Coating efficiencies

Coating efficiency (CE, %) is a convenient term used to indicate the actual separating efficiency of a column compared to the theoretical efficiency, it is not a measure of how efficiently the column wall is coated with stationary phase. 

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Unprotected steel corrodes at a rate which is generally assumed to be 0.1 to 0.2mm per annum. Factors that influence the actual rate of corrosion include the maintenance program applied by the owner - particularly preservation of protective coatings, efficiency of cathodic protection systems in ballast tanks, corrosive properties of the cargo carried and environmental factors such as temperature and humidity. Under extreme conditions it has been known for the annual rate of corrosion on unprotected steel exposed on both surfaces to approach 1mm. 

The efficiency of an open tubular column can be measured in several ways the most widely used methods are the number of theoretical plates (n), the nu3aber of effective theoretical plates (N), the height equivalent to a theoretical plate (HETP) or effective plate, the coating efficiency and the separation number (SM). No single method is ideal, standardization is lacking and... 

The large surface area of whisker colusuts enables any stationary phase to be coated efficiently without droplet fomation and their sa >le capacity is such higher than HCOT columns. On the debit side, whisker surfaces are extremely active and very difficult to deactivate, and, because of the high degree of roughening, they are less efficient than MOOT columns. 

Dewettinck, K. and Huyghebaert, A., Top-spray fluidized bed coating effect of process variables on coating efficiency, Lebensmittel Wissenschaft Technologie, 31 (1998) 568-575. 

Kang, H.A. and Shin, M.G., Effect of inlet air temperature and atomizing air pressure on fluidized bed coating efficiency of broken peanut, Korean J. Food Sci. Tech., 34 (2002) 924-926. 

High gloss Drug release characteristics meet target requirements High (and reproducible) process coating efficiency... 

Good color uniformity requirements coating efficiency... 

Supposing that the HETP resulting from the van Deemter curve is the same as that resulting from the calculation which might be performed when considering Question 4, calculate the coating efficiency. 

Coating efficiency should be determined for the coating operation. The efficiency will determine the amount of coating solution overage that may be required. 

A discussion on spraying is incomplete without a discourse on nozzle maintenance and testing. In any coating application, the spray nozzle is the single most critical component. Its performance dictates droplet size control, the quality of the applied film and the reproducibility of the resultant product properties. These include appearance, potency, film coating efficiency, and release characteristics. In retrospective process troubleshooting, spray nozzle performance is often the leading cause of product deviations. 

The application of NIR for predicting the endpoint of clinical or production scale batches based on the NIR calibration models developed in the laboratory may prove to be very important to the pharmaceutical manufacturer. When drugloading or polymer-coating efficiencies vary, as they do, from lab scale equipment to the larger equipment used for manufacturing, the availability of a rapid on-line or at-line measurement for prediction of process endpoint may save many millions of dollars in time and materials. Although the standard error of prediction may not match the values obtained when... 

It can be deduced that at equivalent coating efficiencies n varies Inversely with r this has led to some recent Interest In very small diameter columns (e.g. (10)). However, such columns are more easily overloaded, and Impose more stringent demands on Injection hardware and Its use. Also, their pressure drop per unit length Is significantly higher, leading to sharper van Deemter curves. It Is probably because of these considerations that such columns are usually limited to short lengths which can be exploited to yield equivalent separations In much shorter times. 

The coating efficiency can then be calculated being equal to 100 times the ratio between the value found using expression 1.33 and that deduced from the efficiency (H = L/N) obtained from the chromatogram. 

Coating efficiency CE, used as a measure of column quality for GC columns by comparing the theoretical minimum plate height (maximum column efficiency), Hmin, with the plate height achieved in practice, //calc-... 

H, HETP H is the height equivalent to a theoretical plate also called the equilibrium step height. It is a measure of column efficiency, H is approximately 0.5 mm in a GC capillary column and 0.01 mm in HPLC. H = L/N where L is column length, N is number of theoretical plates in a column. /fcALC is the practical plate height of a column, Z/ min is the theoretical minimum plate height at optimmn linear velocity and maximum column efficiency, and may be calculated in terms of the retention or capacity factor of a column see A eir, van Deemter equation, capacity factor and coating efficiency. 

In new construction, the current requirement is often calculated from estimates such as those in Table 6. The amount of bare steel depends on the assumed quality of the coating, both to begin with and after several years of operation. A coating efficiency, for example, of 95% equals 5% bare metal. The current requirement is then the total area of the pipe, times the percent bare (as a decimal) times the current per square meter, or... 

Upward air flow can reduce coating efficiency due to the countercurrent flow of air in relation to nozzle spray, which can interfere with gun spray pattern and promote premature drying. 

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