Background. Gas chromatography (GC) and liquid chromatography (LC) coupled with mass spectrometry (MS) are widely used to confirm drug screening results and for urine screening in presumed ...intoxicated patients. These techniques are better suited to targeted analysis than to general unknown screening and, due to the complexity of testing, results are seldom available rapidly enough to contribute to the immediate care of the patient. High resolution (HR)/MS with time-of-flight (TOF) or orbitrap instruments offer potential advantages in clinical toxicology. Comparison of GC-MS, LC-MS/MS and LC-HR/MS. For unknown analyses, GC-MS and LC-MS/MS require comparison of full-scan spectra against preestablished libraries. Operation in full-scan mode greatly reduces sensitivity and some drugs present in low but significant concentrations may be missed. Selected ion monitoring (SIM) in GC/MS and selected reaction monitoring (SRM) in LC-MS/MS, where only targeted ions are monitored, increase sensitivity but require prior knowledge of what compound is to be measured. LC-HR/MS offers mass assignment with an accuracy of 0.001 atomic mass units (amu) compared with 1 amu in conventional MS. Tentative identification is thus directed to a very limited set of compounds (or even one unique compound) based on the exact molecular formula rather than a fragmentation pattern, since HR/MS can discriminate between compounds with the same nominal molecular mass. LC-MS/MS has clear advantages over GC/MS in ease and speed of sample preparation and the opportunities for its automation. LC-HR/MS is more suitable to clinical toxicology because the drugs present in a sample are rarely known a priori, and tentative identifications of unknowns can be made without the availability of a reference standard or a library spectrum. Blood can be used in preference to urine which is more relevant to the patient's current clinical situation. Methods. A literature search was conducted using PUBMED for clinical toxicology, adulterants in illicit drugs and herbal supplements, and case reports using LC-TOF/MS and LC-HR/MS. Only 42 papers in English were identified in these searches. LC-HR/MS in clinical toxicology. LC-HR/MS has been used to detect designer drugs, doping agents, (neurosteroids) and adulterants such as levamisole, a veterinary antihelmitic found in street cocaine, and pharmaceuticals in herbal medications marketed to contain only natural ingredients. LC-HR/MS has proved useful for cases where existing tests were unable to identify the cause of the intoxication. One patient suffered a drug-induced seizure which was originally thought to be caused by an herbal medication, but diphenhydramine was determined to be the culprit. In another, 5-oxoproline was identified as the cause of metabolic acidosis seen in chronic acetaminophen (paracetamol) use. LC-HR/MS has successfully identified medications that were mislabeled or misrepresented street drugs. In one case, medications sold as diazepam were determined to be glyburide instead. The identification of novel designer amines, stimulants found in "bath salts", and synthetic cannabinoids are well suited to LC-HR/MS. Dozens or even hundreds of possible compounds cannot realistically be tested on an individual basis by targeted LC-MS/MS or GC/MS analysis. Conclusions. LC-HR/MS offers unique opportunities for time-sensitive clinical analysis of blood samples from intoxicated patients and for comprehensive screening in a wide range of situations and materials. While the identification is not as definitive as that obtained by conventional fragmentation MS, the presumptive identification can be confirmed later with standards and spectral library matches. Optimum utilization of the presumptive diagnosis requires close collaboration between the laboratory analysts and their clinical counterparts.
In this article, a dataset from a collaborative non-target screening trial organised by the NORMAN Association is used to review the state-of-the-art and discuss future perspectives of non-target ...screening using high-resolution mass spectrometry in water analysis. A total of 18 institutes from 12 European countries analysed an extract of the same water sample collected from the River Danube with either one or both of liquid and gas chromatography coupled with mass spectrometry detection. This article focuses mainly on the use of high resolution screening techniques with target, suspect, and non-target workflows to identify substances in environmental samples. Specific examples are given to emphasise major challenges including isobaric and co-eluting substances, dependence on target and suspect lists, formula assignment, the use of retention information, and the confidence of identification. Approaches and methods applicable to unit resolution data are also discussed. Although most substances were identified using high resolution data with target and suspect-screening approaches, some participants proposed tentative non-target identifications. This comprehensive dataset revealed that non-target analytical techniques are already substantially harmonised between the participants, but the data processing remains time-consuming. Although the objective of a “fully-automated identification workflow” remains elusive in the short term, important steps in this direction have been taken, exemplified by the growing popularity of suspect screening approaches. Major recommendations to improve non-target screening include better integration and connection of desired features into software packages, the exchange of target and suspect lists, and the contribution of more spectra from standard substances into (openly accessible) databases.
Graphical Abstract
Matrix of identification approach versus identification confidence
As S-donor metalloligands, the dithiolato NiN.sub.2S.sub.2 complexes are employed to synthesize the bimetallic model of the active site of NiFe-Hydrogenases (NiFe-H.sub.2ases). In this work, three ...NiN.sub.2S.sub.2 complexes were used to react with NiCl.sub.2(PNP) (PNP = (Ph.sub.2PCH.sub.2).sub.2NCH.sub.3), respectively, to find out the influences of NiN.sub.2S.sub.2 ligands on the structure and property of model complexes. It's interesting to find dianion Ni(phma).sup.2- (H.sub.4phma = N,N'-1,2-phenylenebis(2-mercaptoacetamide)) and Ni(ema).sup.2- (H.sub.4ema = N,N'-1,2-ethylenebis(2-mercaptoacetamide)) could afford the desired dinuclear models Ni(phma)(mu-S,S')Ni(PNP) (1) and Ni(ema)(mu-S,S')Ni(PNP) (2), while the reaction of neutral Ni(bme-dach) (bme-dach = N,N'-bis-2-methyl-mercaptopropyl-1,4-diazacycloheptane) only yielded a trinuclear complex Ni{Ni(bme-dach)(mu-S,S')}.sub.2BF.sub.4.sub.2 (3). The structures of these complexes have been carefully characterized by NMR, high resolution mass spectrometry, elemental analysis, and X-ray diffraction structure analysis. As the model of NiFe-H.sub.2ases, complex 1 could electrocatalyze H.sub.2 evolution with a rate constant of 9.35 x 10.sup.3 M.sup.-1 s.sup.-1 in the presence of CH.sub.3COOH. Graphic
Mass spectrometry (MS) imaging links molecular information and the spatial distribution of analytes within a sample. In contrast to most histochemical techniques, mass spectrometry imaging can ...differentiate molecular modifications and does not require labeling of targeted compounds. We have recently introduced the first mass spectrometry imaging method that provides highly specific molecular information (high resolution and accuracy in mass) at cellular dimensions (high resolution in space). This method is based on a matrix-assisted laser desorption/ionization (MALDI) imaging source working at atmospheric pressure which is coupled to an orbital trapping mass spectrometer. Here, we present a number of application examples and demonstrate the benefit of ‘mass spectrometry imaging with high resolution in mass and space.’ Phospholipids, peptides and drug compounds were imaged in a number of tissue samples at a spatial resolution of 5–10 μm. Proteins were analyzed after on-tissue tryptic digestion at 50-μm resolution. Additional applications include the analysis of single cells and of human lung carcinoma tissue as well as the first MALDI imaging measurement of tissue at 3 μm pixel size. MS image analysis for all these experiments showed excellent correlation with histological staining evaluation. The high mass resolution (
R
= 30,000) and mass accuracy (typically 1 ppm) proved to be essential for specific image generation and reliable identification of analytes in tissue samples. The ability to combine the required high-quality mass analysis with spatial resolution in the range of single cells is a unique feature of our method. With that, it has the potential to supplement classical histochemical protocols and to provide new insights about molecular processes on the cellular level.
The sample preparation and evaluation of the effects of impurities on the determination of .sup.10Be and .sup.26Al by accelerator mass spectrometry (AMS) was performed as an initial part of research ...project determining the timing of early hominin occupation at Korolevo, western Ukraine. The rock samples analysed exhibited various levels of weathering, lithology, and mass. The follow-up mass spectrometry scans revealed Ti impurity in BeO targets which stimulated quantification of Ti in quartz concentrate. The .sup.26Al to .sup.10Be ratios were independent on Ti and Al impurity for samples from the same depositional level. AMS Be current reduction was a function of BeO dilution by TiO.sub.2 molecules.
The radiometric methods, alpha (α)-, beta (β)-, gamma (γ)-spectrometry, and mass spectrometric methods, inductively coupled plasma mass spectrometry, accelerator mass spectrometry, thermal ionization ...mass spectrometry, resonance ionization mass spectrometry, secondary ion mass spectrometry, and glow discharge mass spectrometry are reviewed for the determination of radionuclides. These methods are critically compared for the determination of long-lived radionuclides important for radiation protection, decommissioning of nuclear facilities, repository of nuclear waste, tracer application in the environmental and biological researches, these radionuclides include
3H,
14C,
36Cl,
41Ca,
59,63Ni,
89,90Sr,
99Tc,
129I,
135,137Cs,
210Pb,
226,228Ra,
237Np,
241Am, and isotopes of thorium, uranium and plutonium. The application of on-line methods (flow injection/sequential injection) for separation of radionuclides and automated determination of radionuclides is also discussed.
Lipids are ubiquitous and serve numerous biological functions; thus lipids have been shown to have great potential as candidates for elucidating biomarkers and pathway perturbations associated with ...disease. Methods expanding coverage of the lipidome increase the likelihood of biomarker discovery and could lead to more comprehensive understanding of disease etiology.
We introduce LipidMatch, an R-based tool for lipid identification for liquid chromatography tandem mass spectrometry workflows. LipidMatch currently has over 250,000 lipid species spanning 56 lipid types contained in in silico fragmentation libraries. Unique fragmentation libraries, compared to other open source software, include oxidized lipids, bile acids, sphingosines, and previously uncharacterized adducts, including ammoniated cardiolipins. LipidMatch uses rule-based identification. For each lipid type, the user can select which fragments must be observed for identification. Rule-based identification allows for correct annotation of lipids based on the fragments observed, unlike typical identification based solely on spectral similarity scores, where over-reporting structural details that are not conferred by fragmentation data is common. Another unique feature of LipidMatch is ranking lipid identifications for a given feature by the sum of fragment intensities. For each lipid candidate, the intensities of experimental fragments with exact mass matches to expected in silico fragments are summed. The lipid identifications with the greatest summed intensity using this ranking algorithm were comparable to other lipid identification software annotations, MS-DIAL and Greazy. For example, for features with identifications from all 3 software, 92% of LipidMatch identifications by fatty acyl constituents were corroborated by at least one other software in positive mode and 98% in negative ion mode.
LipidMatch allows users to annotate lipids across a wide range of high resolution tandem mass spectrometry experiments, including imaging experiments, direct infusion experiments, and experiments employing liquid chromatography. LipidMatch leverages the most extensive in silico fragmentation libraries of freely available software. When integrated into a larger lipidomics workflow, LipidMatch may increase the probability of finding lipid-based biomarkers and determining etiology of disease by covering a greater portion of the lipidome and using annotation which does not over-report biologically relevant structural details of identified lipid molecules.
Urinary amino acid analysis is typically done by cation-exchange chromatography followed by post-column derivatization with ninhydrin and UV detection. This method lacks throughput and specificity. ...Two recently introduced stable isotope ratio mass spectrometric methods promise to overcome those shortcomings. Using two blinded sets of urine replicates and a certified amino acid standard, we compared the precision and accuracy of gas chromatography/mass spectrometry (GC–MS) and liquid chromatography–tandem mass spectrometry (LC–MS/MS) of propyl chloroformate and iTRAQ
® derivatized amino acids, respectively, to conventional amino acid analysis. The GC–MS method builds on the direct derivatization of amino acids in diluted urine with propyl chloroformate, GC separation and mass spectrometric quantification of derivatives using stable isotope labeled standards. The LC–MS/MS method requires prior urinary protein precipitation followed by labeling of urinary and standard amino acids with iTRAQ
® tags containing different cleavable reporter ions distinguishable by MS/MS fragmentation. Means and standard deviations of percent technical error (%TE) computed for 20 amino acids determined by amino acid analyzer, GC–MS, and iTRAQ
®–LC–MS/MS analyses of 33 duplicate and triplicate urine specimens were 7.27
±
5.22, 21.18
±
10.94, and 18.34
±
14.67, respectively. Corresponding values for 13 amino acids determined in a second batch of 144 urine specimens measured in duplicate or triplicate were 8.39
±
5.35, 6.23
±
3.84, and 35.37
±
29.42. Both GC–MS and iTRAQ
®–LC–MS/MS are suited for high-throughput amino acid analysis, with the former offering at present higher reproducibility and completely automated sample pretreatment, while the latter covers more amino acids and related amines.
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