Spectral range: 240 to 450 nm.

Solution: 10 µg per mL.

Medium: methanol.

Solution A: a 0.1% (w/v) solution of monobasic potassium phosphate adjusted with 1 N sodium hydroxide to a pH of 6.0.

Solution B: methanol.

Mobile phase— Use variable mixtures of Solution A and Solution B as directed for Chromatographic system. Make adjustments if necessary (see System Suitability under Chromatography 621).

System suitability solution— Transfer about 4 mg of USP Meloxicam RS and about 4 mg each of USP Meloxicam Related Compound A RS and USP Meloxicam Related Compound B RS into a 50-mL volumetric flask, dissolve in 5 mL of methanol and 0.3 mL of 1 N sodium hydroxide, dilute with methanol to volume, and mix.

Standard solution— Transfer about 12 mg of USP Meloxicam RS, accurately weighed, to a 20-mL volumetric flask, dissolve in 5 mL of methanol and 0.3 mL of 1 N sodium hydroxide, dilute with methanol to volume, and mix. Transfer 2 mL of this solution to a 100-mL volumetric flask, dilute with methanol to volume, and mix.

Test solution— Transfer about 80 mg of Meloxicam, accurately weighed, to a 20-mL volumetric flask, dissolve in 5 mL of methanol and 0.3 mL of 1 N sodium hydroxide, dilute with methanol to volume, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a variable wavelength or multi-wavelength UV detector and a 4.6-mm × 15-cm column that contains 5-µm packing L1. The column temperature is maintained at 45. The flow rate is about 1 mL per minute, and the detection wavelengths are 260 nm and 350 nm. The chromatograph is programmed as follows. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the relative retention times based on the meloxicam peak at about 7 minutes are listed in Table 1. At 350 nm, the resolution, R, between meloxicam related compound A and meloxicam is not less than 3.0; at 260 nm, the resolution, R, between meloxicam related compound B and meloxicam is not less than 3.0. Chromatograph the Standard solution, and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 10%.

Procedure— Separately inject equal volumes (about 5 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms at detection wavelengths of 260 nm and 350 nm, and measure the peak responses. Calculate the percentage of each impurity in the portion of Meloxicam taken by the formula: in which CS is the concentration, in mg per mL, of USP Meloxicam RS in the Standard solution; CT is the concentration, in mg per mL, of Meloxicam in the Test solution; F is the relative response factor (see Table 1); rU is the peak response of each impurity obtained from the Test solution; and rS is the peak response of meloxicam at 350 nm obtained from the Standard solution. [note—For the specified impurities, calculate the percentage content of each impurity, using the Test solution peak responses recorded at the detection wavelength given in Table 1. For an unknown impurity, calculate the percentage content, using peak responses recorded at the wavelength that gives the greater response.]

Solution A and Solution B— Prepare as directed in Test 1.

Mobile phase— Use variable mixtures of Solution A and Solution B as directed for Chromatographic system. Make adjustments if necessary (see System Suitability under Chromatography 621).

Diluent A: a mixture of Diluent B and 0.4 N sodium hydroxide (50:3).

Diluent B: a mixture of water and methanol (60:40).

Standard stock solution 1— Prepare a solution having a known concentration of about 50 µg per mL of USP Meloxicam RS in Diluent A. Transfer 2 mL of the solution to a 10-mL volumetric flask, dilute with Diluent B to volume, and mix.

Standard stock solution 2— Transfer about 5 mg each of USP Meloxicam Related Compound B RS, USP Meloxicam Related Compound C RS, and USP Meloxicam Related Compound D RS into a 100-mL volumetric flask, add 6 mL of 0.4 N sodium hydroxide, and sonicate for about 2 minutes. Add 40 mL of methanol to the resulting solution, sonicate for about 2 minutes, dilute with water to volume, and mix.

Standard solution— Transfer 1 mL each of Standard stock solution 1 and Standard stock solution 2 into a 10-mL volumetric flask, dilute with Diluent B to volume, and mix.

System suitability stock solution— Prepare a solution containing about 2 mg per mL of USP Meloxicam RS in Diluent A.

System suitability solution— Transfer 5 mL of System suitability stock solution and 1 mL of Standard stock solution 2 into a 10-mL volumetric flask, dilute with Diluent B to volume, and mix.

Test solution— Transfer about 20 mg of Meloxicam, accurately weighed, to a 20-mL volumetric flask, dissolve in 10 mL of Diluent A, dilute with Diluent B to volume, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a variable wavelength or multi-wavelength UV detector and a 4.6-mm × 25-cm column that contains 5-µm packing L1. The column temperature is maintained at 45. The flow rate is about 1 mL per minute and the detection wavelengths are 260 nm and 350 nm. The chromatograph is programmed as follows. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the relative retention times based on the meloxicam peak at about 5 minutes are listed in Table 2; and the resolution, R, between meloxicam related compound D and meloxicam at 350 nm is not less than 5.0. Chromatograph the Standard solution, and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 5.0% for meloxicam related compound C and for meloxicam related compound D at 350 nm; and not more than 5.0% for meloxicam related compound B at 260 nm.

Procedure— Separately inject equal volumes (about 20 µL) of the Standard solution and Test solution into the chromatograph, record the chromatograms at detection wavelengths of 260 nm and 350 nm, and measure the peak responses. Calculate the percentage of each impurity in the portion of Meloxicam taken by the formula: in which CS is the concentration, in mg per mL, of the corresponding USP Related Compound RS in the Standard solution [note—Use the concentration of the USP Meloxicam RS for unknown impurities.]; CT is the concentration, in mg per mL, of Meloxicam in the Test solution; rU is the peak response of each impurity obtained from the Test solution; and rS is the peak response of the corresponding related compound obtained from the Standard solution. [note—Use the peak response of the USP Meloxicam RS for unknown impurities; for the specified impurities, calculate the percentage content of each impurity using the Test solution peak responses recorded at the detection wavelength given in Table 2. For an unknown impurity, calculate the percentage content using peak responses recorded at the wavelength that gives the greater response.]

100C(rU / rS)