Measurements single/multipoint

The theory for single-point BET measurements is similar however, an assumption is made that the intercept of the PIV(P0-P) versus PIPQ plot equals zero. This assumption is not always valid and can result in surface area values that differ from multipoint values. When the assumption is valid, the single-point method is simpler and faster, and it results in accurate surface area values. 

As the surface area exposed to the site of administration determines the speed with which a particle dissolves in accordance with the Noyes-Whitney equation, these determinations are important. In addition, in those instances where the particle size is difficult to measure, a gross estimation of the surface area is the second best parameter to characterize the drug. The most common methods of surface area measurement, including gas adsorption (nitrogen or krypton), based on what is most commonly described as the Braunauer, Emmet, and Teller (BET) method, is applied either as a multipoint or single-point determination. 

Recall that an analytical method s precision is a measure of the degree to which it can be reproduced or repeated and is evaluated by calculating the standard deviation for the method s instrument calibration verification (ICV) standard following establishment of a single-point or multipoint cali-... 

The fluid static pressures were measured with calibrated Bourdon tube gages, and the differential pressures were measured with mercury-filled, double-legged glass manometers. These pressure measuring instruments were located on a single panel and their indications were recorded photographically. The fluid and wall temperatures were measured with copper-constantan thermocouples and recorded on multipoint temperature recorders. 

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