Ion Atmospheric Pressure Chemical Ionization Research Articles

Direct Three-Dimensional Mass Spectrometry Imaging with Laser Ablation Remote Atmospheric Pressure Photoionization/Chemical Ionization.

The laser ablation remote atmospheric pressure photoionization/chemical ionization (LARAPPI/CI) platform coupled to an ultrahigh resolution quadrupole-time-of-flight (QToF) mass spectrometer was developed and employed for the first direct three-dimensional (3D) mass spectrometry imaging (MSI) of metabolites in human and plant tissues. Our solution for 3D MSI does not require sample modification or cutting into thin slices. Ablation characteristics of an optical system based on a diffraction optical element are studied and used for voxel stacking to directly remove layers of tissues. Agar gel, red radish, kiwi, human kidney cancer, and normal tissue samples were used for the tests of this new system. The 2D and 3D ion images vividly illustrate differences in the abundances of selected metabolites between cancerous and noncancerous regions of the kidney tissue and also between different parts of plant tissues. The LARAPPI/CI MSI setup is also the first example of the successful use of combined dopant-assisted atmospheric pressure photoionization (DA-APPI) and atmospheric pressure chemical ionization (APCI) ion source for mass spectrometry imaging.

Using dopants in the atmospheric pressure chemical ionization ion source to determine the site of protonation by ion mobility spectrometry.

Compounds like caffeine metabolites with more than one proton acceptor site can produce a mixture of isomeric protonated ions (protomers) in electrospray ionization and atmospheric pressure chemical ionization (APCI) ion sources. Discrimination between the protomers is of interest as the charge location influences ion structure and chemical and physical properties. Protonation of caffeine in an APCI ion source was studied using ion mobility spectrometry. The hydronium ions, H3O+(H2O)n, are the main reactant ions in the APCI ion source. Different dopant gases including NO2, NH3, and CH3NH2 were used to produce new reactant ions NO+, NH4 +, and CH3NH3 +, respectively. Density functional theory was employed to explain the experimental results and calculate the energies of the ionization reactions. The ion mobility spectrum of caffeine showed three peaks. In the presence of NO2 dopant and NO+ reactant ion, caffeine was ionized via charge transfer and formation of M+ ion. As NH3 and CH3NH2 are stronger bases than H2O, the reactant ions NH4 + and CH3NH3 + selectively protonated the more basic site of caffeine, that is, the imidazole nitrogen. Using these dopants, we could attribute the first ion mobility peak to M+ ion, the second peak to the protonation of caffeine at the carbonyl oxygen atom, and the third peak to the protonation of the imidazole nitrogen atom. The calculated collisional cross-sections of M+ and the protomers of caffeine confirmed the peaks' assignment. The criterion for the selection of an appropriate dopant is that its proton affinity (PA) should be between those of the proton acceptor sites of the molecule studied.

Novel Liquid Chromatography–Tandem Mass Spectrometry Method for Analysis of 102 Pesticides and Five Mycotoxins Regulated by the State of Colorado in Dried Hemp

A novel liquid chromatography–tandem mass spectrometry (LC–MS/MS) method with a dual electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) source was developed for analyzing 102 pesticides and five mycotoxins that are regulated by the state of Colorado in hemp. The limit of quantitation (LOQ) of the 102 pesticides and five mycotoxins met Colorado state action limit requirements for these analytes in a hemp matrix. For this study, 88 out of 102 pesticides and all five mycotoxins were analyzed using LC–MS/MS with an ESI source, whereas the remaining 14 pesticides were determined using LC–MS/MS with an APCI source. A simple, fast, green, and cheap acetonitrile solvent extraction method was used to extract the pesticides and mycotoxins from the hemp matrix with good extraction efficiency in the range of 80–120%. A hemp matrix is challenging and causes matrix effects such as ion suppression or enhancement. We optimized the LC method and added 30 internal standards to reduce and compensate for these matrix effects to obtain method accuracy in the range of 70–120%. The ionization mechanism of nonpolar pesticides (normally analyzed by gas chromatography–tandem mass spectrometry [GC–MS/MS]) with an APCI ion source was elucidated.

Evidence for the Involvement of Cytokines Modulation and Prokinetic Properties in Gastric Ulcer Healing Effects of Helicteres sacarolha A. St.-Hil. A. Juss.

Preparations of Helicteres sacarolha (Malvaceae) leaves and roots are used in the form of decoction, infusion or maceration, to treat gastrointestinal disturbances, among others. Studies supporting some of its ethnomedicinal uses are still incipient. The present study aimed to investigate it potential effect on chronic ulcer, ulcerative colitis and possible prokinetic activities as part of its mechanism of action. The powdered leaves of Helicteres sacarolha (HEHs) was prepared by maceration in 70 % hydroethanolic solution. Its qualitative phytochemical constituents were investigated by direct flow injection analysis coupled to atmospheric pressure chemical ionization ion trap tandem mass spectrometry (FIA-APCI-IT-MSn ). The gastric ulcer healing effect was evaluated in acetic acid induced chronic ulcer in mice and the lesions were evaluated, including analysis of blood plasma cytokine levels. The prokinetic properties (gastric emptying and intestinal transit) were carried out in mice. Potential anti-ulcerative colitis activity was evaluated in rats using 2,4,6-trinitrobenzenesulfonic acid (5 % TNBS) -induced colitis. All animal experiments were carried out at the doses of 20, 50 and 250 mg/kg (p.o.). Eight compounds were putatively identified, specifically lariciresinol, and its derivatives, kaempferol derivatives and Tricin-O-Glc. The extract promoted increased gastric ulcer healing at all doses tested. Modulation of the cytokines involved inhibition of some key pro-inflammatory cytokines with maximum effect on IL-1β (70 %, 50 mg/kg, p<0.05), TNF-α (79 %, 20 mg/kg, p<0.01), and in the anti-inflammatory cytokines, namely IL-10 (57 %, 50 mg/kg, p<0.05) and IL-17 (79 %, only at 50 mg/kg, p<0.05). Histological findings demonstrated a mitigated inflammatory activity, and tissues undergoing regeneration. HEHs treatment caused delayed gastric emptying, and increased intestinal transit, but had no effect in the experimentally induced ulcerative colitis. We report for the first time putatively the presence of Lariciresinol and tricin derivatives from the hydroethanolic leaves extract of H. sacarolha. Its possible mechanism of actions of gastric ulcer healing involves cytokines modulation, mitigation of inflammatory response and tissue regeneration and provoked opposing effect in the gastrointestinal system. The present study demonstrates the therapeutic potential of H. sacarolha leaves used in Brazilian ethnomedicine in the treatment of chronic gastric ulcer.

Significance of Competitive Reactions in an Atmospheric Pressure Chemical Ionization Ion Source: Effect of Solvent.

Ionization of organic compounds with different structural and energetic properties including benzene derivatives, polycyclic aromatic hydrocarbons (PAHs), ketones, and polyenes was studied using a commercial atmospheric pressure corona discharge (APCI) ion source on a drift tube ion mobility-quadrupole-time-of-flight mass spectrometer (IM-QTOFMS). It was found that the studied cohort of compounds can be experimentally ionized via protonation, charge transfer, and hydride abstraction leading to formation of [M + H]+, [M]+•, and [M – H]+ species, respectively. By experimentally monitoring the product ions and comparing the thermodynamic data for different ionization paths, it was proposed that NO+ is one of the main reactant ions (RIs) in the ion source used. Of particular focus in this work were theoretical and experimental studies of the effect of solvents frequently used for analytical applications with this ion source (acetonitrile, methanol, and chloroform) on the ionization mechanisms. In methanol, the studied compounds were observed to be ionized mainly via proton transfer while acetonitrile suppressed the protonation of compounds and enhanced their ionization via charge transfer and hydride abstraction. Use of chloroform as a solvent led to formation of CHCl2+ as an alternative reactant ion (RI) to ionize the analytes via electrophilic substitution. Density functional theory (DFT) was used to study the different paths of ionization. The theoretical and experimental results showed that by using only the absolute thermodynamic data, the real ionization path cannot be determined and the energies of all competing processes such as charge transfer, protonation, and hydride abstraction need to be compared.

A Flexible Tool to Correct Superimposed Mass Isotopologue Distributions in GC-APCI-MS Flux Experiments.

The investigation of metabolic fluxes and metabolite distributions within cells by means of tracer molecules is a valuable tool to unravel the complexity of biological systems. Technological advances in mass spectrometry (MS) technology such as atmospheric pressure chemical ionization (APCI) coupled with high resolution (HR), not only allows for highly sensitive analyses but also broadens the usefulness of tracer-based experiments, as interesting signals can be annotated de novo when not yet present in a compound library. However, several effects in the APCI ion source, i.e., fragmentation and rearrangement, lead to superimposed mass isotopologue distributions (MID) within the mass spectra, which need to be corrected during data evaluation as they will impair enrichment calculation otherwise. Here, we present and evaluate a novel software tool to automatically perform such corrections. We discuss the different effects, explain the implemented algorithm, and show its application on several experimental datasets. This adjustable tool is available as an R package from CRAN.

Determination of N-nitrosodimethylamine in metformin hydrochloride and its preparations by high performance liquid chromatography-tandem mass spectrometry

A method was established for the determination of N-nitrosodimethylamine (NDMA) in metformin hydrochloride active pharmaceutical ingredient (API) and preparation samples by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Water was used as the extraction solvent for the metformin hydrochloride API and preparation samples. The samples were analyzed by HPLC-MS/MS after vortex mixing, constant temperature shaking, high speed centrifugation and microfiltration. An ACE EXCEL 3 C18-AR column (150 mm×4.6 mm, 3 μm) was used for chromatographic separation. The mobile phases were water and methanol both containing 0.1% formic acid with gradient elution. The flow rate, column temperature, and autosampler temperature were set as 0.8 mL/min, 40℃, and 10℃, respectively. The valve switching technique was used to protect the mass spectrometer, while six-way valve switching was adopted to allow the mobile phase with a retention time of 2.85-7.00 min to enter the mass spectrometer and the mobile phase with other retention times to enter the waste liquid. For the mass spectrometer, an atmospheric pressure chemical ionization (APCI) ion source was used in positive ion MRM scanning mode. The other conditions were as follows:atomizer flow, 3 L/min; heater flow, 10 L/min, interface temperature, 300℃; desolvation line (DL) temperature, 250℃; heating block temperature, 400℃; and dryer flow, 10 L/min. The quantitative transition of NDMA was m/z 75.0→43.1 with a collision energy of-17.0 eV, while the qualitative transition was m/z 75.0→58.2 with a collision energy of-16.0 eV. The external standard method was utilized for quantitative analysis. The established method was validated in detail by investigating the specificity, linear range, limit of detection, limit of quantification, recovery, precision, and stability. This method showed good specificity, since the solvents and excipients did not interfere with the determination of NDMA. A good linear relationship was observed the NDMA peak area and the mass concentrations in the range of 1.00-100.00 ng/mL with an excellent correlation coefficient (r>0.9999). The limit of detection and limit of quantification in solution were 0.20 ng/mL and 1.00 ng/mL, respectively. The recoveries of NDMA at low, medium, and high spiked levels ranged from 94.55% to 114.67%, and the RSDs ranged from 4.73% to 13.46%, indicating good accuracy and precision for the quantification of NDMA. Stability tests showed that NDMA was stable when placed in the autosampler for 0, 8, 24 h, since the RSD of the peak area was as low as 2.08%. The validated method was then applied to the determination of NDMA in metformin hydrochloride raw materials and preparations (tablets, capsules or enteric tablets). The detected amount of NDMA in the API did not exceed the limit in 113 batches of samples, but NDMA was detected and exceeded the limit in eight batches of preparations. This method is sensitive, accurate, and easy to operate, and it can be used for the determination of NDMA in metformin hydrochloride raw materials and preparation samples.

Development of a fast-switching dual (ESI/APCI) ionization source for liquid chromatography/mass spectrometry.

High-throughput liquid chromatography/mass spectrometry (LC/MS) is an increasing topic in analytical chemistry. Especially the idle time of a mass spectrometer should be reduced for an efficient and cost-saving use. Therefore, a fast-switching dual ion source was developed, which uses the most important ionization techniques at atmospheric pressure, electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI), with one or more LC systems. The performance of the developed ion source is shown by infusion experiments and chromatographic analyses of different standard substances. A high-throughput method is demonstrated by coupling two UHPLC systems to the dual ion source with a triple quadrupole mass spectrometer. No decrease in the ion abundance and a stable performance of the mass spectrometer are presented while using the dual ion source. Instrumental limits of detection are 30 ng L-1 for testosterone using ESI and 1 μg L-1 for vitamin D3 using APCI. A fast switching between two UHPLC systems and the dual ion source leads to a high sample throughput of 50 samples in 75 min with relative standard deviations for testosterone and vitamin D3 of 1.5% and 3.8%, respectively. This work presents the development of a dual ESI and APCI ion source operating simultaneously or in switched mode. The results show sensitive and reliable performance as well as the hyphenation to one or more HPLC systems.

Development of an Atmospheric Pressure Chemical Ionization Interface for GC-MS.

A closed atmospheric pressure chemical ionization (APCI) ion source as interface between a gas chromatograph (GC) and a triple quadrupole mass spectrometer (QqQ-MS) was developed. The influence of different ion source conditions, such as humidity, make-up gas flow, and the position of the GC column, were investigated and determined as main factors to increase sensitivity and repeatability of the system. For a performance test under real conditions, the new APCI ion source was used for the determination of plant protection products in commercially available coffee beans from Vietnam. The ionization behavior was investigated and the majority of the analytes were detected as [MH]+, [M]+∙, or as characteristic fragment ions, which have been assigned to ion source fragmentation. The developed GC-MS methods are based on tandem MS (MS/MS) and revealed for the plant protection products limits of detection (LOD) between 1 and 250 pg on column and relative standard derivations for all compounds < 16%. The used ultrasonic solid–liquid extraction yielded recovery rates of approximately 60 to 100%. Residues of herbicide methyl esters, organophosphorus compounds, and organonitrogen compounds have been detected in the analyzed coffee beans.

Regioisomeric and enantiomeric analysis of primary triglycerides in human milk by silver ion and chiral HPLC atmospheric pressure chemical ionization-MS

Triglycerides (TG) not only provide energy for infants but have important physiological functions. Understanding the composition and structure of TG in human milk is conducive to the development of infant formulas. In this study, TG species in human milk from 3 provincial capitals (Zhengzhou, Wuhan, and Harbin) in different regions of China were determined through C18 HPLC electrospray ionization tandem mass spectrometry (MS). The results showed that in human milk from these 3 regions, oleoyl-palmitoyl-linoleoylglycerol (OPL; 16.55, 19.20, and 18.67%, respectively) was more abundant than oleoyl-palmitoyl-oleoylglycerol (OPO; 10.08, 10.22, and 12.03%, respectively). Subsequently, regioisomeric and enantiomeric analysis of main TG in the human milk were performed on silver ion and chiral HPLC atmospheric pressure chemical ionization mass spectrometry (APCI)-MS, respectively. The results showed that rac-OPL (above 85%), rac-OPO (above 85%), rac-palmitoyl-oleoyl-oleoylglycerol (PPO; above 90%), and rac-OLaO (above 70%) were the main regioisomers of OPL, OPO, PPO, and lauroyl-oleoyl-oleoylglycerol (LaOO), respectively. The relative ratios of enantiomer pairs of rac-OPL (rac-OPL1 and rac-OPL2) were about 37 and 63%, respectively.

LC-APCI-MS/MS assay for quantitation of ethyl esters of eicosapentaenoic acid and docosahexaenoic acid in human plasma and its application in a pharmacokinetic study.

A simple and specific LC-MS/MS method was developed and validated for the determination of ethyl ester of eicosapentaenoic acid (EPAEE) and ethyl ester of docosahexaenoic acid (DHAEE). After deproteinized with acetonitrile, the plasma samples were separated on a C18 column using a gradient elution system consisted of methanol and 1.0 mM ammonium acetate in water. The detection used an atmospheric-pressure chemical ionization ion source in positive mode with multiple reaction monitoring for the quantitation of EPAEE and DHAEE. The acceptable linearity was achieved over the concentration ranges of 1.00~1000 ng/mL for EPAEE and 2.50~2500 ng/mL for DHAEE. The method was successfully applied to a pharmacokinetic study of EPAEE and DHAEE in healthy Chinese volunteers after the oral administration of 4 g omega-3-acid ethyl esters 90 soft capsule. The pharmacokinetic profiles of EPAEE and DHAEE were observed for the first time in Chinese volunteers, which reached a maximum concentration of 499 ± 243 ng/mL and 1596 ± 476 ng/mL for EPAEE and DHAEE, respectively. The areas under the plasma concentration-time curve were 1290 ± 765 ng/mL·h for EPAEE and 4369 ± 1680 ng/mL·h for DHAEE, respectively.

Quantitative analysis of pesticide residues in tea by gas chromatography–tandem mass spectrometry with atmospheric pressure chemical ionization

In this study, gas chromatography–tandem mass spectrometry (GC–MS/MS) using an atmospheric pressure chemical ionization (APCI) source was applied for the quantitative analysis of pesticide residues in tea. To determine the optimum ionization conditions for multiresidue analysis, the full-scan mass spectra and peak intensities of pesticides were compared in the presence and absence of water as a modifier. When water was added as a modifier in the ion source, most of the target compounds formed [M+H]+ ions and exhibited enhanced intensities. However, compounds consisting of only carbon, hydrogen, and chlorine, such as aldrin, γ-hexachlorocyclohexane, and p,p′-dichlorodiphenyldichloroethane, typically formed M+· or fragment ions, whose intensities were significantly decreased by the addition of water. GC–MS/MS methods using APCI (without modifier addition) and electron ionization (EI) were validated for 16 pesticides in tea at spiking levels of 0.01 and 0.1 mg/kg. Unlike EI, signal suppression was observed for most compounds at a spiking level of 0.01 mg/kg using APCI; however, dilution of the samples minimized this effect. Using APCI, the trueness of the target compounds ranged from 77% to 121% at both spiking levels, except for pyrethrins owing to matrix effects, with relative standard deviations of less than 14%. For most compounds, these results were comparable with those obtained using EI. However, because the use of APCI limited fragmentation, this ionization technique offered significantly higher sensitivity and specificity than EI. Using APCI, linear calibration curves with coefficients of determination greater than 0.998 were obtained in the range of 0.0005–0.5 μg/mL for all compounds. These findings indicated that GC–MS/MS with APCI is applicable for the routine monitoring of pesticide residues, even in complex samples such as tea.

The screening of identity documents at borders for forensic drug intelligence purpose

The need for law enforcement agencies to obtain results more rapidly has driven the increased use of field-deployable technology in the field. Currently used in a case-by-case approach, the potential of these new technologies, could go beyond the traditional objective of forensic science (i.e. characterisation and identification) and provide timely information about criminal phenomena (i.e. multi-case approach). The use of portable instrumentation could for instance provide rapid information to law enforcement agencies about drug prevalence and drug smuggling if used in a systematic manner.This paper outlines the potential of using portable instrumentation to gather information related to illicit drugs rapidly. An innovative concept is proposed to screen surfaces of passports for the detection of remnants of illicit substances using rapid equipment already deployed at border controls. An experimental procedure was built to determine if powdered drugs could be detected on the surface of contaminated passports. Various scenarios were tested, including transfer, activity and persistence parameters. Experiments were conducted employing two different instruments, i.e. Ion Mobility spectroscopy (IMS) and Atmospheric Pressure Chemical Ionisation coupled to an Ion Trap Mass Spectrometer (APCI-ITMS). Promising results were obtained with the proposed method notably with the APCI-ITMS instrument as drugs were detected in minute amounts even after one hour of activity. High rates of false positives were obtained with the IMS contrary to APCI-ITMS. As a result, APCI-ITMS allows for the detection of remnants of illicit substances on passports’ surfaces and the approach employed in this proof of concept can be deployed in a real environment such as in airports.

Structural characteristics of soluble organic matter in four low-rank coals

Four low-rank coals, Zhaotong lignite, Dayan lignite, Wucaiwan sub-bituminous coal and Shenfu sub-bituminous coal were sequentially dissolved in cyclohexane, acetone and methanol at 300 °C. An Orbitrap mass spectrometry coupled with an atmospheric pressure chemical ionization ion source was used to analyze the 12 thermal dissolution (TD) extracts from coals to obtain and compare the molecular distribution of soluble organic matter. Two statistical methods, principal component analysis and hierarchical clustering analysis, were used to mine the effective information from a large number of mass spectral data. The statistical results showed that the degree of coalification had greater effects on the structure and composition of TD extracts compared to the solvent. In-source collision-activated dissociation further elucidated the characteristics of molecular structure and revealed that most of O atoms distribute on alky chains.

Insight into molecular characteristics of a Chinese coal via separation, characterization, and data processing.

Dayan lignite was subjected to thermal dissolution sequentially with cyclohexane, acetone, and methanol. Each thermal dissolution extract was subjected to further separation/enrichment using column chromatography, which was sequentially eluted with petroleum ether, a mixture of ethyl acetate and petroleum ether (vol:vol=1:1), and ethyl acetate. The three thermal dissolution extracts and nine enrichment subfractions were characterized by an Orbitrap mass spectrometry equipped with an atmospheric pressure chemical ionization ion source. The mass spectrometry data were also statistically analyzed by principal component analysis, which can reduce the dimensionality of data and classify multiple samples according to principal components. Identified compounds in the extracts and subfractions are classified into eight classes according to the heteroatom distribution. Hydrocarbon class is mainly presented in the petroleum ether fraction, and oxygen class, nitrogen class, and oxygen-nitrogen class are distributed in both petroleum ether/ethyl acetate and ethyl acetate subfractions. The combination of different analytical methods enhances the understanding of coal at the molecular level and provides important data for downstream refining processes.

Satureja montana L. Essential Oils: Chemical Profiles/Phytochemical Screening, Antimicrobial Activity and O/W NanoEmulsion Formulations.

Chemical fingerprints of four different Satureja montana L. essential oils (SEOs) were assayed by an untargeted metabolomics approach based on Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry (MS) coupled with either electrospray ionization or atmospheric pressure chemical ionization ion sources. Analysis and relative quantification of the non-polar volatile fraction were conducted by gas chromatography (GC) coupled to MS. FT-ICR MS confirmed significant differences in the polar metabolite composition, while GC-MS analyses confirmed slight fluctuations in the relative amount of major terpenes and terpenoids, known to play a key role in antimicrobial mechanisms. Oil in eater (O/W) nanoemulsions (NEs) composed by SEOs and Tween 20 or Tween 80 were prepared and analyzed in terms of hydrodynamic diameter, ζ-potential and polydispersity index. The results confirm the formation of stable NEs homogeneous in size. Minimum inhibitory and minimum bactericidal concentrations of SEOs were determined towards Gram-positive (Listeria monocytogenes, Staphylococcus aureus, Staphylococcus haemolyticus) and Gram-negative clinical isolates (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Serratia marcescens). Commercial SEO showed strongest antibacterial activity, while SEO 3 was found to be the most active among the lab made extractions. MIC and MBC values ranged from 0.39 to 6.25 mg·mL−1. Furthermore, a SEO structured in NEs formulation was able to preserve and improve antimicrobial activity.

The H3O+(H2O)n Reagent Ion: Calculations of the Structure, Thermodynamic Parameters of Hydration, Equilibrium Composition, and Mobility

The H3O+(H2O)n reagent ion is widely used in ion mobility spectrometry and atmospheric pressure chemical ionization mass spectrometry. In this work, calculated data on the structure and properties of the H3O+(H2O)n (n = 0–4) reagent ion are obtained. They are of interest for the study of the regularities of chemical ionization and the prediction and interpretation of ion mobility spectra and mass spectra. Using quantum chemical methods, we calculated the structures and refined the isomeric composition of the H3O+(H2O)n ions. It was found that ions with n = 2, 3, and 4 have 2, 5, and 15 isomers, respectively. The most stable isomers, which possess branched non-cyclic structures with the H3O+ core, were determined. The thermodynamic parameters of hydration reactions of the most stable isomers of H3O+(H2O)n (n = 0–3) ions and the equilibrium composition of the reagent ion in a wide range of temperatures and concentrations of water vapor are computed. The obtained results agree with the available experimental and calculated data. Using the computed structural data and data on the composition of the reagent ion, its mobility was calculated by the trajectory method. The error of calculations is close to the experimental one.

Fast quantification of whisky lactone in oak wood by ion mobility spectrometer

An Ion Mobility Spectrometry (IMS) apparatus has been used to detect the β-methyl-γ-octalactone (Whisky Lactone – WL) standard in the air and as well WL vapours originating from the oak wood samples. The IMS was equipped with Atmospheric Pressure Chemical Ionisation (APCI) ion source based on a Corona Discharge (CD) and was operated in the positive polarity. The IMS spectrum of WL exhibits two peaks, a monomer with reduced ion mobility value K0 = 1.39 cm2V−1s−1 and dimer K0 = 1.09 cm2V−1s−1. Using Ion Mobility orthogonal acceleration Time of Flight mass spectrometer (IMS-oaTOF MS) these peaks were identified as protonated monomer M.H+.(H2O)0,1 and dimer M2.H+ ions respectively. The limit of detection study resulted in LOD for WL of 50 ppbv. Detection of WL from oak wood samples of different “Quality Level” (QL) categories (categories 1 to 10), indicated strong correlation between the QL category number and the response of the IMS.

Quantitation of vitamin K1 in serum using online SPE-LC-MS/MS and the challenges of working with vitamin K

Vitamin K1 (phylloquinone) is one of the vitamin Ks. Several studies have previously investigated the role of vitamin K1 status in respect to disease, but without consistent results. Since vitamin K deficiency has been associated with different disease states it is important to develop a biochemical analysis with sufficient sensitivity and a low limit of quantitation (LOQ).The vitamin Ks are very fat-soluble. This non-polar nature has given rise to several challenges during the method development, because vitamin K1 sticks to materials used during the process and is lost during evaporation. We found that reducing the sample preparation as much as possible offline, instead using online SPE-LC-MS/MS improves recovery and gives satisfactory chromatograms. An Protein BEH C4 column, 300 Å (50 × 2.1 mm, 1.7 μm particle size) was used as trap column and a Phenyl-Hexyl-LC-column, 100 Å (100 × 2.1 mm, 2.6 μm particle size) was used as analytical column. The mobile phases consisted of 30 μmol/L NH4F in water and 30 μmol/L NH4F in MeOH. A triple quadrupole tandem mass spectrometer with atmospheric pressure chemical ionization (APCI) ion source, positive ion mode, was used to perform the mass spectrometric measurements.The method is simple, highly sensitive and fast. The method was validated for vitamin K1 with good analytical performance. With a LOQ of 0.05 nmol/L it is to our knowledge the vitamin K1 method with lowest LOQ reported to date in the literature. It can easily be automated and applied in a routine diagnostic laboratory.Blood collection tubes with different additives were tested and showed no difference. Stability of vitamin K1 in serum was tested at different temperatures (−20 °C, 4 °C and in light and dark at 20 °C over a period of 30 days) and showed that vitamin K1 is light sensitive in serum even after only one day.

Evaluation of elemental composition obtained by using mass spectrometer and elemental analyzer: A case study on model compound mixtures and a coal-derived liquid

The relative abundances of compound classes (e.g. CHO1, CHO2 and CHNO1) in fossil fuels have been widely used in previous researches based on the data from mass spectrometry (MS). However, such observations are susceptible to the ionization bias of MS due to the variation of ionization efficiency, which may affect the downstream quantitative analysis. Many efforts have been devoted to investigating the ionization efficiencies of a variety of model compounds, but not complex and diverse mixtures. Therefore, it is necessary to investigate how quantitatively ionization bias affects the MS analysis of complex mixtures. In this study, ionization bias was preliminarily investigated by comparing the elemental compositions obtained from MS-analysis via different ionization methods with the data acquired by a standard elemental analyzer. A coal-derived liquid and mixtures of five model compounds were ionized by atmospheric-pressure chemical ionization (APCI), electrospray ionization or direct analysis in real-time, followed by analyzing using a high-resolution Orbitrap MS to obtain elemental compositions. MS-based results via APCI ion source showed the closest elemental compositions to those obtained from the elemental analyzer. For the MS-based analysis, the abundances of S- and O-containing compounds were significantly lower and that of N-containing compounds was clearly higher compared to ultimate analysis. The abundances of compound classes were adjusted to provide a closer approximation of the actual contents, which might better serve for the downstream quantitative analysis. Although absolute quantification still needs additional work, the adjusted MS-based analysis provides not only the molecular level data, but also a better quantification ability compared to previous analytical approaches.