Moisture determination, dried

In studies on the moisture determination of corn by vacuum drying at 100° C., Sair and Fetzer (28) found that an error of about 0.5% in moisture content could be attributed to volatility of oils. The error was negligible in vacuum drying at 70° C. 

The earliest applications for quantitative analysis of liquid samples and solid preparations entailed sample dissolution in an appropriate solvent. A number of moisture determinations in APIs and pharmaceutical preparations based on both reflectance and transmission measurements have been reported. Their results are comparable to those of the KF method. The high sensitivity provided by the NIR technique has fostered its use in the determination of moisture in freeze-dried pharmaceuticals. ° The noninvasive nature of NIR has been exploited in determination of moisture in sealed glass vials. " " ... 

Calculation. Subtract the blank reading from the sample reading in pg K ml read from the graph. This is equal to the g kg of potassium in the sample. Divide the pg K mM by 10 to obtain the % K in the sample. If the sample was not oven-dried, use the separate moisture determination to correct the result to K in DM. 

Run the standard process with 100% loading rate. Collect the dried stoppers in predried glass vessels. The stoppers are afterward cut into pieces of 80 mg and analyzed using the Karl Fischer moisture determination method. The moisture out of the stoppers is obtained at increased temperature and blown over with nitrogen into the reaction vessel. 

In vacuum oven methods for moisture determination, such as the official method of the Association of Official Analytical Chemists, lactose solutions are dried at about 100°C for 2 to 6 hr. The result in the dried product is amorphous lactose glass. Since lactose glass is very hygroscopic, the dried sample must be protected from moisture until final weighing. If a-hydrate crystals are present in the product to be analyzed, the sample is diluted with water to dissolve the crystals, since slow removal of the water of crystallization under the temperature and vacuum conditions of the moisture test unduly prolongs the moisture determination. 

The defined range suitable for acceptable stability may approach the variability of the moisture determination method or may be as great as a few percent. For example, many lyophilized products with the USP have a finished product residual moisture specification of less than 2% of dry weight. Other products, such as amphotericin B, have a residual moisture limit of 8.0% [31]. Whether the allowable residual moisture specification is small or large, a range of acceptable residual moisture needs to be identified and correlated to suitable long-term stability. 

The analytical method for moisture determination must be validated before use during process validation studies. There are numerous techniques for moisture analysis that range from physical methods, such as loss on drying, to chemical methods, such as Karl Fisher titration. A comparative review of the conventional techniques are presented in an overview [32], The measurement of residual moisture is lyophilized pharmaceuticals by near-infrared (NIR) spectroscopy has recently been expanded [33]. 

Analyses reported on a dry basis are calculated on the basis that there is no moisture associated with the sample. The moisture value (ASTM D-3173 ISO 331 ISO 589 ISO 1015 ISO 1018 ISO 11722) is used for converting as determined data to the dry basis. Analytical data that are reported on a dry, ash-free basis are calculated on the assumption that there is no moisture or mineral matter associated with the sample. The values obtained for moisture determination (ASTM D-3173 ISO 589) and ash determination (ASTM D-3174) are used for the conversion. Finally, data calculated on an equilibrium moisture basis are calculated to the moisture level determined (ASTM D-1412) as the equilibrium (capacity) moisture. 

Air drying removes most of the surface moisture of coal, while a temperature of approximately 107°C (225°F) is needed to remove inherent moisture. At temperatures of approximately 200 to 300°C (392 to 572°F), moisture from the decomposition of organic materials is driven off, but water of hydration requires a considerable amount of energy for expulsion. For example, the water of hydration in clay minerals may require a temperature in excess of 500°C (932°F). However, the issues of decomposition moisture and water of hydration of mineral matter are not usually dealt with in conventional analysis because the temperatures specified in the test methods for moisture determination are well below those needed to remove such moisture. 

A moisture determination can be carried out in the following manner Weigh duplicate samples of 5 g to the nearest 0.001 e into previously dried and weighed moisture cans with covers. Place the samples in an oven maintained at 105°C and beat for 4 hr. Cod in a desiccator and weigh. 

The sample for analysis is mixed with a spatula and quartered. The quarter reserved for analysis is rolled with a wooden rolling pin and then passed through a sieve with 2-mm round holes. Two samples of each soil are weighed out at the same time, a 10-g sample for analysis and a 5-g sample for moisture determination. The latter is dried at 105 deg C for 16 hrs, cooled in a desiccator, and weighed. The 10-g sample is placod in a 250-cu cm pyrex electrolytic beaker. 

To determine the effect of adding moisture to dried contaminated pages, 1 mL of the phosphate buffered saline solution at pH 7.0 was added to a section of each of several muddy-moldy pages before treatment with ethylene oxide. Swabs were taken from these selected areas before and after the gaseous treatment. Duplicate plates were made of all samples. 

Figure 26 Freeze-drying of cytostatica. The high desorption rate value (x) and the scattering of the residual moisture determined with the Karl Fischer method ( ) confirms that the transition phase from main drying to secondary drying was not finished after 22.5 h. The secondary drying could be terminated after 28 h. Product temperature (A).

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