Sintered-Glass Valves. Application to Spectrometer Calibration and to Preparation of Known Mixtures

Abstract

A method which utilizes sintered disk valves is presented for both the storage and use of liquid and gaseous calibrating compounds and mixtures. A technique also Involving a sintered-disk valve is presented for preparing small quantities of liquid mixtures having accurately known compositions. These methods should find considerable application in the calibration and testing in infrared and mass spectrometers, particularly where calibrating compounds are available only in very small quantities. THE recent application of mass and infrared spectrometers to the analysis of complex hydrocarbon mixtures necessitates the repeated use of large numbers of highly purified compounds for calibrating and testing purposes. At present the methods in use for handling such compounds, which in many cases are available only in small quantities, are only partially adequate and often excessively time-consuming. There appears to be a need for methods of storing and using these calibrating compounds, and for preparing, storing, and using known mixtures of them which would be more rapid than existing methods, W'ould handle liquids as well as gases in a uniform manner, w'ould be free from the disadvantages common to the use of stopcocks, and would tend to conserve the limited supplies of pure hydrocarbons available.Principle of Method. The usefulness of the sintered-glass disk valve for introducing calibrating compounds into a mass spectrometer was originally proposed and successfully demonstrated by Hunter (S). The extension and development of this technique have proved highly successful, and it is felt that the principle may be applied equally well to infrared spectrometers. The control of gas flow by means of such sintered-glass disks has been proposed several times, particularly by Pyrtz (ß), Stock(5, 7), and Prausnitz {5). The disks used are porous to gases and liquids in general, but nonporous to mercury. Material may be transferred simply by touching together two sintered disks, thereby displacing the mercury seal covering them and allowing flow to take place through the disks.

Mass Spectrometer Analysis of Alcohols and Other Oxygenated Derivatives

“…In all the work involving calibration spectra or mixture analysis, the liquid samples were introduced into the mass spectrometer by means of a micropipet and mercury-covered sintered disk as described by Young et al (7). The liquid volume read on the pipet was calibrated against microns pressure by running n-pentane, introduced by two methods, on the mass spectrometer.…”

“…In instruments available for analytical purposes the sample is admitted as a continuous gas flow through the tube at a rather low pressure and the gas is intercepted at a certain region by a welldefined beam of electrons (7). In order to obtain reproducible results the concentration of the gas in the ionization and dissociation region must be constant, which means a steady gas flow through the tube at all times.…”

Mass Spectrometer Analyses of Oxygenated Compounds

“…All oxygenated compounds discussed in this paper were introduced into the mass spectrometers as liquid samples. Introductions were made by means of sintered-glass disks as described by Taylor and Young (8). Sample introduction lines were heated to within a few inches of the mercury pool which covered the sintered-glass disks.…”

Standardization of Mass Spectra by Means of Total Ion Intensity

“…accurately the small sample pressures a t the high inlet temperatures (200" to 350" C.) required to vaporize petroleum oils in the mass spectrometer. Therefore, the usual procedure for high mass work has been to attempt to introduce a known liquid volume of a sample (2, 4, 6,9) and to compare the resulting mass spectrum with that of an equal volume of a reference standard (such as n-CIG or n-Cr4) which has been run during the same day.…”