Analysis of supramolecular complexes of 3-methylxanthine with field asymmetric waveform ion mobility spectrometry combined with mass spectrometry

Miniaturised field asymmetric waveform ion mobility spectrometry (FAIMS), combined with mass spectrometry (MS), has been applied to the study of self-assembling, non-covalent supramolecular complexes of 3-methylxanthine (3-MX) in the gas phase. 3-MX forms stable tetrameric complexes around an alkali metal (Na+, K+) or ammonium cation, to generate a diverse array of complexes with single and multiple charge states. Complexes of (3-MX)n observed include: singly charged complexes where n = 1-8 and 12 and doubly charged complexes where n = 12-24. The most intense ions are those associated with multiples of tetrameric units, where n = 4, 8, 12, 16, 20, 24. The effect of dispersion field on the ion intensities of the self-assembled complexes indicates some fragmentation of higher order complexes within the FAIMS electrodes (in-FAIMS dissociation), as well as in-source collision induced dissociation within the mass spectrometer. FAIMS-MS enables charge state separation of supramolecular complexes of 3-MX and is shown to be capable of separating species with overlapping mass-to-charge ratios. FAIMS selected transmission also results in an improvement in signal-to-noise ratio for low intensity complexes and enables the visualisation of species undetectable without FAIMS

Increasing peak capacity in nontargeted omics applications by combining full scan field asymmetric waveform ion mobility spectrometry with liquid chromatography–mass spectrometry

Full scan field asymmetric waveform ion mobility spectrometry (FAIMS) combined with liquid chromatography and mass spectrometry (LC-FAIMS-MS) is shown to enhance peak capacity for omics applications. A miniaturized FAIMS device capable of rapid compensation field scanning has been incorporated into an ultrahigh performance liquid chromatography (UHPLC) and time-of-flight mass spectrometry analysis, allowing the acquisition of full scan FAIMS and MS nested data sets within the time scale of a UHPLC peak. Proof of principle for the potential of scanning LC-FAIMS-MS in omics applications is demonstrated for the nontargeted profiling of human urine using a HILIC column. The high level of orthogonality between FAIMS and MS provides additional unique compound identifiers with detection of features based on retention time, FAIMS dispersion field and compensation field (DF and CF), and mass-to-charge (m/z). Extracted FAIMS full scan data can be matched to standards to aid the identification of unknown analytes. The peak capacity for features detected in human urine using LC-FAIMS-MS was increased approximately threefold compared to LC-MS alone due to a combination of the reduction of chemical noise and separation of coeluting isobaric species across the entire analytical space. The use of FAIMS-selected in source collision induced dissociation (FISCID) yields fragmentation of ions, which reduces sample complexity associated with overlapping fragmentation patterns and provides structural information on the selected precursor ions

Characterization of crude oil and its saturate, aromatic and resin fractions by high-field asymmetric waveform ion mobility spectrometry – high resolution mass spectrometry

High-field asymmetric waveform ion mobility spectrometry (FAIMS) was coupled to a high-resolution Orbitrap mass spectrometer (MS) with a heated electrospray ionization (HESI) source for the analysis of crude oil and respective saturate, aromatic, and resin fractions. Four classes of compounds N1, N1S1, O1S1, and O2S1 were investigated using FAIMS one-dimensional compensation field scans from −3 to 5 Td for the crude oil and FAIMS static scans from 0.5 to 2.5 Td with 0.5 Td increments for fractions. In all cases, the incorporation of FAIMS into the analysis resulted in an increased number of detected peaks for both the crude oil and fractions. The most significant change was noticed in the aromatic fraction, with an increase of 218% for N1 and up to 514% for the O2S1 class of compounds observed. In addition, pre-analytical fractionation combined with FAIMS–MS enabled a higher number of molecular features to be observed in comparison to whole oil for three classes of compounds N1, O1S1, and O2S1 by 19, 45, and 83%, respectively

Combined hydrophilic interaction liquid chromatography-scanning field asymmetric waveform ion mobility spectrometry-time-of-flight mass spectrometry for untargeted metabolomics

Untargeted metabolite profiling of biological samples is a challenge for analytical science due to the high degree of complexity of biofluids. Isobaric species may also not be resolved using mass spectrometry alone. As a result of these factors, many potential biomarkers may not be detected or are masked by co-eluting interferences in conventional LC-MS metabolomic analyses. In this study, a comprehensive liquid chromatography-mass spectrometry workflow incorporating a fast-scanning miniaturised high-field asymmetric waveform ion mobility spectrometry separation (LC-FAIMS-MS) is applied to the untargeted metabolomic analysis of human urine. The time-of-flight mass spectrometer used in the study was scanned at a rate of 20 scans s−1 enabling a FAIMS CF spectrum to be acquired within a 1-s scan time, maintaining an adequate number of data points across each LC peak. The developed method is demonstrated to be able to resolve co-eluting isomeric species and shows good reproducibility (%RSD < 4.9%). The nested datasets obtained for fresh, aged, and QC urine samples were submitted for multivariate statistical analysis. Seventy unique biomarker ions showing a statistically significant difference between fresh and aged urine were identified with optimal transmission CF values obtained across the full CF spectrum. The potential of using FAIMS to select ions for in-source collision-induced dissociation is demonstrated for FAIMS-selected methylxanthine ions yielding characteristic fragment ion species indicative of the precursor

The use of shift reagents in ion mobility-mass spectrometry: studies on the complexation of an active pharmaceutical ingredient with polyethylene glycol excipients

Gas-phase ion mobility studies of mixtures containing polyethylene glycols (PEG) and an active pharmaceutical ingredient (API), Lamivudine, have been carried out using electrospray ionization-ion mobility spectrometry-quadrupole-time-of-flight mass spectrometry (ESI-IMS-Q-TOF). In addition to protonated and cationised PEG oligomers, a series of high molecular weight ions were observed and identified as non-covalent complexes formed between Lamivudine and PEG oligomers. The non-covalent complex ions were dissociated using collision induced dissociation (CID) after separation in the ion mobility drift tube to recover the protonated Lamivudine free from interfering matrix ions and with a drift time associated with the precursor complex. The potential of PEG excipients to act as ‘shift reagents’, which enhance selectivity by moving the mass/mobility locus to an area of the spectrum away from interferences, is demonstrated for the analysis of Lamivudine in a Combivir formulation containing PEG and Lamivudine

The quantitative surface analysis of an antioxidant additive in a lubricant oil matrix by desorption electrospray ionization mass spectrometry

Rationale Chemical additives are incorporated into commercial lubricant oils to modify the physical and chemical properties of the lubricant. The quantitative analysis of additives in oil-based lubricants deposited on a surface without extraction of the sample from the surface presents a challenge. The potential of desorption electrospray ionization mass spectrometry (DESI-MS) for the quantitative surface analysis of an oil additive in a complex oil lubricant matrix without sample extraction has been evaluated. Methods The quantitative surface analysis of the antioxidant additive octyl (4-hydroxy-3,5-di-tert-butylphenyl)propionate in an oil lubricant matrix was carried out by DESI-MS in the presence of 2-(pentyloxy)ethyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate as an internal standard. A quadrupole/time-of-flight mass spectrometer fitted with an in-house modified ion source enabling non-proximal DESI-MS was used for the analyses. RESULTS An eight-point calibration curve ranging from 1 to 80 μg/spot of octyl (4-hydroxy-3,5-di-tert-butylphenyl)propionate in an oil lubricant matrix and in the presence of the internal standard was used to determine the quantitative response of the DESI-MS method. The sensitivity and repeatability of the technique were assessed by conducting replicate analyses at each concentration. The limit of detection was determined to be 11 ng/mm additive on spot with relative standard deviations in the range 3-14%. CONCLUSIONS The application of DESI-MS to the direct, quantitative surface analysis of a commercial lubricant additive in a native oil lubricant matrix is demonstrated

Identification of plasma protease derived metabolites of glucagon and their formation under typical laboratory sample handling conditions

Copyright © 2014 John Wiley & Sons, Ltd. RATIONALE Glucagon modulates glucose production, and it is also a biomarker for several pathologies. It is known to be unstable in human plasma, and consequently stabilisers are often added to samples, although these are not particularly effective. Despite this, there have not been any studies to identify in vitro plasma protease derived metabolites; such a study is described here. Knowledge of metabolism should allow the development of more effective sample stabilisation strategies. METHODS Several novel metabolites resulting from the incubation of glucagon in human plasma were identified using high-resolution mass spectrometry with positive electrospray ionisation. Tandem mass spectrometric (MS/MS) scans were acquired for additional confirmation using a QTRAP. Separation was performed using reversed-phase ultra-high-performance liquid chromatography. The formation of these metabolites was investigated during a time-course experiment and under specific stress conditions representative of typical laboratory handling conditions. Clinical samples were also screened for metabolites. RESULTS Glucagon 3-29 and [pGlu] 3 glucagon 3-29 were the major metabolites detected, both of which were also present in clinical samples. We also identified two oxidised forms of [pGlu] 3 glucagon 3-29 as well as glucagon 19-29 , or 'miniglucagon', along with the novel metabolites glucagon 20-29 and glucagon 21-29 . The relative levels of these metabolites varied throughout the time-course experiment, and under the application of the different sample handling conditions. Aprotinin stabilisation of samples had negligible effect on metabolite formation. CONCLUSIONS Novel plasma protease metabolites of glucagon have been confirmed, and their formation characterised over a time-course experiment and under typical laboratory handling conditions. These metabolites could be monitored to assess the effectiveness of new sample stabilisation strategies, and further investigations into their formation could suggest specific enzyme inhibitors to use to increase sample stability. In addition the potential of the metabolites to affect immunochemistry-based assays as a result of cross-reactivity could be investigated

Direct determination of urinary creatinine by reactive-thermal desorption-extractive electrospray-ion mobility-tandem mass spectrometry.

A direct, ambient ionization method has been developed for the determination of creatinine in urine that combines derivatization and thermal desorption with extractive electrospray ionization and ion mobility-mass spectrometry. The volatility of creatinine was enhanced by a rapid on-probe aqueous acylation reaction, using a custom-made thermal desorption probe, allowing thermal desorption and ionization of the monoacylated derivative. The monoacyl creatinine [M + H] ion (m/z 156) was subjected to mass-to-charge selection and collision induced dissociation to remove the acyl group, generating the protonated creatinine [M + H] product ion at m/z 114 before an ion mobility separation was applied to reduce chemical noise. Stable isotope dilution using creatinine-d as internal standard was used for quantitative measurements. The direct on-probe derivatization allows high sample throughput with a typical cycle time of 1 min per sample. The method shows good linearity (R = 0.986) and repeatability (%RSD 8-10%) in the range of 0.25-2.0 mg/mL. The creatinine concentrations in diluted urine samples from a healthy individual were determined to contain a mean concentration of 1.44 mg/mL creatinine with a precision (%RSD) of 9.9%. The reactive ambient ionization approach demonstrated here has potential for the determination of involatile analytes in urine and other biofluids. © 2013 American Chemical Society

Direct analysis of oil additives by high-field asymmetric waveform ion mobility spectrometry-mass spectrometry combined with electrospray ionization and desorption electrospray ionization

© 2016 American Chemical Society. The analysis of corrosion inhibitors in the presence and absence of an oil matrix is reported using electrospray ionization (ESI) and desorption electrospray ionization (DESI), hyphenated with miniaturized high-field asymmetric waveform ion mobility spectrometry (FAIMS) and mass spectrometry (MS). The target analytes were successfully ionized in solution by ESI and directly from steel surfaces using DESI ambient ionization at levels ≥0.0004% w/w (4 ppm) in oil. Differences in the mass spectral profiles observed for the additive/oil mixture are attributed to differences between the ESI and DESI ionization processes. The use of FAIMS improved selectivity for ESI generated analyte ions through reduction in the chemical noise resulting from the oil matrix. DESI enabled the direct, rapid, native state interrogation of oil samples on steel surfaces without sample pretreatment, and the hyphenation of DESI with the miniaturized FAIMS enhanced the relative analyte responses of the surface-active corrosion inhibitors

Rapid determination of N-Methylpyrrolidine in Cefepime by combining direct infusion electrospray ionisation-time-of-flight mass spectrometry with field asymmetric waveform ion mobility spectrometry

The determination of N-methyl pyrrolidine, a potential impurity in the cephalosporin antibiotic cefepime, by direct infusion ESI combined with field asymmetric waveform ion mobility spectrometry-mass spectrometry (ESI-FAIMS-MS) is demonstrated. The addition of a chip-based FAIMS separation prior to detection by time-of-flight mass spectrometry enables selective transmission of NMP in the presence of cefepime without interference from NMP formed by CID in the mass spectrometer interface. The limits of detection and quantification of NMP in cefepime were 0.011% (w/w) and 0.036% (w/w) NMP in cefepime respectively, well below the 0.3% (w/w) threshold concentration for NMP in cefepime. The % relative standard deviation was 3.9% with linearity for standard additions in the range 0.005 – 0.5 μg/ml NMP. Novel Aspect (ToC) FAIMS separation prior to mass spectrometry enables selective transmission of NMP in cefepime without interference from NMP formed by in-source CID