Direct-insertion devices

These direct-insertion devices are often incorporated within an autosampling device that not only loads sample consecutively but also places the sample carefully into the flame. Usually, the sample on its electrode is first placed just below the load coil of the plasma torch, where it remains for a short time to allow conditions in the plasma to restabilize. The sample is then moved into the base of the flame. Either this last movement can be made quickly so sample evaporation occurs rapidly, or it can be made slowly to allow differential evaporation of components of a sample over a longer period of time. The positioning of the sample in the flame, its rate of introduction, and the length of time in the flame are all important criteria for obtaining reproducible results. 

Solid samples can be analyzed using a plasma torch by first ablating the solid to form an aerosol, which is swept into the plasma flame. The major ablation devices are lasers, arcs and sparks, electrothermal heating, and direct insertion into the flame. 

Direct insertion probe pyrolysis mass spectrometry (DPMS) utilises a device for introducing a single sample of a solid or liquid, usually contained in a quartz or other non-reactive sample holder, into a mass spectrometer ion source. A direct insertion probe consists of a shaft having a sample holder at one end [70] the probe is inserted through a vacuum lock to place the sample holder near to the ion source of the mass spectrometer. The sample is vaporized by heat from the ion source or by heat from a separate heater that surrounds the sample holder. Sample molecules are evaporated into the ion source where they are then ionized as gas-phase molecules. In a recent study, Uyar et al. [74] used such a device for studying the thermal stability of coalesced polymers of polycarbonate, PMMA and polylvinyl acetate) (PVAc) [75] and their binary and ternary blends [74] obtained from their preparation as inclusion compounds in cyclodextrins. 

Polarization. The central cone of the synchrotron beam from a bending magnet and, in general, the beam from insertion devices is polarized in the plane of the orbit (i.e., horizontally). Due to relativistic effects the cone of the radiation characteristics is narrow even if the beam is emitted from a bending magnet (cf. [10], p. 9-13 and Sect. 2.2.2). If necessary, polarization correction should be carried out directly at the synchrotron radiation facility by means of the locally available computer programs. 

The coupling of a GLC column with the sample inlet system of a mass spectrometer is relatively easy, as the effluents are already in gaseous form. The main problem is the relatively high pressure at which these effluents reach the spectrometer and the excess of carrier gas in the stream. Several experimental devices now allow separation of the sample from the carrier gas, either by an effusion process or with the help of a thin, semi-permeable membrane222,353. The use of capillary columns permits direct insertion of the GLC effluent into the ion source without overtaxing the pumping capacity of the mass spectrometer 311 3 5 5 >3 5 6. 

Further detailed studies In this (39) and other laboratories (47) Indicate that It Is possible to Induce Internal excitation In the products of supersonic expansion by Inserting devices Into the oven expansion chamber which restrict the sodium expansion creating a "cloud" In the region directly In front of the oven. 

The pneumatic nebulizer has for many years been the most universal sample insertion device for plasma-based spectrometry. The inherent lack of transport efficiency, coupled with the continuing need for increased sensitivity, has promoted research into the use of ultrasonic nebulizers to boost detection capabilities. Such research has focused on various aspects including fundamental aerosol properties [86-88], instrument development [89], nebulizer comparisons [90,91], desolvation effects [92,93], direct nebulization applications [94,95] and speciation [96]. 

Salin E. D. and Horlick G. (1979) Direct sample insertion device for ICP... 

Application of a wire loop direct sample-insertion device for ICP-MS, Anal Chem 58 975-976. 

One important aspect which should he pointed out is that there is a basic incompatibihty between GC and MSD, the mass spectrometer operate at pressures of 10- torr or less, whereas the gas chromatograph effluent operates at about 760 torr. An interface device is necessary to handle the pressure differences. The simplest and most efficient interface in GC/MSD is a direct capillary column interface. The low flow rate of the narrow bore column and the high pumping rate of an oil diffusion pump backed by a suitable direct drive mechanical pump assure pressures less than lO " torr and allow for the direct insertion of the colmnn end into the mass spectrometer. Interfacing megabore... 

Pyrolysis-gas chromatography was performed using a Horizon Curie-Point Pyrolator with a pyrolsis temperature of 710°C held for 10 s. The interface was heated to 300°C and the capillary column was directly inserted into the pyrolysis chamber. Parameters for the gas chromatographic separation are described below. For Py-GC/MS analyses the same Pyrolysator device was linked to a GC/MS-system with chromatographic and mass spectrometric conditions as described below. 

Insertion devices are placed into straight sections of the storage ring. As shown schematically in Fig. 3 b, the emitted photons add up in the observation direction. Note that the photons are emitted into cones of opening angle 1/y (FWHH), where ... 

Figure 4.12 Schematic of a conventional insertion device. The magnetic field is parallel to the vertical direction (Oz). It is a sinusoidal function of the longitudinal coordinates. The trajectory of an electron submitted to this field is a sinusoid in the horizontal plane (0s,0 c). From Ellaume (1989b) with permission of the author and Gordon and Breach Science Publishers SA.

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