Solution: 27 µg per mL.

Medium: 0.1 M hydrochloric acid.

Mobile phase— Prepare as directed in the Assay.

Standard solution— Prepare as directed for Standard preparation in the Assay under Fludarabine Phosphate.

System suitability solution— Prepare as directed for System suitability solution in Chromatographic purity Test A under Fludarabine Phosphate.

Sensitivity check solution— Dilute the Standard solution with Mobile phase to obtain a solution having a concentration of 0.0005 mg per mL.

Test solution— Inject 2.0 mL of water into each of 5 vials of Fludarabine Phosphate for Injection. Quantitatively transfer the contents of the vials into a single 250-mL volumetric flask, using water rinses. Dilute the volumetric flask with Mobile phase to volume, and mix to obtain a solution having a concentration of about 1 mg of fludarabine phosphate per mL.

Chromatographic system— Proceed as directed for Chromatographic system in Chromatographic purity Test A under Fludarabine Phosphate.

Procedure— Separately inject equal volumes (about 10 µL) of the Standard solution and the Test solution, record the chromatograms, and measure all of the peak responses up to and including the fludarabine phosphate peak. Calculate the percentage of each early-eluting impurity present in the portion of Fludarabine Phosphate taken by the formula: in which F1 is a relative response factor equal to the values given in Table 1, and equal to 1.0 for any other individual early-eluting degradation product not appearing in Table 1; rU is the response for each individual impurity in the Test solution; and rS is the response for the fludarabine phosphate peak in the Test solution. In addition to meeting the limits for the individual degradation products given in Table 1, not more than 0.2% of any other early-eluting fludarabine phosphate degradation peak is found.

Mobile phase— Prepare a mixture of filtered, degassed 10 mM monobasic potassium phosphate and methanol (4:1).

Standard solution, System suitability solution, and Sensitivity check solution— Prepare as directed for Chromatographic purity Test A under Fludarabine Phosphate.

Test solution— Prepare as directed for Related compounds Test A.

Chromatographic system— Proceed as directed for Chromatographic purity Test B under Fludarabine Phosphate.

Procedure— Separately inject equal volumes (about 10 mL) of the Standard solution and the Test solution, record the chromatograms at 260 nm, and measure all of the peak responses starting with the fludarabine phosphate peak. Calculate the percentage of each late-eluting impurity present in the portion of Fludarabine Phosphate taken by the formula: in which F2 is a relative response factor equal to the values given in Table 1, and 1.0 for any other individual late-eluting degradation peak not appearing in Table 1; rU is the response for each individual impurity in the Test solution; and rS is the response for the fludarabine phosphate peak in the Test solution. In addition to meeting the limits for the individual degradation products given in Table 1, not more than 0.2% of any other late-eluting fludarabine phosphate degradation product is found; and the sum of all fludarabine phosphate degradation products found in Test A and Test B is not more than 2.0%.

2500C(rU / rS)