Glass heated inlet system

Auger electron spectroscopy Phosphorous/nitrogen-selective alkali/flame ionisation detector Atomic force microscopy Atomic fluorescence spectrometry All-glass heated inlet system... 

It has been reported that exchange of protons activated by enolization can be performed directly in a glass inlet system of the mass spectrometer prior to analysis by heating the sample at about 200° with deuterium oxide vapor for a few minutes. " Exchange has been observed with 2-, 3-, 6-, 11- and 17-keto steroids, but the resulting isotopic purity is usually poor,... 

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. 

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,... 

The samples were pyrolyzed in two modes. In the batch technique, 10 mg of sample were heated at 450°C under vacuum (10 torr) and tars collected at room temperature. The potassium salts of these tars were prepared by exchange with 10% KOH in THF. In the second method the samples were flash pyrolysed at 650°C on a platinum mesh using a quartz probe inserted into an all glass inlet system designed in this laboratory. 

A nitrogen inlet is constructed using a fine capillary held through a screw-top Quickfit thermometer adapter, placed on top of the glass tube. The system is adjusted such that the capillary reaches the bottom of the glass tube. The side-arm is connected to a gas bubbler. The glass tube is then placed in a Wood s metal bath, which is heated by means of a Bunsen burner (care ). 

Figure 1. An outer glass tube provides partial insulation for the inlet system, in addition to holding the heating wires in place.

The outer wall of this holder is provided with a spiral groove for insertion of a heating wdre. The holder is installed into a pressure vessel via a few screw connections, giving a gas-tight system. Quartz glass inspection flanges at both ends of the vessel serve for pyrometric inspection to judge the catalyst temperatures at the stack inlet and outlet. 

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