Investigation of the quantitative properties of the quadrupole orthogonal acceleration time-of-flight mass spectrometer with electrospray ionisation using 3,4-methylenedioxymethamphetamine

T-2 toxin, a trichothecene mycotoxin: review of toxicity, metabolism, and analytical methods

This review focuses on the toxicity and metabolism of T-2 toxin and analytical methods used for the determination of T-2 toxin. Among the naturally occurring trichothecenes in food and feed, T-2 toxin is a cytotoxic fungal secondary metabolite produced by various species of Fusarium. Following ingestion, T-2 toxin causes acute and chronic toxicity and induces apoptosis in the immune system and fetal tissues. T-2 toxin is usually metabolized and eliminated after ingestion, yielding more than 20 metabolites. Consequently, there is a possibility of human consumption of animal products contaminated with T-2 toxin and its metabolites. Several methods for the determination of T-2 toxin based on traditional chromatographic, immunoassay, or mass spectroscopy techniques are described. This review will contribute to a better understanding of T-2 toxin exposure in animals and humans and T-2 toxin metabolism, toxicity, and analytical methods, which may be useful in risk assessment and control of T-2 toxin exposure.

Time of flight mass spectrometry applied to the liquid chromatographic analysis of pesticides in water and food

Liquid chromatography coupled to mass spectrometry (LC-MS) is an excellent technique to determine trace levels of polar and thermolabile pesticides and their degradation products in complex matrices. LC-MS can be equipped with several mass analyzers, each of which provides unique features capable to identify, quantify, and resolve ambiguities by selecting appropriate ionization and acquisition parameters. We discuss in this review the use of LC coupled to (quadrupole) time-of-flight mass spectrometry (LC-(Q)ToF-MS) to determine the presence of target and non-target pesticides in water and food. This technique is characterized by operating at a resolving power of 10,000 or more. Therefore, it gives accurate masses for both parent and fragment ions and enables the measurement of the elemental formula of a compound achieving compound identification. In addition, the combination of quadrupole-ToF permits tandem mass spectrometry, provides more structural information, and enhances selectivity. The purpose of this article is to provide an overview on the state of art and applicability of liquid chromatography time-of-flight mass spectrometry (LC-ToF-MS), and liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF-MS) for the analysis of pesticides in environmental matrices and food. The performance of such techniques is depicted in terms of accurate mass measurement, fragmentation, and selectivity. The final section is devoted to describing the applicability of LC-(Q)ToF-MS to routine analysis of pesticides in food matrices, indicating those operational conditions and criteria used to screen, quantify, and identify target and "suspected" pesticides and their degradation products in water, fruits, and vegetables. The potential and future trends as well as limitations of LC-(Q)ToF-MS for pesticide monitoring are highlighted.

Application of liquid chromatography/quadrupole time-of-flight mass spectrometry (LC-QqTOF-MS) in the environmental analysis

This paper gives an overview of the potentials of liquid chromatography-hybrid quadrupole time-of-flight mass spectrometry (LC-QqTOF) in the environmental analysis. Examples of applications of QqTOF instruments for target analysis of pharmaceuticals and pesticides are presented and discussed, as well as applications aimed on the identification of unknown compounds present in environmental waters or on the elucidation of structures of biodegradation and photodegradation products. Specific issues such as uncertainty of mass measurement and quantitative performances are discussed in details.

On-line concentration of neomycin and screening aminoglycosides in milk by short capillary column and tandem mass spectrometry

An MS-MS method was established for the trace analysis of neomycin and screening aminoglycoside antibiotics (such as amikacin, gentamicin, kanamycin, and tobramycin) in a milk sample. The extraction and purification are based on ion-pair SPE technology on a short fused-silica capillary RP C18 column. The capillary SPE column provided the stationary phase to retain aminoglycoside antibiotics and MS-MS compatible organic acid heptafluorobutyric acid (HFBA) was used as protein precipitation and ion-pair reagent. Aminoglycosides were extracted in this short column and directly eluted to MS-MS without evaporating to dryness and reconstituted with MS-MS compatible solvent after SPE. The LOQ was 0.1 microg/mL and the calibration curve was linear up to 6.4 microg/mL. A small amount of milk product, 10 microL, is sufficient for the analysis and application of this method as the trace analysis of neomycin in the biological matrix proved simple and workable.

Development of a liquid chromatography/time-of-flight mass spectrometric method for the simultaneous determination of trichothecenes, zearalenone and aflatoxins in foodstuffs

A liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (LC/APCI-MS) method based on time-of-flight MS (TOFMS) with a real-time reference mass correction technique was developed for the simultaneous determination of Fusarium mycotoxins (nivalenol, deoxynivalenol, fusarenon X, 3-acetyldeoxynivalenol, 15-acetyldeoxynivalenol, HT-2 toxin, T-2 toxin, diacetoxyscirpenol, zearalenone) and Aspergillus mycotoxins (aflatoxin B1, aflatoxin B2, aflatoxin G1, aflatoxin G2) in corn, wheat, cornflakes and biscuits. Samples were cleaned up with a MultiSep #226 column. Detection of the mycotoxins was carried out in exact mass chromatograms with a mass window of 0.03 Th. Calibration curves were linear from 2 to 200 ng x mL(-1) for trichothecenes and zearalenone, and 0.2 to 20 ng x mL(-1) for aflatoxins, by 20 microL injection. The limits of detection ranged from 0.1 to 6.1 ng x g(-1) in foodstuffs analyzed in this study. The LC/TOFMS method was found to be suitable for the screening of multiple mycotoxins in foodstuffs rapidly and with high sensitivity, and its performance was demonstrated for the confirmation for target mycotoxins.

LC-MS/MS in the elucidation of an isomer of the recreational drug methylenedioxy ethylamphetamine: Methylenedioxy dimethylamphetamine

This paper describes the surplus value of a quadrupole-orthogonal acceleration TOF mass spectrometer, coupled to a liquid chromatographic separation system, for the unequivocal identification and structural elucidation of an unknown compound in the field of designer drugs. In a patient sample set (blood, tissues, vitreous humor, etc.), analyzed with a dedicated liquid chromatographic-fluorescence detection method for the determination of methylenedioxy amphetamine, methylenedioxy methamphetamine, and methylenedioxy ethylamphetamine (MDEA), a "strange" inexplicable peak appeared at a retention time not corresponding to any of our reference materials. Based on the identical excitation and emission wavelengths in detection, and a retention behavior comparable to MDEA, it was assumed that this unknown compound was an isomer of the recreational drug MDEA. With a simple and straightforward methodological crossover between LC fluorescence detection and LC-MS/MS, additional information for structural elucidation was easily obtained. Chromatographic separation was achieved on a Hypersil BDS C18 column (fluorescence detection part) and on a Hypersil BDS phenyl column (mass spectrometric detection part). MS showed that the unknown compound's molecular mass was identical to that of MDEA, and, in addition, its fragmentation pattern too proved quite similar to that of MDEA. A thorough literature overview and study of the fragmentation pattern by means of the MS/MS spectrum led to an evidence-based hypothesis of 3,4-methylenedioxy N,N-dimethylamphetamine (MDDM) being the unknown compound. To confirm this hypothesis, MDDM was synthesized and its presence in our biological sample was finally demonstrated by co-injection with alternatively synthesized MDDM and MDEA. This application shows the synergism between LC and MS in the elucidation of unknown compounds, nevertheless emphasizing the essence of chromatographic separation when dealing with isomers.

Development of new methodologies for the mass spectrometry study of bioorganic macromolecules

In recent years, mass spectrometry has been increasingly used for the analysis of various macromolecules of biological, biomedical, and biochemical interest. This increase has been made possible by two key developments: the advent of electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) sources. The two new techniques produce a significant increase in mass range and in sensitivity that led to the development of new applications and of new analyzer designs, software, and robotics. This review, apart from the description of the status of mass spectrometry in the analysis of bioorganic macromolecules, is mainly devoted to the illustration of the more recent promising techniques and on their possible future evolution.

Potential of gas chromatography-orthogonal acceleration time-of-flight mass spectrometry (GC-oaTOFMS) in flavor research

Gas chromatography-orthogonal acceleration time-of-flight mass spectrometry (GC-oaTOFMS) is an emerging technique offering a straightforward access to a resolving power up to 7000. This paper deals with the use of GC-oaTOFMS to identify the flavor components of a complex seafood flavor extract and to quantify furanones formed in model Maillard reactions. A seafood extract was selected as a representative example for complex food flavors and was previously analyzed using GC-quadrupole MS, leaving several molecules unidentified. GC-oaTOFMS analysis was focused on these unknowns to evaluate its potential in flavor research, particularly for determining exact masses. N-Methyldithiodimethylamine, 6-methyl-5-hepten-2-one, and tetrahydro-2,4-dimethyl-4H-pyrrolo[2,1-d]-1,3,5-dithiazine were successfully identified on the basis of the precise mass determination of their molecular ions and their major fragments. A second set of experiments was performed to test the capabilities of the GC-oaTOFMS for quantification. Calibration curves were found to be linear over a dynamic range of 10(3) for the quantification of furanones. The quantitative data obtained using GC-oaTOFMS confirmed earlier results that the formation of 4-hydroxy-2,5-dimethyl-3(2H)-furanone was favored in the xylose/glycine model reaction and 2(or 5)-ethyl-4-hydroxy-5(or 2)-methyl-3(2H)-furanone in the xylose/alanine model reaction. It was concluded that GC-oaTOFMS may become a powerful analytical tool for the flavor chemist for both identification and quantification purposes, the latter in particular when combined with stable isotope dilution assay.

Quantification of [Dmt1]DALDA in ovine plasma by on-line liquid chromatography/quadrupole time-of-flight mass spectrometry

The synthetic peptide [Dmt(1)]DALDA (Dmt-D-Arg-Phe-Lys-NH(2); Dmt = 2',6'-dimethyltyrosine; 'super-DALDA') is a mu opioid-receptor agonist. On-line liquid chromatography/quadrupole time-of-flight mass spectrometry and the corresponding stable isotope-incorporated synthetic peptide internal standard were used to quantify [Dmt(1)]DALDA that had been extracted from ovine plasma samples. The [M+2H](2+) ion was used to construct the calibration curve, and the product ion was used for verification of the peptide. The detection sensitivity for the [Dmt(1)]DALDA [M+2H](2+) ion was 12.5 fmol and 50 fmol for the m/z 432.3 product ion. The concentration profile of [Dmt(1)]DALDA was determined from a set of ovine plasma samples. The molecular specificity of the peptide quantification was confirmed by tandem mass spectrometry (MS/MS).

Quadrupole time-of-flight mass spectrometry: a method to study the actual expression of allergen isoforms identified by PCR cloning

BACKGROUND

Over the past 2 decades, molecular biology has shown that most major allergens exist in multiple isoforms. Very little is known about the relevance of allergen isoforms at the level of expressed protein (ie, actual allergen exposure).

OBJECTIVE

The aim of this study was to evaluate the applicability of state-of-the-art quadrupole time-of-flight mass spectrometry (Q-TOF MSMS) to the identification and quantification of allergen isoforms at the protein level.

METHODS

Q-TOF MSMS is a mass spectrometric approach for sequencing peptides and proteins. In our study it was applied to recombinant (r)Mal d 1, rBet v 1a and rBet v 1d, and natural (n)Mal d 1 from fruits of Malus domestica, cultivar Granny Smith.

RESULTS

Q-TOF MSMS allowed sequencing of about 70% of all amino acids in Mal d 1 and about 60% of those in Bet v 1. Mixing experiments with rBet v 1 isoforms and with rMal d 1 and nMal d 1 revealed that the technique allows identification of isoforms in mixtures down to a level of at least 5%. Recombinant Mal d 1 was identified as a Mal d 1a representative, whereas Granny Smith apples were shown to contain Mal d 1b-like allergen isoforms. In this apple cultivar hitherto unreported modifications of Mal d 1b were identified. Q-TOF MSMS allowed semiquantitative measurement of allergen at the femtomole to picomole level.

CONCLUSION

Q-TOF MSMS is a powerful tool to find out whether an allergen isoform, detected at the cDNA level, is really expressed in quantities relevant for the allergic patient.

Progress of liquid chromatography-mass spectrometry in clinical and forensic toxicology

The use of liquid chromatography-mass spectrometry (LC-MS) has recently exploded in various analytic fields, including toxicology and therapeutic drug monitoring (although still far behind pharmacokinetics). There is no doubt that LC-MS is currently competing with gas chromatography (GC)-MS for the status of the reference analytic technique in toxicology. This review presents, for the nonspecialist reader, the principles, advantages, and drawbacks of LC-MS systems using atmospheric pressure interfaces. It also gives an overview of the analytic methods for xenobiotics that could be set up with these instruments for clinical or forensic toxicology. In particular, as far as quantitative techniques are concerned, this review tries to underline the large number and variety of drugs or classes of drugs (drugs of abuse, therapeutic drugs) or toxic compounds (e.g., pesticides) that can be readily determined using such instruments, the respective merits of the different ionization sources, and the improvements brought about by tandem MS. It also discusses new applications of LC-MS in the field of toxicology, such as "general unknown" screening procedures and mass spectral libraries using LC-atmospheric pressure ionization (API)-MS or MS-MS, presenting the different solutions proposed to overcome the naturally low fragmentation power of API sources. Finally, the opportunities afforded by the most recent or proposed instrument designs are addressed.

Investigation of an enhanced resolution triple quadrupole mass spectrometer for high-throughput liquid chromatography/tandem mass spectrometry assays

Triple quadrupole mass spectrometers, when operated in multiple reaction monitoring (MRM) mode, offer a unique combination of sensitivity, specificity, and dynamic range. Consequently, the triple quadrupole is the workhorse for high-throughput quantitation within the pharmaceutical industry. However, in the past, the unit mass resolution of quadrupole instruments has been a limitation when interference from matrix or metabolites cannot be eliminated. With recent advances in instrument design, triple quadrupole instruments now afford mass resolution of less than 0.1 Dalton (Da) full width at half maximum (FWHM). This paper describes the evaluation of an enhanced resolution triple quadrupole mass spectrometer for high-throughput bioanalysis with emphasis on comparison of selectivity, sensitivity, dynamic range, precision, accuracy, and stability under both unit mass (1 Da FWHM) and enhanced (<or=0.1 Da FWHM) resolution. The advantage of enhanced resolution was demonstrated in the case of mometasone with polypropylene glycol (PPG) interference. At unit mass resolution, the transmitted precursor ion from the first quadrupole contained not only protonated molecules from mometasone, but also PPG interference. At enhanced resolution only selected mometasone peaks were transmitted, and no interference from PPG was detected. Sensitivity of the instrument was demonstrated with 10 femtograms of descarboethoxyloratadine injected on-column, for which a signal-to-noise (S/N) ratio of 24 was obtained for MRM chromatograms at both unit and enhanced resolution. Absolute signals obtained at enhanced resolution were about one-third those obtained at unit mass resolution. However, S/N was maintained at enhanced resolution due to the proportional decrease in noise level. Finally, the stability of the instrument operating at enhanced resolution was demonstrated during an overnight 17 h period that was used to validate a liquid chromatography/tandem mass spectrometry (LC/MS/MS) assay for the quantitation of loratadine and descarboethoxyloratadine in human plasma. Assay performances (dynamic range, correlation coefficients for standard curves, precision and accuracy for QC samples) under unit and enhanced resolution were both within current pharmaceutical and regulatory guidelines demonstrating the stability of the mass spectrometer operating at enhanced resolution for typical bioanalytical high-throughput applications.

Applications of new liquid chromatography-tandem mass spectrometry technologies for drug development support

We have evaluated (i) a multiplexed electrospray interface, (ii) serial sample introduction, and (iii) a quadrupole time-of-flight mass spectrometer for quantitative bioanalysis in compliance with good laboratory practice. These evaluations were done using a 96-well plate liquid chromatography-tandem mass spectrometry method for the quantitation of loratadine and its metabolite, descarboethoxyloratadine. The assay has a dynamic range of 1-1000 ng/ml with 5.56 pg of each analyte being injected on-column at the limit of quantitation. For the four-channel multiplexed electrospray experiments, one-run validations were performed simultaneously in rat, rabbit, mouse and dog plasma. In the four-stream serial experiments, the total run time of the assay was reduced from 3.5 to 0.35 min, resulting in a net acquisition time of 11 s. Four simulated validation runs with standard and quality control solutions were analyzed. Precision and accuracy for standards and quality control samples met US Food and Drug Administration recommended criteria for both the drug and the metabolite using those two approaches. In addition, a quadrupole time-of-flight mass spectrometer was used as a detector in the tandem mass spectrometry mode for the loratadine assay. Our results demonstrated that a dynamic range of three orders of magnitude could be achieved using the quadrupole time-of-flight mass spectrometer, making it useful for quantitation in preclinical toxicology studies.

Comparison between liquid chromatography-time of-flight mass spectrometry and selected reaction monitoring liquid chromatography-mass spectrometry for quantitative determination of idoxifene in human plasma

This study compares HPLC electrospray time-of-flight mass spectrometry and selected reaction monitoring (SRM) LC-MS for high throughput quantitative determination of a small molecule drug in biological samples. A high throughput LC-MS method was developed for quantitatative determination of idoxifene in human plasma and the evaluation was accomplished with the cross-validation of the developed LC-MS method between the time-of-flight mass spectrometer, and a triple quadrupole mass spectrometer operated in the SRM mode. A simple one-step semi-automated 96-well liquid-liquid extraction procedure was used to prepare 96 samples in approximately 30 min and a rapid gradient was used to shorten the LC run time. Time-of-flight mass spectrometry provides acquisition of full-scan mass spectra and extracted ion current chromatograms, which may be extracted from the total ion current chromatogram for peak area determination. The limit of quantitation for idoxifene in human plasma obtained with the time-of-flight mass spectrometer was 5 ng/ml based on 100-microl aliquots of human plasma, and the linear dynamic range was from 5 ng/ml to 2000 ng/ml. The quantitative LC-MS results from the time-of-flight mass spectrometer demonstrated that precision did not exceed 7.1% and accuracy did not exceed 1.7% with reference to quality control samples at three concentration levels in replicates of six. In contrast, the limit of quantitation for idoxifene in human plasma using a tandem triple quadrupole mass spectrometer was 0.5 ng/ml with a linear dynamic range to 1000 ng/ml. The results from the triple quadrupole instrument show that the precision did not exceed 2.2% and accuracy did not exceed 2.9%. The overall results suggest time-of-flight mass spectrometry may be a viable technique for high throughput bioanalytical work for the quantitative determination of a representative small molecule drug in the low ng/ml range in human plasma.

Determination of the Designer Drugs 3,4-Methylenedioxymethamphetamine, 3,4-Methylenedioxyethylamphetamine, and 3,4-Methylenedioxyamphetamine with HPLC and Fluorescence Detection in Whole Blood, Serum, Vitreous Humor, and Urine

Background: The popular designer drugs 3,4-methylenedioxymethamphetamine (MDMA) and 3,4-methylenedioxyethylamphetamine (MDEA) can be determined in serum, whole blood, and urine, but also in vitreous humor. The latter matrix is interesting when dealing with decomposed bodies in a toxicological setting.

Methods: After extraction, chromatographic separation was achieved on a narrow-bore C18 column by gradient elution with fluorometric detection; results were confirmed by liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Results: The method was linear over the range of 2–1000 μg/L for whole blood, serum, and vitreous humor, and 0.1–5 mg/L for urine. Extraction recoveries were &gt;70%, imprecision (CV) was 2.5–19%, and analytical recoveries were 95.5–104.4%. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.8 and 2 μg/L, respectively, for whole blood, serum, and vitreous humor, and 2.5 μg/L and 0.1 mg/L, respectively, for urine. Excellent correlations between the quantitative LC-fluorescence and LC-MS/MS results were obtained. We found the following concentrations in a thanatochemical distribution study in rabbits: in serum, 5.3–685 μg/L for MDMA and from the LOQ to 14.5 μg/L for 3,4-methylenedioxyamphetamine (MDA); in whole blood, 19.7–710 μg/L for MDMA and from the LOQ to 17.8 μg/L for MDA; in vitreous humor, 12.1–97.8 μg/L for MDMA and from the LOQ to 3.86 μg/L for MDA. In routine toxicological urine samples, concentrations ranged from LOQ to 14.62 mg/L for MDA, from LOQ to 157 mg/L for MDMA, and from LOQ to 32.54 mg/L for MDEA.

Conclusions: The HPLC method described is sensitive, specific, and suitable for the determination of MDMA, MDEA, and MDA in whole blood, serum, vitreous humor, and urine.

Liquid chromatography-mass spectrometry in forensic toxicology

Liquid chromatography-mass spectrometry has evolved from a topic of mainly research interest into a routinely usable tool in various application fields. With the advent of new ionization approaches, especially atmospheric pressure, the technique has established itself firmly in many areas of research. Although many applications prove that LC-MS is a valuable complementary analytical tool to GC-MS and has the potential to largely extend the application field of mass spectrometry to hitherto "MS-phobic" molecules, we must recognize that the use of LC-MS in forensic toxicology remains relatively rare. This rarity is all the more surprising because forensic toxicologists find themselves often confronted with the daunting task of actually searching for evidence materials on a scientific basis without any indication of the direction in which to search. Through the years, mass spectrometry, mainly in the GC-MS form, has gained a leading role in the way such quandaries are tackled. The advent of robust, bioanalytically compatible combinations of liquid chromatographic separation with mass spectrometric detection really opens new perspectives in terms of mass spectrometric identification of difficult molecules (e.g., polar metabolites) or biopolymers with toxicological relevance, high throughput, and versatility. Of course, analytical toxicologists are generally mass spectrometry users rather than mass spectrometrists, and this difference certainly explains the slow start of LC-MS in this field. Nevertheless, some valuable applications have been published, and it seems that the introduction of the more universal atmospheric pressure ionization interfaces really has boosted interests. This review presents an overview of what has been realized in forensic toxicological LC-MS. After a short introduction into LC-MS interfacing operational characteristics (or limitations), it covers applications that range from illicit drugs to often abused prescription medicines and some natural poisons. As such, we hope it can act as an appetizer to those involved in forensic toxicology but still hesitating to invest in LC-MS.

Approaches to higher-throughput pharmacokinetics (HTPK) in drug discovery

With pressure on pharmaceutical companies to reduce time-to-market and improve the success rate of new drug candidates, higher-throughput pharmacokinetic (HTPK) support has become an integral part of many drug discovery programmes. This report details the amalgamation of robotics, new sample preparation technologies and highly sensitive and selective mass spectrometric detection systems to deliver the promise of HTPK. A historical perspective on automated bioanalysis with the current approaches and future prospects for the discipline are described.

Evaluation of automated single mass spectrometry to tandem mass spectrometry function switching for comprehensive drug profiling analysis using a quadrupole time-of-flight mass spectrometer

A liquid chromatographic mass spectrometric strategy for systematic toxicological analysis (STA) is presented using the automatic 'on-the-fly' single mass spectrometry mode to tandem mass spectrometry mode (MS to MS/MS) switching abilities of a quadrupole time-of-flight (Q-TOF) instrument. During the chromatographic run, the quadrupole is initially set to transmit all masses until (an) ion(s) reaches a certain set threshold. Thereupon, the quadrupole automatically switches to the MS/MS mode, selecting the ion(s), which are subsequently fragmented in the high-efficiency hexapole collision cell, thus generating product ions that are further mass analyzed by the TOF. By limiting the TOF spectral accumulation time in the MS/MS mode to a statistically acceptable minimum, the quadrupole almost instantly switches back to the MS mode. Qualitative information, comprising the complementary MS ([M + H](+) ion mass) and MS/MS (informative product ion profile) data, as well as quantitative information obtained by integration of the MS extracted ion chromatogram(s), can be obtained in one single acquisition. Optimization of the automatic switching parameters, such as threshold, TOF spectral accumulation time, detection window and collision energy, was carried out by injection of a mix of 17 common drugs which were not necessarily baseline separated in the chromatographic system used. Indeed, the complete separation of the drugs is not deemed necessary since up to 8 different ions can 'simultaneously' be selected for MS/MS if they reach the preset criteria. In addition, the quantitative performance of the method was defined. In a second phase, the developed method was field-tested. To that end, the resulting data from extracts of urine samples were compared with and found to be in close concordance with those obtained by a standard toxicological analysis. This innovative approach clearly holds the potential for a substantial advance in the introduction of LC/MS in STA.