Cyclohexane, 1,2,3,4,5,6-hexachloro-, (1,2,3,4,5,6)-.
» Lindane is the gamma isomer of hexachlorocyclohexane. It contains not less than 99.0 percent and not more than 101.0 percent of lindane (-C6H6Cl6).
Packaging and storage Preserve in well-closed containers.
USP Reference standards 11
Identification, Infrared Absorption 197K.
Congealing temperature 651: not less than 112.0.
Water, Method I 921: not more than 0.5%.
Chloride ion Place about 100 mg in a test tube with 10 mL of water, shake, and filter. Add 1 mL of nitric acid and 3 mL of silver nitrate TS to the filtrate: no turbidity develops.
Internal standard solution Dissolve n-octadecane in methylene chloride to obtain a solution having a concentration of about 0.5 mg per mL.
Standard preparation Dissolve an accurately weighed quantity of USP Lindane RS in Internal standard solution to obtain a solution having a known concentration of about 2 mg per mL.
System suitability solution Prepare solutions of -benzene hexachlorides (BHC) at 1000 µg per mL of methanol, -BHC at 1000 µg per mL of acetone, and -BHC at 1000 µg per mL of methanol. Transfer 100 µL each of -BHC, -BHC and -BHC solutions to a 4-mL conical vial, and evaporate under a stream of nitrogen to dryness. Add to the vial a 100-µL aliquot of the Standard preparation. Insert the stopper, and shake vigorously to dissolve the residue.
Assay preparation Transfer about 10 mg of Lindane, accurately weighed, to a 5-mL volumetric flask. Dissolve in and dilute with Internal standard solution to volume.
Chromatographic system (see Chromatography 621)The gas chromatograph is equipped with a flame-ionization detector and a 0.32-mm×30-m fused-silica column coated with a 1-µm phase G46. The chromatograph is programmed as follows. The initial column temperature is maintained at 120 for 1 minute. Then, the temperature is increased at a rate of 20 per minute to 150, and then ramped at a rate of 10 per minute to 280 and maintained at that temperature for 4 minutes. The injection port and detector temperatures are maintained at 300. The injection split ratio is 50:1. Chromatograph the Standard preparation and the System suitability solution, and record the peak responses as directed for Procedure: the relative retention times for n-octadecane and lindane are about 0.85 and 1.0, respectively. [noteTypical retention times for -BHC, -BHC, -BHC, -BHC, and n-octadecane are 15.7, 17.8, 16.5, 18.8, and 13.9 minutes, respectively. ] The resolution, R, between n-octadecane and -BHC is not less than 21, between lindane (-BHC) and -BHC is not less than 9, between -BHC and lindane is not less than 14, and between -BHC and -BHC is not less than 8; the tailing factors for n-octadecane and lindane are less than 1.5 and 1.2, respectively; and the relative standard deviation of the ratios of peak area responses of lindane to n-octadecane for replicate injections of Standard preparation is not more than 1.5%.
Procedure Separately inject equal volumes (about 1 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of -C6H6Cl6 in the portion of Lindane taken by the formula:
5C(RU / RS)in which C is the concentration, in mg per mL, of USP Lindane RS in the Standard preparation; and RU and RS are the ratios of the peak responses of lindane to n-octadecane, obtained from the Assay preparation and the Standard preparation, respectively.
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