Simethicone Emulsion is a water-dispersible form of Simethicone composed of Simethicone, suitable emulsifiers, preservatives, and water. It may contain suitable viscosity-increasing agents. It contains an amount of polydimethylsiloxane ([(CH3)2SiO]n) that is NLT 85.0% and NMT 110.0% of the labeled amount of simethicone.
• Infrared Absorption 197A
[NoteUse the Blank to set the instrument. ]
Blank, Standard solution, and Sample solution: Prepare as directed in the Assay.
Analysis: Place a suitable amount of the Sample solution (typically 525 drops) in the sample trough, and dry it with a stream of nitrogen or other appropriate means to evaporate the solvent. Examine the spectrum in the range between 1400 cm1 and 700 cm1.
Acceptance criteria: It exhibits maxima only at the same wavelengths as a similarly obtained spectrum of the Standard solution.
[NoteUse glass apparatus only; avoid use of plasticware. Proper mixing of the Emulsion before sampling and testing is crucial. ]
Standard solution: 2 mg/mL of USP Polydimethylsiloxane RS in toluene. [NoteTreat a 25.0-mL aliquot in the same manner as the Blank, beginning with add 50 mL of dilute hydrochloric acid (2 in 5) . ]
Sample: Equivalent to 50 mg of simethicone from Emulsion
Sample solution: To the Sample add 25.0 mL of toluene, and treat in the same manner as the Blank, beginning with add 50 mL of dilute hydrochloric acid (2 in 5) .
Mode: IR spectrophotometry
Cell: 0.5 mm
Analytical wavelength: Maximum absorbance at about 7.9 µm (1259 cm1)
Blank: To 25.0 mL of toluene add 50 mL of dilute hydrochloric acid (2 in 5), close the bottle securely with a cap having an inert liner, vigorously shake by hand for 5 s, and then shake for 520 min on a suitable shaker. [NoteThe following shakers were found suitable: (1) a reciprocating shaker at a rate about 200 oscillations/min and a stroke of 38 ± 2 mm or (2) a wrist-action shaker with a radius of 13.3 ± 0.4 cm (measured from center of shaft to center of bottle) using an arc of 10 at a frequency of 300 ± 30 strokes/min. The recommended shaking time is about 20 min, which can be adjusted as needed. ] Centrifuge the mixture. [NoteThe following centrifuging conditions were found suitable: at 1500 × g for 3040 min. ] Remove from the centrifuge, and immediately transfer about 5 mL of the upper organic (toluene) layer to a 15-mL screw-capped test tube, containing about 1 g of anhydrous sodium sulfate. Close the tube with a screw-cap having an inert liner, agitate vigorously, and centrifuge the mixture until a clear supernatant is obtained. [NoteThe following centrifuging conditions were found suitable: at 1500 × g for about 10 min. ]
[NoteWash the cell with copious amounts of toluene, to ensure that there is no carryover or residue. ]
Samples: Standard solution, Sample solution, and Blank
Calculate the percentage of [(CH3)2SiO]n in the Emulsion:
Result = (AU/AS) × (CS/CU) × 100
Acceptance criteria: 85.0%110.0%
• Heavy Metals
Standard solution: To 20 mL of chloroform add 1.0 mL of a freshly prepared 0.002% solution of dithizone in chloroform, 0.5 mL of Standard Lead Solution (see Heavy Metals 231) (containing 10 µg of lead/mL), and 0.5 mL of a mixture of 1 volume of ammonia TS and 9 volumes of a 0.2% solution of hydroxylamine hydrochloride.
Sample solution: 1.0 g of simethicone from Emulsion in 10 mL of chloroform. Dilute with the same solvent to 20 mL. Add 1.0 mL of a freshly prepared 0.002% solution of dithizone in chloroform, 0.5 mL of water, and 0.5 mL of a mixture of 1 volume of ammonia TS and 9 volumes of a 0.2% solution of hydroxylamine hydrochloride.
Analysis: Immediately shake both solutions vigorously for 1 min.
Acceptance criteria: NMT 5 ppm. Any red color in the Sample solution is not more intense than that in the Standard solution.
• Microbial Enumeration Tests 61: The total aerobic microbial count does not exceed 100 cfu/g.
• Defoaming Activity
Foaming solution: 10 mg/mL of octoxynol 9 in water
Sample solution: Transfer a quantity of Emulsion, equivalent to 300 mg of simethicone, to a 60-mL bottle. Dilute with water to 30 g, cap the bottle, and shake vigorously.
[NoteFor each test, use a clean, unused, 250-mL glass jar. ]
Add, dropwise, 500 µL of the Sample solution to a clean, unused, cylindrical 250-mL glass jar, fitted with a 50-mm cap, containing 100 mL of the Foaming solution. Cap the jar, and clamp it in an upright position on a wrist-action shaker. Using a radius of 13.3 ± 0.4 cm (measured from the center of the shaft to the center of the bottle), shake for 10 s through an arc of 10 degrees at a frequency of 300 ± 30 strokes/min. Record the time required for the foam to collapse. The time, in s, for foam collapse is determined at the instant the first portion of foam-free liquid surface appears, measured from the end of the shaking period.
Acceptance criteria: The defoaming activity time does not exceed 15 s.
• Packaging and Storage: Preserve in tight containers.
• USP Reference Standards 11
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USP35NF30 Page 4638Pharmacopeial Forum: Volume No. 35(6) Page 1477