Particle counter, high concentration

The basic instrumentation in the present work is a Royco Model 225/518 High Concentration Particle Counter. The location of the air inlet and light sensing unit of the instrument in the card room has been described previously (2). The inlet was fitted with a vertical elutriator preseparator designed to prevent particles >15 vin aerodynamic diameter from entering the light sensor. Thus the collection efficiency of this instrumentation as a function of particle size should be similar to that of the Vertical Elutriator Cotton Dust Sampler. 

The situation is more complicated when the particles are charged because the smaller counter-ions sediment at a slower rate than do the larger colloidal particles. This creates an electrical potential that tends to speed up the counter-ions and slow down (drag) the colloidal particles. At high enough electrolyte concentrations the electric potentials are quickly dissipated and this effect vanishes. 

Micellar liquid chromatography (MLC) is another variation on reversed-phase and ion-pair chromatography. In this mode, the counter ion is a surfactant of high concentration and a long-chain hydrocarbon. Micelles form when the concentration of the surfactant is increased to the point at which aggregation occurs and spherical particles are formed. The hydrophilic parts of the long-chain hydrocarbon are oriented toward the outside of the sphere with the hydrophobic end in the center of the sphere. A mixture of compounds of varying polarity partitions between the... 

Notice that, although the particle mass concentration emitted in the Test 2 is lower than the Test 4, the total concentration number is higher in Test 2.. Additionally the concentration number measured with the optical counter is higher in Test 2. An efficient combustion, as occurring in Test 2 favours the presence of fine particles as opposed to the poor combustion of Test 4 which produced a high concentration of coarse particles, thus increasing the mass concentration. 

A limitation of the use of a particle counter within this field of application, was that turbidity of the water under investigation needed to be low on the one hand, and that the concentration of the one dominant planktonic organism had to attain high values. If these 2 conditions were not fulfilled, then the particle counter was not able to discriminate between clay or silt particles in suspension and algae cells. 

Optical particle counters require dilution of highly concentrated particle suspensions to a concentration level below the concentration limit of the sensor. The low "overconcentration" limit of a OPC was in the past the major disadvantage, limiting the use of optical single particle counters. The main objectives of the sample delivery procedure are ... 

Single-particle optical counters cannot be easily used for measuring high aerosol concentrations. Whitby and Liu (1967) have shown that if many small particles are in the illuminated sensitive volume of this type of instrument at the same time, significant errors are introduced because the particles are considered by the detector to be fewer in number and greater in size. Thus there is a practical upper limit on the aerosol concentration that can be measured by such an instrument, being on the order of 1000 to 10,000 particles per cubic centimeter. 

Condensation nucleus (CN) concentration CN counter Expose particles to a high supersaturation, typically of butanol vapor particles grow to size where they can be optically detected and counted -b... 

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