Activated Attapulgite

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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1 DEFINITION

Activated Attapulgite is a highly heat-treated, processed, native magnesium aluminum silicate.

2 IDENTIFICATION

A. X-Ray Powder Diffraction 〈941〉

Sample: 2 g

Analysis: Add the Sample in small portions to 100 mL of water, with vigorous agitation. Allow to stand for at least 12 h to ensure complete hydration. Place 2 mL of the resulting mixture on a suitable glass slide, and allow to air-dry at room temperature to produce a uniform film.Place the slide in a vacuum desiccator over a free surface of ethylene glycol. Evacuate the desiccator, and close the stopcock so that the ethylene glycol saturates the desiccator chamber. Allow to stand for 12 h. Record the X-ray diffraction pattern and calculate the d values.

Acceptance criteria: Several peaks are observed; the characteristic peak corresponds to a d value between 10.3 and 10.7 Å.

3 IMPURITIES

3.1 Loss on Ignition 〈733〉

Analysis: Ignite at 1000° for 1 h.

Acceptance criteria: 4.0%–12.0%

Delete the following:

3.2 Arsenic and Lead

Sample solution: 50 mg/mL of Activated Attapulgite prepared as follows. To 5.0 g add 50 mL of 1 N nitric acid, and boil for 30 min, adding 1 N nitric acid at times to maintain the volume. Filter into a 100-mL volumetric flask, wash the filter with water, and dilute the combined filtrate and washings with water to volume.

Instrumental conditions

Mode: Atomic absorption spectrophotometry equipped with graphite furnace

Atomization Source: Graphite furnace, as directed by the manufacturer of the instrument used

Analytical wavelength

Arsenic: 189.0 nm

Lead: 283.3 nm

Analysis

Sample: Sample solution

Determine the arsenic or lead in the solution against the corresponding standard

Acceptance criteria

Arsenic: NMT 2 ppm

Lead: NMT 0.001% (USP 1-Aug-2022)

3.3 Acid-Soluble Matter

Sample: 2.0 g

Analysis: Boil the Sample with 100 mL of 0.2 N hydrochloric acid for 5 min, and cool. Add water to adjust the volume to 100 mL, and filter.

Evaporate 50 mL of the filtrate so obtained to dryness. Ignite the residue at 600°.

Acceptance criteria: NMT 0.25 g (25%)

3.4 Carbonate

Sample: 1.0 g

Analysis: Mix the Sample with 15 mL of 0.5 N sulfuric acid.

Acceptance criteria: No effervescence occurs.

3.5 Volatile Matter

Analysis: Ignite at 600° for 1 h.

Acceptance criteria: 3.0%–7.5% on the dried basis

4 SPECIFIC TESTS

4.1 Loss on Drying 〈731〉

4.2 Analysis: Dry at 105° to constant weight.

Acceptance criteria: NMT 4.0%

Powder Fineness

Sample: 50 g

Analysis: Add the Sample to 450 mL of water containing 5 g of sodium pyrophosphate, and stir for 10 min. Pour the resulting dispersion slowly through a No. 325 standard sieve (see Particle Size Distribution Estimation by Analytical Sieving 〈786〉), and carefully wash the residue until clean. Dry the residue at 105° to constant weight.

Acceptance criteria: The dry weight of the residue is NMT 0.10% of the weight of the sample taken.

4.3 pH 〈791〉

Sample solution: 100 mg/mL of Activated Attapulgite prepared as follows. Disperse 1.0 g of Activated Attapulgite in 10 mL of carbon dioxide-free water, and mix.

Acceptance criteria: 7.0–9.5

4.4 Adsorptive Capacity

Barium chloride solution: 20 mg/mL of barium chloride in water

Methylene blue solution: 1 mg/mL of methylene blue in water

Standard solution: 1.5 μg/mL of methylene blue in water

Sample solution: Prepare a solution of 100 mg/mL of Activated Attapulgite in water. To 10 mL of this solution add 80 mL of Methylene blue solution, and shake. Add 10 mL of Barium chloride solution, and shake. Allow to stand for 15 min. Transfer 40 mL of the supernatant to a 50-mL centrifuge tube, and centrifuge. To 5 mL of the clear supernatant add 495 mL of water, and mix.

Analysis

Samples: Standard solution and Sample solution

Compare the color of the Sample solution to that of the Standard solution.

Acceptance criteria: The color of the Sample solution is not deeper than that of the Standard solution.

Microbial Enumeration Tests 〈61〉 and Tests for Specified Microorganisms 〈62〉: It meets the requirements of the test for absence of Escherichia coli.

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers.