Ion Source Temperature Research Articles

Differentiation of Xylene Isomers by Chemical Ionization Mass Fragmentography

Three kind of isomers of xylene and ethylbenzene were analyzed using a gas chromatogrph-chemical ionization mass spectrometer with mass fragmentograhy technique to find any difference between these isomers in the various conditions, such as different reagent gases(CH4, i-C4H10 and NH3)and ion source temperature(200°C∼280°C). With iso-buthane as a reagent gas, the peak intensity of m/e 107(QM+)and the peak intensity ratio of m/e 106 to m/e 107 show remarkable differences between m-xylene and the other isomers at 200°C of the ion source temperature, and the differences decrease with increasing temperature. With ammonia as a reagent gas, the peak intensity of m/e 106 and the peak intensity ratio of m/e 108 to m/e 106 show much differences between p-xylene and the other isomers, and the differences are unchanged by the ion source temperature 200°∼280°C. Peak intensity ratio of m/e 105 to m/e 107 of ethylbenzene is much higher than the one of xylene isomers with iso-buthane as a reagent gas at 200°C of ion source temperature, and the differences decrease with increasing temperature.

Differentiation of Cresol-TMS Isomers by Chemical Ionization Mass Spectrometry

Three kinds of isomers of cresol trimethylsilyl ethers were analyzed using a gas chromatograph-chemical ionization mass spectrometer with mass fragmentography technique to find any difference between these isomers in various conditions, such as reagent gases(anmonia, methane and iso-butane)and the ion source temperature(200°C∼290°C). With anmonia as a reagent gas, the peak intensity ratios of m/e 180 to m/e 181 show remarkable differences between m-, o-and p-cresol trimethylsilyl ethers at 290°C of the ion source temperature.

Field-ionization relative sensitivities for analysis of coal-derived liquids determined as a function of ion-source temperature and binary-mixture composition

Field-ionization relative sensitivities for analysis of coal-derived liquids determined as a function of ion-source temperature and binary-mixture composition

Negative ion mass spectra of a series of fluorinated β‐diketones

AbstractElectron capture by and the subsequent fragmentation of a series of eleven fluorinated β‐diketones of general formula CF3COCH2COR has been studied in an MS‐50 mass spectrometer. Consecutive loss of two HF molecules from molecular anions occurs with all compounds, as does elimination of CHF3 from [M  H]− ions. Elimination of CO occurs from either \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm M - HF}} \right]_{}^{_.^ - } $\end{document} or \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm M - 2HF}} \right]_{}^{_.^ - } $\end{document} ions for five compounds where R  CF3 or a cyclic substituent. Kinetic energy release in metastable transitions associated with these HF and CO eliminations has been measured. Intensities of various fragment ions are in part influenced by the ion source temperature. Interaction of \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm O}} \right]_{}^{_.^ - } $\end{document} reagent ions with five of the β‐diketones under chemical ionization conditions gave [M  H]− ions as the only significant ion‐molecule reaction product.

Gas phase ion equilibria studies of the proton in hydrogen sulfide and hydrogen sulfide – water mixtures. Stabilities of the hydrogen bonded complexes: H+(H2S)x(H2O)y

The temperature dependence of the equilibria [Formula: see text] was measured for n = 1 to 5 in a pulsed electron beam mass spectrometer with a high pressure ion source. The ΔHn+1,n values obtained were (2,1) 15.4, (3,2) 9.1, (4,3) 8.4, (5,4) 6.7 kcal/mol. Possible structures of the clustered ions are proposed.Addition of water vapor leads to mixed cluster ions such as H+(H2S)x(H2O)y, with x + y from 1 to 6, observed as the ion source temperature was decreased to −100 °C. The temperature dependence of the equilibria for the exchange reactions [Formula: see text]and the association reaction [Formula: see text]were also measured. For all ions measured, the hydration process is energetically more favorable than the solvation by H2S.

Application of Dual Electron Impact-Chemical Ionization Ion Source to Gaschromatograph-Mass spectrometer

The construction and performances of a dual EI/CI ion source designed for the Shimadzu GCMS-9000 are described. Some design considerations on the construction of the combined gaschromatograph-EI/CI mass spectrometer are also described. Among various operating parameters for chemical ionization, ion source temperature has noticeable effects on CI spectra. Several measurements on temperature effect were carried out. As CI spectra are generally simpler and have greater abundance of quasi molecular ion than EI spectra, it is favourable to detect trace amount of sample with mass frag-mentography technique. Typical example which will show the minimum detectable amount is also shown. It is possible with this source to measure various mass spectra such as EI, CI, CE and combined CE/CI spectra of the same sample. Examples of such spectra data are presented.

Mass spectrometry of onium compounds. XXIII—ionisation potentials in the structural assignment of [M – N2] ions from diazo‐oxides

AbstractThe ionisation potential shows that fulven‐6one is formed pyrolytically from o‐benzo‐diazo‐oxide. Appearance potential measurements show increasing pyrolytic contribution to the [M – N2] species with increase in ion source temperature.

ChemInform Abstract: OBSERVATIONS ON HOT BANDS IN THE MOLECULAR AND DISSOCIATIVE PHOTOIONIZATION OF ACETYLENE AND THE HEAT OF FORMATION OF THE ETHYNYL ION

Photoion yield curves in the vicinity of threshold are obtained for the molecular and the ethynyl ions of acetylene and acetylene‐d2 at ion source temperatures of 360, 298, and 130 °K. Weak ionization below the adiabatic threshold for C2H2+ and C2D2+ is ascribed to the ionization of molecules excited by one quantum of the bending vibrations, ν4 and ν5. Consideration of selection rules suggests a change in symmetry from the linear ground state molecule to a bent gound state ion. The 0 °K curves for C2H+ and C2D+ are estimated from the observed 130 °K data. Satisfactory agreement is obtained when the 298 °K data are compared with a curve calculated from the 0 °K curve by convolution with vibrational and rotational distributions. The 0 °K thresholds corrected for kinetic energy are used to calculate Δ H f0°(C2H+)=17.47 ± 0.01 eV (402.8 ± 0.2 kcal mol−1) and ΔH f °0(C2D+) = 17.43 ± 0.02 eV (402.0 ± 0.5 kcal mol−1). The ionization energy of the ethynyl radical is estimated to be 11.96 ± 0.05 eV.

Observations on hot bands in the molecular and dissociative photoionization of acetylene and the heat of formation of the ethynyl ion

Photoion yield curves in the vicinity of threshold are obtained for the molecular and the ethynyl ions of acetylene and acetylene-d2 at ion source temperatures of 360, 298, and 130 °K. Weak ionization below the adiabatic threshold for C2H2+ and C2D2+ is ascribed to the ionization of molecules excited by one quantum of the bending vibrations, ν4 and ν5. Consideration of selection rules suggests a change in symmetry from the linear ground state molecule to a bent gound state ion. The 0 °K curves for C2H+ and C2D+ are estimated from the observed 130 °K data. Satisfactory agreement is obtained when the 298 °K data are compared with a curve calculated from the 0 °K curve by convolution with vibrational and rotational distributions. The 0 °K thresholds corrected for kinetic energy are used to calculate Δ H f0°(C2H+)=17.47 ± 0.01 eV (402.8 ± 0.2 kcal mol−1) and ΔH f °0(C2D+) = 17.43 ± 0.02 eV (402.0 ± 0.5 kcal mol−1). The ionization energy of the ethynyl radical is estimated to be 11.96 ± 0.05 eV.

Precision of fragmentation patterns in high-resolution mass spectrometry

The effect of controlling the temperature of the ion source of a high-resolution mass spectrometer is to increase the confidence in mass spectral pattern coefficients of saturated molecules. Results are presented for both controlled and uncontrolled ion-source temperatures. Standard deviations have been calculated for selected summations of ion intensities and criteria have been suggested for maintaining meaningful analytical results in the study of petroleum distillates.

Analysis of BHC Isomers by Gas Chromatograph-Mass Spectrometer Combined System. Identification of β-BHC

Stereoisomers of benzene hexachloride, especially β-BHC, could be identified using a Shimadzu LKB 9000 gas chromatograph-mass spectrometer combined system by diversification of the ion source temperature. We believe this technique will widen the application of the GC-MS combined system in the field of isomerical study.

Effect of hot bands on the ionization threshold of some diatomic halogen molecules

Photoion-yield curves are obtained for the molecular ions of the homonuclear diatomic halogens and for iodine monochloride and iodine monobromide. Excepting iodine, ionization thresholds of ground-state and vibrationally-excited molecules are separately identified by measurements made at several ion-source temperatures. The adiabatic ionization energies (in eV) are: I(F 2 = 15.69, I(Cl 2) = 11.48, I(Br 2) = 10.52, I(ICl) = 10.07, and I(IBr) = 9.79. A preferred value of I(I 2) = 9.37 eV is proposed.

Massenspektrometrische Untersuchungen an Trirutheniumdodekacarbonyl bei verschiedenen Elektronenenergien und Temperaturen

With an ion source temperature of 100 to 250° the 70 eV spectra of Ru 3(CO) 12 are identical. Between 11 and 70 eV the fractional abundances of the Ru 3(CO) + n -ions are in accordance with a stepwise elimination of CO down to Ru + 3. At 9 eV Ru 3(CO) + 8 and Ru 3(CO) + 7 species predominate. At this electron energy their production must take place according to another, unknown mechanism. The intensity of the CO + ions increases with the operating time of the ion source.

Power Supply for Ion Source of Mass Spectrometer in Electrotechnical Laboratory

This paper describes the design and the construction of power supply for the ion source of mass spectrometer in Electrotechnical Laboratory. The power supply consists of following four parts: d. c. high voltage source for ion focusing and acceleration(0.3-10KV), stabilizing and accelerating circuits for bombarding electron(0-150V), controlling and measuring system ion source temperature(150'C-300T), and exciting supply for ion source magnet(0-2A). Several special designs are adopted for above four parts so as to keep the stabilities of the order of 10-4?10-5which is enough for the ion source of mass spectrometer. Tests on these supplies showed that long time stability of10-4/hr and ripple voltage of20mV were obtained as for the high voltage supply over the range of1-10KV. Some results of the tests on other parts were described.

Studies on Mass Spectra and Appearance Potentials of Acetic Acid and Deuteroacetic Acid CD3COOH

Abstract In order to obtain information on the decomposition process of acetic acid in radiation chemistry, not only mass spectra of both acetic acid and deuteroacetic acid but also appearance potentials of parent and main fragment ions of both acids have been measured. By studying the effects of ion source temperature and of electron accelerating voltage on the spectra, and by comparing the mass spectra of both acids, it has been possible to identify the chemical species produced by electron impact without ambiguity and also to estimate the process of their production to some extent. It has been found that, although the appearance potentials of the parent ion of both acids coincide fairly well, those of CH3+ and COOH+ from CH3COOH are higher than those of corresponding ions from deuterated acid. The breaks of ionization-efficiency curves have been observed in CH3+ and CD3+ ions at about 6 volts higher than the appearance potentials suggesting a possibility of the presence of an excited state of the product ions.

A survey of negative ions in mass spectra of polyatomic molecules

A s urvey was made of negative-ion production in 27 different molecules covering a wide variety of chemical compounds. In nine compounds no ions were found. For the other cOlr>pounds rough measurements of the appearance potentials and relative abundance of the ions are reported . About 60 different ionization processes are observed in 18 compounds. Formation of ion s by dissociative resonance attachment is t he most common process, but there are several cases of ion pair formation and of attachment without dissociation. Perchlorylfluoride gives by far t he greatest abundance and variety of ions. with lanthanum boride was substituted for the pure tungsten filament that is used routinely as an electron source. This resulted in an ion source temperature of about 150 0 C instead of 250 0 C. Negative ions formed by attachment processes were first detected by repeated sweeping of portions of the spectrum while varying t h e electron energy from 0 to 20 v, and negative ions formed by ion-pair processes were detected at 100 v. Data for ioniza­ tion-efficiency curves were then obtained by varyin g t he electron energy in 0.2-v step s from 0 to 20 v and in larger increments up to 100 v. Curves were plotted on a lineal' scale. The r elative efficiency for collecting negative ions produced by resonance capture as compared with positive ions depends criticall y on the operating conditions. The collecting efficiency of the 1800 mass spectrometer has been estimated by a method used by Marriott and Craggs (2). Lozier (6) made measurements of the relative abundance of positive and negative ions from oxygen in a nearly field-free space and found the ratio 0 - 10 +=0.04 at 35 v. This instrument gave a ratio of about 0.0125 and the collecting efficiency is taken to be 31 percel~t. This paper reports observed appearance potentials without any correction for effects of contact poten­ tials and the electric field across the ionization chamber. A comparison with published resul ts in­ dicates t.hat the correction would be less than 1 v. 3. Results