USP 35Chemical Tests / 〈281〉 Residue on Ignition 151
CONTROL OF THE INSTRUMENT’S
PERFORMANCE鼻子山根>和谐城市
As the mercury porosimetry technique is considered as a comparative test, no details are given in this chapter. How-ever, it is recommended that a stable comparison material should be tested on a regular basis to monitor instrument calibration and performance.v USP35
Figure 2. Volume–pressure curve as milogarithmic plot.
〈271〉 READILY CARBONIZABLE
SUBSTANCES TEST
REPORTING OF RESULTS管理是什么意思
The pressure readings are converted to pore diameter by In tests for readily carbonizable substances, unless other-means of the Washburn equation or by another model.wi directed, add the specified quantity of the substance,The surface tension of mercury, σ, depends not only on finely powdered if in solid form, in small portions to the the temperature and the material, but also—in the ca of comparison container, which is made of colorless glass resis-markedly curved surface areas—on the radius of curvature.tant to the action of sulfuric acid and contains the specified In general, values between 0.41 N ·m –1 and 0.52 N ·m –1volume of sulfuric acid (e under Reagent Specifications in are measured at room temperature. If the value is not the ction Reagents, Indicators, and Solutions ).
known, σ = 0.48 N ·m –1 can be ud.
Stir the mixture with a glass rod until solution is com-The contact angle of mercury θ in most cas is more plete, allow the solution to stand for 15 minutes, unless than 90°. It may be determined using a contact angle in-otherwi directed, and compare the color of the solution strument. If the θ value is not known, 130° can be ud.with that of the specified Matching Fluid (e Color and Report the values of contact angle, surface tension, and the Achromicity 〈631〉) in a comparison container, which also is model ud in the calculation. Visualization of the data can of colorless glass and has the same internal and cross-c-be done with veral types of graphs. Frequently, in a tion dimensions, viewing the fluids transverly against a graphical reprentation, the pore diameter is plotted on background of white porcelain or white glass.
the abscissa and the dependent intruded specific volume on When heat is directed in order to effect solution of the the ordinate to give the pore size distribution. It is appropri-substance in the sulfuric acid, mix the sample and the acid ate here to choo a logarithmic scale for the abscissa (e in a test tube, heat as directed, and transfer the solution to Figure 3). The spaces between the particles of the solid sam-the comparison container for matching with the designated ple are included as pores in the calculation. If the pores Matching Fluid (e Color and Achromicity 〈631〉).
differ in size from the voids, the latter can be parated by choosing the relevant pore size range.最强病毒
Extrusion curves may not be ud for calculating the pore size distribution (for hysteresis, e Figure 2), becau an in-truded part of the mercury always remains in the pore sys-tem. The retention ratio may be uful for the qualitative characterization of pores that are only accessible via narrow openings (“ink-bottle pores”).
〈281〉 RESIDUE ON IGNITION
The most common characteristic values, such as the total intruded specific volume, the mean, and the median pore diameter are calculated from the pore size distribution.Portions of this general chapter have been harmonized Moreover, sufficient information should be documented with the corresponding texts of the European Pharmacopoeia about the sample, the sample preparation, the evacuation and the Japane Pharmacopoeia . The portions that are not conditions, and the instrument ud.
harmonized are marked with symbols (33). The harmonized texts of the pharmacopeias are therefore interchangeable,and the methods of the European Pharmacopoeia and/or the Japane Pharmacopoeia may be ud for demonstration of compliance instead of the prent United States Pharmaco-
peia general chapter. The pharmacopeias have undertaken not to make any unilateral change to this harmonized chapter.
如何种菜
The Residue on Ignition/Sulfated Ash test us a procedure to measure the amount of residual substance not volatilized from a sample when the sample is ignited in the prence of sulfuric acid according to the procedure described below.This test is usually ud for determining the content of inor-ganic impurities in an organic substance.
Figure 3. Pore volume distribution as milogarithmic plot.
Procedure—Ignite a suitable crucible (for example, silica,platinum, quartz, or porcelain) at 600±50° for 30 minutes,cool the crucible in a desiccator (silica gel or other suitable desiccant), and weigh it accurately. Weigh accurately 31 to 2g of the substance, or 3 the amount specified in the indi-vidual monograph, in the crucible.
152〈281〉 Residue on Ignition / Chemical Tests USP 35
Moisten the sample with a small amount (usually 1 mL) of mL of water. Transfer the solution with the aid of about 20 sulfuric acid, then heat gently at a temperature as low as mL of water to a 150-mL beaker, and heat gently to the practicable until the sample is thoroughly charred. Cool;boiling temperature. Boil for 10 minutes, and allow the solu-then,3unless otherwi directed in the individual tion to cool to room temperature.
monograph,3 moisten the residue with a small amount (usu-Procedure—Treat the Standard Solution, the Test Solution, ally 1 mL) of sulfuric acid; heat gently until white fumes are and the reagent blank consisting of 25 mL of dilute nitric no longer evolved; and ignite at 600±50°, 3unless another acid (1 in 30) and 25 mL of water, concomitantly and in temperature is specified in the individual monograph,3 until parallel, as follows. Add ammonium hydroxide solution (1 in the residue is completely incinerated. Ensure that flames are2) to adjust to a pH of 2.0 ± 0.2. Dilute with water to 60 not produced at any time during the procedure. Cool the mL, and transfer to a low-actinic parator with the aid of crucible in a desiccator (silica gel or other suitable desic-10 mL of water, adding the 10 mL of rinsings to the cant), weigh accurately, and calculate the percentage of parator. Add 200 mg of hydroxylamine hydrochloride, residue.swirl to dissolve, immediately add 5.0 mL of Diami-
Unless otherwi specified, if the amount of the residue so nonaphthalene Solution, inrt the stopper, and swirl to mix. obtained exceeds the limit specified in the individual mono-Allow the solution to stand at room temperature for 100 graph, repeat the moistening with sulfuric acid, heating and minutes. Add 5.0 mL of cyclohexane, shake vigorously for 2 igniting as before, using a 30-minute ignition period, until minutes, and allow the layers to parate. Discard the aque-two concu
tive weighings of the residue do not differ by ous layer, and centrifuge the cyclohexane extract to remove more than 0.5 mg or until the percentage of residue com-any disperd water. Determine the absorbances of the cy-plies with the limit in the individual monograph.clohexane extracts of the Test Solution and the Standard So-3Conduct the ignition in a well-ventilated hood, but pro-lution in a 1-cm cell at the wavelength of maximum absorb-tected from air currents, and at as low a temperature as is ance at about 380 nm, with a suitable spectrophotometer, possible to effect the complete combustion of the carbon. A using the cyclohexane extract of the reagent blank as the muffle furnace may be ud, if desired, and its u is recom-blank, and compare the absorbances: the absorbance of the mended for the final ignition at 600±50°.Test Solution is not greater than that of the Standard Solution Calibration of the muffle furnace may be carried out using where a 200-mg test specimen has been taken, or is not
an appropriate digital temperature meter and a working greater than one-half that of the Standard Solution where a thermocouple probe calibrated against a standard thermo-100-mg test specimen has been taken.
couple traceable to the National Institute of Standards and
Technology.
Verify the accuracy of the measuring and controlling cir-
cuitry of the muffle furnace by checking the positions in the O THER T ESTS AND A SSAYS furnace at the control t point temperature of intended
u. Select positions that reflect the eventual method of u
with respect to location of the specimen under test. The
tolerance is ±25° at each position measured.3
〈301〉 ACID-NEUTRALIZING
CAPACITY
〈291〉 SELENIUM
NOTE—All tests shall be conducted at a temperature of
37±3°.
Standardization of pH Meter—Standardize a pH meter Stock Solution—Dissolve 40.0 mg of metallic lenium using the 0.05 m potassium biphthalate and 0.05 m potas-
in 100 mL of dilute nitric acid (1 in 2) in a 1000-mL volu-sium tetraoxalate standardizing buffers as described under metric flask, warming gently on a steam bath if necessary to pH 〈791〉.
effect solution, add water to volume, and mix. Pipet 5 mL
Magnetic Stirrer—Transfer 100 mL of water to a 250-mL of this solution into a 200-mL volumetric flask, add water to
beaker containing a 40- × 10-mm (or other suitable size) volume, and mix. Each mL of the resulting solution contains
magnetic stirring bar that is coated with solid perfluoro-
the equivalent of 1 µg of lenium (Se).
carbon and has a spin ring at its center. Adjust the power Diaminonaphthalene Solution—Dissolve 100 mg of 2,3-tting of the magnetic stirrer to produce a stirring rate of
diaminonaphthalene and 500 mg of hydroxylamine hydro-300±30 rpm when the stirring bar is centered in the chloride in 0.1 N hydrochloric acid to make 100 mL. Pre-beaker, as determined by a suitable optical tachometer. pare this solution fresh on the day of u.
Test Preparation—
梦见糕点Standard Solution—Pipet 6 mL of Stock Solution into a
Powders—Transfer the accurately weighed portion of the 150-mL beaker, and add 25 mL of dilute nitric acid (1 in
substance specified in the individual monograph to a 250-30) and 25 mL of water.
mL beaker, add 70 mL of water, and mix on the Magnetic Test Solution—Clean combustion of the test material is Stirrer for 1 minute.
an important factor in conducting the test. For compounds
Effervescent Solids—Transfer an accurately weighed quan-that burn poorly and produce soot, the addition of magne-
鹿茸食用tity, equivalent to the minimum labeled dosage, to a 250-sium oxide usually results in more thorough combustion
mL beaker, add 10 mL of water, and swirl the beaker gently and reduces soot formation. Where the need to add magne-
while allowing the reaction to subside. Add another 10 mL sium oxide has been identified, it is specified in the individ-
of water, and swirl gently. Wash the walls of the beaker
ual monograph. Using a 1000-mL combustion flask and us-
with 50 mL of water, and mix on the Magnetic Stirrer for 1 ing 25 mL of dilute nitric acid (1 in 30) as the absorbing
minute.
liquid, proceed as directed under Oxygen Flask Combustion
〈471〉, using a test specimen weighing 100 to 200 mg, un-Suspensions and Other Liquids—Shake the container until less directed otherwi in the individual monograph. Upon the contents are uniform, and determine the density. Trans-completion of the combustion, place a few mL of water in fer an accurately weighed quantity of the uniform mixture, the cup, loon the stopper, and rin the stopper, the equivalent to the minimum labeled dosage, to a 250-mL specimen holder, and the sides of the flask with about 10
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