Dual Mass Research Articles

Chemiluminescent immunoassay overestimates hormone concentrations and obscures testosterone sex differences relative to LC-MS/MS in a field study of diverse adolescents

BackgroundMethodological comparisons of hormone quantification techniques have repeatedly demonstrated that, in adults, enzyme immunoassay (EIA) inflates steroid hormone concentrations relative to mass spectrometry. However, methodological comparisons in adolescent samples remain rare, and few studies have examined how chemiluminescent immunoassay (CLIA), another popular immunoassay, compares to mass spectrometry. Additionally, no studies have examined how differences in analytical techniques may be affecting relationships between steroid hormone levels and outcomes of interest, such as psychopathology. This pre-registered analysis of an existing dataset measured salivary cortisol and testosterone using both CLIA and liquid chromatography dual mass spectrometry (LC-MS/MS) in a repeated measures (516 samples) sample of 207 9th graders. MethodsIn aim 1, this study sought to expand on past findings by 1) measuring inflation of testosterone and cortisol by CLIA in a relatively large adolescent sample, and 2) showing that CLIA (like EIA) testosterone inflation was especially true in groups with low ‘true’ testosterone levels. In aim 2, this study sought to examine the impact of hormone quantification method on relationships between hormone levels and psychopathological measures (the Children's Depression Inventory, the Perceived Social Stress Scale, the UCLA Loneliness Scale, and the Anxious Avoidant and Negative Self Evaluation subscales of the Social Anxiety Scale for Adolescents). ResultsWe found that CLIA, like EIA, inflated testosterone and cortisol levels and overestimated female testosterone resulting in suppressed sex differences in testosterone. We did not observe these same patterns when examining testosterone in individuals with differing levels of pubertal development. Results of psychopathology analyses demonstrated no significant method differences in hormone-psychopathology relationships. ConclusionsOur findings show that CLIA introduces proportional bias in cortisol and testosterone in a manner that suppresses sex differences in testosterone. Steroid measurement method did not significantly moderate the relationship between hormones and psychopathology in our sample, though more work is needed to investigate this question in larger, clinical samples.

Isotope analysis of human dental calculus δ13 CO3 2- : Investigating a potential new proxy for sugar consumption.

RationaleDental calculus (mineralised dental plaque) is composed primarily of hydroxyapatite. We hypothesise that the carbonate component of dental calculus will reflect the isotopic composition of ingested simple carbohydrates. Therefore, dental calculus carbonates may be an indicator for sugar consumption, and an alternative to bone carbonate in isotopic palaeodiet studies.MethodsWe utilised Fourier transform infrared attenuated total reflectance analysis to characterise the composition and crystallisation of bone and dental calculus before isotope analysis of carbonate. Using a Sercon 20‐22 mass spectrometer coupled with a Sercon GSL sample preparation system and an IsoPrime 100 dual inlet mass spectrometer plus Multiprep device to measure carbon, we tested the potential of dental calculus carbonate to identify C4 resources in diet through analysis of δ13C values in paired bone, calculus and teeth mineral samples.ResultsThe modern population shows higher δ13C values in all three tissue carbonates compared to both archaeological populations. Clear differences in dental calculus δ13C values are observed between the modern and archaeological individuals suggesting potential for utilising dental calculus in isotope palaeodiet studies. The offset between dental calculus and either bone or enamel carbonate δ13C values is large and consistent in direction, with no consistent offset between the δ13C values for the three tissues per individual.ConclusionsOur results support dental calculus carbonate as a new biomaterial to identify C4 sugar through isotope analysis. Greater carbon fractionation in the mouth is likely due to the complex formation of dental calculus as a mineralized biofilm, which results in consistently high δ13C values compared to bone and enamel.

Detection of atomoxetine and its metabolites in the urine by thin-layer chromatography and mass spectrometry

The aim of the study was the detection of atomoxetine and its biotransformation products in the urine under TLC screening conditions and identification of the metabolites using mass spectrometry method. Materials and methods. The volunteer’s urine samples after taking a single therapeutic dose of atomoxetine (2 capsules of 60 mg each of Strattera®) were studied. Sample preparation included diluting acid hydrolysis followed by the native compound and metabolites extraction with chloroform from the saturated solution of ammonium sulfate at pH of 11–12. Thin-layer chromatography studies of the extracts were carried out in 18 mobile phases including those proposed by The International Association of Forensic Toxicologists for general drug screening, and those widely used in forensic toxicological studies. The color reactions were carried out using a range of chromogenic reagents. A Varian 1200 L mass spectrometer (Netherlands) equipped with a dual quadrupole mass analyzer was applied for analysis of the eluates from chromatograms. Identification was undertaken at the direct introduction of the sample into the ion chamber, electron-impact ionization (70 eV), and full ion scanning mode. Results. The spot of the native drug on the chromatogram was identified by the Rf, value. Two atomoxetine biotransformation products were identified by the molecular weights that correspond to the molecular ion peaks in the mass spectra. Conclusions. Atomoxetine and its biotransformation products were detected in the urine under TLC screening conditions and identified using mass spectrometry method. Chromatographic mobility of the native compound, hydroxyatomoxetine, and dihydroxyatomoxetine in the TLC screening systems as well as the results of their visualization using chromogenic reagents applied for toxicological drug screening in the systematic toxicological analysis have been determined.

A Two-Year Evaluation of Flualprazolam Concentrations in Orange County Drivers: Effects on Driving and Field Sobriety Test Performance.

Starting in early 2017, flualprazolam was detected in toxicology and seized drug cases across the USA. Due to the addition of fluorine to alprazolam, flualprazolam's chemistry was enough to bypass targeted toxicology confirmations, and it has become increasingly available for purchase both on the dark web and in counterfeit pills. Flualprazolam was added to the exact mass screening regiment of the Orange County forensic laboratory in December 2018. Through data mining of previously analyzed cases, data were evaluated beginning from August 2018. Flualprazolam was subsequently added to the laboratory's validated quantitative liquid chromatography dual mass spectrometry method in the summer of 2020, and all driving cases from August 2018 to June 2020 were re-analyzed to obtain concentrations. The police and drug recognition evaluation (if available) reports were collected and reviewed for all cases where flualprazolam was detected. Of the 203 cases containing quantifiable drug, the average flualprazolam concentration (median, range) was 22.8 ng/mL (15.4 ng/mL, 4.0-133.3 ng/mL). Only two cases had flualprazolam detected with no other drugs. The other most common drugs detected were cannabinoids (62%), ethanol (20%) and cocaine and/or methamphetamine (32%). The most common reason for the police investigation was an accident/collision (50%), and the most common time of officer contact was evening (18:00 to 23:59). The field sobriety test (FST) results were evaluated and showed a higher frequency of impaired performance in cases of flualprazolam in combination with other drugs. No conclusion could be made regarding the effect of flualprazolam alone on FST performance.

Wet surface wall model for latent heat exchange during evaporation.

Air conditioning is a dual heat and mass transfer process, and the human nasal cavity achieves this through the mucosal wall surface, which is supplied with an energy source through the sub‐epithelial network of capillaries. Computational studies of air conditioning in the nasal cavity have included temperature and humidity, but most studies solved these flow parameters separately, and in some cases, a constant mucosal surface temperature was used. Recent developments demonstrated that both heat and mass transfer need to be modeled. This work expands on existing modeling efforts in accounting for the nasal cavity's dual heat and mass transfer process by introducing a new subwall model, given in the Supplementary Materials. The model was applied to a pipe geometry, and a human nasal cavity was recreated from CT‐scans, and six inhalation conditions were studied. The results showed that when the energy transfer from the latent heat of evaporation is included, there is a cooling effect on the mucosal surface temperature.

Surface complexation reactions in sandy porous media: Effects of incomplete mixing and mass-transfer limitations in flow-through systems

Although mixing and surface complexation reactions are key processes for solute transport in porous media, their coupling has not been extensively investigated. In this work, we study the impact of mass-transfer limitations on heterogeneous reactions taking place at the solid-solution interface of a natural sandy porous medium under advection-dominated flow-through conditions. A comprehensive set of 36 column experiments with different grain sizes (0.64, 1.3 and 2.3 mm), seepage velocities (1, 30 and 90 m/day), and hydrochemical conditions were performed. The injection of NaBr solutions of different concentrations (1–100 mM) led to the release of protons via deprotonation reactions of the quartz surface. pH and solute concentration breakthrough curves were measured at the outlet of the columns and the propagation of pH fronts in the column setups was tracked inside the porous medium with non-invasive optode sensors. The experimental results show that the deprotonation of the reactive surfaces, resulting from their interactions with the injected ionic species, strongly depends on the hydrodynamic conditions and differs among the tested porous media despite their apparent similar surface properties. Reactive transport modeling was used to quantitatively interpret the experimental results and to analyze the effects of mass-transfer limited physical processes on surface complexation reactions, propagation of pH fronts, transport of major ions and spatio-temporal evolution of surface composition. A dual domain mass transfer formulation (DDMT) combined with a surface complexation model (SCM) allowed capturing the effects of incomplete mixing on the surface reactions and to reproduce the experimental observations collected in the experiments with high flow velocities. The SCM was parameterized with a single set of surface complexation parameters, accounting for the similar surface properties of the porous media, and was capable of describing the surface complexation mechanisms and their impact on the hydrochemistry over the large range of tested ionic strengths.

Dual ambient plasma source ionization mass spectrometry for the rapid detection of trace sterols in urban water.

A direct analytical method based on dual ambient plasma ion source tandem mass spectrometry was used for the simultaneous determination of four sterols in the environment. This technology has very high sensitivity and the method detects the four sterols in methanol-water (1:3) solutions with limits of detection (LOD) and limits of quantification (LOQ) ranging from 1.2ng/L to 6.9ng/L and 7.6ng/L to 10.0ng/L, respectively. The method was also used to test water quality at three locations within the city and successfully detected all four sterols at very low concentrations. The dual plasma source tandem mass spectrometry technique is extremely simple, rapid, sensitive and highly efficient compared to other traditional methods, providing a useful screening tool for sterols in water.

Simplified coaxial ion trap: Simulation-based geometry optimization, unidirectional ejection, and trapping conditions

We have simulated the design and performance of the simplified coaxial ion trap – a dual ion trap mass spectrometer consisting of an outer simplified toroidal trap and an inner cylindrical trap. The device can perform tandem mass analysis by initially trapping ions in the toroidal region, and then transferring ions mass-selectively to the cylindrical region where they can be fragmented, isolated, and mass-scanned. The key benefit of the coaxial trap is the ability to store and retain the original ion population in the toroidal region while tandem mass analysis is being done in the cylindrical region for a selected mass. This study models a miniaturized simplified coaxial ion trap using the ion trajectory simulation software, SIMION, and characterizes its performance in terms of mass resolution and selectivity of transfer from toroidal to cylindrical regions, ion ejection direction from the toroidal trap, and trapping efficiency in the cylindrical trap. Mass resolution was maximized with a slightly positive octopole term in the toroidal trapping region, and the desired inward radial ejection of ions was achieved with a positive hexapole term. We demonstrate the possibility to obtain an optimized electric field for a given aspect ratio of the toroidal trap by varying only three geometric parameters. Simulated mass resolution from the optimized geometry was 0.3 Da for aspect ratio 8. The trapping efficiency was found to be affected by RF and AC voltages, RF phase, as well as the pressure. A mismatch between the kinetic energy of transferred ions and the RF phase in the cylindrical trap at the time of transfer was found to account for most of the ion loss during transfer. The intricate dependence of trapping efficiency on a number of operational variables was found to lead to trade-offs between itself and other operational parameters such as mass resolution and transfer efficiency. The results demonstrate successful operation of the simplified coaxial trap and reveal the geometric and operational constraints to be considered in its operation.

Wear Based Lifetime Estimation of a Clutch Facing using Coupled Field Analysis

Repetitive use of the clutch, over a period of time, causes the friction material at the contact surfaces (clutch facing and flywheel/pressure plate) to wear, thus deteriorating its performance and usable life. The working life of a rigid clutch is the limiting factor when it comes to extracting maximum performance from a dual mass flywheel system, which is used in a lot of modern vehicles nowadays to lower fuel consumption and improve ride quality. In this study, we investigate the influence of different groove patterns on wear in rigid clutch facings and estimate their life using a comprehensive finite element model. The wear is calculated and analysed for five different groove patterns across two different inorganic materials, namely FTL180 and TF1600-MC2, using Archard’s Adhesive Wear Model. Coupled multi-physics elements are employed in the analysis to capture the effect of frictional heat generation on wear. We found that the Waffle pattern offered a decrease of 10.4% in volumetric wear loss, a 5.78% decrease in maximum wear thickness and an increase of 11.51% in the average working life is used in city like conditions with frequent engagements. This work sheds light on the impact of groove patterns on clutch facing wear and opens a new path for the design and development of more resilient rigid clutches.

Dual regulation both intrinsic activity and mass transport for self-supported electrodes using in anion exchange membrane water electrolysis

Anion exchange membrane water electrolysis (AEMWE) is considered as a promising approach to large-scale hydrogen production. However, the performance of AEMWE is limited by the slow reaction kinetics of the catalyst and poor mass transport of gases and electrolyte at high current densities. Herein, we report Fe0.2Ni0.8-P0.5S0.5 nanoisland arrays as an efficient bifunctional catalyst with ultralow overpotentials of 85 mV (for HER) and 180 mV (for OER) to achieve a current density of 10 mA cm−2. Density functional theory calculations reveal that bimetallic doping of Fe0.2Ni0.8-P0.5S0.5 effectively improve the intrinsic activity. Particularly, the Fe0.2Ni0.8-P0.5S0.5 electrode is endowed with superhydrophilicity and aerophobicity, which not only facilitates to the exposure of active sites, but also markedly enhance gas and electrolye diffusion at high current density. Therefore, the AEMWE based on the Fe0.2Ni0.8-P0.5S0.5 bifunctional electrodes delivers a current density of 2.5 A cm−2 at 2.0 V. Moreover, the AEMWE maintained long-term operation without obvious performance degradation for 300 h.

Three-dimensional liquid chromatography with parallel second dimensions and quadruple parallel mass spectrometry for adult/infant formula analysis

Three dimensions of chromatographic separation, using split-flow two-dimensional liquid chromatography (SF-2D-LC) with two parallel second dimensions, LC × 2LC, combined with quadruple parallel mass spectrometry (LC3MS4) is demonstrated for analysis of NIST SRM 1849a adult/infant formula. The first dimension, 1D, was a conventional non-aqueous reversed-phase (NARP) HPLC separation using two C18 columns in series, followed by detection using an ultraviolet (UV) detector, a fluorescence detector (FLD), with flow then split to a corona charged aerosol detector (CAD), and then dual parallel mass spectrometry (MS), conducted in atmospheric pressure photoionization (APPI) and electrospray ionization (ESI) modes. The first second dimension, 2D(1), UHPLC was conducted on a 50.0 mm C30 column using a NARP-UHPLC parallel gradient for separation of short-chain triacylglycerols (TAGs) from long-chain TAGs, with detection by UV and ESI-MS. The second dimension, 2D(2), UHPLC was conducted using a 100.0 mm C30 column with a NARP-UHPLC parallel gradient for improved separation of TAG isomers, with detection by UV, an evaporative light scattering detector, and high-resolution, accurate-mass (HRAM) ESI-MS. Transferred eluent dilution was used to refocus peaks and keep them sharp during elution in both 2Ds. The separation space in the 2D(2) was optimized using multi-cycle (aka, “constructive wraparound”) elution, which employed flow rate programming. In the 1D, calibration lines for quantification of fat-soluble vitamins were constructed. A lipidomics approach to TAG identification and quantification by HRAM-ESI-MS was applied to the 2D(2). These experiments can be represented: LC1MS2 × (LC1MS1 + LC1MS1) = LC3MS4, or three-dimensional liquid chromatography with quadruple parallel mass spectrometry.

Effect of particle mass inhomogeneity on the two-dimensional Rayleigh–Bénard system of Yukawa liquids: A molecular dynamics study

The effect of particle mass inhomogeneity on the evolution of macroscale fluid flow in the Rayleigh–Bénard system of two-dimensional Yukawa liquids is studied using “first principles” classical molecular dynamics simulations. We find that Rayleigh–Bénard convection cells (RBCCs) formed in the quasi-steady-state become unstable at later times as a result of introducing a small fraction (≤2% of the total particles) of particle mass inhomogeneity in a Yukawa system made up of point particles of uniform charges. The unstable RBCCs, after passing through several intermediate states, give rise to a unidirectional shear flow in the direction perpendicular to the external gravity. Depending on the fraction and phase space of the particle mass inhomogeneity introduced in the system, the unidirectional shear flow further evolves to give shearless parallel flow. We use single or dual particle mass distributions of various forms, such as Gaussian distribution, Dirac-delta distribution, or a combination of both, around different mean values in order to introduce particle mass inhomogeneity. The role of system size on the emergence of various intermediate fluid flow states is also investigated. Furthermore, by introducing an inhomogeneity in charge commensurate with mass inhomogeneity, we demonstrate the robustness of our findings. Finally, for the case of decreasing correlation strength and for otherwise identical parameters, it is shown that the particle mass inhomogeneity fails to generate shear flows from RBCCs in 2D Yukawa liquids.

A double-mass block acceleration sensor based on FBG

A double-mass block acceleration sensor based on Fiber Bragg Grating (FBG) is proposed to meet the needs of acceleration sensors in vibration monitoring. The proposed sensor is composed of FBG, beam and double mass block, and the FBG is fixed in the middle of the upper surface of the dual mass block by epoxy glue. Through theoretical analysis and experimental verification, the resonant frequency, sensitivity and lateral anti-interference ability of the sensor have been investigated. The experimental results show that the natural frequency of the sensor is 1000 Hz, the sensitivity is 26.7 pm/g when the frequency is 250 Hz, and the lateral anti-interference degree is less than 6%. And the sensor structure in this paper is simple and easy to fabricate. Therefore, it has a great application prospect in the vibration monitoring of bridges, roads and buildings.

Numerical Studies on the Stiffness of Arc Elliptical Cross-section Helical Spring Subjected to Circumference Force

Due to its excellent properties, elliptical cross-section helical spring has been widely used in automobile industry, such as valve spring, arc spring used in Dual Mass Flywheel and so on. Existing stiffness formulae of helical spring remain to be tested, and stiffness property of elliptical cross-section arc spring has been little studied. Hence, study on the stiffness of elliptical cross-section helical spring is significant in the development of elliptical cross-section helical spring. This paper proposes a method to study the stiffness property of elliptical cross-section helical spring that the experiment design method is adopted with finite element analysis. Firstly, the finite element analysis method was used to verify the cylindrical (circular cross-section and elliptical cross-section) springs. Then, the regression formula was designed and derived compared with the reference springs’ stiffness formulae by experimental design. Last, regression formula was verified with existing experiment data. The novelty in this paper is that simulation technology of arc spring was investigated and a stiffness regression equation of arc elliptical cross-section spring was obtained using orthogonal regression design, with significance in wide use of the arc elliptical cross-section helical spring promotion.

Dynamic Characteristics Analysis of a Circumferential Short Spring Dual Mass Flywheel with the Influence of Centrifugal Force and Friction

Multiple sets of spring, spring seat structures are uniformly arranged in circumferential short spring dual mass flywheel (DMF), which generally have a symmetrical structure. The internal springs and spring seats are constrained by the shape of the primary flywheel and the secondary flywheel. At different rotational speeds, the springs and spring seats have different centrifugal forces. To study the dynamic characteristics of the DMF including torque and stiffness with considering the influence of centrifugal force and friction, the discrete method is used to analyze the mechanical actions of the transmission parts in DMF. The torque action between the spring seat and the secondary flywheel is deduced. The dynamic characteristics of the DMF are obtained through analyzing and calculating. Due to the symmetry of the structure, the torque transmitted and the stiffness of the DMF also have specific symmetrical characteristics. Namely, at two relative rotational angles of the same magnitude and opposite direction, the magnitude of the transmitted torque is the same, the direction is opposite. The magnitude and direction of stiffness are the same. The influence of speed, friction coefficient, spring mass, and spring seat mass on the torque and stiffness characteristics are analyzed. Finally, the theoretical analysis is proved to be valid by the torque characteristics test of DMF.

Properties of Car-Embedded Vibrating Type Piezoelectric Harvesting System

We investigated the harvesting performance of a double piezoelectric generator, which was embedded into the engine block of a small passenger car. The resonance frequency is approximately between 37 and 52 Hz, where the cantilever showed maximum displacement. In reality, the cantilever has a vibrating characteristic, which dramatically reduces displacement, even when the operating frequency deviates slightly from the resonance frequency. To acquire a large mechanical energy-to-electrical energy conversion, a multiple-piezoelectric generator was employed to absorb the energy even when the vibration switched from a resonance to a non-resonance frequency. In this study, a variable mass box was designed and installed in the engine block of a car. The variable mass box consisted of the serial connection of two masses with different weights. The operating frequency deviated from a resonance to a non-resonance frequency within a few hertz (3~4 Hz); the reduction in vibration was lower, leading to a significant acquisition of the resulting power. This is due to the variable matching of the generator, realized by the action of dual mass. This type of generator was installed in the engine block and produced up to 0.038 and 0.357 mW when the engine was operating at 2200 and 3200 rpm, respectively.

Recommendation with Diversity: Mass Diffusion Model Based on Trust Network and Object Reputation

The traditional mass diffusion recommendation algorithm only relies on the user’s object collection relationship, resulting in poor recommendation performance for users with small purchases (i.e., small-degree user), and it is difficult to balance the accuracy and diversity of the recommendation system. This paper introduces the trust relationship into the resource allocation process of the traditional mass diffusion algorithm and proposes the Dual Wing Mass Diffusion model (DWMD), which constructs a dual wing graph based on trust relationships and object collection relationships. Implicit trust is mined according to the network structure of the trust relationship and integrated into the resource allocation process, and then merging the positive effects of object reputation on a recommendation through tunable scaling parameters. The user controls the tunable scaling parameter to achieve the best recommendation performance. The experimental results show that the DWMD method significantly improves diversity and novelty while ensuring high accuracy and effectively improves the accuracy and diversity balance. The improved recommendation performance for small-degree users proves that the trust relationship can effectively alleviate the generalized cold start problem of the recommendation algorithm for users who collect a small number of objects.

Design and modeling of a MEMS accelerometer based on coupled mode-localized nonlinear resonators under electrostatic actuation

A novel dual proof mass accelerometer is proposed by introducing mode localization in two electrostatically coupled resonators. The levering mechanism is utilized to amplify the inertial force applied axially to the two weakly coupled resonators. The dynamic model considering the electrostatic and mechanical nonlinearities is established and solved by the method of multiple scales, and also is validated by the harmonic balance method (HBM) coupled with the asymptotic numerical method (ANM). The linear and nonlinear sensitivities depicted as the difference of relative shift of amplitude ratio are investigated as well as the main influencing factors. It has been found that linear sensitivity is up to 4 orders of magnitude higher than that expressed by the difference of relative frequency shift. Also, the nonlinear sensitivity is further increased by 1.47 times comparing to the linear sensitivity. Moreover, the resolution is also greatly improved when the sensor is driven beyond its critical amplitude. Finally, the effect of the electrostatic coupling on the sensing performances is explored, and the optimal coupling voltage is theoretically identified at the limit of mode aliasing.

Multi-objective optimization of a dual mass flywheel with centrifugal pendulum vibration absorbers in a single-shaft parallel hybrid electric vehicle powertrain for torsional vibration reduction

This research deals with an optimization of a dual mass flywheel (DMF) with centrifugal pendulum vibration absorbers (CPVAs) used in a single-shaft parallel hybrid electric vehicle (HEV) powertrain for the reduction of the torsional vibration at the rotor of the electric motor and the total moment of inertia of the DMF and CPVAs. Unlike the previous studies, this research considers the overall behavior of an entire powertrain with an in-line four-cylinder engine and a five-speed automatic transmission for the optimization of the DMF with CPVAs. For this purpose, the multibody dynamics model of the HEV powertrain is constructed and used to analyze the transient response of the system for a given gas pressure map and acceleration condition of the vehicle. Then, a multi-objective genetic algorithm is applied to determine the Pareto optimal front that yields the design parameter values of the DMF and CPVAs effective in the torsional vibration reduction and inertia minimization. The result of the optimization is compared with the HEV powertrain system with a flywheel only, and shows that the vibrations transmitted to the motor are significantly reduced in all the solutions of the Pareto front. By using the method proposed in this research, various parameter combinations of the DMF and CPVAs can be considered in the early design process.

Reactivity of para-benzynes in solution and in the gas phase

To rationally design less cytotoxic synthetic drugs based on biologically active para-benzyne intermediates, it is essential to obtain a better understanding on the reactivity of para-benzynes. However, little is still known about their fundamental chemical properties, which requires examination of pure species in simple solvents instead of biological matrices. While fundamental solution studies are limited, the solvent-free reactivity of protonated para-benzynes has been examined previously in the gas phase by using mass spectrometry. In order to facilitate the comparison of results obtained in the gas phase and in solution, we attempted to compare the reactivity of a neutral para-benzyne analog toward dimethyldisulfide in solution to that of its protonated form in the gas phase. The neutral para-benzyne analog, 5,8-didehydroquinoline, was successfully generated via photolysis of an enediyne precursor in dimethyldisulfide/methanol solution and the reaction products were analyzed using a dual linear quadrupole ion trap tandem mass spectrometrometer. However, examination of of the reactions of the same para-benzyne in its protonated form in the gas phase in the mass spectrometer proved to be challenging. Therefore, an analogous, isomeric para-benzyne cation, the 5,8-didehydroisoquinolinium cation, was instead generated in the gas phase from the 5-iodo-8-nitroisoquinoline precursor and its reactions with dimethyldisulfide were examined. This protonated para-benzyne reacted with dimethyl disulfide in the gas phase in the same manner as its neutral isomer in solution; both predominantly abstracted a thiomethyl group by each of the two radical sites. The structures of these products were verified by tandem mass spectrometry experiments based on collision-activated dissociation and using an authentic model compound. These findings suggest that the reactivity of the studied para-benzynes toward dimethyldisulfide is similar in spite of their different protonation states and the different phases in which the reactions were carried out.