Assessing the Impact of Drift Gas Polarizability in Polyatomic Ion Mobility Experiments

Naylor, Cameron N.; Reinecke, Tobias; Clowers, Brian H.

doi:10.1021/acs.analchem.9b04468

Cited by 18 publications

(52 citation statements)

References 55 publications

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“…The flow rate for all gases was controlled by one or more mass flow controllers (Cole-Parmer EW-32907–69, Cole Parmer, Vernon Hills, CT) with a combined flow rate of 1 L/min with an uncertainty of 0.3% in the flow reading and uncertainty of 0.2% in the set flow rates. Mole fractions were calculated based on the flow rates using the respective gas densities at the experimental temperature, as described previously . A similar process was used to introduce the mixed gases (i.e., mixtures of N 2 /Ar and N 2 /CO 2 ) into the TIMS, as shown in Figure S6.…”

Section: Experimental Sectionmentioning

confidence: 99%

“…A similar process was used to introduce the mixed gases (i.e., mixtures of N 2 /Ar and N 2 /CO 2 ) into the TIMS, as shown in Figure S6. To provide adequate desolvation while bypassing the built-in flow controller of the micrOTOF, the flow rates on the flow controllers were added to a cumulative flow rate of 2 L/min, and the gas mixtures were calculated based on the mole fractions in the same methods as they were for the drift tube experiments . For the experiments where 100% air and 100% nitrogen elution voltages are measured in the TIMS, the default flow controller in the micrOTOF was used.…”

Section: Experimental Sectionmentioning

confidence: 99%

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Implications of Blanc’s Law for Use in Trapped Ion Mobility Spectrometry

Naylor

Reinecke

Ridgeway

et al. 2021

J. Am. Soc. Mass Spectrom.

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Blanc’s Law has served as a way to predict the mobilities of ions in mixed drift gases for over 100 years yet has remained largely unexplored using newer ion mobility spectrometry (IMS) configurations, including traveling wave and trapped IMS (TIMS) systems. Here, we evaluate a drift-tube IMS (DTIMS) and compare it to a similar set of experiments performed in TIMS. We found that Blanc’s Law can be applied in a DTIMS to determine the mobility of an analyte in the minor gas component of a ternary mixed drift gas system within 2% error. Additionally, the calibration procedure for TIMS to convert elution voltages into a mobility value corrects for significant deviations (>4%) from Blanc’s Law in the elution voltage domain. For the range of gas identities probed in this effort, up to an 11% error in calibrated mobilities was observed when using a gas mixture in the TIMS that differed from the gas used for the reference mobility. However, when the gas mixture within the TIMS was the same as the respective calibrant mobilities, calibration errors within the TIMS were as low as 0.01%. Interestingly, when probing the behavior of ions with argon-containing mixtures within the TIMS, the current accepted paradigm of elution voltage being proportional to inverse mobilities in TIMS calibrations procedures was shown to deviate substantially from the trends observed with DTIMS measurements. With this initial effort, foundations for future mixed drift gas measurements in TIMS are set for expanded analyte classes and larger molecules.

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Section: Experimental Sectionmentioning

confidence: 99%

Section: Experimental Sectionmentioning

confidence: 99%

Implications of Blanc’s Law for Use in Trapped Ion Mobility Spectrometry

Naylor

Reinecke

Ridgeway

et al. 2021

J. Am. Soc. Mass Spectrom.

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“…80 % nitrogen and 20 % oxygen. According to Blanc's law 55,56 were also investigated. In the supporting information, the measured reduced ion mobilities are summarized in dependence on the reduced electric drift field strength and the effective ion temperatures calculated according to the Wannier equation.…”

Section: No + (H 2 O) Nmentioning

confidence: 99%

Field-Dependent Reduced Ion Mobilities of Positive and Negative Ions in Air and Nitrogen in High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS)

Allers

Kirk

Schaefer

et al. 2020

J. Am. Soc. Mass Spectrom.

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In High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS), ions are formed in a reaction region and separated in a drift region, which is similar to classical drift tube ion mobility spectrometers (IMS) operated at ambient pressure. However, in contrast to the latter, the HiKE-IMS is operated at decreased background pressure of 10 -40 mbar and achieves high reduced electric field strengths of up to 120 Td in both the reaction and the drift region. Thus, the HiKE-IMS allows insights into the chemical kinetics of ion bound water cluster systems at effective ion temperatures exceeding 1000 K, although it is operated at the low absolute temperature of 45 °C. In this work, a HiKE-IMS with high resolving power of R P = 140 is used to study the dependence of reduced ion mobilities on the drift gas humidity and the effective ion temperature for the positive reactant ions H 3 O + (H 2 O) n , O 2 + (H 2 O) n , NO + (H 2 O) n , NO 2 + (H 2 O) n , and NH 4 + (H 2 O) n , as well as the negative reactant ions O 2 -(H 2 O) n , O 3 -(H 2 O) n , CO 3 -(H 2 O) n , HCO 3 -(H 2 O) n , and NO 2 -(H 2 O) n . By varying the reduced electric field strength in the drift region, cluster transitions are observed in the ion mobility spectra. This is demonstrated for the cluster systems H 3 O + (H 2 O) n and NO + (H 2 O) n .

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“…The ease of access to IMS instrumentation fueled the generation of libraries of IMS data that currently support modern metabolomic, lipidomic, and proteomic workflows. − Specifically, these libraries consist of ion-neutral collision cross sections (CCSs), − which correspond to the orientationally averaged collision area between the charged analyte and its neutral collision partner (typically ambient air, N 2 , or He). An ion-neutral CCS is specific to a particular analyte and buffer gas used in the IMS experiment, providing an orthogonal separation dimension to conventional liquid chromatography (LC). Thus, coupling ion mobility to traditional LC–MS–MS workflows has facilitated greater confidence in compound identification through matching measured CCSs with those curated in the literature. , However, not all IMS technologies are able to perform CCS evaluations; unlocking this potential for differential ion mobility remains a challenge for the field.…”

Section: Introductionmentioning

confidence: 99%

“…12−18 Specifically, these libraries consist of ion-neutral collision cross sections (CCSs), 19−25 which correspond to the orientationally averaged collision area between the charged analyte and its neutral collision partner (typically ambient air, N 2 , or He). An ion-neutral CCS is specific to a particular analyte and buffer gas used in the IMS experiment, 26 providing an orthogonal separation dimension to conventional liquid chromatography (LC). Thus, coupling ion mobility to traditional LC−MS−MS workflows has facilitated greater confidence in compound identification through matching measured CCSs with those curated in the literature.…”

Section: ■ Introductionmentioning

confidence: 99%

Determining Collision Cross Sections from Differential Ion Mobility Spectrometry

et al. 2021

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The experimental determination of ion-neutral collision cross sections (CCSs) is generally confined to ion mobility spectrometry (IMS) technologies that operate under the so-called low-field limit or those that enable empirical calibration strategies (e.g., traveling wave IMS; TWIMS). Correlation of ion trajectories to CCS in other non-linear IMS techniques that employ dynamic electric fields, such as differential mobility spectrometry (DMS), has remained a challenge since its inception. Here, we describe how an ion’s CCS can be measured from DMS experiments using a machine learning (ML)-based calibration. The differential mobility of 409 molecular cations (m/z: 86–683 Da and CCS 110–236 Å2) was measured in a N2 environment to train the ML framework. Several open-source ML routines were tested and trained using DMS-MS data in the form of the parent ion’s m/z and the compensation voltage required for elution at specific separation voltages between 1500 and 4000 V. The best performing ML model, random forest regression, predicted CCSs with a mean absolute percent error of 2.6 ± 0.4% for analytes excluded from the training set (i.e., out-of-the-bag external validation). This accuracy approaches the inherent statistical error of ∼2.2% for the MobCal-MPI CCS calculations employed for training purposes and the <2% threshold for matching literature CCSs with those obtained on a TWIMS platform.

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Assessing the Impact of Drift Gas Polarizability in Polyatomic Ion Mobility Experiments

Cited by 18 publications

References 55 publications

Implications of Blanc’s Law for Use in Trapped Ion Mobility Spectrometry

Implications of Blanc’s Law for Use in Trapped Ion Mobility Spectrometry

Field-Dependent Reduced Ion Mobilities of Positive and Negative Ions in Air and Nitrogen in High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS)

Determining Collision Cross Sections from Differential Ion Mobility Spectrometry

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