Direct inlet

Batch inlet. The historic term for a reservoir inlet. The term reservoir inlet is preferred because a direct-inlet probe is also a form of batch inlet. Batch gas inlet or batch vapor inlet are, however, completely descriptive terms. 

Continuous inlet. An inlet in which sample passes continuously into the mass spectrometer ion source, as distinguished from a reservoir inlet or a direct-inlet probe. 

Crucible direct-inlet probe. Holds the sample in a cup-shaped device (the crucible) rather than on an exposed surface. A direct-inlet probe is assumed to be a crucible type unless otherwise specified. 

Direct-inlet probe. A shaft or tube having a sample holder at one end that is inserted into the vacuum system of a mass spectrometer through a vacuum lock to place the sample near to, at the entrance of, or within the ion source. The sample is vaporized by heat from the ion source, by heat applied from an external source, or by exposure to ion or atom bombardment. Direct-inlet probe, direct-introduction probe, and direct-insertion probe are synonymous terms. The use of DIP as an abbreviation for these terms is not recommended. 

Vacuum-lock inlet. An inlet through which a sample is first placed in a chamber the chamber is then pumped out, and a valve is opened so that the sample can be introduced to the mass spectrometer ion source. A vacuum-lock inlet commonly uses a direct-inlet probe, which passes through one or more sliding seals, although other kinds of vacuum-lock inlets are also used. 

Direct inlet fogging, is a type of evaporative cooling method, where de-mineralized water is converted into a fog by means of high-pressure nozzles operating at 1000-3000 psi. (67-200 Bar) This fog then provides cooling... 

Lindstrom and Schubert63 applied GC-MS, GC-MS-MS and direct inlet MS-MS to determine 1,1-dichlorodimethyl sulfone (201, DDS) in aquatic organisms outside a pulp mill bleach plant. Both GC-MS-MS and direct inlet MS-MS of tissue extracts of fish and mussel appeared to be sensitive, selective and fast techniques for the determination of DDS. 

For non-volatile sample molecules, other ionisation methods must be used, namely desorption/ionisation (DI) and nebulisation ionisation methods. In DI, the unifying aspect is the rapid addition of energy into a condensed-phase sample, with subsequent generation and release of ions into the mass analyser. In El and Cl, the processes of volatilisation and ionisation are distinct and separable in DI, they are intimately associated. In nebulisation ionisation, such as ESP or TSP, an aerosol spray is used at some stage to separate sample molecules and/or ions from the solvent liquid that carries them into the source of the mass spectrometer. Less volatile but thermally stable compounds can be thermally vaporised in the direct inlet probe (DIP) situated close to the ionising molecular beam. This DIP is standard equipment on most instruments an El spectrum results. Techniques that extend the utility of mass spectrometry to the least volatile and more labile organic molecules include FD, EHD, surface ionisation (SIMS, FAB) and matrix-assisted laser desorption (MALD) as the last... 

State-of-the-art ToF-MS employs reflection lenses and delayed extraction [176] to improve resolution by minimising small differences in ion energies, and in these cases up to 12000 mass resolution (FWHM, m/z 600) is available. This is sufficient for most modern applications. Solid probe ToF-MS (or direct inlet high-resolution mass spectrometry, DI-HRMS) is a breakthrough. DIP-ToFMS is a thermal separation technique. Advantages of DIP-ToFMS are ... 

Tandem MS (DFS equipped with EI/F1/FD source) in conjunction with off-line direct inlet HPLC-UV was used for separation and quantification of isomeric antioxidants, C22H30O2S (MW 358 Scheme 6.3), as antioxidants in THF extracts of surgeons gloves [232]. Collision activation MS enabled differentiation between the three isomeric structures (Fig. 6.20). Quantification was achieved by chromatographic analysis of the isomeric species, which are not distinguishable by MS. On-line LC-MS facilitates this kind of analysis. 

Also, direct determination of additives by means of laser desorption in solid polymeric materials rather than in polymer extracts has been reported [266], Takayama et al. [267] have described the direct detection of additives on the surface of LLDPE/(Chimassorb 944 LD and Irgafos P-EPQ) after matrix (THAP)-coating. As shown in Scheme 7.13, direct inlet mass spectrometry is also applicable to transfer TLC-MS and TLC-MS/MS analyses without the need for prior analysis. For direct sample introduction a small amount of the selected... 

LC-MS interfaces generally produce ions with a relatively wide energy and spatial distribution. Table 7.49 lists the main LC-MS interface types. The most important types of contemporary LC-MS interfaces are direct inlet systems PB, TSP, API, ICPI and MIP (the latter two for plasma source detection, cf. Section 7.3.3.5). Three main types of LC-MS coupling systems are usually distinguished ... 

Data were obtained anew on a high resolution mass spectrometer by direct inlet probe at 70 eV (Ref. 13). 

Reference a b Fluid Flow direction Inlet quality (%) Exit quality (%) K basis... 

Regert, M. and C. Rolando (2002), Identification of archeological adhesives using direct inlet electron ionization mass spectrometry, Anal. Chem. 74(5), 965-975. 

M. Regert, C. Rolando, Identification of archaeological adhesives using Direct Inlet Electron Ionization Mass Spectrometry, Analytical Chemistry, 74, 965 975 (2002). 

Figure 2.1 Mass spectrometric approach. Dl, direct inlet GC, gas chromatography HPLC, high performance liquid chromatography CZE, capillary zone electrophoresis El, electron ionization Cl, chemical ionization ESI, electrospray ionization DESI, desorption electrospray ionization APCI, atmospheric pressure chemical ionization MALDI, matrix assisted laser desorption ionization B, magnetic analyzer E, electrostatic analyzer...

The simplest way is the introduction of a sample directly in the ion source through a direct inlet whose design depends upon the ionization technique used. As an example,... 

Through a direct inlet or a separation technique the sample is introduced into the ion source (the region in which the ionization occurs, i.e. the mass spectrometer region where a neutral molecule is transformed into an ion). The design of the ion source is dependent on the ionization technique. 

Case Studies Direct inlet mass-spectrometry (DI-MS)... 

In addition to GC/MS, high performance liquid chromatography (HPLC/MS) has been used to analyse natural resins in ancient samples, particularly for paint varnishes containing mastic and dammar resins [34]. A partial limitation of chromatographic techniques is that they do not permit the analysis of the polymeric fraction or insoluble fraction that may be present in the native resins or formed in the course of ageing. Techniques based on the direct introduction of the sample in the mass spectrometer such as direct temperature resolved mass spectrometry (DTMS), direct exposure mass spectrometry (DE-MS) and direct inlet mass spectrometry (DI-MS), and on analytical pyrolysis (Py-GC/MS), have been employed as complementary techniques to obtain preliminary information on the... 

Figure 4 Rotating flow mixing devices having two (A) and three (B) directional inlets.

The most straightforward tool for the introduction of a sample into a mass spectrometer is called the direct inlet system. It consists of a metal probe (sample rod) with a heater on its tip. The sample is inserted into a cmcible made of glass, metal, or silica, which is secured at the heated tip. The probe is introduced into the ion source through a vacuum lock. Since the pressure in the ion source is 10-5 to 10-6 torr, while the sample may be heated up to 400°C, quite a lot of organic compounds may be vaporized and analyzed. Very often there is no need to heat the sample, as the vapor pressure of an analyte in a vacuum is sufficient to record a reasonable mass spectrum. If an analyte is too volatile the cmcible may be cooled rather than heated. There are two main disadvantages of this system. If a sample contains more than one compound with close volatilities, the recorded spectrum will be a superposition of spectra of individual compounds. This phenomenon may significantly complicate the identification (both manual and computerized). Another drawback deals with the possibility of introducing too much sample. This may lead to a drop in pressure, ion-molecule reactions, poor quality of spectra, and source contamination. 

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