Analysis in Real Time

When the DART ion sonrce is placed near the opening to the mass spectrometer, the ions are sacked in by vacnnm. 

Direct analysis in real time (DART) was introduced in 2005 by Cody et al. [109]. Similarly to DESI samples can be analyzed directly without preparation. While analytes in the small protein range can be analyzed by DESI, DART is in practice limited to analysis of ions in the region below 1 kDa or slightly above. However, as in SIMS, for example, fragment spectra of larger componds can be acquired, which can provide useful information, although the molecular ion cannot be observed. 

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A new family of ionization techniques allows ions to be created under ambient conditions and then collected and analyzed by MS. They can be divided into two major classes desorption electrospray ionization (DESI) and direct analysis in real time (DART). 

DGE a AC AMS APCI API AP-MALDI APPI ASAP BIRD c CAD CE CF CF-FAB Cl CID cw CZE Da DAPCI DART DC DE DESI DIOS DTIMS EC ECD El ELDI EM ESI ETD eV f FAB FAIMS FD FI FT FTICR two-dimensional gel electrophoresis atto, 10 18 alternating current accelerator mass spectrometry atmospheric pressure chemical ionization atmospheric pressure ionization atmospheric pressure matrix-assisted laser desorption/ionization atmospheric pressure photoionization atmospheric-pressure solids analysis probe blackbody infrared radiative dissociation centi, 10-2 collision-activated dissociation capillary electrophoresis continuous flow continuous flow fast atom bombardment chemical ionization collision-induced dissociation continuous wave capillary zone electrophoresis dalton desorption atmospheric pressure chemical ionization direct analysis in real time direct current delayed extraction desorption electrospray ionization desorption/ionization on silicon drift tube ion mobility spectrometry electrochromatography electron capture dissociation electron ionization electrospray-assisted laser desorption/ionization electron multiplier electrospray ionization electron transfer dissociation electron volt femto, 1CT15 fast atom bombardment field asymmetric waveform ion mobility spectrometry field desorption field ionization Fourier transform Fourier transform ion cyclotron resonance... 

Direct analysis in real time DART Discharge Nonvolatile molecular ions Direct, preparation-free analysis of samples... 

API offers unique opportunities for the implementation of new sources or to develop new applications. Atmospheric pressure matrix assisted laser desorption (AP-MALDI) [21] can be mounted on instruments such as ion traps which were originally designed only for electrospray and LC-MS. New API desorption techniques such as desorption electrospray (DESI) [22] or direct analysis in real time (DART) [23] have been described and offer unique opportunities for the analysis of surfaces or of solid samples. 

Desorption Electrospray and Direct Analysis in Real Time... 

DART Direct analysis in real time (DART) is an analogous technique to DESI that does not require the electrospray solvent (Cody et al., 2005 McEwen et al., 2005 Williams et al., 2006). 

Sedimentation FFF implies application of the centrifugal field, which is produced by placing the channel in a centrifuge basket. SdFFF instruments can be linked readily to analytical instruments to provide analysis in real time. For the first time, Beckett (1991) introduced FFF-ICP-mass spectroscopy (MS) as a powerful analytical tool for characterizing macromolecules and particles. Taylor et al. (1992) illustrated the characterization of some inorganic colloidal particles and river-borne suspended particulate matter of size range <1 pm using SdFFF and ICP-MS. 

For elucidation of biosynthesis and TA identification in plants mass spectromet-ric procedures including LC-MS [16, 17], LC-MS/MS [18] and DART MS (direct analysis in real time MS) [19] were successfully applied. 

Yew, J.Y., Cody, R.B., and Kravitz, E. A. (2008). Cuticular hydrocarbon analysis of an awake behaving fly using direct analysis in real-time time-of-flight mass spectrometry. Proc. Natl. Acad. Sci. USA, 105, 7135-7140. 

A new ion source has been developed for rapid, non-contact analysis of materials at ambient pressure and at ground potential [8,9], The new source, termed direct analysis in real time (DART), is based on the atmospheric pressure interactions of long-lived electronic excited-state atoms or vibronic excited-state molecules with the sample and atmospheric gases. Figure 5 shows a schematic diagram of the DART ion source. 

Fig. 5. Schematic diagram of direct analysis in real time (DART) ion source. Reproduced with permission from Cody et al. [9]. Copyright 2005 American Chemical Society.

The direct analysis in real time (DART) method has been described by Cody et al. [88] and commercialized by JEOL. This method allows direct detection of chemicals on surfaces, in liquids and in gases without the need for sample preparation. All of these analyses take place under ambient conditions in a space just in front of the inlet of the mass spectrometer. The sample is not altered because no exposure to high voltage or to vacuum is required. 

Fig. 10. Ellipsometry analysis in real-time of Si exposed to a CF4 plasma, V and A as a function of pressure or of gas mixture (reprinted with permission from J. Vac. Sci. Technol., A 11 (1993) 34 [39]).

Amorphous phases are attractive to study mechanisms of cocrystal formation because they require very small samples (3-5 mg) and can be prepared and studied in situ (by melt-quenching) in a calorimeter or on a microscope stage. Cocrystallization pathways can then be identified and kinetics measured from the analysis of thermal events, photomicrographs and spectroscopic analysis in real time. An example of the cocrystallization of CBZ NCT from an amorphous film of equimolar composition of reactants is shown in Fig. 24. 

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