Dissolution rate measurement

C Nystrom, J Mazur, MI Barnett, M Glazer. Dissolution rate measurements of sparingly soluble compounds with the Coulter counter model TAIL J Pharm Pharmacol 37 217-221, 1985. 

Since the rate of absorption of many drugs from the gastrointestinal tract is controlled by their dissolution rate, this becomes the rate-limiting step. Accurate and reliable measurements of dissolution rate are therefore required in the pharmaceutical sciences. The measurement and interpretation of the dissolution rates of solid drugs in the pure state or from formulations, such as tablets, capsules, and suppositories, has an extensive pharmaceutical literature [95-100]. Moreover, the design, operation, and interpretation of dissolution rate measurements on pharmaceutical solids have been the subject of considerable scientific study, technical development, and debate. 

Delage, F. Dussossoy, J. L. 1991. R7T7 glass initial dissolution rate measurements using a high-temperature soxhlet device. In Abrajano, T., Jr. Johnson, L. H. (eds) Scientific Basis for Nuclear Waste Management XIV. Material Research Society Symposium Proceedings, 212, 41-47. 

The dissolution rate is directly proportional to the equilibrium solubility if the appropriate experimental conditions such as the ones used for intrinsic dissolution rate measurements are selected. The rotating-disk method is the most useful and most widely used technique for measuring intrinsic dissolution rates. The theoretical considerations and experimental details of this method will be considered later in this chapter in the discussion dealing with dissolution. 

Figure 6. Dissolution rates measured by interferometry using MIBK at 30 C for (a) high molecular weight PM IA and (b) CO PMMA, 1 4.

Figure 12. Log of the rate of dissolution of synthetic calotte in seawater containing different phosphate concentrations vs. the log of 1 — n. Based on the data of Berner and Morse (SO). The two lowest dissolution rates measured have been excluded as they are highly anomalous.

Weathering rates in the field are as much as one to two orders of magnitude slower than dissolution rates measured in the laboratory (Benedetti et al., 1994 see Chapter 5.05). The difference is due to a number of factors (i) there are differences in surface area between laboratory minerals and natural minerals (ii) secondary precipitates may protect primary mineral surfaces in the field (iii) in soils, most flow is through macropores and not all mineral surfaces are continually exposed to flowing solutions as they are in laboratory experiments and (iv) most... 

Dissolution Rate Measurements Sample films were spun onto silicon wafers from isoamyl acetate solutions of sample resins or sample resin and PMPS. The films were immersed in an aqueous solution of tetramethylammonium hydroxide. Dissolution rates were obtained from a plot of the measured residual film thickness against the immersion time. The film thickness was measured with an interferometer. 

Rodriguez, P.D. Krasicky, and R.G. Groele, Dissolution rates measurements, Solid State Technol. 28(5), 125 (1985). 

The concept of acid labile crosslinked units in polymers for positive DUV resist was evaluated with poly-(4-hydroxystyrene/4-vinylcyclohexanol) and implemented on a poly-4-hydroxystyrene backbone. The principle to increase the molecular weight by a transacetalization reaction was used to improve acetal protected phenolic resins for advanced chemically amplified resists. The polymer chains were linked via diols with acetal bridges. This type of linkage can be applied to a wide range of phenolic polymer binders. Resolution and thermal stability of the photoresist patterns were improved. Gel permeation chromatography and dissolution rate measurements prove that the crosslinked units remain essentially intact in the unexposed areas, thus enhancing... 

Dissolution Measurements. Dissolution rate measurements of the benzophenone series were made on a Perkin-Elmer Dissolution Rate Monitor (DRM-5900) in puddle development mode with 0.25 N KOH developer. The DRM was computer-controlled using Perkin Elmer DRM analytical software (DREAMS 3.0). Measurements of the sulfonyl/carbonyl esters were made with 0.26 N tetramethyl-ammonium hydroxide (TMAH). Reported dissolution rates DRj/i) are at half film thickness. 

To measure the current transient of film repair on bare metal, a lot of specific experiments have been designed where bare metal can be obtained by cathodic reduction, by a scratching technique, or by fast straining (see Sec. 5.2.4.2, Fig. 5-17). Each of these techniques has mechanical or electrochemical drawbacks, but the main difficulty, which makes many results questionable, is to perform the measurements in environment and electrochemical conditions representative of a crack tip. Nevertheless, Fig. 5-48 from Lacombe and Parkins (1977) shows good correlation between the bare surface dissolution rate measured by a fast strain rate technique and the crack growth rate on a series of different materials. 

Experimental method and apparatus for alumina dissolution rate measurement... 

PHA Pham, V.Q., Rao, N., and Ober, C.K., Swelling and dissolution rate measurements of polymer thin films in supercritical carbon dioxide, J. Supercrit. Fluids, 31, 323, 2004. 

A combination of uncertainty in thermodynamic data accuracy at elevated temperatures and overall lack of completeness with respect to organic compound class and interaction types (complex formation, adsorption, solid precipitate) poses some real limitations in the use of chemical and reaction path models. Thus, a cautionary note is that to compare results of different numerical studies it is necessary to know whether similar thermodynamic data bases were used. As we will show below, apparently discrepant conclusions drawn from modeling studies probably result from the use of more or less complete thermodynamic data. Of concern in the investigation of organic acid interactions in silicate rocks is the complete lack of any equilibrium measurements of silica-organic acid anion interactions, although dissolution rate measurements have been made (Bennett et al. 1988 Bennett 1991). 

Fluorinated butyl methacrylate (FBM) has been reported to be about seven times more sensitive than PMMA. In addition, dissolution rate measurements indicate that a very high contrast should be expected since a threshold jump in dissolution rate of about 100 at around 90 mJcm exposure has been observed. 

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