Counting emulsion

Electrical pulse counting, emulsion droplet size determination, 581, 583-584, 586-588... 

FAT EMULSIONS. When a fat emulsion is administered, the nurse must monitor the patient s ability to eliminate the infused fat from the circulation. The lipidemia must clear between daily infusions. The nurse monitors for lipidemia through assessing the result of the following laboratory exams hemogram, blood coagulation, liver function tests, plasma lipid profile, and platelet count. The nurse reports an increase in any of these laboratory examinations as abnormal. 

Formation and transport of radon ) In the present work, lead isotopes were chemically separated from the sample gas as lead sulfide since the formation of lead sulfide was inevitable under the presence of H2S in the fumarolic gas. The lead sulfide was then dissolved in a small amount of concentrated HCI and mixed with the Insta Gel(emulsion scintillator solution, Insta Gel, Packard Inc.) for the liquid scintillation counting. The chemical yield and the volume of the collected non-condensing gas were obtained from the measurement of the activities of Pb-214 and its progeny which were in radioequilibrium with their precursor Rn-222 whose concentration was determined separately by the direct method. 

The general method of procedure was to disperse a known volume pf parafl n in water with the aid of the soap. The average diameter of the kerosene emulsion droplets was determined by counting with the aid of a microscope and hemacytometer, from which the total interfacial area could be calculated. 

The distribution of particles in a vertical column of the emulsion was determined by Perrin with the aid of a microscope and micrometer focussing arrangement. The height of the column under the microscope was 0 1 mm. and the number at various depths was counted with the aid of the eye. The following results are typical of such determinations. 

The LPL catalytic assay measures the hydrolysis of a [14C[- or [3H]-triolein emulsion producing the 14C- or 3H -labeled free oleic acid [6]. The 14C- or 3H-labeled oleic acid is isolated by a selective extraction procedure and its radioactivity is determined by liquid scintillation counting [40]. Lipase activity is calculated as nanomoles of oleic acid released per minute per milliliter of postheparin plasma [41]. 

Quality attributes of food emulsions, such as appearance, stability, and rheology, are strongly influenced by the size of the droplets that they contain (Friberg and Larsson, 1997 McClements, 1999). For example, the creaming stability of an emulsion decreases as droplet size increases. Analytical techniques that provide quantitative information about droplet size are therefore required to aid in the development and production of high-quality emulsion-based food products. A variety of analytical techniques have been developed to measure droplet size, e.g., laser diffraction, electrical pulse counting, sedimentation techniques, and ultrasonic spectrometry (McClements, 1999). These techniques are used for fundamental research, product development, and quality assurance. This unit focuses on the two most commonly used techniques in the food industry, laser diffraction and electrical pulse counting. 

Laser diffraction is most suitable for analyzing dilute emulsions that are fluid, and therefore competes directly with electrical pulse counting methods, which are applicable to similar systems (see Alternate Protocol). Most laser diffraction instruments can cover a wider range of particle sizes (i.e., 0.01 to 1000 pm) than electrical pulse counting instruments (i.e., 0.4 to 1000 pm using a number of different aperture sizes), and do not require the presence of electrolyte in the aqueous phase, which could destabilize some electrostatically stabilized emulsions. Nevertheless, electrical pulse counting techniques are considered to have greater resolution. 

The major disadvantage of the laser diffraction and electrical pulse counting techniques is that they are only directly applicable to dilute emulsions or emulsions that can be diluted without disturbing the particle size distribution. However, many food emulsions are not dilute and cannot be diluted, either because dilution alters the particle size distribution or because the original sample is partially solid. For concentrated systems it is belter to use particle-sizing instruments based on alternative technologies, such as ultrasonic spectrometry or NMR (Dickinson and McClements, 1996). 

During the first day after the operation the erythrocytes were reduced to 300000—500000. During the following days the erythrocyte count in the animals treated with silatranes increased, attaining the normal value within 10 days. At the same time, the erythrocyte count of the animals treated with Vishnevsky ointment and synthomycin emulsion normalized in only 15 days. The erythrocyte count in the control group animals did not reach the normal value even after 20 days. 

One day after the operation the leucocyte count both in treated and untreated animals increased by 4000—50006s On the 5th day the leucocyte count of the animals treated with silatrane ointments reduced to 9000 500. The leucocyte count of the animals treated with Vishnevsky ointment, synthomycin emulsion and cygerol reduced to 10800 100, 10200 300 and 10000 200, respectively. The leucocyte count of the untreated animals was 11000 100 5 days after the operation. The leucocyte count of the silatrane-treated animals was normal after 15 days, i. e. by the time of complete healing of the wound, in the untreated animals not even after 20 days. 

Assessment of the stability of an emulsion against coalescence involves droplet counting218. The most unequivocal method (but one which is rather laborious) is to introduce a suitably diluted sample of the emulsion into a haemocytometer cell and count the microscopically visible particles manually. 

Fig. 12.5. Effect of length of autoradiographic exposure on grain count. BHK21/C13 cells labelled with [3H]uridine were covered with Ilford L4 emulsion (diluted with an equal volume of water) dried in a horizontal position and exposed in air at room temperature for the indicated times. (Courtesy of K. Shaw and Dr. J.D. Pitts.)...

Fig. 12.6. Grain count distribution. L cells labelled for 10 min with [3H]thymidine (2.5/1 Ci/ml 0.36 Ci/mmol) and processed for autoradiography using NTB3 emulsion. Those cells (62% of the total) with one or more grains are recorded. A Poisson distribution with a mean of 30 is included for comparison. (Reproduced from Cleaver, 1967, with kind permission of the author.)...

Unfortunately, most emulsions do not have a single droplet size. There are small, medium and large droplets present, and it is important to be able to characterise the emulsion for this. This is done by counting the number of particles that is smaller than a specific size, for many different sizes. The resulting data can then be plotted on a curve, the cumulative distribution curve. Alternatively, one can count all particles that have a size within an interval of sizes (e.g., 1-2 pm), and do this for all intervals. Plotting all the numbers obtained for all intervals, then results in a frequency distribution. The two distributions are closely related the derivative of the cumulative curve to the particle size, will give a (continuous) curve that is similar to the discrete frequency distribution obtained earlier, and the smaller the intervals are chosen, the closer the derivative will follow the frequency distribution (see Figure 15.4). 

There are different ways of counting particles to obtain the distribution. One can simply count the number of particles smaller than a specific size. This means that in the curve, a droplet of 0.1 pm will count for one, just as a droplet of size 10 pm. However, the amount of oil present in the 10-pm droplet is 100, or one million times larger. Such a distribution therefore stresses the presence of small particles. Another way is to not use the number of particles but the total interfacial area present on the particles. Since the interfacial area of a small droplet is much smaller than that of larger droplets, smaller droplets are counted less extremely, and the resulting distribution is more realistic. Remember that the amount of surfactant needed to stabilize the interface is proportional to the total interfacial area present on the droplets, and the total energy needed to put into the emulsion is proportional to the total interfacial area. As a third option, one can use the volume of the particles smaller than a specific size. In this case the distribution gives that total amount of oil that is present in small, medium or larger droplets. It depends on the application which type of distribution should be used. 

A fourth way is to count droplets individually. First, one has to dilute the emulsion strongly. Then, this diluted emulsion is pushed through a small hole. At the same time, the electrical conductivity through the hole is measured. Every time an emulsion droplet moves through the hole, the droplet will obscure part of the hole, which suddenly reduces the conductivity through the hole— the larger the droplet is, the stronger is the effect. Also in this way a droplet size distribution can be obtained. This method is usually referred to as the Coulter counter method, after an important manufacturer of this type of equipment. 

In the dipping method, the insects are picked up with a pair of forceps and dipped into the insecticide preparation, which is either a suspension or an emulsion. A dipping net or a screened container can also be devised for exposure of the insects for a few seconds. The dose is varied by increasing the concentrations in a series of beakers. After treatment, the insects are placed in clean containers and mortality counts are made after a suitable interval. 

Various methods can be used to measure the intensity of radioactive emissions. These exploit the ability of radiation from radioactive isotopes to cause ionisation (Geiger-Miiller counting), to excite fluorophores (scintillation counting), or to cause exposure of light-sensitive photographic emulsion (autoradiography) (Slater 1990 Rickwood et al. 1993). 

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