J. Marsel

An investigation into the reactivity of ions arising from different regions of a translational, energy release distribution: a need for angular collimation

Abstract A new method which enables ion from various portions of a metastable peak to be isolated for study is presented. Reactions have been found in which ions, m 2 + formed as products of fragmentation of metastable ions, m 1 + , will themselves undergo unimolecular fragmentation to form ions m 3 + . By selecting ions m 2 2 from various parts of the metastable peak for the reaction step m 1 + → m 2 + , their reactivity can be studied as a function of their position within the metastable peak. Such studies have enabled ions m 2 + containing different amounts of internal energy to be identified. The work has also demonstrated that the ability to obtain accurate translational energy release distributions from the shapes of metastable peaks is dependent upon good angular collimation of the reactant ions.

Comparison of gas chromatographic and spectrophotometric techniques for the determination of formaldehyde in water

Abstract Formaldehyde was determined in aqueous samples by four different analytical procedures (two spectrphotometric and two gas chromatographic). In the spectrophotometric procedures chromatogropic acid and 3-methyl-2-benzothiazolone hydrazone were used. For gas chromatography either an electron-captive or a flame ionization detector were used, and for sample preparation liquid-liquid extraction in the former and solid-phase extraction in the latter case were used. The concentration range covered was between 0.06 and 20 mg/l. Calibration plots and detection limits were optimized for all four procedures.

Optimization of an analytical procedure for the determination of triazine herbicides in environmental samples

Abstract A clean-up procedure and high-performance liquid chromatographic conditions were optimized for the determination of triazines in drinking and surface water. Two extraction systems were tested: off-line solid-phase extraction (SPE) with C18-bonded silica gel cartridges and on-line SPE with PLRP-S (styrene-divinylbenzene copolymer) preconcentration cartridges. The on-line SPE procedure was chosen for further work. Chromatographic conditions were optimized for UV absorbance and particle beam (PB) MS detection. The LC-UV analytical system with on-line preconcentration showed excellent linearity over the concentration range tested and low detection limits (below 0.05 μg/l) for drinking water. With preconcentration from large volumes of water, some triazines and other pesticide pollutants could be detected in drinking and river water by PB-MS. Quantification was achieved by means of the standard addition method. For soil samples, the extraction procedure was off-line and more elaborate.

Modification of a mattauch—herzog mass spectrometer for ion kinetic energy measurements

Abstract Two major modifications have been made to a type CEC 21-110 C Mattauch—Herzog double focussing mass spectrometer. In the first of these, provision has been made for independent scanning of the electric sector and ion kinetic energy (IKE) spectra can be plotted at high sensitivity on a channeltron multiplier placed between the sectors. In the second modification an extra electric sector has been fitted, following the magnetic sector, so that mass-analyzed ion kinetic energy (MIKE) spectra can also be obtained. Examples of the performance achieved in both the modes of operation are given.

The influence of exposure time and transportation routes on the pattern of organochlorines in plants from a polluted region

Abstract The levels and residue profiles of polychlorobiphenyls (PCB), polychloronaphthalenes (PCN) and chlorobenzenes (CBz) in plants (grass, pine needles) from a region contaminated with the corresponding technical compounds from an electroindustrial plant are presented. Levels and residue profiles of these compounds are influenced by the distance from the source of pollution, the exposure time and the transportation routes. PCB levels in pine needles decrease with distance from the site of pollution: at 50 m they were 2.2; at 200 m 0.15; and at 10 km 0.01 μg/kg dry wt., respectively. PCN were detected only nearby the source of contamination. Tri- and tetra-CBz were about 1:100 of the PCB level at 50 m and 1:4 of the PCB level at 10 km from the source of contamination. Higher chlorinated and planar compounds of low vapour pressure were enriched in plants. Enrichment in plants increases with Koa of the organochlorine and the exposure time. Different transportation routes from the source of pollution to plants via (i) air-plant; (ii) river water-air-plant influence the composition of chlorine homologues in plants. The differences in the profile of organochlorines in plants was compared with physicochemical data on the individual components. Analyses were performed by GC/ECD and GC/MS/MS.

Mass spectrometric studies of tungsten bromides and oxybromides

Abstract The reaction products obtained by the bromination of tungsten oxides, metallic tungsten and tungsten hexacarbonyl were studied by means of the Knudsen effusion mass spectrometric method. The fragmentations of WO 2 Br 2 , WBr 4 , WOBr 4 , WBr 4 and W 2 Br 6 were determined, the appearance potentials of ions present in higher intensities were measured and the heats of formation of these ions calculated. The sublimation enthalpies of the compounds were determined. During vaporization of WBr 4 , an intense W 2 Br 6 + ion was detected. For the formation of metal-metal bonded cluster compounds, the following reaction was proposed: 2WBr 4( g ) ⇌W 2 Br 6( g ) . The enthalpy change of this reaction and the heat of formation of W 2 Br 6( g ) were determined. According to vaporization experiments in vacuo , no WBr 6 exists in the gaseous phase. On the basis of the experiments, the following decomposition process seems to be probable: WBr 6( s ) → WBr 5( s ) + 1 2 Br 2( g ) . By measuring the change of Br 2 pressure as a function of temperature, the thermodynamic data for this reaction were calculated. From the ionisation potential measurements the average WBr bond strength was determined.

Application of tandem mass spectrometry to the analysis of chlorinated compounds

The application of high-resolution gas chromatography–mass spectrometry and tandem mass spectrometry (MS–MS) in environmental analysis is demonstrated with three typical compound types, i.e., polychlorinated biphenyls (PCBs), polychlorinated alkanes (PCAs) and polychlorinated naphthalenes (PCNs), found in/or during the preparation of some environmental samples from a contaminated area. With ‘multiple reaction monitoring’ of some selected reaction products from a collision cell (i.e., loss of one or two chlorine radicals from a molecular ion) by the Q-analyser of a VG-AutospecQ mass spectrometer, unambiguous qualitative and quantitative data for various isomeric PCBs and PCNs could be obtained. By using this approach, time consuming and extremely demanding sample preparation could be reduced or avoided. In addition, the determination of trace amounts of higher chlorinated PCBs in paraffin oil illustrates the unique capability of MS–MS.

Mass spectrometric investigations of NiTe2O5 and Ni2Te3O8 at high temperatures

Abstract The dissociation of NiTe 2 O 5 and Ni 2 Te 3 O 8 was investigated between 900 and 1000 K using the mass spectrometric Knudsen effusion method. It was found that both substances evaporate incongruently according to the following reactions. 2 NiTe 2 O 5 ( s )  Ni 2 Te 3 O 8 ( s ) + TeO 2 ( g ) Ni 2 Te 3 O 8 ( s )  2 NiO ( s ) + 3 TeO 2 ( g ) From the measured equilibrium vapour pressure of TeO 2 for both reactions in the given temperature interval and from the values of C p for TeO 2 (s) and TeO 2 (g), the entropy S 298 K and C p for Ni 2 Te 3 O 8 and NiTe 2 O 5 were estimated, allowing the calculation of some thermodynamical data according to the second and third law methods. The second law heats of reactions at 298 K were found to be 283.3 ± 12.6 and 880.7 ± 25.1 kJ mol −1 and for the third law heats of reaction 269.9 ± 4.1 and 851.0 ± 8.1 kJ mol −1 for the first and second reaction respectively. The standard enthalpies of formation of Ni 2 Te 3 O 8 and NiTe 2 O 5 were found as 1549.8 ± 25.0 and 948.0 ± 37.1 kJ mol −1 respectively.

Mass spectrometric investigation of reaction between tungsten and bromine at high temperature

The reaction between tungsten and bromine has been studied in the temperature interval between 1000 and 1500 K by means of a Knudsen double cell connected to a mass spectrometer. At pressures of bromine between 6 and 50 torr in the reaction cell only WBr4(g) is formed while at higher pressures formation of W2Br6(g) could be observed as the result of a secondary gas-phase reaction. From the measured intensities of different ions the pressure-temperature curve obtained for WBr4(g) exhibits abnormalities which could be explained in terms of the reaction kinetics leading to equilibrium conditions above 1270 K. On the basis of these considerations ΔH4o (−36.7 ± 1.7 kcal/mole), ΔGTo(−8.6 ± 0.6 kcal/mole) and ΔSTo(−21.3 ± 1 e.u.) have been obtained and compared with some thermodynamic data calculated using the third-law method.

Molecular composition and thermodynamic equilibria in vapour over the NaI-HoI3 condensed phase

Abstract The molecular composition and thermodynamic properties of the equilibrium vapour species over condensed NaI-HoI 3 mixtures was investigated by Knudsen effusion mass spectrometry. Results show that in addition to the pure components (NaI(g), HoI 3 (g)) homocomplexes (Na 2 I 2 (g), Dy 2 I 6 (g)) and heterocomplexes (NaHoI 4 (g), Na 2 HoI 5 (g)) are formed in the saturated vapour. The second and third laws of thermodynamics were used for the determination of the thermodynamic parameters for homogeneous and heterogeneous processes. The resulting mean values are as follows: NaI ( s ) + HoI 3 ( s ) = NaHoI 4 ( g ); Δ r H o 298 K = 257.8 ± 6 kJ mol −1 , Δ r S o 298 K = 225.7 ± 8 mJ mol −1 K −1 . NaI ( g ) + HoI 3 ( s ) = NaHoI 4 ( g ); Δ r H o 298 K = 63.5 ± 4 kJ mol −1 , Δ r S o 298 K = 76.6 ± 6 J mol −1 K −1 . NaI ( s ) + HoI 3 ( g ) = NaHoI 4 ( g ); Δ r H o 298 K = −20.4 ± 7 kJ mol −1 , Δ r S o 298 K = 20 ± 9 J mol −1 K −1 . NaI ( g ) + HoI 3 ( g ) = NaHoI 4 ( g ); Δ r H o 298 K = −213.7 ± 5 kJ mol −1 , Δ r S o 298 K = −122.8 ± 4 J mol −1 K −1 .