Plasma chromatography of alkyl amines

Karasek, F.W.; Kim, S. H.; Rokushika, Souji

doi:10.1021/ac50036a019

Cited by 39 publications

(30 citation statements)

References 12 publications

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“…It has been shown (19) that isomers of alkyl amines can be distinguished bly their mobility spectra. In this study we present similar results for a set of alkyl amines and a set of aromatic amines.…”

Section: Resultsmentioning

confidence: 99%

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Multiwavelength-selective ionization of organic compounds in an ion mobility spectrometer

Lubman¹,

Kronick²

1983

Anal. Chem.

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Laser multlphotlon lonlratlon Is used to demonstrate the posslblllty ob an added dlmenslonallty In analysls for plasma chromatography, Le., wavelength selectlvlty. I n resonant two-photon lonliratlon a molecule wlll lonlre If the two-photon energy Is greaterr than the lonlratlon potentlal of the molecule and there Is a rieal lntermedlate state resonant wlth the flrst photon. With Khls scheme a crude spectral selectlvlty Is posslble among groups of molecules wlth widely dlfferlng lonlratlon potentlals. This technlque may be useful for slmpllfylng the anallysls of mixtures of molecules In a plasma chromatograph and may aid In the separatlon and Identlflcatlon of molecules, In partlcular, Isomers. A wide range of useful data are collected and presented In an Ion moblllty spectrometer at elevated temperatures. I n addltlon, an ArF exclmer laser operating at 194 nm Is Introduced as a general lonlratlon souroe, capable of lonlrlng the vast majorlty of organlc compouinds.In previous papers we introduced a unique method for producing ions for plasma chromatography (1-3). This method uses laser multiphoton ionization to ionize molecules directly under atmospheric conditions in an ion mobility spectrometer. The main advantage of using laser radiation as the ionization source is that it minimizes the problem of nonspecific ionization. The conventional method of producing ions for plasma chromatography involves using a Ni-@ source to initiate a series of ion-molecule reactions which transfer charge to the species under study (4-22). 'This technique often produces data difficult to interpret since the ion-molecule reactions may cireate several different ion-molecule combinations with the trace compounds. The laser source permits direct ionization of molecules with ultraviolet (UV) light, thus obviating the need for the ion-molecule reactor. In addition, the multiphoton ionization (MPI) process can provide extremely efficient ionization of large organic molecules with only the molecular ion appearing when the laser operates a t sufficiently low intensity. Thus, only one peak appears in the ion mobility spectrum corresponding to each molecule ionized.In our work, wle are using UV radiation to produce resonant two-photon ionization. This process involves absorption of one UV photon to a real resonant state, followed by absorption of a second photon which will produce ionization if the energy of the two photons exceeds the ionization potential of the molecule. This process has been shown to be extremely efficient when it proceeds through a real resonant state. If no real state exists, bhen the process must occur through a very short livedl virtual state and the cross section for ionization becomes negligible. Most large molecules however do have strong absorptions between 350 and 200 nm, although the absorption spectra of these molecules are often broad and featureless at the elevated working temperature of an ion mobility spectrometer (IMS) due to the large number of Povibronic stpates populated. In addition, most large organic ...

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Section: Resultsmentioning

confidence: 99%

“…The mobility of a compound typically decreases with ion mass, but it also depends on the size and shape of the ions (19). Bulky ions generally require a longer drift time than compact ions of similar structure (19). Thus, isomers of a compound oftlen have different reduced mobilities.…”

mentioning

confidence: 99%

Multiwavelength-selective ionization of organic compounds in an ion mobility spectrometer

Lubman¹,

Kronick²

1983

Anal. Chem.

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show abstract

“…(17) was integrated for the experimental conditions used by Karasek, Kim, and Rokushika when they studied the IMS response to the homologous tri-n-alkylamines. 32 The electric field was constant at 142 V/cm, and the drift temperature was constant at 423 K. Because of the constant electric field, linear ion trajectories were obtained with slopes proportional to ion mobility. The mobilities deduced from these slopes are compared with the experimental data in Table 3.…”

Section: Properties Of the Momentum-transfer Equationmentioning

confidence: 99%

“…Equation (32) gives the velocity change that an ion experiences when it is exposed to a high electric field. The electric field of significance for RF-IMS is the asymmetric field that disperses the ion perpendicular to the gas flow within the device.…”

Section: Ion Dispersionmentioning

confidence: 99%