Ion Trap Detector Research Articles

Distribution profiles of nitroxide spin probes in human skin—a combined study using spatially resolved electron spin resonance spectroscopy and mass spectrometry

Electron spin resonance spectroscopy and mass spectrometry are two analytical methods that are very rarely used in combination. In this paper, we will show that the methods complement one another in the example of the distribution of stable nitroxide radicals in human skin, including the spatial resolution of these distribution processes. There are many ESR investigations dealing with this subject, but unfortunately, they are all limited to the detection of paramagnetic species. The combination with MS allows the successful examination of the distribution profile of the main biotransformation product of the nitroxide radicals, the respective "ESR-silent" hydroxylamines. In order to maintain the biological state of the sample material as far as possible, atmospheric pressure matrix-assisted laser desorption/ionization with ion trap detection has been used for the mass spectrometric investigations. The results validate the former findings of the strong reduction of stable free radicals by biological material; moreover, the diamagnetic species formed during these processes have been identified.

Determination of dimethyl fumarate (DMFu) in silica gel pouches using gas chromatography coupled ion trap mass spectrometry

A simple method for the determination of dimethyl fumarate (DMFu) in silica gel pouches has been developed. The gas chromatographic behaviour of DMFu was investigated; the instrumental method, based on EI mass spectrometry coupled with an Ion Trap Detector operating whether in full scan mode or in MS/MS mode was also investigated. Several factors have been evaluated and optimized during the development process: solvent and temperature of extraction, type of stationary phase in capillary column. The analytical procedure consists of two steps as follows: (a) the sample preparation using 10 g of sample extracted with acetonitrile in an ultrasonic, heated bath and (b) the determination by gas chromatography-ion trap mass spectrometry. Mass spectrometry in conjunction with chromatographic separation is a very powerful combination for identification of an analyte in the extract in spite of selective detectors employed with GC, such as ECD, FPD and NPD, that offer only limited specificity. Blank samples show no interfering peaks in the areas of interest, so the specificity of the method was assured under the investigated GC/MS conditions. The method has been validated in terms of recovery, repeatability, linearity, detection limits and measurement uncertainty. The results obtained meet both the method validation criteria and requirements of the European/National legislation. The method was verified to be accurate with 97 % mean recoveries at 0.05 mg/kg and 1.00 mg/kg levels; the repeatability (expressed as RSD %) was found to be better than 15 %. Good linearity was found in the range between 0.05 μg/mL and 5.0 μg/mL and a value of R2> 0.9998 was calculated. The procedure ensures high specificity and a good sensitivity with detection limit (ld) of 0.02 mg/kg and quantification limit (LOQ) of 0.05 mg/kg. This procedure has been successfully applied for the analysis of several hundred of real samples collected during a monitoring control plan started last year in our country. All samples exceeding the maximum allowed level of DMFu (0, 1 mg/kg) were confirmed by GC/MS/MS (ITD) for a higher degree of confidence in identification. The main advantages of this method include: rapidity, simplicity (few, simple steps), reliability, cheapness, no need for long and difficult clean-up and evaporation steps, high specificity by using GC/MS and GC/MS/MS, availability for routine monitoring.

Levels, Distribution and Source Characterization of Polycyclic Aromatic Hydrocarbons (PAHs) in Topsoils and Roadside Soils in Esbjerg, Denmark

A soil survey was performed to determine the levels, distributions and sources of 6 polycyclic aromatic hydrocarbons (PAHs) in 9 selected soil environments in Esbjerg, Denmark. In all, 24 soil samples were collected and the PAHs present were extracted with dichloromethane and analysed using GC/MS/MS with ion trap detector (TCD). There were elevated levels of the individual as well as the total PAHs in the soil samples and also, all 6 PAHs were present in all the soil samples. The most abundant components were fluoranthene, benzo(b)fluoranthene and benzo(a)pyrene. The average sum of the 6 PAHs in all soil samples was 2.5mg.kg(-1), with range from 0.24 to 7.6mgkg(-1). The total mean PAH concentration obtained was 1.67 times higher than the total limit set by the Danish Environmental Protection Agency (DEPA) whiles the mean benzo(a)pyrene (BaP) concentration (0.6mgkg(-1)) also 6 times the Soil Quality Criteria (Human Health) (0.1mgkg(-1)) by DEPA and 2 times the Maximum Permissible Concentrations (0.26mgkg(-1)) by the Netherlands for BaP. This shows that there are elevated levels of PAH deposition on the Esbjerg soil environment which needs an urgent attention. The diagnostic ratios and the correlation analysis identified mixed petrogenic and pyrogenic sources as the main contributors of PAHs on the Esbjerg environment.

Liquid chromatography tandem mass spectrometry with ion trap and triple quadrupole analyzers for determination of thyreostatic drugs in urine and muscle tissue

Liquid chromatography tandem mass spectrometry methods were developed and validated to screen for and confirm residues of the thyreostatic drugs: tapazole, thiouracil, methylthiouracil, propylthiouracil, and phenylthiouracil in bovine and porcine urine and muscle tissues using dimethylthiouracil as internal standard. Thyreostats were extracted from urine samples with diethyl ether after derivatisation with 3-iodobenzylbromide in basic medium (pH 8.0) and analyzed by gradient elution on a Nucleosil C18 column with ion trap mass spectrometry detection using an electrospray source and triple quadrupole MS detection with turbo spray source. Thyreostats were extracted from muscle tissue with methanol, the denaturation of matrix protein was performed and then the same steps as for the urine samples were carried out. The methods were validated in accordance with the Commission Decision 2002/657/EC. Good thyreostats recoveries were obtained (from 82% to 117%) as well as acceptable within-lab reproducibility. The values of the decision limit CCα and the detection capability CCβ of five thyreostatic drugs are found to be below the recommended concentration set at 10 μg L −1 (kg −1). The results of the validation demonstrate that liquid chromatography mass spectrometry with ion trap detection does not meet the criteria for confirmation for some thyreostats and therefore was applied for screening purpose only.

Unknown Exposures: Gaps in Basic Characterization Addressed with Person-Portable Gas Chromatography-Mass Spectrometry Instrumentation

A newly developed person-portable gas chromatography-mass spectrometry (GC-MS) system was used to analyze several solvent standards, contact cement, paint thinner, and polychlorinated biphenyl samples. Passive solid phase microextraction sampling and fast chromatography with a resistively heated low thermal mass GC column were used. Results (combined sampling and analysis) were obtained in <2 min for solvent, contact cement, and paint thinner samples, and in <13 min for the polychlorinated biphenyl sample. Mass spectra produced by the small toroidal ion trap detector used were similar to those produced with heavily used transmission quadrupole mass spectrometers for polychlorinated biphenyl compounds, simple alkanes, and cycloalknes, while mass spectra for benzene and the ketone compounds analyzed showed evidence for ion/molecule reactions in the ion trap. For one of the contact cement samples analyzed, no evidence was found to indicate the presence of n-hexane, although the relevant material safety data sheet listed this ingredient. Specific chemical constituents corresponding to a potentially wide range of petroleum distillate compounds were identifiable from GC-MS analyses. The possibility for an improved basic characterization step in the exposure assessment process exists with the availability of fast, person-portable GC-MS, although work is needed to further refine this tool and understand the best ways it may be used.

Assay for Screening for Six Antimalarial Drugs and One Metabolite Using Dried Blood Spot Sampling, Sequential Extraction and Ion-Trap Detection

Background:More parasites are becoming resistant to antimalarial drugs, and in many areas a change in first-line drug treatment is necessary. The aim of the developed assay is to help determine drug use in these areas and also to be a complement to interviewing patients, which will increase reliability of surveys.Results:This assay detects quinine, mefloquine, sulfadoxine, pyrimethamine, lumefantrine, chloroquine and its metabolite desethylchloroquine in a 100-µl dried blood spot. Most of the drugs also have long half-lives that make them detectable at least 7 days after administration. The drugs are extracted from the dried blood spot with sequential extraction (due to the big differences in physicochemical properties), solid-phase extraction is used as sample clean-up and separation is performed with gradient-LC with MS ion-trap detection.Conclusion:Detection limits (S/N > 5:1) at 50 ng/ml or better were achieved for all drugs except lumefantrine (200 ng/ml), and thus can be used to determine patient compliance. A major advantage of using the ion-trap MS it that it will be possible to go back into the data and look for other drugs as needed.

Field-portable gas chromatography with transmission quadrupole and cylindrical ion trap mass spectrometric detection: Chromatographic retention index data and ion/molecule interactions for chemical warfare agent identification

Field-portable gas chromatography–mass spectrometry (GC–MS) is well-suited for the reliable identification of dangerous chemicals. The chemical warfare agent (CWA) O-ethyl- S-2-diisopropylaminoethyl methylphosphonothiolate (VX) and many VX degradation products are challenging GC–MS analytes for a transmission quadrupole detector, as resulting 70 eV electron ionization mass spectra contain little high mass information. Approaches were explored to detect these analytes using two field-portable GC–MS systems having either a transmission quadrupole or a cylindrical ion trap (CIT) detector. Spectral matching alone for the transmission instrument did not unambiguously identify VX and several related analytes, while use of mass spectra and retention index information resulted in accurate identification. Ion/neutral interactions in the CIT produced pseudomolecular ions ([M +H] +) for VX-related compounds and also for other CWA nerve agent compounds. In addition to [M +H] +, protonated dimers ([2M +H] +) were produced in the CIT for phosphonofluoridate compounds such as sarin. The CIT ion/molecule reactions were concentration-dependent, and mass assignment shifts were not unusual with increasing analyte concentrations. For these reasons the CIT detector is potentially problematic for reliable chemical identification by technician-level users under non-laboratory conditions.

Study of the Se-containing metabolomes in Se-rich yeast by size-exclusion—cation-exchange HPLC with the parallel ICP MS and electrospray orbital ion trap detection

Strong cation exchange HPLC with the parallel ICP MS and electrospray hybrid linear ion trap quadrupole orbital trap mass spectrometry (ESI Orbitrap MS) detection was developed for the study of the metabolomic pattern of selenium in selenium-rich yeast. The mobile phase composition (gradient of ammonium formate in 20% methanol) was optimized to obtain separation in conditions guaranteeing the identical ICP MS sensitivity during the entire chromatographic run and the compatibility with electrospray ionization. Twenty seven Se-containing metabolites observed in the HPLC-ICP MS chromatogram were identified by ESI Orbitrap MS based on the Se isotopic pattern, the accurate molecular mass, and the multistage fragmentation patterns. The method allowed for the first time the correlation of the differences observed in HPLC-ICP MS chromatography of water extracts of Se-rich yeast samples from different manufacturers with the identity of the eluted compounds determined by ESI MS.

Analysis of tandem mass spectra by FTMS for improved large-scale proteomics with superior protein quantification.

Using a newly developed dual-cell quadrupole linear ion trap-orbitrap hybrid mass spectrometer (dcQLT-orbitrap), we demonstrate the utility of collecting high-resolution tandem mass spectral data for large-scale shotgun proteomics. Multiple nanoLC-MS/MS experiments on both an older generation quadrupole linear ion trap-orbitrap hybrid (QLT-orbitrap) and the dcQLT-orbitrap, using both resonant-excitation CAD and beam-type CAD (HCD), were performed. Resulting from various technological advances (e.g., a stacked ring ion guide AP inlet, a dual cell QLT), the dcQLT-orbitrap exhibited increased duty cycle (approximately 1.5-2 times) and sensitivity for both CAD (ion trap detection) and HCD (orbitrap detection) methods. As compared to the older system, the dcQLT-orbitrap produced significantly more unique peptide identifications for both methods (approximately 30% improvement for CAD and approximately 115% improvement for HCD). The sizable improvement of the HCD method on the dcQLT-orbitrap system outperforms the current standard method of CAD with ion trap detection for large-scale analysis. Finally, we demonstrate that the increased HCD performance translates to a direct and substantial improvement in protein quantitation precision using isobaric tags.

Analysis of aminoglycoside residues in bovine milk by liquid chromatography electrospray ion trap mass spectrometry after derivatization with phenyl isocyanate

A derivatization procedure using phenyl isocyanate was adapted to liquid chromatography ion trap mass spectrometry (LC–MSn) for confirmation and quantification of aminoglycoside residues in milk. Aminoglycoside residues were extracted from milk with acid and isolated from the matrix with a weak cation exchange solid-phase extraction cartridge. After isolating the compounds from the milk, derivatives of gentamicin, neomycin, and tobramycin were formed by reacting the drugs with phenyl isocyanate in the presence of triethylamine. The analytes were separated using a dilute formic acid/acetonitrile gradient on a reversed-phase LC column. The derivatized compounds were analyzed using positive ion electrospray LC–MSn with ion trap detection. Product ion spectra were generated from the derivatized protonated molecules. Specific ion transitions were evaluated for quantitative determination and qualitative confirmation of residues in milk. Using this procedure, residues were qualitatively confirmed in milk samples fortified with gentamicin and neomycin at levels ranging from 15 to 300ngmL−1. Gentamicin has four major components that were successfully separated and confirmed independently; for quantitative determination the peak areas from the four analogs were summed. Tobramycin was added as an internal standard for quantitation to mitigate the effects of matrix ion suppression and variable recoveries. Overall recoveries for this method ranged from 80% to 120% with relative standard deviations of less than 25%. The method detection limits are 9.8ngmL−1 for NEO and 12.8ngmL−1 for total GEN residues.

How to decrease ion suppression in a multiresidue determination of β-agonists in animal liver and urine by liquid chromatography–mass spectrometry with ion-trap detector

A new liquid chromatography–mass spectrometry with ion-trap detection method for the determination of clenbuterol, ractopamine, clenpenterol, brombuterol, hydroxyclenbuterol, mapenterol and mabuterol in animal liver and urine is described to decrease ion suppression in both matrices. The developed method consists of an aqueous extraction and a two-step clean-up. Final extract was injected in a liquid chromatograph with ion trap mass spectrometer optimized to obtain MS 3 ions which provided more specificity and better signal to noise ratio in the investigated analytes. Those steps have been essential to reach decision limits (CCα) values below the proposed MRPL values for each substance. The CCα were determined and their values were 0.05 μg kg −1 for clenbuterol, 0.2 μg kg −1 for ractopamine and 0.1 μg kg −1 for the other analytes in liver and the same values in μg L −1 for urine samples.

Extraction and Analysis Methods for the Determination of Pyrethroid Insecticides in Surface Water, Sediments and Biological Tissues at Environmentally Relevant Concentrations

The aim of this study was to develop and validate chemical methods for measuring pyrethroid insecticides at environmentally relevant concentrations in different matrices. The analytes included six synthetic pyrethroids with the highest agricultural and commercial structural uses in California: bifenthrin, cyfluthrin, cypermethrin, esfenvalerate/fenvalerate, lambda-cyhalothrin, permethrin, and their corresponding stereoisomers, which includes enantiomers, diastereomers and racemic mixtures. Fortified water samples were extracted for analysis of synthetic pyrethroids using liquid-liquid extraction, while fortified sediment and fish tissue samples were extracted using pressurized fluid extraction followed by gel permeation chromatography (GPC) to remove matrix interferences. A florisil column was used for additional cleanup and fractionation of sediment and tissue extracts. Extracts were analyzed using dual column high resolution gas chromatography with electron capture detection (GC/ECD) and confirmation was obtained with gas chromatography mass spectrometry using a quadrupole ion trap detector in MS-MS mode. Method detection limits (MDLs) have been established for water (1-3 ng/L), sediment (0.5-4 ng/g dry weight) and tissue (1-3 ng/g fresh weight). Mean percent recoveries of fortified blanks and samples ranged from 75 to 115% with relative standard deviation (RSD) values less than 20% for all target compounds.

PATHOGEN CONTROL BY ANTIOXIDATIVE CHARACTERISTICS OF CUMINUM CYMINUM AND ROSMARINUS OFFICINALIS ESSENTIAL OILS

PATHOGEN CONTROL BY ANTIOXIDATIVE CHARACTERISTICS OF CUMINUM CYMINUM AND ROSMARINUS OFFICINALIS ESSENTIAL OILS

Development of an SPME–GC–MS/MS procedure for the monitoring of 2-phenoxyethanol in anaesthetised fish

2-Phenoxyethanol (ethylene glycol monophenyl ether, C 8H 10O 2) is a promising anaesthetic agent used in fisheries and aquaculture. The aim of this study was to develop a fast and easy method to determine 2-phenoxyethanol residue levels in fish tissue and blood plasma, and, subsequently, to use the method to monitor the dynamics of 2-phenoxyethanol residues in fish treated with anaesthetic. We developed a new procedure that employs solid phase microextraction (SPME) of the target analyte from the sample headspace followed by gas chromatography–mass spectrometry (GC–MS). Both sample handling, aimed at maximum transfer of 2-phenoxyethanol into the headspace, and SPME–GC–MS conditions were carefully optimised. Using a divinylbenzene/Carboxen/polydimethylsiloxane (PDMS/CAR/DVB) fiber for 60 min sampling at 30 °C and an ion trap detector operated in MS/MS mode, we obtained detection (LOD) and quantification (LOQ) limits of 0.03 and 0.1 mg kg −1 of sample, respectively. The method was linear in a range of 0.1–250 mg kg −1 and, depending on the sample matrix and spiking level, a repeatability (expressed as relative standard deviation, R.S.D.) of between 3% and 11% was obtained.

Qualitative and quantitative analysis of polar pesticide multiresidues in leaf samples with a liquid chromatography–ion-trap mass-selective detector

Since 1995, in Austria, an agricultural programme (ÖPUL) has promoted an environmentally friendly and extensive production with restricted pesticide use. To observe the achievement of this goal, the pesticides in leaf samples are monitored. This study aimed to develop a multiresidue method for the qualitative and quantitative analysis of 46 pesticides in leaf samples with HPLC-IT-MS equipped with an electrospray ionization in positive mode after extraction with the QuECheRS method. The method has been validated for leaf samples based on the SANCO European Guideline at two fortification levels (LOQ and 10 times LOQ). The recoveries of the pesticides, with a few exceptions, were between 70 and 110% at both fortification levels and modes (full scan and selected reaction monitoring, SRM) with acceptable precision (RSD < 16%). For most pesticides, the method was linear over two orders of magnitude, repeatable, and accurate. Although the matrix effect was relevant for only a few pesticides, matrix-matched standards were used. The quantification of real samples in both modes fitted well, but a confirmation in the SRM mode was always necessary to avoid false-positive samples. Unfortunately, the method is not yet sensitive enough for organic farming foodstuff, since the limits of detection and quantification are still too high (between 1.5 and 218 µg kg−1 and between 4.8 and 725 µg kg−1 in full scan, respectively) compared with the Austrian authorized value of 100 µg kg−1 fresh leaf sample defined in the ÖPUL programme.

Development of an Automated Cylindrical Ion Trap Mass Spectrometer for the Determination of Atmospheric Volatile Organic Compounds

Volatile organic compounds released from the biosphere are known to have a large impact on atmospheric chemistry. Field instruments for the detection of these trace gases are often limited by the lack of instrument portability and the inability to distinguish compounds of interest from background or other interfering compounds. We have developed an automated sampling and preconcentration system, coupled to a lightweight, low-power cylindrical ion trap mass spectrometer. The instrument was evaluated by measuring isoprene concentrations during a field campaign at the University of Michigan Biological Station PROPHET lab. Isoprene was preconcentrated by sampling directly into a short capillary column precooled without the aid of cryogens. The capillary column was then rapidly heated by moving the column to a preheated region to obtain fast separation of isoprene from other components, followed by detection with a cylindrical ion trap. This combination yielded a detection limit of approximately 80 ppt (parts per trillion) for isoprene with a measurement frequency of one sample every 11 min. The data obtained by the automated sampling and preconcentration system during the PROPHET 2005 campaign were compared to those of other field instruments measuring isoprene at this site in an intercomparison exercise. The intercomparisons suggest the new inlet system, when coupled with this ion trap detector, provides a viable field instrument for the fast, precise, and quantitative determination of isoprene and other trace gases over a variety of atmospheric conditions.

Studies on the dechlorination and detoxificaton of organochlorine compounds. I. PCBs and PCNs

In the analysis of organochlorines such as polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs), levels of, for example, PCB concentration are often expressed as a ‘total PCB’ value, using a straight GC pattern-matching technique with electron capture detection. Such methods provide little information about the identity of the individual components. In the present study, preliminary investigations using dechlorination with a NiCl2/NaBH4 catalyst indicated that the technique offered a comprehensive method for the analysis of PCBs and PCNs, as well as a method of detoxification of the ‘priority pollutants’ . This paper reports the use of capillary column GC-MS with an ion trap detector (ITDTM) for the analysis of a number of PCBs and PCNs, including the commercially produced Aroclor 1254 and 1221, employing this dechlorination technique.

A simple and fast method for the simultaneous determination of polychlorinated biphenyls and polybrominated diphenyl ethers in small volumes of human serum

A fast extraction and clean-up method for the simultaneous determination of PCBs and PBDEs has been developed. The procedure consisted of a solid-phase extraction (SPE) of the analytes on an Oasis ® HLB cartridge and the subsequent on-line fat elimination by directly dropping the eluate from the SPE cartridge onto a second cartridge containing layers of activated neutral silica gel and sulphuric acid modified silica gel. Detection limits using a gas chromatography coupled with an ion trap detector in the tandem mass spectrometry mode were from 0.03 to 0.3 pg/μL for PCBs and from 0.07 to 1.3 pg/μL for PBDEs. Repeatability (lower than 11%) and reproducibility (lower than 17%), expressed as relative standard deviation (RSD, n = 4), were satisfactory. The feasibility of the method developed for the determination of the target compounds was evaluated by participation in several rounds of interlaboratory exercises involving human serum with a wide range of PBDE and PCB concentrations. The method has been applied to the evaluation of PBDEs and PCBs in human serum samples of up to 1 mL.

De novo peptide sequencing and identification with precision mass spectrometry.

The recent proliferation of novel mass spectrometers such as Fourier transform, QTOF, and OrbiTrap marks a transition into the era of precision mass spectrometry, providing a 2 orders of magnitude boost to the mass resolution, as compared to low-precision ion-trap detectors. We investigate peptide de novo sequencing by precision mass spectrometry and explore some of the differences when compared to analysis of low-precision data. We demonstrate how the dramatically improved performance of de novo sequencing with precision mass spectrometry paves the way for novel approaches to peptide identification that are based on direct sequence lookups, rather than comparisons of spectra to a database. With the direct sequence lookup, it is not only possible to search a database very efficiently, but also to use the database in novel ways, such as searching for products of alternative splicing or products of fusion proteins in cancer. Our de novo sequencing software is available for download at http://peptide.ucsd.edu/.

Rapid method for the determination of non-steroidal anti-inflammatory drugs in animal tissue by liquid chromatography–mass spectrometry with ion-trap detector

A rapid and new liquid chromatography–mass spectrometry with ion-trap detection method for the determination of meloxicam (MLX), flunixin meglumine (FLU), carprofen (CPF), and tolfenamic acid (TOLF) in animal tissue is described.MRLs between 10 and 500μgkg−1 in muscle and between 65 and 1000μgkg−1 in liver, from different animal species have been established in the EU for these compounds.After chemical hydrolysis, an organic extraction from homogenised tissue was performed. Final extract was injected in a liquid chromatograph with an ion-trap mass spectrometer with electrospray interface.Four identification points (one precursor and two product ions) and a minimum of one ion ratio was monitored for each compound.For quantitative purposes flunixin-D3 (FLU-D3) was used as internal standard.The method was validated using fortified blank muscle and liver from different animal species according to the 2002/657/EC European decision criteria.The decision limits (CCα) and detection capabilities (CCβ) were determined and their values were at concentrations near the MRL for each substance.