» Methylene Chloride contains not less than 99.0 percent of CH2Cl2.
Caution Perform all steps involving evaporation of methylene chloride in a well-ventilated fume hood.
Packaging and storage Preserve in tight containers.
Identification Place about 5 mL into a glass-stoppered, 10-mL conical flask, and shake for several minutes. Remove the stopper, quickly withdraw a portion of the vapor into a 50-mL syringe that is not fitted with a needle, and inject the vapor into a suitable evacuated gas cell: the IR absorption spectrum of the vapor shows strong doublet peaks at 7.8 µm and 7.9 µm and at 13.2 µm and 13.4 µm, and relatively few minor peaks.
Specific gravity 841: between 1.318 and 1.322.
Water, Method I 921: not more than 0.02%.
Limit of hydrogen chloride Into each of 2 glass-stoppered, 50-mL color-comparison cylinders having an internal diameter of 20 mm place 10 mL of water, 2 drops of phenolphthalein TS, and sufficient 0.010 N sodium hydroxide to produce a pink color that persists after vigorous shaking for 30 seconds, and is of equal intensity in each cylinder. [noteIn the following steps, take special care to avoid contamination with carbon dioxide.] Into one of the cylinders place 20.0 mL of Methylene Chloride and 0.70 mL of 0.010 N sodium hydroxide, and shake again. The pink color in the test cylinder is at least as intense as that in the comparison cylinder, and the color persists for not less than 15 minutes (0.001%).
Limit of nonvolatile residue Evaporate 50 g in a platinum or porcelain dish on a steam bath, and dry at 105 for 30 minutes: the weight of the residue does not exceed 1 mg (0.002%).
Heavy metals, Method I 231 Evaporate 15 mL (20 g) in a glass evaporating dish on a steam bath to dryness. Cool, add 2 mL of hydrochloric acid, and slowly evaporate again on a steam bath to dryness. Dissolve the residue in 1 mL of 1 N acetic acid, add 24 mL of water, and mix: the limit is 1 ppm.
Free chlorine To 10 mL add 10 mL of water and 0.1 mL of potassium iodide TS, shake for 2 minutes, and allow the liquids to separate: the lower layer does not show a violet tint.
Chromatographic system Under typical conditions, the instrument is equipped with a thermal conductivity detector, and contains a 4-mm × 1.8-m column packed with 15% liquid phase G18 on 30- to 60-mesh S1C unsilanized support. The temperatures of the column, the injection port, and the detector are maintained at 60, 200, and 250, respectively; and helium is used as the carrier gas, at a flow rate of about 20 mL per minute.
System suitability Chromatograph five 1-µL injections of a mixture of 3 mL of methylene chloride with 7 mL of chloroform. The relative standard deviation of the peak response ratio does not exceed 2%, the resolution factor is not less than 4.0, and the tailing factor is not more than 1.4 (see Chromatography 621).
Procedure Inject about 1 µL of Methylene Chloride, and determine the peak responses by any convenient means. The order of elution is amylenes (5 or 6 peaks), if present, and then methylene chloride. Calculate the percentage of CH2Cl2 in the Methylene Chloride by dividing the response due to the methylene chloride by the sum of the responses for all the peaks and multiplying by 100.
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USP32NF27 Page 1282
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.