Mobile phase, System suitability solution, Standard preparation, System sensitivity solution, and Chromatographic system— Proceed as directed in the Assay.

Test solution— Use the stock solution reserved from the Assay preparation.

Procedure— Inject a volume (about 10 µL) of the Test solution into the chromatograph, record the chromatogram, and measure the peak responses. Calculate the percentage of each impurity in the volume of Injection taken by the formula: in which ri is the peak response for each impurity, and rs is the sum of the responses of all of the peaks: not more than 1.0% of any individual impurity is found, and not more than 1.5% of total impurities is found.

Mobile phase— Dissolve 2.0 g of monobasic potassium phosphate in 800 mL of water. Add 5 mL of 1.0 M tetrabutylammonium dihydrogen phosphate solution, dilute with water to 980 mL, and mix. Add 20 mL of acetonitrile, mix, filter, and degas. Make adjustments if necessary (see System Suitability under Chromatography 621).

System suitability solution— Dissolve accurately weighed quantities of USP Adenosine RS and inosine in warm water (50 to 55), and dilute quantitatively, and stepwise if necessary, with water to obtain a solution having known concentrations of about 0.03 mg each of adenosine and inosine per mL.

Standard preparation— Dissolve an accurately weighed quantity of USP Adenosine RS in warm water (50 to 55), and dilute quantitatively, and stepwise if necessary, with water to obtain a solution having a known concentration of about 0.03 mg per mL. If sodium chloride is present in the Injection, add 0.01 mL of sodium chloride solution (0.9 in 100) per mL of the anticipated final volume of the Standard preparation before the addition of the warm water.

System sensitivity solution— Pipet 3.0 mL of the Standard preparation into a 200-mL volumetric flask, dilute with water to volume, and mix.

Assay preparation— Transfer an accurately measured volume of Injection, equivalent to about 30 mg of adenosine, to a 100-mL volumetric flask, dilute with water to volume, and mix. Reserve a portion of this stock solution for use in the test for Chromatographic purity. Pipet 5.0 mL of the stock solution into a 50-mL volumetric flask, dilute with water to volume, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm × 30-cm column that contains packing L1. The flow rate is about 2.5 mL per minute. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the tailing factor for the adenosine peak is not more than 2.0; and the resolution, R, between adenosine and inosine is not less than 6.0. Similarly chromatograph the Standard preparation: the relative standard deviation for replicate injections is not more than 1.5%. Chromatograph the System sensitivity solution, and adjust the run time to 2½ times the retention time of adenosine.

Procedure— Separately inject equal volumes (about 10 µL) of the Assay preparation and the Standard preparation into the chromatograph, record the chromatograms, and measure the areas of the adenosine peak responses. Calculate the quantity, in mg, of adenosine (C10H13N5O4) in each mL of the Injection taken by the formula: in which C is the concentration, in mg per mL, of USP Adenosine RS in the Standard preparation; D is the concentration, in mg per mL, of adenosine in the Assay preparation, based on the labeled quantity per mL and the extent of dilution; and rU and rS are the peak responses for adenosine obtained from the Assay preparation and the Standard preparation, respectively.