Batch 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. 

Mass Spectrometry. The mass spectra were obtained on a CEC 21-llOB mass spectrometer with the batch inlet system maintained at 250°C to assure complete vaporization of the samples. Sensitivity factors for quantitative analysis were obtained from standards of di-, tetra-, hexa-, and octa-chlorodibenzo-p-dioxin. The factors for the intermediate chlorinated species were estimated by interpolation. The analyses were based... 

Roussis, S.G. Cameron, A.S. Simplified Hydrocarbon Compound Type Analysis Using a Dynamic Batch Inlet System Coupled to a Mass Spectrometer. Energy... 

Many manufacturers now offer other sample injection systems compatible with the vacuum lock used for the solids probe. These include small (e.g., 75-ml) heatable batch inlet systems, usually accessible via syringe (gas syringe or GC microliter syringe for liquids), which can be particularly useful as inlets for mass reference compounds. Other probes are designed as flexible, easily removed connections to a gas chromatograph via some form of interface. 

Batch inlet systems are in many ways the most convenient for gases and volatile, thermally stable liquids or solids, provided there is sufficient sample available. They consist of reservoirs, varying in volume from 20 ml to several liters, which are connected to the ion source via a molecular leak, usually a porous ceramic material, or a pinhole in thin gold foil or glass. The leak serves to reduce the pressure from 10 torr in the inlet system to torr in the ion source. Large ballast bulbs... 

Of all the inlets, the GC is the most foolproof, since operation of high vacuum valving, the chief danger with probe and batch inlets, is not necessary. Thus, once the instrument is properly tuned and operating, even novices may run their own GC/MS with minimum supervision. 

Perhaps the most common problem is that of thermal decomposition of the sample, either in the batch inlet, for which the cure is a lower inlet temperature or use of the direct probe, or in the source itself. A common misconception among mass spectroscopists, often promulgated by manufacturers, is that if the source is kept hot, the decomposition of contaminants is minimized. The ion source should routinely be run no hotter than 180°-200°C. A source at the common temperature of 250°C is much more likely to result in decomposition of sample and contamination of the source, and should be used only rarely. On our AEI MS-30 we run 200 samples per month, many of which are organometallic or inorganic, and we are seldom forced to exceed 200°C more than once a month. If some sample condenses into the source it is far better to sublime it away slowly by carefully raising the temperature than to pyrolyze it. 

Glass or glass-lined heated batch inlet systems and transfer lines are to be preferred to the older metal systems since metals tend to accelerate decomposition, although metal deposited by decomposing compounds does have a particularly strong catalytic action 8,13, 114,... 

Electron impact Heated batch inlet Application to all volatile Samples thermally Low ( 1000)... 

Heated batch inlet Heated direct insertion... 

Batch inlet. This classical method of sample introduction is still a very useful and necessary inlet for both liquids and gases giving a steady sample flow rate. However it requires fairly large samples of materials which are thermally stable and of adequate vapour pressure. Mixed spectra result from multicomponent samples. 

The purpose of the inlet system is to permit introduction of a representative sample into the ion soutca with minimal loss of vacuum. Most modern mass spectrom-ciers are equipped with several types of inlets to accommodate various kinds of samples these include batch inlets, direct probe inlets, chromatographic inlets, and capillary electrophoretic inlets. 

Most analytical mass spectrometers have two inlet systems a batch inlet for gases and liquids and for solids of moderately high vapor pressure, and a direct inlet for high-molecular-weight nonvolatile solids and for thermally unstable compounds. A typical design for a batch inlet is shown in Figure 16.1. 

Figure 16.1. Schematic diagram of a typical batch-inlet system. This inlet is used for gases, volatile liquids, and volatile solids.

Field ionization involves the removal of electrons from a species by quantum mechanical tunneling in a high electric field. In practice, FI-MS refers to the technique in which the sample to be analyzed is introduced as a vapor using a heatable direct probe, heated batch inlet, or GC/MS interface. 

Inerting venting At the roof or side doors (weight/area < 40 kg/m ) Top and bottom section of the vertical tube On die roof for continuous duty d side vent fw batch Inlet and discharge hoods (vent area = dryer cross-section)... 

Introduction of Gases and Volatile Liquids Using Batch Inlets... 

Batch inlets should enable a constant and reliable flow rate of the sample during the analysis, and be inert to the analytes. Gases and volatile liquids are introduced into El or Cl sources from a glass or metal reservoir of known volume (that can be heated to 350°C) by way of a gold or steel foil that has one (or several) pinhole(s) (0.005 to 0.02 mm diameter). The introduction of liquids can be controlled by placing the... 

The most common use of batch inlets is to introduce a controlled flow of compounds for calibrating the mass scale. Frequently used calibration compounds include perfluorotributylamine (FC-43, heptacosa) and perfluorokerosene (PFK) both are effective with electron ionization (El) but give limited responses in chemical ionization (Cl). If used for calibration in Cl, or to provide lock masses (Section 3.1.1), the concentration of the reagent gas must be reduced. This reducation somewhat compromises the effectiveness of the Cl process. 

CO2 sample is used to calibrate the detector responses and the analyte is introduced by a batch inlet process. The correction at miz 45 for is made from the amount of present at m z 46 by assuming that the 0/ 0 ratio remains constant. 

A basic batch inlet is shown in Figure 2. A small quantity of gas is expanded into an evacuated volume, so that the pressure is low enough for molecular flow to occur in the leak to the mass spectrometer. No mixing of flow regimes occurs, so fractionation is absent. However, it involves more hardware than other inlets, and cannot give truly... 

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