The mass distribution of ions influences separations in ion mobility spectrometry-mass spectrometry (IMS-MS). Herein, we introduce a method to induce mass distribution shifts for various analytes using hydrogen-deuterium exchange (HDX) immediately prior to ionization using a dual syringe approach. By replacing labile hydrogens on analytes with deuteriums, we were able to differentiate isomers using separations of isotopologues. For each analyte studied, every possible level of deuteration (from undeuterated to fully deuterated) was generated and then separated using cyclic ion mobility spectrometry-mass spectrometry (cIMS-MS). The information gained from such separations (relative arrival times; tRel. values) was found to be orthogonal to conventional IMS-MS separations. Additionally, the observed shifts were linearly additive with increasing deuteration, suggesting that this methodology could be extended to analytes with a larger number of labile hydrogens. For one isomer pair, as few as two deuteriums were able to produce a large enough mass distribution shift to differentiate isomers. In another experiment, we found that the mass distribution shift was large enough to overcome the reduced mass contribution, resulting in a “flipped” arrival time where the heavier deuterated isotopologue arrived before the lighter one. In this work, we present a proof-of-concept demonstration that mass-distribution-based shifts, tRel. values, could potentially act as an added dimension to characterize molecules in IMS-MS. We anticipate, along with future work in this area, that mass-distribution-based shifts could enable the identification of unknown molecules through a database-driven approach in an analogous fashion to collision cross section (CCS) measurements.

The American Society for Mass Spectrometry was founded in 1969. (1) Over the years, the Society has experienced rapid growth and is composed of >7500 members, representing a diverse group of individuals from varied industry, government, and academic settings. The stated goal of ASMS is “to promote and disseminate knowledge of mass spectrometry and allied topics”. (1) One component of that mission is the publication of the Journal of the American Society for Mass Spectrometry (JASMS). As the publication industry is adapting to rapidly evolving policies, JASMS seeks to ensure it fully represents the diverse interests of all subdisciplines of mass spectrometry while aligning to modern publication standards. We hope this editorial helps to inspire and provide you with an opportunity to help shape JASMS to suit the needs of each ASMS member. As a 501(c)(3) charitable organization duly formed in the United States, ASMS is bound by laws that dictate aspects of the Society, including membership and governing structure. ASMS is led by a nine-member Board of Directors who have been elected by the members of the Society. As the Board of Directors provides governance through directing Society functions and ensuring financial security, it is critical to the success of ASMS. To manage specific aspects of the Society, the Board relies on committees. The board structure consists of the offices of President, Vice President for Programs, Vice President for Arrangements, Treasurer, Secretary, and Past President. In addition to these individuals, three Members-at-Large direct the efforts of the Membership, Education, and Publication committees. The members of the committees serve two-year terms and are selected from the ASMS membership as recommended by the committee members and approved by the Board of Directors. Here, we introduce you to the current members of the Publications Committee. Stephen Valentine, ASMS Member-at-Large for Publications, is an Associate Professor of Chemistry at West Virginia University where he develops new MS instrumentation and techniques for ‘omics analyses. Vanessa Phelan is an Assistant Professor of Pharmaceutical Science at University of Colorado Anschutz Medical Campus, where she develops new methods to investigate microbial metabolomics. Mowei Zhou (PNNL) is a national lab staff scientist who specializes in native top-down MS. Stefani Thomas (University of Minnesota Medical School) is an Assistant Professor of Laboratory Medicine and Pathology who applies mass spectrometry-based proteomics methods to elucidate the biology of ovarian cancer; she is also a Clinical Chemist serving as the Associate Medical Director of the M Health Fairview West Bank Laboratory. Joe Cannon is a Scientific Associate Director of Biotransformation at Bristol Myers Squibb. The Publications Committee is chaired by the ASMS Member-at-Large for Publications. The committee performs several main functions, namely: (1) review content and assist with testing of online conference proceedings; (2) act as liaison between ASMS and JASMS; (3) develop educational publications (with the Education Committee) such as brochures and posters on specific topics; (4) contribute content to the Society Web site; and (5) meet at the annual conference and prepare a report for the ASMS Board of Directors. While all of this work is important, for the remainder of this informational editorial, we focus on our efforts to interface with the board and the JASMS team. In performing its liaison duties mentioned above, the Publications Committee meets regularly with Professor Vicki Wysocki, the current Editor-in-Chief (EIC) of JASMS. This interaction provides an effective channel for bidirectional information flow between the ASMS Board of Directors and the EIC. In these meetings, specific concerns are discussed such as suggested actions to recompose the Editorial Board. The Publications Committee also holds discussions regarding the performance of JASMS. One topic of consideration is how to increase the impact factor of the journal while not sacrificing its commitment to represent all relevant MS topics. Still other discussions are concerned with plans to increase the visibility of JASMS. As part of these efforts, the committee has worked with outstanding JASMS Twitter account managers. Past managers include graduate students Cameron Worthington and Tiffany Cummings (UNC Chapel Hill); the current managers are graduate students Liam Dugan (Carnegie Mellon University) and Kimberly Fabijanczuk (Purdue University). These individuals have volunteered numerous hours to provide increased visibility (with a dash of fun) for JASMS. Because board governance is only as good as the support received from the members of the Society, in closing we issue a call to arms. We ask, “what can you do to help us in our service?” First, it is important to become/maintain membership in ASMS. The Society benefits from all perspectives and the work performed by each of the members. Second, get to know the individual members of the committee, which enables you to make appropriate suggestions to improve JASMS. Third, make suggestions for new committee members as well as the Member-at-Large position. The suggestions for new committee members can be provided to the current committee members; the suggestion for the latter position can be made to members of the ASMS Board of Directors. While making such suggestions, please note the commitment by the society to ensure that the members of the board and each standing committee reflect its diverse membership. Finally, vote! We recently held elections to replace outgoing Board of Directors members, including the Member-at-Large for Publications. We are excited to welcome Kelly Hines (University of Georgia) as the newly elected Member-at-Large for Publications. We know that the work of this committee is in good hands. We also wish to thank you all for all your efforts and your support. Sincerely, This article references 1 other publications. This article has not yet been cited by other publications. This article references 1 other publications.

Since the beginning of the industrial revolution, humans have burned enormous quantities of coal, oil, and natural gas, rivaling nature’s elemental cycles of C, N, and S. The result has been a disruption in a steady state of CO2 and other greenhouse gases in the atmosphere, a warming of the planet, and changes in master variables (temperature, pH, and pε) of the sea affecting critical physical, chemical, and biological reactions. Humans have also produced copious quantities of N and P fertilizers producing widespread coastal hypoxia and low dissolved oxygen conditions, which now threaten even the open ocean. Consequently, our massive alteration of state variables diminishes coral reefs, fisheries, and marine ecosystems, which are the foundation of life on Earth. We point to a myriad of actions and alternatives which will help to stem the tide of climate change and its effects on the sea while, at the same time, creating a more sustainable future for humans and ecosystems alike.

Here we describe a state-of-the-art, integrated, multi-instrument automated system designed to execute methods involved in mass spectrometry characterization of biotherapeutics. The system includes liquid and microplate handling robotics and utilities, integrated LC-MS, along with data analysis software, to perform sample purification, preparation, and analysis as a seamless integrated unit. The automated process begins with tip-based purification of target proteins from expression cell-line supernatants, which is initiated once the samples are loaded onto the automated system and the metadata are retrieved from our corporate data aggregation system. Subsequently, the purified protein samples are prepared for MS, including deglycosylation and reduction steps for intact and reduced mass analysis, and proteolytic digestions, desalting, and buffer exchange via centrifugation for peptide map analysis. The prepared samples are then loaded into the LC-MS instrumentation for data acquisition. The acquired raw data are initially stored on a local area network storage system that is monitored by watcher scripts that then upload the raw MS data to a network of cloud-based servers. The raw MS data are processed with the appropriately configured analysis workflows such as database search for peptide mapping or charge deconvolution for undigested proteins. The results are verified and formatted for expert curation directly in the cloud. Finally, the curated results are appended to sample metadata in the corporate data aggregation system to accompany the biotherapeutic cell lines in subsequent processes.

Mass spectrometry in parallel with real-time machine learning techniques were paired in a novel application to detect and identify chemically specific, early indicators of fires and near-fire events involving a set of selected materials: Mylar, Teflon, and poly(methyl methacrylate) (PMMA). The volatile organic compounds emitted during the thermal decomposition of each of the three materials were characterized using a quadrupole mass spectrometer which scanned the 1–200 m/z range. CO2, CH3CHO, and C6H6 were the main volatiles detected during Mylar thermal decomposition, while Teflon’s thermal decomposition yielded CO2 and a set of fluorocarbon compounds including CF4, C2F4, C2F6, C3F6, CF2O, and CF3O. PMMA produced CO2 and methyl methacrylate (MMA, C5H8O2). The mass spectral peak patterns observed during the thermal decomposition of each material were unique to that material and were therefore useful as chemical signatures. It was also observed that the chemical signatures remained consistent and detectable when multiple materials were heated together. Mass spectra data sets containing the chemical signatures for each material and mixtures were collected and analyzed using a random forest panel machine learning classification. The classification was tested and demonstrated 100% accuracy for single material spectra and an average of 92.3% accuracy for mixed material spectra. This investigation presents a novel technique for the real-time, chemically specific detection of fire related VOCs through mass spectrometry which shows promise as a more rapid and accurate method for detecting fires or near-fire events.

High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) are usually operated at absolute pressures around 20 mbar in order to reach high reduced electric field strengths of up to 120 Td for influencing reaction kinetics in the reaction region. Such operating points significantly increase the linear range and limit chemical cross sensitivities. Furthermore, HiKE-IMS enables ionization of compounds normally not detectable in ambient pressure IMS, such as benzene, due to additional reaction pathways and fewer clustering reactions. However, operation at higher pressures promises increased sensitivity and smaller instrument size. In this work, we therefore study the theoretical requirements to prevent dielectric breakdown while maintaining high reduced electric field strengths at higher pressures. Furthermore, we experimentally investigate influences of the pressure, discharge currents and applied voltages on the corona ionization source. Based on these results, we present a HiKE-IMS that operates at a pressure of 60 mbar and reduced electric field strengths of up to 105 Td. The corona experiments show shark fin shaped curves for the total charge at the detector with a distinct optimum operating point in the glow discharge region at a corona discharge current of 5 μA. Here, the available charge is maximized while the generation of less-reactive ion species like NOx+ is minimized. With these settings, the reactant ion population, H3O+ and O2+, for ionizing and detecting nonpolar substances like n-hexane is still available even at 60 mbar, achieving a limit of detection of just 5 ppbV for n-hexane.

Per- and polyfluoroalkyl substances (PFAS) are a class of manufactured chemicals that have been extensively utilized worldwide. We hypothesize that the presence, uptake, and accumulation of PFAS in aquatic vegetation (AV) is dependent upon several factors, such as the physiochemical properties of PFAS and proximity to potential sources. In this study, AV was collected from eight locations in Florida to investigate the PFAS presence, accumulation, and spatiotemporal distribution. PFAS were detected in AV at all sampling locations, with a range from 0.18 to 55 ng/g sum (∑)PFAS. Individual PFAS and their concentrations varied by sampling location, time, and AV species. A total of 12 PFAS were identified, with the greatest concentrations measured in macroalgae. The average bioconcentration factor (BCF) among all samples was 1225, indicating high PFAS accumulation in AV from surface water. The highest concentrations, across all AV types, were recorded in the Indian River Lagoon (IRL), a location with a history of elevated PFAS burdens. The present study represents the first investigation of PFAS in naturally existing estuarine AV, filling an important gap on PFAS partitioning within the environment, as well as providing insights into exposure pathways for aquatic herbivores. Examining the presence, fate, and transport of these persistent chemicals in Florida’s waterways is critical for understanding their effect on environmental, wildlife, and human health.

The diversity of ubiquitin modifications calls for methods to better characterize ubiquitin chain linkage, length, and morphology. Here, we use multiple linear regression analysis coupled with ion mobility mass spectrometry (IM-MS) to quantify the relative abundance of different ubiquitin dimer isomers. We demonstrate the utility and robustness of this approach by quantifying the relative abundance of different ubiquitin dimers in complex mixtures and comparing the results to the standard, bottom-up ubiquitin AQUA method. Our results provide a foundation for using multiple linear regression analysis and IM-MS to characterize more complex ubiquitin chain architectures.

To capture the structure of assembled hemagglutinin (HA) nanoparticles at single-particle resolution, HA-specific antigen binding fragments (Fabs) were labeled by fluorescent (FLR) dyes as probes to highlight the HA trimers displayed on the assembled tetravalent HA nanoparticles for a qualitative localization microscopic study. The FLR dyes were conjugated to the Fabs through N-hydroxysuccinimide (NHS) ester mediated amine coupling chemistry. The labeling profile, including labeling ratio, distribution, and site-specific labeling occupancy, can affect the imaging results and introduce inconsistency. To evaluate the labeling profile so as to evaluate the labeling efficiency, a combination of intact mass measurement by MALDI-MS and peptide mapping through LC-MS/MS was implemented. At the intact molecular level, the labeling ratio and distribution were determined. Through peptide mapping, the labeled residues were identified and the corresponding site-specific labeling occupancy was measured. A systematic comparative investigation of four different FLR-labeled 1H01-Fabs (generated from H1 strain HA specific mAb 1H01) allowed accurate profiling of the labeling pattern. The data indicate that the labeling was site-specific and semiquantitative. This warrants the consistency of single-particle fluorescent imaging experiments and allows a further imaging characterization of the single nanoparticles.

The analysis of large molecules is challenging, as they often have salts and adducts retained through the electrospray process, which increase the observed mass and compromise the achievable mass resolution. Mild collisional activation has been shown to be very effective for the removal of adducts and increases both measurement accuracy and mass resolution of large (>100 kDa) protein complexes. Collisionally activated protein ions are more completely desolvated due to the increased number of collisions when trapped following activation. A short square quadrupole maintained at 300 mTorr by a mechanical pump was added between the ion funnel and transmission quadrupole. This configuration and operation effectively removed adducts from the 800 kDa tetradecamer GroEL as well as fragmented smaller protein complexes like C-reactive protein. Due to the gas high pressure, ions of low size-to-charge ratio, such as those in charge reducing buffers, had low ejection efficiency. We show that segmenting the quadrupole rods greatly improves signal intensity for charge reduced GroEL D398A mutant compared to nonsegmented rods when operating at high pressure.

This article discusses from a personal and present-day perspective the first studies of large highly charged individual molecular ions that were conducted using electrospray ionization with Fourier transform ion cyclotron resonance MS in the mid-1990s. These studies are distinguished from Current Charge Detection Mass Spectrometry (CDMS) primarily by their use of individual ion charge state changes due to reactions for accurate charge determination. This work describes the key differences in technologies and methods with present CDMS and the likely implications of these differences. I comment on surprising individual ion behavior observed in some measurements involving increases in charge state, as well as their possible basis, and also briefly discuss the potential utility of the reaction-based mass measurement approach used in the context of what might more globally be referred to as “Charge Determination Mass Spectrometry”.

Semiquantitation of suspect per- and polyfluoroalkyl substances (PFAS) in complex mixtures is challenging due to the increasing number of suspect PFAS. Traditional 1:1 matching strategies require selecting calibrants (target–surrogate standard pairs) based on head group, fluorinated chain length, and retention time, which is time-consuming and requires expert knowledge. Lack of uniformity in calibrant selection for estimating suspect concentrations among different laboratories makes comparing reported suspect concentrations difficult. In this study, a practical approach whereby the area counts for 50 anionic and 5 zwitterionic/cationic target PFAS were ratioed to the average area of their respective stable-isotope labeled surrogates to create “average PFAS calibration curves” for suspects detected in negative- and positive-ionization mode liquid chromatography quadrupole time-of-flight mass spectrometry. The calibration curves were fitted with log–log and weighted linear regression models. The two models were evaluated for their accuracy and prediction interval in predicting the target PFAS concentrations. The average PFAS calibration curves were then used to estimate the suspect PFAS concentration in a well-characterized aqueous film-forming foam. Weighted linear regression resulted in more target PFAS that fell within 70–130% of their known standard value and narrower prediction intervals than the log–log transformation approach. The summed suspect PFAS concentrations calculated by weighted linear regression and log–log transformation were within 8 and 16% of those estimated by a 1:1 matching strategy. The average PFAS calibration curve can be easily expanded and can be applied to any suspect PFAS even if the confidence in the suspect structure is low or unknown.

With 28–34 times the greenhouse effect of CO2 over a 100-year period, methane is regarded as the second largest contributor to global warming. Reducing methane emissions is a necessary measure to limit global warming to below 1.5 °C. Photocatalytic conversion of methane is a promising approach to alleviate the atmospheric methane concentrations due to its low energy consumption and environmentally friendly characteristics. Meanwhile, this conversion process can produce valuable chemicals and liquid fuels such as CH3OH, CH3CH2OH, C2H6, and C2H4, cutting down the dependence of chemical production on crude oil. However, the development of photocatalysts with a high methane conversion efficiency and product selectivity remains challenging. In this review, we overview recent advances in semiconductor-based photocatalysts for methane conversion and present catalyst design strategies, including morphology control, heteroatom doping, facet engineering, and cocatalysts modification. To gain a comprehensive understanding of photocatalytic methane conversion, the conversion pathways and mechanisms in these systems are analyzed in detail. Moreover, the role of electron scavengers in methane conversion performance is briefly discussed. Subsequently, we summarize the anthropogenic methane emission scenarios on earth and discuss the application potential of photocatalytic methane conversion. Finally, challenges and future directions for photocatalytic methane conversion are presented.

The femtoamp electrospray ionization (femtoESI) mode has been shown to exhibit unique characteristics that may facilitate ionization efficiency studies and experiments requiring low ion beam flux. Investigation of femtoESI was hindered by a tiny, applied voltage window of 10–100 V, beyond which ionization currents quickly jumped to nanoamps. This window was difficult to locate because the exact onset voltage fluctuates due to variations in ion source alignments. Large resistors (0.1–100 TΩ) in series effectively expanded the femtoESI applied voltage range, up to 1400 V. By swapping resistors, rapid alternation allows for the comparison of both ESI modes under the same alignment. In peptide mixtures, analytes with lower surface activity are suppressed in the nanoESI mode whereas the femtoESI mode shows signal enhancement of less surface-active species. For protein solutions, there is little change in the charge states generated but the femtoESI mode does show a decrease in the average charge state of protein peaks. Peptides and proteins analyzed in the femtoESI mode also tend to generate higher intensity sodiated peaks over protonated peaks at specific charge states compared with nanoESI mode operation.

Rising CO2 emissions are responsible for increasing global temperatures causing climate change. Significant efforts are underway to develop amine-based sorbents to directly capture CO2 from air (called direct air capture (DAC)) to combat the effects of climate change. However, the sorbents’ performances have usually been evaluated at ambient temperatures (25 °C) or higher, most often under dry conditions. A significant portion of the natural environment where DAC plants can be deployed experiences temperatures below 25 °C, and ambient air always contains some humidity. In this study, we assess the CO2 adsorption behavior of amine (poly(ethyleneimine) (PEI) and tetraethylenepentamine (TEPA)) impregnated into porous alumina at ambient (25 °C) and cold temperatures (−20 °C) under dry and humid conditions. CO2 adsorption capacities at 25 °C and 400 ppm CO2 are highest for 40 wt% TEPA-incorporated γ-Al2O3 samples (1.8 mmol CO2/g sorbent), while 40 wt % PEI-impregnated γ-Al2O3 samples exhibit moderate uptakes (0.9 mmol g–1). CO2 capacities for both PEI- and TEPA-incorporated γ-Al2O3 samples decrease with decreasing amine content and temperatures. The 40 and 20 wt % TEPA sorbents show the best performance at −20 °C under dry conditions (1.6 and 1.1 mmol g–1, respectively). Both the TEPA samples also exhibit stable and high working capacities (0.9 and 1.2 mmol g–1) across 10 cycles of adsorption–desorption (adsorption at −20 °C and desorption conducted at 60 °C). Introducing moisture (70% RH at −20 and 25 °C) improves the CO2 capacity of the amine-impregnated sorbents at both temperatures. The 40 wt% PEI, 40 wt % TEPA, and 20 wt% TEPA samples show good CO2 uptakes at both temperatures. The results presented here indicate that γ-Al2O3 impregnated with PEI and TEPA are potential materials for DAC at ambient and cold conditions, with further opportunities to optimize these materials for the scalable deployment of DAC plants at different environmental conditions.

A mechanism of unusual tandem (MS/MS) fragmentation of protonated species of N-(triphenyl-λ5-phosphanylidene) derivatives, [M + H]+ to generate triphenylphosphine oxide (TPPO) within the mass spectrometer has been investigated and reported. Collision-induced dissociation of these molecules resulted in the generation of TPPO as a signature fragment. This fragment suggested the presence of a P–O bond in the structure which was contrary to the structure of the compound identified by nuclear magnetic resonance spectrometry (NMR) and single-crystal X-ray diffractometry (SXRD) techniques with a P═N bond rather than a P–O bond. In order to confirm the generation of the TPPO fragment within the mass spectrometer, 14 different N-(triphenyl-λ5-phosphanylidene) derivatives containing amide, 18O-labeled amide, thiamide, and nonacyl phosphazene derivatives were synthesized and their MS/MS behavior was studied by liquid chromatography–high-resolution mass spectrometry. Fragmentation of these amide derivatives generated TPPO/TPPS or their 18O-labeled analogues as the major fragment in almost all cases under similar MS conditions. Based on the outcome of these experiments, a plausible mechanism for such fragmentation, involving the intramolecular shifting of oxygen from carbon to phosphorus, has been proposed. DFT calculations for the protonated species at B3LYP-D3/6-31+G(d,p) further supported the proposed mechanism involving a four-membered ring, P–O–C–N, as the transition state. Details of this work are presented here.

Phospholipases have diverse roles in lipid and cell membrane biology. In animal venoms, they can have roles as neurotoxins or myotoxins that disrupt the integrity of cell membranes. In this work, we describe a temperature-controlled, continuous electrospray ionization mass spectrometry (ESI-MS) assay for measuring phospholipase A2 activity against liposomes. The enzyme used in this assay was paradoxin, which is a neurotoxic trimeric phospholipase A2 from inland taipan snake venom. Previously developed ESI-MS-based phospholipase assays have been discontinuous and analyzed hydrolysis of single lipid molecules by liquid chromatography ESI-MS. In this work, a continuous assay was developed against liposomes, a more complex substrate that more closely reflects the natural substrate for paradoxin. The assay confirmed the requirement for Ca2+ and allowed measurement of Michaelis–Menten-type parameters. The use of ESI-MS for lipid detection enabled nuanced insights into the effect of changing assay conditions not only on the enzyme but also on the liposome substrate. Changing the metal ion concentrations did not significantly change the liposomes but did affect enzymatic activity. Increasing temperature did not substantially affect the secondary structure of paradoxin but affected liposome size, resulting in increased enzymatic activity consistent with the disruption of the phosphatidylcholine membrane, increasing accessibility of sn-2 ester bonds. The continuous ESI-MS method described herein can be applied to other enzyme reactions, particularly those which utilize complex lipid substrates.

The number of points across a chromatographic peak has long been recognized as a key determinant of the accuracy and precision of the measured peak area. In LC–MS-based quantitation experiments in drug discovery and development, the “rule-of-thumb” has been to use 15 or more points. This “rule” is based on the literature describing chromatographic methods where the goal was to achieve the lowest possible imprecision in the measurements, especially when unknown analytes are being detected. Restricting methods to the requirement of at least 15 points across a peak can be detrimental to the development methods that fully optimize the signal-to-noise ratio for the assay using longer dwell times and/or transition summing. This study aims to show that 7 points across the peak for peaks that are 9 s or less wide provide more than sufficient accuracy and precision for drug quantitation studies. Data from simulated Gaussian curves using a sampling interval of 7 points across the peak gave peak area calculations within 1% of the expected total peak area using the Trapezoidal and Riemann rules and 0.6% for the Simpson rule. Low and high concentration samples (n = 5) were assayed using three different LC methods on three different days on two different instruments (API5000 and API5500). The difference in peak area (%ΔPA) and relative standard deviation of the peak areas (%RSD) was less than ∼5%. No significant difference was observed from the data that were obtained from different sampling intervals, different peak widths, different days, different peak sizes, and different instruments. Three core analytical runs were performed on three different days. In each core run, the lower limit of quantitation (LLOQ, n = 5), low quality control (LQC, n = 5), middle quality control (MQC, n = 5), and high-quality control samples (HQC, n = 5) were processed and run simultaneously with a standard curve. The range of the intra- and interday accuracy and precision for 3 core runs was 98.0–105% and 0.9–3.0% for 7 data points and 97.5–105% and 0.8–4.3% for 17 data points, respectively. No significant difference was observed for the different sampling intervals. The results show a sampling interval of 7 points for peaks up to 9 s wide is sufficient to define a peak accurately and precisely for drug quantitation studies in drug discovery and development.

N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD)-quinone (6PPD-Q), a transformation byproduct of 6PPD used in tires as an antiozonant and antioxidant, was recently discovered as the chemical primarily responsible for the acute lethal toxicity of urban storm runoff to coho salmon. The asphalt concrete (AC) surface layer is the primary medium to contact 6PPD-Q immediately upon its release from tires, and the addition of recycled tire rubber (RTR) to the asphalt binder and mixture is a widely accepted practice in asphalt production. Therefore, it is urgent to understand the fate of 6PPD-Q at the asphalt concrete surface layer–water interface. This study analyzed the sorption and desorption of 6PPD-Q by compacted and crushed loose (loose particles, ∼5 mm) rubberized asphalt mixtures and their mobilization from compacted asphalt mixtures during simulated rainfall events. It should be noted that the crushed loose asphalt mixtures demonstrated the physicochemical properties of the asphalt materials, while the compacted asphalt mixtures represent in-service AC layers. Sorption of 6PPD-Q by crushed loose and compacted asphalt mixtures reached equilibrium within 12 days, with a sorption coefficient of 151.57–257.51 L/kg for compacted asphalt mixtures. Within 12 days, desorption of 6PPD-Q from crushed loose and compacted rubberized asphalt mixtures (20 g particles/L) to the double deionized (DDI) water and synthetic stormwater was 0.01–0.09 and 0.025–0.05 μg/L, respectively. Through the rainfall simulation experiments, 0.0015–0.0049 μg/L 6PPD-Q was detected in the runoff water, much lower than the lethal concentration (LC50) of 6PPD-Q of 0.095 μg/L and 308.67 μg/L for coho salmon and zebrafish larvae. Our results indicate that, while the release of 6PPD-Q from compacted rubberized asphalt mixtures is minor, the mixtures can serve as sorbents for tire-derived 6PPD-Q and retain this emerging contaminant.

Glycosylation is an important protein post-translational modification that plays a pivotal role in the bioactivity of therapeutic proteins and in the infectivity of viral proteins. Liquid chromatography with tandem mass spectrometry readily identifies protein glycans with site specificity. However, the overnight incubation used in conventional in-solution proteolysis leads to high turnaround times for glycosylation analysis, particularly when sequential in-solution digestions are needed for site-specific glycan identification. Using bovine fetuin as a model glycoprotein, this work first shows that in-membrane digestion in ∼3 min yields similar glycan identification and quantitation when compared to overnight in-solution digestion. Protease-containing membranes in a spin column enable digestion of therapeutic proteins (trastuzumab and erythropoietin) and a viral protein (SARS-CoV-2 receptor binding domain) in ∼30 s. Glycan identification is similar after in-solution and in-membrane digestion, and limited in-membrane digestion enhances the identification of high-mannose glycans in trastuzumab. Finally, stacked membranes containing trypsin and chymotrypsin allow fast sequential proteolytic digestion to site-specifically identify the glycans of SARS-CoV-2 receptor binding domain. One can easily assemble the protease-containing membranes in commercial spin columns, and spinning multiple columns simultaneously will facilitate parallel analyses.