Structural analysis of dinitriles by chemical ionization mass spectrometry

Price, Philip C.; Swofford, H. S.; Buttrill, S. E.

doi:10.1021/ac60367a010

Cited by 8 publications

(7 citation statements)

References 14 publications

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“…Purity was confirmed by GC and CIMS. The water used as reagent gas was purified as described previously (9). Spectra were obtained by injecting aliquots of 500-ppm solutions of the esters in water into the 120 °C batch inlet system.…”

Section: Methodsmentioning

confidence: 99%

“…There are also considerable data available on the temperature dependence of ester Cl spectra (7), and the mechanisms of the formation of the major fragment ions have been elucidated (8) through deuterium labeling studies. Furthermore, since most esters are at least sparingly soluble in water, they may be introduced very conveniently into the Cl mass spectrometer as dilute aqueous solutions (9,10), thereby allowing precise control of the pressures of both the ester and the water reagent gas. All of these considerations, plus their widespread occurrence both in nature and in widely used chemical processes and products, led us to choose esters for this initial study of the potential analytical applications and utility of the new drift tube chemical ionization source.…”

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confidence: 99%

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Drift tube chemical ionization mass spectrometry of esters

Price¹,

Swofford²,

Buttrill³

1978

Anal. Chem.

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A series of carboxylic acid esters are examined by a new technique: drift tube chemical ionization mass spectrometry. Using water as the chemical ionization reagent gas, there Is very little fragmentation of most esters at low values of E/P in the drift tube. At higher E/P, the extent of formation of analytically useful fragments is greater than can be obtained by increasing temperature or switching to methane reagent gas. As E/P is Increased, the onset of each fragment is correlated with the endothermicity of the reaction which forms it. The absence of M+ and (M -1)+ ions In water chemical ionization mass spectra increases the usefulness of the technique for assessing sample purity while the ability to induce extensive fragmentation with the drift tube enables one to obtain structural information from the same sample.

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Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Drift tube chemical ionization mass spectrometry of esters

Price¹,

Swofford²,

Buttrill³

1978

Anal. Chem.

Self Cite

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show abstract

“…Hence the repeller was usually run at 5 V or less. As in previous work with a more conventional Cl source (17)(18)(19), maximum total ion current and stable operation were obtained by tuning the ion focusing and beam steering lenses to maximize the H904+ ion from water reagent gas. Very detailed descriptions of the drift tube ion source (20) and the new source housing and ion optics (21) are available elsewhere.…”

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confidence: 97%

New drift-tube source for use in chemical ionization mass spectrometry

Price¹,

Swofford²,

Buttrill³

1977

Anal. Chem.

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A new ion source incorporating an Integral drift tube allows control over the extent of fragrnentatlon of the quasknolecular ions produced in chemical ionlratlon mass spectrometry. Increasing the electric fleid strength in the drift-tube region causes fragmentation slmllar to that observed at higher source temperatures or with more energetic reagent gases. Effectlve /on temperatures in excess of 1000 K are available at the highest drifl fields. Slnce a slngle drlft voltage settlng controls the extent of fragmentatlon, It is possible to obtain both molecular ion spectra and extenslve fragmentation on successlve scans of a single sample.Chemical ionization mass spectrometry (CIMS) has gained very wide acceptance as an analytical tool in the decade since its initial development ( I ) . One of the greatest advantages of CIMS over electron impact ionization is the great reduction or elimination of fragment ions, simplifying the spectrum and usually producing an intense quasi-molecular ion, i.e., either MH+ or (M -l)+. CI conditions under which only quasimolecular ions are present are ideal for quantitation of a compound, and they greatly facilitate the determination of the number of components or the purity of an unknown sample. However, the molecular weight alone is not sufficient to identify a compound; considerable additional information, such as is available from the masses and intensities of fragment ions, is almost always required.The extent of fragmentation of the quasi-molecular ions in CIMS may be increased by increasing the source temperature (Z), or by using a more energetic reagent gas (3). Both of these methods are relatively slow and experimentally inconvenient and would certainly require the introduction of additional samples with conventional instrumentation.Early in the development of CIMS, it was recognized that increasing the electric field inside the ion source increased the relative intensities of fragment ions (4-6). This effect was attributed to unimolecular fragmentation of the MH' ions activated by energetic collisions with neutral reagent gas molecules in the source. This report describes a drift-tube chemical ionization source which uses this effect to provide a variable degree of fragmentation of the quasi-molecular ions in the CI spectrum.A drift tube is a cylindrical chamber in which a uniform longitudinal electric field is maintained by a series of ring shaped electrodes. Ions introduced into one end of the tube by an ion source may be accelerated through a neutral buffer gas by applying a voltage gradient down the tube. The theory of ion motion in drift tubes has been reviewed by several authors (7-11). Briefly, ions entering a drift tube w i l l acquire energy from the electric field. It has been shown that this energy is related to a parameter EIP, where E = electric field strength, and P = neutral gas pressure in the tube. E / P has lPresent address, Union Carbide 770-120, P.O. Box 8361, South Present address, Stanford Research Institute, Menlo Park, Calif. Charleston, W. Va. 25303. ...

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“…H20+ + H20 -H30+ + OH (2) OH+ + H20 -H30+ + O (3) H+(H20)" + H20 H+(H20)"+1 (4) The reactions of the hydronium ion and its hydrates with the sample molecules produce ions characteristic of the sample, H30+ + -MH+ + H20 (5) H+(H20)" + -MH+ + «H20 (6) H+(H20)" + M -MH+(H20)m + (nm)H20 (7) In addition to these bimolecular processes (eq 5-7), the protonated sample may also form a hydrogen-bonded cluster with one or more water molecules through termolecular reactions.…”

Section: Introductionmentioning

confidence: 99%

“…When instrumental parameters, such as source temperature and pressure, are carefully controlled, these peaks provide analytically useful information on the structure and stereochemistry of the sample. 6 In order to study the origins of these useful and interesting effects, we have constructed a pulsed high-pressure ion source which enables us to monitor the time dependence of the ion concentrations and obtain both kinetic and thermochemical information about the formation of the hydrogen-bonded cluster ions. This paper reports our results from both conventional and pulsed high-pressure water chemical ionization mass spectrometry for some substituted phenols.…”

Section: Introductionmentioning

confidence: 99%