Temperature dependent mobilities of NH+4 and Br− ions in N2 and O2

Perkins, Mark D.; Chelf, R. D.; Eisele, F. L.; McDaniel, E. W.

doi:10.1063/1.445651

Cited by 5 publications

(4 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Most ions have close mobilities in N 2 and O 2 , as one might expect from similar molecular mass, size, and other physical properties of these gases. For example, ,− K 0 (0) of Rb + , Cs + , Cl - , Br - , Cl 2 - , NH 4 + , NO 2 - , NO 3 - , and CO 3 - in O 2 equal those in N 2 within 10%. Then, setting K 0 (0) = 2.4 cm 2 /(Vs) for the orthophthalic acid anion in both N 2 and O 2 , at b = 0 we determine a = 4.36 × 10 -6 Td -2 in N 2 (CV = 7.2 V) and a = 5.18 × 10 -6 Td -2 in O 2 (CV = 8.5 V).…”

Section: Experimental Evaluation Of Predictionsmentioning

confidence: 99%

Understanding and Designing Field Asymmetric Waveform Ion Mobility Spectrometry Separations in Gas Mixtures

2004

View full text Add to dashboard Cite

Field asymmetric waveform ion mobility spectrometry (FAIMS) has significant potential for post-ionization separations in conjunction with MS analyses. FAIMS fractionates ion mixtures by exploiting the fact that ion mobilities in gases depend on the electric field in a manner specific to each ion. Nearly all previous work has used pure gases, for which FAIMS fundamentals are understood reasonably well; however, unexpected phenomena observed in some gas mixtures (e.g., N(2)/CO(2)) but not in others (N(2)/O(2)) remain unexplained. Here, we introduce and experimentally test a universal model for FAIMS separations in mixtures, derived from formalisms that determine high-field mobilities in heteromolecular gases. Overall, the theoretical findings are consistent with data for N(2)/CO(2) (although quantitative discrepancies remain), while results for N(2)/O(2) fit Blanc's law, in agreement with measurements. Calculations for He/N(2) and He/CO(2) are also consistent with observations and suggest why adding He to the working gas generally enhances FAIMS performance. As predicted, mixtures of gases with extremely disparate molecular masses and collision cross sections, such as He/SF(6), exhibit spectacular non-Blanc effects, which greatly improve the resolution and peak capacity of technique. Understanding FAIMS operation in gas mixtures is expected to enable the rational design of media for both targeted and global analyses.

show abstract

Section: Experimental Evaluation Of Predictionsmentioning

confidence: 99%

Understanding and Designing Field Asymmetric Waveform Ion Mobility Spectrometry Separations in Gas Mixtures

2004

View full text Add to dashboard Cite

show abstract

“…The pre- Ellis et al [1978]; b, K 0 estimated from H 3 O + (H 2 O) 2 À N 2 by applying the reduced mass change and assuming an increase in the collision integral of $2% for each water ligand added. A small increase of 1,1 with the number of ligands is consistent with the results of de Gouw et al [1997]; c, K 0 was taken to vary as T 0.37 , the dependencies observed for NO 3 À in N 2 [Eisele et al, 1980] and for NH 4 + in N 2 [Perkins et al, 1983]; d, Eisele et al [1980]; e, K 0 estimated from NO 3 --N 2 by applying the reduced mass change and assuming an increase in the collision integral of 5% upon addition of the HNO 3 ligand (see note b); f, Estimated from the NO 3 À (HNO 3 ) 2 À N 2 values by applying only the change in the reduced mass. Figure A1.…”

Section: A2 Ion Mobility and Reaction Ratesmentioning

confidence: 99%

Measurement of prenucleation molecular clusters in the NH₃, H₂SO₄, H₂O system

2002

View full text Add to dashboard Cite

[1] The molecular cluster ions HSO 4 À (H 2 SO 4 ) nÀ1 (NH 3 ) m corresponding to the neutral species (H 2 SO 4 ) n (NH 3 ) m for n = 2 to 6 and m = 0 to nÀ1 have been observed at temperatures up to $285 K. A transverse chemical ionization apparatus was located inside a cooled flow tube where water, sulfuric acid, and ammonia vapors mixed and formed clusters. The complexities of the experimental technique and the interpretation of the results are extensively discussed. Typical NH 3 and H 2 SO 4 concentrations were 2 Â 10 9 cm À3 , i.e, $100 pptv at atmospheric pressure. For these conditions, cluster concentrations were estimated to be a few times 10 6 cm À3 and the critical, particle-forming cluster likely contained 2 H 2 SO 4 molecules at 275 K. The results are consistent with the species (H 2 SO 4 ) 2 NH 3 playing an important role in the formation of new particles in the atmosphere.

show abstract

“…f K 0 (0) is from reference [51] (measurements at ambient conditions); a, b were derived from measured CVs [7]. g K 0 (0) is extrapolated from the measurements for Cl Ϫ (ϳ 2.9) [52] and Br Ϫ (ϳ 2.5) [53]; a, b are from reference [39]. To address these questions, we modeled the response of FAIMS with bisinusoidal waveform of eq 2 while varying g and w c and fixing all other parameters.…”

Section: Analytical Gap Width and Waveform Frequencymentioning

confidence: 99%

Optimization of the design and operation of FAIMS analyzers

Shvartsburg

Tang

Smith

2005

J. Am. Soc. Mass Spectrom.

141

View full text Add to dashboard Cite

Field asymmetric waveform ion mobility spectrometry (FAIMS) holds significant promise for post-ionization separations in conjunction with mass-spectrometric analyses. However, a limited understanding of fundamentals of FAIMS analyzers has made their design and operation largely an empirical exercise. Recently, we developed an a priori simulation of FAIMS that accounts for both ion diffusion (including anisotropic components) and Coulomb repulsion, and validated it by extensive comparisons with FAIMS/MS data. Here it is corroborated further by FAIMS-only measurements, and applied to explore how key instrumental parameters (analytical gap width and length, waveform frequency and profile, the identity and flow speed of buffer gas) affect FAIMS response. We find that the trade-off between resolution and sensitivity can be managed by varying gap width, RF frequency, and (in certain cases) buffer gas, with equivalent outcome. In particular, the resolving power can be approximately doubled compared to "typical" conditions. Throughput may be increased by either accelerating the gas flow (preferable) or shortening the device, but below certain minimum residence times performance deteriorates. Bisinusoidal and clipped-sinusoidal waveforms have comparable merit, but switching to rectangular waveforms would improve resolution and/or sensitivity. For any waveform profile, the ratio of two between voltages in high and low portions of the cycle produces the best performance. (J Am Soc Mass Spectrom 2005, 16, 2-12) © 2004 American Society for Mass Spectrometry S eparation of gas-phase ionic mixtures by field asymmetric waveform ion mobility spectrometry (FAIMS) extends back over a decade in the technical literature [1][2][3], but has attracted a broad interest in the analytical and mass-spectrometry communities only recently [4 -29]. FAIMS separates ions by the difference between mobilities at high (K H ) and low (K L ) electric fields, in other words the average slope of mobility as a function of field, K(E). The form of K(E) may be complex: with increasing E, mobilities (of both cations and anions) may increase (termed species of Type A), decrease (Type C), or initially increase, but decrease at yet higher E (Type B) [4,5]. Usually, small and structurally rigid species belong to Type A and large flexible ones (e.g., proteins) belong to Type C. K(E) can be represented by a polynomial of even powers of E/N:At moderately high E/N relevant to FAIMS (up to ϳ60 -80 Td), eq 1 can usually be truncated after theExperimentally, a gas stream entraining ions passes between two electrodes that carry a time-dependent potential V D (t) that alternates between "high" and "low" voltages, such that the integral value over the cycle is null but time-averaged positive and negative voltages differ [4,5]. Then only a hypothetical ion with constant K(E) would be transmitted, while species exhibiting variable K(E) drift towards one of the electrodes and eventually neutralize upon impact [4,5]. For a particular ion, this may be prevented by applying ...

show abstract

Temperature dependent mobilities of NH+4 and Br− ions in N2 and O2

Cited by 5 publications

References 3 publications

Understanding and Designing Field Asymmetric Waveform Ion Mobility Spectrometry Separations in Gas Mixtures

Understanding and Designing Field Asymmetric Waveform Ion Mobility Spectrometry Separations in Gas Mixtures

Measurement of prenucleation molecular clusters in the NH₃, H₂SO₄, H₂O system

Optimization of the design and operation of FAIMS analyzers

Contact Info

Product

Resources

About

Temperature dependent mobilities of NH+4 and Br− ions in N2 and O2

Cited by 5 publications

References 3 publications

Understanding and Designing Field Asymmetric Waveform Ion Mobility Spectrometry Separations in Gas Mixtures

Understanding and Designing Field Asymmetric Waveform Ion Mobility Spectrometry Separations in Gas Mixtures

Measurement of prenucleation molecular clusters in the NH3, H2SO4, H2O system

Optimization of the design and operation of FAIMS analyzers

Contact Info

Product

Resources

About

Measurement of prenucleation molecular clusters in the NH₃, H₂SO₄, H₂O system