Aerosol loss efficiency

For purposes of the aerosol chamber discussion, % Loss Efficiency (% LE) as a function of particle diameter is defined in Equation 2 as... 

Loss Efficiency for Different Aerosol Chamber Internal Volumes. 

Loss Efficiency of S1O2 Aerosol Nanoparticles Through Nominally Identical Filter Housings that Do Not Contain Filter Media. 

The aerosol then passes along the plastic expansion chamber. Large droplets collect on the walls of the chamber and, to ensure that only the smallest particles reach the flame, spoilers or baffles may be placed in the path of the gases. The chamber also allows for mixing of the gases and tends to damp fluctuations in nebulization efficiency. Some loss of solvent by evaporation will also occur. The chamber requires a drain tube which must be sealed to provide a back-pressure for the flame. This is usually... 

If aerosolization is a major contributor to a hazard, a portion of the airborne liquid can be removed by placing an angled plate over the release point. The released material strikes the plate, which disperses much of the momentum and enhances coagulation of liquid droplets. In this way a portion of the liquid will drop out of the cloud. However, the loss of momentum may result in less efficient vapor dispersion and, hence, a larger hazard area. 

This experiment presents the measurement of uranium with an inductively coupled plasma mass spectrometer (ICP-MS). In this system, a nebulizer converts the aqueous sample to an aerosol carried with argon gas. A torch heats the aerosol to vaporize and atomize the contents in quartz tubes. The atoms are ionized with an efficiency of about 95% by an RF (radiofrequency) coil. The plasma expands at a differentially-pumped air-vacuum interface into a vacuum chamber. The positive ions are focused and injected into the MS while the rest of the gas is removed by the pump. The ions are then accelerated, collected, and measured as a function of their mass. Losses at various stages, notably the vacuum interface, result in a detection efficiency of about 0.1 %, which is still sufficient to provide great sensitivity. The amounts of uranium isotopes in the sample are determined by comparisons to standards. Because different laboratories have different instruments, the instructor will provide instrument operating instmctions. Do not use the instrument until the instructor has checked the instrument and approved its use. 

It is important to understand the sources and loss mechanisms of stratospheric sulfate aerosols. These aerosols are linked to the decrease in ozone at mid-latitudes because they hydrolyse N2O5, reducing the amount of NOx that would otherwise limit the efficiency of chlorine-catalysed ozone depletion. In addition these aerosols scatter light, cooling the planet [127]. Their concentration increases dramatically following major volcanic eruptions however they are always present at background levels. The source of these background aerosols is a matter of debate. In 1976 Paul Crutzen presented the idea that sulfate aerosols result from the photolysis of carbonyl sulphide [128] ... 

Consequently, ion attachment to aerosols should not be an efficient loss process for stratospheric ions. 

The unique part of the Universal Interface is the membrane separator or gas diffusion cell which allows the solvent vapor to be efficiently removed with essentially no loss of sample contained in the aerosol particles. In this device the aerosol is transported through a central channel bounded on the sides by a gas diffusion membrane or filter medium which is in contact with a countercurrent flow of a sweep gas. For El mass spectrometry helium appears to be most useful for both the carrier and sweep gas. The properties of the... 

The graph of the two efficiencies and of their ratio (enhancement) is presented in Fig. 3.9. For nuclides with tg/tx equal 4, 3, 2, 1 and 0, the ratio is 3.31, 2.28, 1.62, 1.20 and 1, respectively. The enhancement is larger with shorter lx, with longer lc or with slower w. It does not compensate for decay losses, which increase the same way still, generally the aerosol jet transportation is preferable. 

It is concluded on the basis of equation [4.S] that the intensity of the particle loss due to the thermal coagulation is directly proportional to square of the particle concentration, while the coagulation efficiency increases with decreasing particle radius. This means that the coagulation of small particles at a high concentration is a very rapid process. Equation [4.S] is valid only for monodisperse aerosols, i.e. aerosols composed of particles of uniform size. However, the same qualitative conclusion can also be drawn in the case of polydisperse systems. 

---