Moisture determination Karl Fischer method

Dry the sieve and count and examine any particles remaining on the sieve. Brush any particles retained on No 60 sieve onto No 40 sieve. Note if the particles are grit as indicated by their lack of uniformity land a scratching noise when pressing and rubbing the material on a smooth glass slide with.a. smooth steel spatula. Report die number of particles on No 60 sieve and on No 40 sieve 4.4-3.1 Determination of Moisture Use Karl Fischer Method, described in MIL-STD-650 as Method 101.4, with methanol as the special solvent. A detailed description... 

Ibid, E170 (Electrolytic Hygrometer Method) Ibid, E171-L to E172-L (Moisture Determination in Propellants and Explosives by Distillation Method) Ibid, E172-L to E173-L (Moisture Determination in Propellants and Explosives by the Karl Fischer Method)... 

MOISTURE.dat Section 4.4 At 10 selected locations inside a dryer samples of eight tablets each were drawn to determine water content by the Karl Fischer method using MULTI, the hypothesis Ho is tested that all 10 sample means and standard deviations are indistinguishable. 

Borer et al. developed a NIR method to determine moisture in a highly hygroscopic product. Because the sample absorbed water very rapidly (0.02%/min), use of the Karl Fischer method as reference was very complicated. This led them to the choice of NIR spectroscopy, where the sample can be kept inside a sealed vial instead. Analyses were completed within a few seconds and the samples not exposed to ambient air at any time, which prevented moisture absorption and the ensuing determination errors. 

Ammonium chloride is analyzed by treatment with formaldehyde (neutralized with NaOH) and the product HCl formed is analyzed by titration using an acid-base color indicator such as phenolphthalein. Alternatively, it may be mixed with caustic soda solution and distdled. The distillate may be analyzed for NH3 by titration with H2SO4 or by colorimetric Nesslerization or with an ammonia-selective electrode (APHA, AWWA, WEF. 1995. Standard Methods for the Examination of Water and Wastewater. 19th ed. Washington, DC, American Pubhc Health Association). The presence of ammonia or any other ammonium compound would interfere in the test. The moisture content in NH4CI may be determined by Karl—Fischer method. 

Karl Fischer Method for Determination of Moisture. See under Dynamites in Vol 5, p D1622-L and under Ethanol in Vol 6, p E158-R... 

III. Moisture Determination in Propellants and Explosives by Karl Fischer Method 101,5, Prescribed by MIL-STD-286B (1 Dec 1967). Detailed description of Fischer method as applied to various substances is given in the following works ... 

The chemical methods of water determination invoke the concepts of direct titration of the water or a chemical reaction between the water and specific reagents that causes the evolution of gases the water is determined by measurement of the volume produced. Chemical methods used for determining moisture also include (1) application of the Karl Fischer method of determining water content, and (2) reaction of quicklime with water in coal and subsequent measurement of the heat generated by the reaction. 

The authors concluded that water which cannot be removed at 100 °C is bound in such a way that it cannot jeopardize the pharmaceutical product. Only the free water can diffuse from the stopper to the product. The moisture content is measured by the Karl Fischer method with different temperatures in the oven, 100 °C to determine the free water content and up to 300 °C to measure the free and bound water. The authors suggested developing a similar program for other stoppers, since the time for such measurements is relatively short (1 week) instead of observing the RM in a product over long times. Table 1.15.2 summarizes the results with the stoppers described above. Table 1.15.3 lists the limits of the free moisture content in 2 types of stoppers and for different cake weights under the assumption that a maximum RM increase of 0.5% in the product is acceptable. 

Using an Existing Method. This is the easiest of the three method-generation options. An example of this would be the use of a Karl Fischer method developed for moisture determination in DS hydrochloride being used in DS sulfate. Regardless of the apparent suitability, the decided use of an existing method must be confirmed with method-feasibility experiments. 

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).

The methods for the determination of residual moisture currently used at the Center for Biologies Evaluation and Research at the U.S. FDA are the gravimetric (loss on drying) method, the Karl Fischer method, and the thermogravimetric (TG) and thermogravimetric/mass spectrometric (TG/MS) method. Current work in progress involves the use of vapor pressure moisture measurements to provide additional information about residual moisture content and its interaction with the components of the freeze-dried final container and its contents. 

In order to determine the endpoint of the process, many procedures have been suggested, including pressure rise measurement, the Karl Fischer method, weight curves, vapor tension, moisture equilibration, nuclear magnetic resonance, and dielectric measurement. 

This study of methods to determine the moisture content of humic substances has yielded no absolute values for moisture content. The loss on drying shows no end point for water loss and the potential interferences of the Karl Fischer titration prevent definition of absolute values. Certainly, additional research needs to be done in this area. For example, techniques such as NMR and IR might be utilized to define and correlate the moisture status of these substances. In many cases it is sufficient to have a reference point to bring these substances to for comparison purposes. Based on Figure 1, loss on drying at 60°C should be the most consistent reference point, however, the interlaboratory study results showed very poor agreement. Based on this limited study we conclude that the Karl Fischer method gives more consistent results on these samples. 

The moisture content of seeds has been determined (Hart et al., 1962) by near-infrared spectrophotometry of their methanol extracts. The absorbance of water at 1.93 fi was used. The standard deviation of the results from those obtained by titration with Karl Fischer reagent was +0.24%. The infrared method was more rapid and less exacting than the Karl Fischer method. 

Karl Fischer method This is primarily used for low-moisture products and is suitable for determining moisture in dried vegetables and legumes. This sensitive titration method is based on the nonstoichio-metric reaction of water with iodine and sulfur dioxide in pyridine/methanol solution. 

To conduct a water sorption study, the product was stored in desiccators with solid salt or saturated salt solutions for 48 h of equilibration at an ambient temperature (Figure 8). The salts included phosphorus pentoxide, lithium chloride, potassium acetate, magnesium chloride, potassium carbonate, and sodium chloride, which generated relative humidities of, approximately, 0, 11, 23, 33, 43, and 75%, respectively. The vials were sealed immediately after equilibration. The moisture in the lyophilized product was determined by the Karl Fischer method. 

As part of this development work, residual moisture is routinely measured by the Karl Fischer method (in a dry box as recommended by May et al. [13], see Section III.B), with control liquid samples of known moisture, to determine the residual moisture in the freeze-dried material. See Table 3 which shows residual moistures of some of the materials established by ECBS in the year 1999/2000, and Figure 2 which shows the reproducibility and variability of the control liquid of known moisture. 

A minimum of six of the ampoules/vials used for check weighing are marked and numbered at intervals throughout the fill to determine the dry weight (by weighing before filling and after freeze drying and/or further desiccation) of the final material. These samples are used to determine the percentage residual moisture content of the freeze-dried material by the Karl Fischer method. 

The most common method for the determination of moisture in botanical materials and dry flavorings is the Karl Fischer. The Karl Fischer method is based on the titration of water in the sample with the Karl Fischer reagents as noted below... 

Applications The coulometric Karl Fischer titration is a widely used moisture determination method (from ppm to 100%). In the presence of water, iodine reacts with sulfur dioxide through a redox process, as follows ... 

The water (moisture) content can rapidly and accurately be determined in polymers such as PBT, PA6, PA4.6 and PC via coulometric titration, with detection limits of some 20 ppm. Water produced during heating of PET was determined by Karl Fischer titration [536]. The method can be used for determining very small quantities of water (10p,g-15mg). Certified water standards are available. Karl Fischer titrations are not universal. The method is not applicable in the presence of H2S, mercaptans, sulfides or appreciable amounts of hydroperoxides, and to any compound or mixture which partially reacts under the conditions of the test, to produce water [31]. Compounds that consume or release iodine under the analysis conditions interfere with the determination. 

The near-IR technique has been used very successfully for moisture determination, whole tablet assay, and blending validation [23]. These methods are typically easy to develop and validate, and far easier to run than more traditional assay methods. Using the overtone and combination bands of water, it was possible to develop near-IR methods whose accuracy was equivalent to that obtained using Karl-Fischer titration. The distinction among tablets of differing potencies could be performed very easily and, unlike HPLC methods, did not require destruction of the analyte materials to obtain a result. 

Thermogravimetry (TG) is a measure of the thermally induced weight loss of a material as a function of the applied temperature [39], Thermogravimetric analysis is restricted to studies involving either a mass gain or loss, and it is most commonly used to study desolvation processes and compound decomposition. Thermogravimetric analysis is a very useful method for the quantitative determination of the total volatile content of a solid, and it can be used as an adjunct to Karl Fischer titrations for the determination of moisture. 

The amount of water present is fundamental to the stability of confectionery products. Unsurprisingly, therefore, measuring water content is an important exercise. Various methods are used. Some oven drying moisture content determinations are still carried out. This sort of work is difficult since the moisture contents are normally low and the samples can only be dried with difficulty. In particular, there are problems in drying the product in a reasonable time without charring it. Various other methods of water content determination are in use. One such is the Karl Fischer titration. 

The Karl Fischer titration is a generally accepted method for the determination of moisture in a sample [2],... 

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