and quantification), and 412 commodity-pesticide combinations are identified in our scope. The approach proved to be a cost-effective, time-saving and powerful strategy for routine large-scope screening of pesticides.

Liquid chromatography-quadrupole-time-of-flight mass spectrometry screening procedure for urine samples in forensic casework compared to gas chromatography-mass spectrometry

This work represents the development, validation, and application of a liquid chromatography-quadrupole-time-of-flight mass spectrometry (LC-QTOF-MS) screening method for the detection of pharmaceutical substances and illicit drugs (acidic, basic, and neutral organic drugs) in urine samples. Time-of-flight mass spectrometry was performed using an LC-Triple TOF 5600 system with electrospray ionization operated in both positive and negative mode, respectively. The limits of detection (LODs), determined for 34 substances, were < 10 ng/mL for 91% of the compounds. The limits of quantitation (LOQs) were < 20 ng/mL for 91% of the substances. The identification of the compounds was based on exact mass (< ± 5 ppm), retention time (<2%) if available, isotopic pattern fit (<10%) and library hit (>70%). These four parameters served as identification criteria and are discussed according to their role in identifying compounds even without reference substances. In routine casework, two in-house XIC (extracted ion chromatogram) lists, consisting of 456 protonated and 26 deprotonated compounds were used and retention times for 365 compounds were available. Compared to the results found with the established gas chromatography-mass spectrometry (GC-MS) procedure, the findings with the LC-QTOF-MS screening method showed a good comparability. Results that were not detected by LC-QTOF-MS because of a missing entry in the targeted XIC list could retrospectively be confirmed by simply entering the elemental formula of the relevant substance into the software and reprocessing the sample. LC-QTOF-MS offers an attractive technique for the fast and specific identification of illicit drugs and toxic compounds in urine samples. Copyright © 2016 John Wiley & Sons, Ltd.

Broad Screening and Identification of Novel Psychoactive Substances in Plasma by High-Performance Liquid Chromatography-High-Resolution Mass Spectrometry and Post-run Library Matching

Drug abuse is today a growing global problem. Often the consumers are not aware about the type of substances they are using and the correlated risks. In recent years, new psychoactive substances (NPS) appeared in the illicit market. The presence of NPS, such as synthetic cathinones, cannabinoids and phenethylamines, which are known to be pharmacologically and toxicologically hazardous, has been frequently reported. The aim of this study was the development of a liquid chromatography-high-resolution mass spectrometry (LC-HRMS) method for a broad screening of NPS in plasma. Data acquisition was in MS/MS and full-scan modes and the method was validated for 25 NPS belonging to different chemical classes. Quantitative results have been obtained for these analytes with limits of quantification ranging from 0.03 to 0.4 ng/mL. The method was proven to be suitable for the screening of additional substances; to this aim, a post-run library matching was conducted for every sample with an in-house database containing over 300 NPS and known metabolites. The library may be constantly expanded with new drugs, in order to obtain a broad screening of NPS in biological matrices.

Glucocorticoid receptor isoforms direct distinct mitochondrial programs to regulate ATP production

The glucocorticoid receptor (GR), a nuclear receptor and major drug target, has a highly conserved minor splice variant, GRγ, which differs by a single arginine within the DNA binding domain. GRγ, which comprises 10% of all GR transcripts, is constitutively expressed and tightly conserved through mammalian evolution, suggesting an important non-redundant role. However, to date no specific role for GRγ has been reported. We discovered significant differences in subcellular localisation, and nuclear-cytoplasmic shuttling in response to ligand. In addition the GRγ transcriptome and protein interactome was distinct, and with a gene ontology signal for mitochondrial regulation which was confirmed using Seahorse technology. We propose that evolutionary conservation of the single additional arginine in GRγ is driven by a distinct, non-redundant functional profile, including regulation of mitochondrial function.

Successful adaption of a forensic toxicological screening workflow employing nontargeted liquid chromatography-tandem mass spectrometry to water analysis

Forensic toxicology and environmental water analysis share the common interest and responsibility in ensuring comprehensive and reliable confirmation of drugs and pharmaceutical compounds in samples analyzed. Dealing with similar analytes, detection and identification techniques should be exchangeable between scientific disciplines. Herein, we demonstrate the successful adaption of a forensic toxicological screening workflow employing nontargeted LC/MS/MS under data-dependent acquisition control and subsequent database search to water analysis. The main modification involved processing of an increased sample volume with SPE (500 mL vs. 1-10 mL) to reach LODs in the low ng/L range. Tandem mass spectra acquired with a qTOF instrument were submitted to database search. The targeted data mining strategy was found to be sensitive and specific; automated search produced hardly any false results. To demonstrate the applicability of the adapted workflow to complex samples, 14 wastewater effluent samples collected on seven consecutive days at the local wastewater-treatment plant were analyzed. Of the 88,970 fragment ion mass spectra produced, 8.8% of spectra were successfully assigned to one of the 1040 reference compounds included in the database, and this enabled the identification of 51 compounds representing important illegal drugs, members of various pharmaceutical compound classes, and metabolites thereof.

Fully automated semi-quantitative toxicological screening in three biological matrices using turbulent flow chromatography/high resolution mass spectrometry

BACKGROUND

In clinical and forensic toxicology, fast and specific methods are needed for the screening of different classes of drugs. A complete general unknown screening procedure was developed using turbulent flow chromatography with electrospray ionization and Orbitrap mass spectrometry.

METHODS

After protein precipitation, samples were injected directly into the turbulent flow chromatographic system and analyzed with an Orbitrap mass spectrometer. The Exactive® operated in positive and negative modes with alternated high collision dissociation in order to obtain characteristic fragments. We built a library containing 616 compounds by analyzing a reference standard for all the molecules.

RESULTS

Identification was based on retention time, accurate measured mass, isotopic pattern and presence of specific fragments. For each substance, we set a calibration range encompassing infra-therapeutic, therapeutic, supra-therapeutic and toxic concentrations in order to generate semi-quantitative result. For 65% of the components, the limit of detection was below 5 ng/mL. The validation process showed the approach to be selective, sensitive, accurate and precise.

CONCLUSION

The method has been accredited by COFRAC (French Accreditation Committee) according to the ISO 15189 standard. Applicability was successfully tested by analyzing authentic serum, urine and whole blood samples.

Compound identification in forensic toxicological analysis with untargeted LC-MS-based techniques

Untargeted LC-MS/MS techniques have become indispensable tools for systematic toxicological analysis. Compound identification is based on the mass spectrometric information obtained, and this may include m/z, isotopic pattern, retention time and fragmentation information. All these different kinds of analytical features can be stored in libraries and databases. Currently, the most competent approach for compound identification involves tandem mass spectral library search. State-of-the-art databases were shown to be sensitive, specific, robust and instrument-independent. Low- and high-resolution instruments can both be used to develop efficient screening workflows. For automated and unattended acquisition of tandem mass spectral data, data-dependent acquisition control is the method of choice. Due to their impressive detection sensitivity, data-independent acquisition techniques are finding increased applicability.

Structural characterization of muropeptides from Chlamydia trachomatis peptidoglycan by mass spectrometry resolves "chlamydial anomaly"

The "chlamydial anomaly," first coined by James Moulder, describes the inability of researchers to detect or purify peptidoglycan (PG) from pathogenic Chlamydiae despite genetic and biochemical evidence and antibiotic susceptibility data that suggest its existence. We recently detected PG in Chlamydia trachomatis by a new metabolic cell wall labeling method, however efforts to purify PG from pathogenic Chlamydiae have remained unsuccessful. Pathogenic chlamydial species are known to activate nucleotide-binding oligomerization domain-containing protein 2 (NOD2) innate immune receptors by as yet uncharacterized ligands, which are presumed to be PG fragments (muramyl di- and tripeptides). We used the NOD2-dependent activation of NF-κB by C. trachomatis-infected cell lysates as a biomarker for the presence of PG fragments within specific lysate fractions. We designed a new method of muropeptide isolation consisting of a double filtration step coupled with reverse-phase HPLC fractionation of Chlamydia-infected HeLa cell lysates. Fractions that displayed NOD2 activity were analyzed by electrospray ionization mass spectrometry, confirming the presence of muramyl di- and tripeptides in Chlamydia-infected cell lysate fractions. Moreover, the mass spectrometry data of large muropeptide fragments provided evidence that transpeptidation and transglycosylation reactions occur in pathogenic Chlamydiae. These results reveal the composition of chlamydial PG and disprove the "glycanless peptidoglycan" hypothesis.

Simultaneous determination of three banned psychiatric drugs in pig feed and tissue using solid-phase reactor on-line oxidizing and HPLC-fluorescence detection

The banned addition of psychiatric drugs such as phenothiazines to animal feed and foodstuffs increases the risk of human organ lesion. Phenothiazines usually exhibit weak native fluorescence and can be oxidized to strongly fluorescent compounds. In this study, a novel, sensitive and convenient method of HPLC-fluorescence detection based on post-column on-line oxidizing with lead dioxide solid-phase reactor has been developed for simultaneous determination of three banned psychotropic drugs, promethazine, chlorpromazine and thioridazine. Three compounds were successfully separated on an Agilent TC-C18 column with mobile phase of acetonitrile (A) and water (B), both containing 0.5% (v/v) formic acid. A gradient elution was programmed and fluorimetric detection was performed at λex /λem of 332/373 nm for promethazine, 340/380 nm for chlorpromazine and 352/432 nm for thioridazine. The calibration graphs gave good linearity over the concentration ranges of 30.0-4976.4 µg/L for promethazine, 2.0-2153.2 µg/L for chlorpromazine, and 15.0-3088.0 µg/L for thioridazine, and correlation coefficients (r) were ≥0.995. The method was applied to the determination of phenothiazines in pig feed and pig tissue, and the average spiked recoveries were in the range 69.1-115.4%.

Liquid chromatography, in combination with a quadrupole time-of-flight instrument (LC QTOF), with sequential window acquisition of all theoretical fragment-ion spectra (SWATH) acquisition: systematic studies on its use for screenings in clinical and forensic toxicology and comparison with information-dependent acquisition (IDA)

Forensic and clinical toxicological screening procedures are employing liquid chromatography-tandem mass spectrometry (LC-MS/MS) techniques with information-dependent acquisition (IDA) approaches more and more often. It is known that the complexity of a sample and the IDA settings might prevent important compounds from being triggered. Therefore, data-independent acquisition (DIA) methods should be more suitable for systematic toxicological analysis (STA). The DIA method sequential window acquisition of all theoretical fragment-ion spectra (SWATH), which uses Q1 windows of 20-35 Da for data-independent fragmentation, was systematically investigated for its suitability for STA. Quality of SWATH-generated mass spectra were evaluated with regard to mass error, relative abundance of the fragments, and library hits. With the Q1 window set to 20-25 Da, several precursors pass Q1 at the same time and are fragmented, thus impairing the library search algorithms to a different extent: forward fit was less affected than reverse fit and purity fit. Mass error was not affected. The relative abundance of the fragments was concentration dependent for some analytes and was influenced by cofragmentation, especially of deuterated analogues. Also, the detection rate of IDA compared to SWATH was investigated in a forced coelution experiment (up to 20 analytes coeluting). Even using several different IDA settings, it was observed that IDA failed to trigger relevant compounds. Screening results of 382 authentic forensic cases revealed that SWATH's detection rate was superior to IDA, which failed to trigger ∼10% of the analytes.

Applying 'Sequential Windowed Acquisition of All Theoretical Fragment Ion Mass Spectra' (SWATH) for systematic toxicological analysis with liquid chromatography-high-resolution tandem mass spectrometry

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) has become an indispensable analytical technique in clinical and forensic toxicology for detection and identification of potentially toxic or harmful compounds. Particularly, non-target LC-MS/MS assays enable extensive and universal screening requested in systematic toxicological analysis. An integral part of the identification process is the generation of information-rich product ion spectra which can be searched against libraries of reference mass spectra. Usually, 'data-dependent acquisition' (DDA) strategies are applied for automated data acquisition. In this study, the 'data-independent acquisition' (DIA) method 'Sequential Windowed Acquisition of All Theoretical Fragment Ion Mass Spectra' (SWATH) was combined with LC-MS/MS on a quadrupole-quadrupole-time-of-flight (QqTOF) instrument for acquiring informative high-resolution tandem mass spectra. SWATH performs data-independent fragmentation of all precursor ions entering the mass spectrometer in 21m/z isolation windows. The whole m/z range of interest is covered by continuous stepping of the isolation window. This allows numerous repeat analyses of each window during the elution of a single chromatographic peak and results in a complete fragment ion map of the sample. Compounds and samples typically encountered in forensic casework were used to assess performance characteristics of LC-MS/MS with SWATH. Our experiments clearly revealed that SWATH is a sensitive and specific identification technique. SWATH is capable of identifying more compounds at lower concentration levels than DDA does. The dynamic range of SWATH was estimated to be three orders of magnitude. Furthermore, the >600,000 SWATH spectra matched led to only 408 incorrect calls (false positive rate = 0.06 %). Deconvolution of generated ion maps was found to be essential for unravelling the full identification power of LC-MS/MS with SWATH. With the available software, however, only semi-automated deconvolution was enabled, which rendered data interpretation a laborious and time-consuming process.

Liquid chromatography high-resolution TOF analysis: investigation of MSE for broad-spectrum drug screening

BACKGROUND

High-resolution mass spectrometry (HRMS) has the potential to supplement other drug screening platforms used in toxicology laboratories. HRMS offers high analytical specificity, which can be further enhanced by incorporating a fragment ion for each analyte. The ability to obtain precursor ions and fragment ions using elevated collision energies (MS(E)) can help improve the specificity of HRMS methods.

METHODS

We developed a broad-spectrum screening method on an ultraperformance liquid chromatography TOF mass spectrometer (UPLC-TOF-MS) using the MS(E) mode. A diverse set of patient samples were subjected to a simple dilute, hydrolyze, and shoot protocol and analyzed in a blind manner. Data were processed with 3 sets of criteria with increasing stringency, and the results were compared with the reference laboratory results.

RESULTS

A combination of retention time match (±0.2 min), a protonated analyte, and fragment ion mass accuracy of ±5 ppm produced zero false-positive results. Using these criteria, we confirmed 92% (253/275) of true positives. The positive confirmation rate increased to 98% (270/275) when the requirement for a fragment ion was dropped, but also produced 53 false positives. A total of 136 additional positive drug findings not identified by the reference methods were identified with the UPLC-TOF-MS.

CONCLUSIONS

MS(E) provides a unique way to incorporate fragment ion information without the need of precursor ion selection. A primary limitation of requiring a fragment ion for positive identification was that certain drug classes required high-energy collisions, which formed many fragment ions of low abundance that were not readily detected.

Evaluation of the sensitivity of the 'Wiley registry of tandem mass spectral data, MSforID' with MS/MS data of the 'NIST/NIH/EPA mass spectral library'

Tandem mass spectral libraries are versatile tools for small molecular identification finding application in forensic science, doping control, drug monitoring, food and environmental analysis, as well as metabolomics. Two important libraries are the 'Wiley Registry of Tandem Mass Spectral Data, MSforID' (Wiley Registry MSMS) and the collection of MS/MS spectra part of the 2011 edition of the 'NIST/NIH/EPA Mass Spectral Library' (NIST 11 MSMS). Herein, the sensitivity and robustness of the Wiley Registry MSMS were evaluated using spectra extracted from the NIST 11 MSMS library. The sample set was found to be heterogeneous in terms of mass spectral resolution, type of CID, as well as applied collision energies. Nevertheless, sensitive compound identification with a true positive identification rate ≥95% was possible using either the MSforID Search program or the NIST MS Search program 2.0g for matching. To rate the performance of the Wiley Registry MSMS, cross-validation experiments were repeated using subcollections of NIST 11 MSMS as reference library and spectra extracted from the Wiley Registry MSMS as positive controls. Unexpectedly, with both search algorithms tested, correct results were obtained in less than 88% of cases. We examined possible causes for the results of the cross validation study. The large number of precursor ions represented by a single tandem mass spectrum only was identified as the basic cause for the comparably lower sensitivity of the NIST library.

Testing an alternative search algorithm for compound identification with the 'Wiley Registry of Tandem Mass Spectral Data, MSforID'

A tandem mass spectral database system consists of a library of reference spectra and a search program. State-of-the-art search programs show a high tolerance for variability in compound-specific fragmentation patterns produced by collision-induced decomposition and enable sensitive and specific 'identity search'. In this communication, performance characteristics of two search algorithms combined with the 'Wiley Registry of Tandem Mass Spectral Data, MSforID' (Wiley Registry MSMS, John Wiley and Sons, Hoboken, NJ, USA) were evaluated. The search algorithms tested were the MSMS search algorithm implemented in the NIST MS Search program 2.0g (NIST, Gaithersburg, MD, USA) and the MSforID algorithm (John Wiley and Sons, Hoboken, NJ, USA). Sample spectra were acquired on different instruments and, thus, covered a broad range of possible experimental conditions or were generated in silico. For each algorithm, more than 30,000 matches were performed. Statistical evaluation of the library search results revealed that principally both search algorithms can be combined with the Wiley Registry MSMS to create a reliable identification tool. It appears, however, that a higher degree of spectral similarity is necessary to obtain a correct match with the NIST MS Search program. This characteristic of the NIST MS Search program has a positive effect on specificity as it helps to avoid false positive matches (type I errors), but reduces sensitivity. Thus, particularly with sample spectra acquired on instruments differing in their setup from tandem-in-space type fragmentation, a comparably higher number of false negative matches (type II errors) were observed by searching the Wiley Registry MSMS.

Detection and identification of drugs and toxicants in human body fluids by liquid chromatography-tandem mass spectrometry under data-dependent acquisition control and automated database search

Systematic toxicological analysis (STA) is aimed at detecting and identifying all substances of toxicological relevance (i.e. drugs, drugs of abuse, poisons and/or their metabolites) in biological material. Particularly, gas chromatography-mass spectrometry (GC/MS) represents a competent and commonly applied screening and confirmation tool. Herein, we present an untargeted liquid chromatography-tandem mass spectrometry (LC/MS/MS) assay aimed to complement existing GC/MS screening for the detection and identification of drugs in blood, plasma and urine samples. Solid-phase extraction was accomplished on mixed-mode cartridges. LC was based on gradient elution in a miniaturized C18 column. High resolution electrospray ionization-MS/MS in positive ion mode with data-dependent acquisition control was used to generate tandem mass spectral information that enabled compound identification via automated library search in the "Wiley Registry of Tandem Mass Spectral Data, MSforID". Fitness of the developed LC/MS/MS method for application in STA in terms of selectivity, detection capability and reliability of identification (sensitivity/specificity) was demonstrated with blank samples, certified reference materials, proficiency test samples, and authentic casework samples.

Screening of methylenedioxyamphetamine- and piperazine-derived designer drugs in urine by LC-MS/MS using neutral loss and precursor ion scan

This study describes a method for the screening of methylenedioxyamphetamine- and piperazine-derived compounds in urine by liquid chromatography-tandem mass spectrometry. These substances, characterized by possessing common moieties, are screened using precursor ion and neutral loss scan mode and then quantified in multiple reaction monitoring acquisition mode. Based on the product-ion spectra of different known molecules, chosen as 'model', characteristic neutral losses and product ions were selected: piperazines were detected in precursor ion scan of m/z 44 and neutral loss of 43 and 86 while amphetamines in precursor ion scan of m/z 133, 135 and 163. The applicability of the screening approach was studied in blank urine spiked with selected analytes and processed by solid-phase extraction. Linearity, matrix effect, precision, accuracy, limits of detection and limits of quantification were evaluated both for the screening and the quantification methods. The ability of the screening method to provide semi-quantitative data was demonstrated. This method appears to be a useful tool for the identification of designer drugs derived from piperazines or methylenedioxyamphetamines and can be potentially applied to other drug classes.

On the inter-instrument and the inter-laboratory transferability of a tandem mass spectral reference library. 3. Focus on ion trap and upfront CID

Mass spectral libraries represent versatile tools for the identification of small bioorganic molecules. Libraries based on electron impact spectra are rated robust and transferable. Tandem mass spectral libraries are often considered to work properly only on the instrument that has been used to build the library. An exception from that rule is the 'Wiley Registry of Tandem Mass Spectral Data, MSforID'. In various studies with data sets from different kinds of tandem mass spectrometric instruments, the outstanding sensitivity and robustness of this tandem mass spectral library search approach was demonstrated. The instrumental platforms tested, however, mainly included various tandem-in-space instruments. Herein, the results of a multicenter study with a focus on upfront and tandem-in-time fragmentation are presented. Five laboratories participated and provided fragment ion mass spectra from the following types of mass spectrometers: time-of-flight (TOF), quadrupole-hexapole-TOF, linear ion trap (LIT), 3-D ion trap and LIT-Orbitrap. A total number of 1231 fragment ion mass spectra were collected from 20 test compounds (amiloride, buphenin, cinchocaine, cyclizine, desipramine, dihydroergotamine, dyxirazine, dosulepin, ergotamine, ethambutol, etofylline, mefruside, metoclopramide, phenazone, phentermine, phenytoin, sulfamethoxazole, sulfamoxole, sulthiame and tetracycline) on seven electrospray ionization instruments using 18 different instrumental configurations for fragmentation. For 1222 spectra (99.3%), the correct compound was retrieved as the best matching compound. Classified matches (matches with 'relative average match probability' >40.0) were obtained for 1207 spectra (98.1%). This high percentage of correct identifications clearly supports the hypothesis that the tandem mass spectral library approach tested is a robust and universal identification tool.

Towards a universal LC-MS screening procedure - can an LIT LC-MS(n) screening approach and reference library be used on a quadrupole-LIT hybrid instrument?

In contrast to libraries with highly reproducible gas chromatography electron ionization mass spectra, current liquid chromatography (LC-MS) libraries are limited to specific instrument types. Therefore, the aim of the study was to prove whether a recently developed linear ion trap (LIT) LC-MS(n) screening approach and reference library can be transferred to an LC-MS/MS system with a quadrupole-LIT hybrid mass analyzer using SmileMS, a sophisticated search algorithm. The LIT reference library was built with MS² and MS³ wideband spectra recorded on a ThermoFisher LXQ LIT with electrospray ionization in positive mode and full-scan data-dependent acquisition (DDA). Collision parameter optimizations, including different scan types and energies, were performed on an Applied Biosystems QTRAP 4000 system using electrospray ionization in positive mode and full-scan DDA. Modified library sets were generated to improve the detection of a compound by the used search algorithm. Additionally, 100 authentic human urine samples were screened by both systems for proof of applicability. In the applicability study, 533 compounds were detected by the LXQ and 477 by the QTRAP system using enhanced product ion scan and a modified database. The presented data showed that the LIT screening approach and reference library could be used successfully on a QTRAP instrument with some limitations. These should be overcome by further optimizations regarding DDA settings for better sensitivity and further library modifications to reduce spectra mismatches.

Spectrophotometric Determination of Thioridazine Hydrochloride in Tablets and Biological Fluids by Ion-Pair and Oxidation Reactions

Two simple, sensitive and selective spectrophotometric methods have been described for the determination of the psychoactive drug, thioridazine HCl in tablets and in biological fluids. The first method is based on the oxidation of thioridazine HCl with measured excess of KMnO4under acidic conditions followed by the determination of unreacted oxidant using indigo carmine and methyl orange. The second method is based on the formation of ion-pair complexes with the acidic sulphophthalein dyes such as bromocresol green and bromocresol purple at pH 1.8 of KCl-HCl buffer. The formed complexes were extracted into methylene chloride and their absorbance was measured at 412 nm. Optimizations of the different experimental conditions are described for both methods. The proposed methods were successfully applied for determination of the drug in tablets and biological fluids with good accuracy and precision. Statistical comparison of the results with those obtained by an official method showed good agreement and indicated no significant difference in accuracy and precision.

Combined use of liquid chromatography-hybrid quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) and high performance liquid chromatography with photodiode array detector (HPLC-DAD) in systematic toxicological analysis

Time of flight mass spectrometry provides new possibilities of substance identification by determination of the molecular formula from accurate molecular mass and isotope pattern. However, the huge number of possible isomers requires additional evidence. As a suitable way for routine performance of systematic toxicological analysis, a method for combined use of liquid chromatography-hybrid quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) and high performance liquid chromatography with diode array detector (HPLC-DAD) was developed and applied to blood samples from 77 death cases. The blood samples were prepared by extraction with CH(2)Cl(2) and by protein precipitation with acetonitrile (1:4 (v/v)). The evaporated extracts were reconstituted in 35% acetonitril/0.1% formic acid/H(2)O and aliquots were injected for analysis by LC-QTOF-MS (Agilent 6530) and HPLC-DAD (Agilent 1200). A valve switching system enabled simultaneous operation of both separated chromatographic lines under their respective optimal conditions using the same autosampler. The ESI-QTOF-MS instrument was run in data dependent acquisition mode with switching between MS and MS/MS (cycle time 1.1s) and measuring the full mass spectra and the collision induced dissociation (CID) fragment spectra of all essential [M+H](+) ions. Libraries of accurate mass CID spectra (~2500 substances) and of DAD-UV spectra (~3300 substances) of the authors were used for substance identification. The application of this procedure is demonstrated in detail at four examples with multiple drug intake or administration. In the 77 cases altogether 198 substances were identified (87 by DAD and 195 by QTOF-MS) with a frequency between 1 and 20. In practical application, the sample preparation proved to be suitable for both techniques and for a wide variety of substances with different polarity. The automatic performance of the measurements was efficient and robust. Mutual confirmation, decrease of false positive and false negative identifications, and the semi-quantitative estimation of the concentrations by HPLC-DAD for a first assessment of the toxicological relevance of the qualitative result were shown to be the main advantages of the method combination.

Development and practical application of a library of CID accurate mass spectra of more than 2,500 toxic compounds for systematic toxicological analysis by LC-QTOF-MS with data-dependent acquisition

A library of collision-induced dissociation (CID) accurate mass spectra has been developed for efficient use of liquid chromatography in combination with hybrid quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) as a tool in systematic toxicological analysis. The mass spectra (Δm < 3 ppm) of more than 2,500 illegal and therapeutic drugs, pesticides, alkaloids, other toxic chemicals and metabolites were measured, by use of an Agilent 6530 instrument, by flow-injection of 1 ng of the pure substances in aqueous ammonium formate-formic acid-methanol, with positive and negative electrospray-ionization (ESI), selection of the protonated or deprotonated molecules [M+H](+) or [M-H](-) by the quadrupole, and collision induced dissociation (CID) with nitrogen as collision gas at CID energies of 10, 20, and 40 eV. The fragment mass spectra were controlled for structural plausibility, corrected by recalculation to the theoretical fragment masses and added to a database of accurate mass data and molecular formulas of more than 7,500 toxicologically relevant substances to form the "database and library of toxic compounds". For practical evaluation, blood and urine samples were spiked with a mixture of 33 drugs at seven concentrations between 0.5 and 500 ng mL(-1), prepared by dichloromethane extraction or protein precipitation, and analyzed by LC-QTOF-MS in data-dependent acquisition mode. Unambiguous identification by library search was possible for typical basic drugs down to 0.5-2 ng mL(-1) and for benzodiazepines down to 2-20 ng mL(-1). The efficiency of the method was also demonstrated by re-analysis of venous blood samples from 50 death cases and comparison with previous results. In conclusion, LC-QTOF-MS in data-dependent acquisition mode combined with an accurate mass database and CID spectra library seemed to be one of the most efficient tools for systematic toxicological analysis.

Laboratory diagnostics in acute poisoning: critical overview

Laboratory diagnostics play an important role in the treatment of patients with acute poisoning. The classical clinical chemistry and hematology tests help initiate supportive treatment, and specialized methods enable elucidation of the poisons involved. In this context, two different analytical approaches are used: the direct quantification of a potentially involved compound or screening procedures looking either for a distinct drug class or a wide variety of different compounds. The most common tests are immunoassays, which have the advantage of being fast and highly automated. These assays are available for the substances which are often involved in intoxications. The other analytical technique which is widely used is hyphenated chromatography consisting of either high-performance liquid chromatography or gas chromatography as chromatographic systems and detection with a diode-array or mass spectrometer. Whereas gas chromatography mass spectrometry screening procedures have been known for a long time, liquid chromatography mass spectrometry screening methods are now developed by different research groups and still need to prove their reliability. In this review, the different analytical technologies and their application will be discussed.

Detection and identification of 700 drugs by multi-target screening with a 3200 Q TRAP LC-MS/MS system and library searching

The multi-target screening method described in this work allows the simultaneous detection and identification of 700 drugs and metabolites in biological fluids using a hybrid triple-quadrupole linear ion trap mass spectrometer in a single analytical run. After standardization of the method, the retention times of 700 compounds were determined and transitions for each compound were selected by a "scheduled" survey MRM scan, followed by an information-dependent acquisition using the sensitive enhanced product ion scan of a Q TRAP hybrid instrument. The identification of the compounds in the samples analyzed was accomplished by searching the tandem mass spectrometry (MS/MS) spectra against the library we developed, which contains electrospray ionization-MS/MS spectra of over 1,250 compounds. The multi-target screening method together with the library was included in a software program for routine screening and quantitation to achieve automated acquisition and library searching. With the help of this software application, the time for evaluation and interpretation of the results could be drastically reduced. This new multi-target screening method has been successfully applied for the analysis of postmortem and traffic offense samples as well as proficiency testing, and complements screening with immunoassays, gas chromatography-mass spectrometry, and liquid chromatography-diode-array detection. Other possible applications are analysis in clinical toxicology (for intoxication cases), in psychiatry (antidepressants and other psychoactive drugs), and in forensic toxicology (drugs and driving, workplace drug testing, oral fluid analysis, drug-facilitated sexual assault).

Rapid screening and confirmation of drugs and toxic compounds in biological specimens using liquid chromatography/ion trap tandem mass spectrometry and automated library search

Recent advances in liquid chromatography/tandem mass spectrometry (LC/MS/MS) technology have provided an opportunity for the development of more specific approaches to achieve the 'screen' and 'confirmation' goals in a single analytical step. For this purpose, this study adapts the electrospray ionization ion trap LC/MS/MS instrumentation (LC/ESI-MS/MS) for the screening and confirmation of over 800 drugs and toxic compounds in biological specimens. Liquid-liquid and solid-phase extraction protocols were coupled to LC/ESI-MS/MS using a 1.8-microm particle size analytical column operated at 50 degrees C. Gradient elution of the analytes was conducted using a solvent system composed of methanol and water containing 0.1% formic acid. Positive-ion ESI-MS/MS spectra and retention times for each of the 800 drugs and toxic compounds were first established using 1-10 microg/mL standard solutions. This spectra and retention time information was then transferred to the library and searched by the identification algorithm for the confirmation of compounds found in test specimens - based on retention time matches and scores of fit, reverse fit, and purity resulting from the searching process. The established method was found highly effective when applied to the analyses of postmortem specimens (blood, urine, and hair) and external proficiency test samples provided by the College of American Pathology (CAP). The development of this approach has significantly improved the efficiency of our routine laboratory operation that was based on a two-step (immunoassay and GC/MS) approach in the past.