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Improving ion mobility measurement sensitivity by utilizing helium in an ion funnel trap.

ABSTRACT: Ion mobility instruments that utilize nitrogen as buffer gas are often preceded by an ion trap and accumulation region that also uses nitrogen, and for different inert gases, no significant effects upon performance are expected for ion mobility spectrometry (IMS) of larger ions. However, we have observed significantly improved performance for an ion funnel trap upon adding helium; the signal intensities for higher m/z species were improved by more than an order of magnitude compared to using pure nitrogen. The effect of helium upon IMS resolving power was also studied by introducing a He/N2 gas mixture into the drift cell, and in some cases, a slight improvement was observed compared to pure N2. The improvement in signal can be largely attributed to faster and more efficient ion ejection into the drift tube from the ion funnel trap.

SUBMITTER: Ibrahim YM

PROVIDER: S-EPMC4051256 | biostudies-literature | 2014 Jun

REPOSITORIES: biostudies-literature

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Improving ion mobility measurement sensitivity by utilizing helium in an ion funnel trap.

Ibrahim Yehia M YM Garimella Sandilya V B SV Tolmachev Aleksey V AV Baker Erin S ES Smith Richard D RD

Analytical chemistry 20140513 11

Ion mobility instruments that utilize nitrogen as buffer gas are often preceded by an ion trap and accumulation region that also uses nitrogen, and for different inert gases, no significant effects upon performance are expected for ion mobility spectrometry (IMS) of larger ions. However, we have observed significantly improved performance for an ion funnel trap upon adding helium; the signal intensities for higher m/z species were improved by more than an order of magnitude compared to using pur ...[more]

PMID: 24786390

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Project description:ObjectiveTo identify quantitative measurement variables that characterize mobility in older adults, meet reliability and validity criteria, distinguish fall risk, and predict future falls.DesignObservational study with 1-year weekly falls follow-up.SettingMobility laboratory.ParticipantsCommunity-dwelling volunteers (N=74; age, 65-94y) categorized at entry as 27 nonfallers or 47 fallers by using Medicare criteria (1 injury fall or >1 noninjury fall in the previous year).InterventionsNone.Main outcome measuresTest-retest and within-subject reliability, criterion and concurrent validity; predictive ability indicated by observed sensitivity and specificity to entry fall-risk group (falls status), Tinetti Performance Oriented Mobility Assessment (POMA), computerized dynamic posturography Sensory Organization Test (SOT), and subsequent falls reported weekly.ResultsMeasurement variables were selected that met reliability (intraclass coefficient of correlation >.6) and/or discrimination (P<.01) criteria (clinical variables: turn steps and time, gait velocity, step-in-tub time, downstairs time; forceplate variables: quiet standing Romberg ratio sway area, maximal lean anterior-posterior excursion, sit-to-stand medial-lateral excursion, sway area). Sets were created (3 clinical, 2 forceplate) using combinations of variables appropriate for older adults with different functional activity levels, and composite scores were calculated. Scores identified entry falls status and concurred with POMA and SOT scores. The full clinical set (5 measurement variables) produced sensitivity of 80% and specificity of 74% to falls status. Composite scores were more sensitive and specific overall in predicting subsequent injury falls and multiple falls compared with falls status and POMA or SOT score.ConclusionsSets of quantitative measurement variables obtained with this mobility battery provided sensitive prediction of future injury falls and screening for multiple subsequent falls by using tasks that should be appropriate to diverse participants.

Dataset Information

Improving ion mobility measurement sensitivity by utilizing helium in an ion funnel trap.

Publications

Improving ion mobility measurement sensitivity by utilizing helium in an ion funnel trap.

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