Residual air

The hexapole cannot act as a mass filter by applying a DC field and is used only in its all-RF mode, in which it allows all ions in a beam to pass through, whatever their m/z values. In doing so, the ion beam is constrained, so it leaves the hexapole as a narrow beam. This constraint is important because the ion beam from the inlet system tends to spread due to mutual ion repulsion and collision with residual air and solvent molecules. By injecting this divergent beam into a hexapole unit, it can be refocused. At the same time, vacuum pumps reduce the background pressure to about 10 mbar (Figure 22.1). The pressure needed in the TOF analyzer is about 10 ... 

A finely powdered solid sample of an osmium oxide (which melts at 40. °C and boils at 130.°C) with a mass of 1.509 g is placed into a cylinder with a movable piston that can expand against the atmospheric pressure of 745 Torr. Assume that the amount of residual air initially present in the cylinder is negligible. When the sample is heated to 200.°C, it is completely vaporized and the volume of the cylinder expands by 235 mL. What is the molar mass of the oxide Assuming that the oxide is OsOv, find the value of x. 

The relationship between temperature and pressure holds true only in the presence of pure steam adulteration with air contributes to a partial pressure but not to the temperature of the steam. Thus, in the presence of air the temperature achieved will reflect the contribution made by the steam and will be lower than that normally attributed to the total pressure recorded. Addition of further steam will raise the temperature but residual air surrounding articles may delay heat penetration or, if a large amount of air is present, it may collect at the bottom of the sterilizer, completely altering the temperature profile of the sterilizer chamber. It is for these reasons that efficient air removal is a major aim in the design and operation of a boiler-fed steam sterilizer. 

Extraction with ethanol Alcohol insoluble residue (AIR)... 

Preparation of AIR and extraction of pectic fractions For the preparation of the alcohol-insoluble residue (AIR) the apples were peeled, cut into small pieces and boiled in 96% ethanol for lOmin. After this enzyme inactivation step, the sample material was blended, homogenised and filtered through a G3 sintered glass niter funnel. The residue was washed with 96% ethanol, followed by acetone and diethyl-ether, dried overnight at 40°C under vacuum and stored at -20°C in the dark. Portions of about lOg of AIR were fractionated according to the method of Selvendran et al. [10] as shown in figure 1. 

The TGA system was a Perkin-Elmer TGS-2 thermobalance with System 4 controller. Sample mass was 2 to 4 mgs with a N2 flow of 30 cc/min. Samples were initially held at 110°C for 10 minutes to remove moisture and residual air, then heated at a rate of 150°C/min to the desired temperature set by the controller. TGA data from the initial four minutes once the target pyrolysis temperature was reached was not used to calculate rate constants in order to avoid temperature lag complications. Reaction temperature remained steady and was within 2°C of the desired temperature. The actual observed pyrolysis temperature was used to calculate activation parameters. The dimensionless "weight/mass" Me was calculated using Equation 1. Instead of calculating Mr by extrapolation of the isothermal plot to infinity, Mr was determined by heating each sample/additive to 550°C under N2. This method was used because cellulose TGA rates have been shown to follow Arrhenius plots (4,8,10-12,15,16,19,23,26,31). Thus, Mr at infinity should be the same regardless of the isothermal pyrolysis temperature. A few duplicate runs were made to insure that the results were reproducible and not affected by sample size and/or mass. The Me values were calculated at 4-minute intervals to give 14 data points per run. These values were then used to... 

Example The changes in the electron ionization spectra of residual air are well suited to demonstrate the effect of increasing resolution (Fig. 3.18). Setting R = 1000 yields a peak width of 28 mmu for the m/z 28 signal. An increase to R = 7000 perfectly separates the minor contribution of CO", m/z 27.995, from the predominating N2 at m/z 28.006 (The CO ion rather results from fragmenting C02 ions than from carbon monoxide in laboratory air.)... 

Fig. 3.18. El mass spectra of residual air (a) at R = 1000 and (b) at R = 7000. The relative intensities are not affected by the different settings of resolution. The decimal places of the mass labels give an estimate of achievable mass accuracies under the respective conditions.

Fig. 3.20. Partial 70 eV El mass spectrum of perfluorokerosene, PFK. The peaks are evenly spaced over a wide m/z range. In the low m/z range peaks from residual air do occur.

Fig. 3.21. Reproduction of a PFK calibration table of a magnetic sector instrument covering the m/z 1 05 range. In order to expand the PFK reference peak hst to the low m/z range, H, He and peaks from residual air are included, but for intensity reasons H, He and CO2 have not been assigned in this particular case.

Fig. 6.34. LR- (a) and HR-EI (b) mass spectra of 2-(l-methylpropyl)-phenol. The elemental compositions as obtained from accurate mass measurement are directly attached to the corresponding peaks. Peaks with small-lettered labels belong to PFK and residual air used for internal mass calibration (Chap. 3.3).

Aliphatic alcohols show a strong tendency to thermally eliminate a water molecule. This is of special relevance if volatile alkanols are introduced via the reference inlet system or by means of a gas chromatograph. Then, the mass spectra correspond to the respective alkenes rather than to the alkanols that were intended to be analyzed. The water is often not detected, simply because mass spectra are frequently acquired starting from m/z 40 to omit background from residual air. 

Check which ionization method was used and examine the general appearance of the mass spectrum. Is the molecular ion peak intensive (as with aromatic, heterocyclic, polycyclic compounds) or weak (as with aliphatic and multifunctional compounds) Are there typical impurities (solvent, grease, plasticizers) or background signals (residual air, column bleed in GC-MS) ... 

Possible to use residual air, water, and heat of fuel effluent from fuel cell and other downstream components. 

Work by Altshuler et al. with 0.4-fim particles and a tidal volume of 500 ml showed that only about 11-27% of new air in each successive breath actually mixes with residual air. Theoretical particle-deposition models developed by Altshuler, Beeckmans, and Davies have accounted for the mixing of inhaled aerosol with residual air. 

Residual air only now produces the required overpressure and opens the discharge valve, but the vapor has already condensed and the droplets are precipitated in the pump. 

With characteristic thoroughness Cavendish had passed the 166 ounces of residual air hack again through fresh burning charcoal into another receiver. After another treatment with the soap lye there remained 162 ounces of a gas which he described as follows ... 

Daniel Rutherford, the investigation of this residual air in partial fulfillment of the requirements for the degree of doctor of medicine. 

Lavoisier established that the residual air lacked the characteristic pro-... 

Lenhart SW, Kawamoto MM. 1994. Residual air concentrations of pesticides in a commercial greenhouse. Appl Occup Environ Hyg 9(1) 9-15. 

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