A: Unbound pertechnetate—Apply a measured volume of Injection, appropriately diluted, such that it provides a count rate of about 20,000 counts per minute, about 10 mm from one end of a thin-layer chromatographic strip impregnated with silica gel (see Chromatography 621). Immediately develop the chromatogram over a suitable period by ascending chromatography, using methyl ethyl ketone as the solvent. Allow the chromatogram to dry. Determine the radioactivity distribution of the chromatogram by scanning with a suitable radiation detector. Not more than 10.0% of the total radioactivity is found at the solvent front as unbound pertechnetate.

B: Soluble 99mTc species—

Acetate buffer— Transfer 20.0 mL of 0.2 M acetic acid and 30.0 mL of 0.2 M sodium acetate to a 100-mL volumetric flask, dilute with water to volume, and mix.

Procedure— Transfer 1 mL of the Injection containing about 925 to 1110 MBq (25 to 30 mCi) to a 12-mL centrifuge tube, and add 4 mL of Acetate buffer. Determine the radioactivity with a suitable counting assembly. Centrifuge at a force of 34,600 g (gravity) for 15 minutes. Separate the supernatant, and determine its radioactivity. Correct both measurements for decay to the same reference time. Calculate the percentage of soluble 99mTc species taken by the formula: in which S is the radioactivity of the supernatant, and I is the radioactivity of the specimen before centrifuging. Not more than 10.0% of the total radioactivity is found in the supernatant.

Albumin reagent— Transfer 3.3 g of Poloxamer 188, 56.6 g of dibasic sodium phosphate, and about 800 mL of Water for Injection to a 1-liter volumetric flask, and mix. Add 120 mL of 25% Albumin Human, dilute with Water for Injection to volume, and mix. The pH of the resulting solution is 8.2 ± 0.7. Store at 2 to 8. Just prior to use, transfer 6.2 mL of this solution, measured at room temperature, to a 100-mL volumetric flask. Dilute with Sodium Chloride Injection to volume, and mix.

Procedure— Inject 0.5 mL of Injection into a 25-mL evacuated or nitrogen-filled vial. Inject 4.5 mL of Albumin reagent, and shake. Using a syringe, remove 0.2 mL of the resulting mixture, and attach the syringe by means of a locking-type connection to the top of a 25-mm filter housing assembly consisting of a 5.0-µm polycarbonate membrane filter on top followed by a distance of 3 cm by a 0.1-µm polycarbonate membrane filter. Pass the mixture through the filters, collecting the filtrate in a suitable container. Wash the filters by passing 12 mL of Albumin reagent through the filter housing assembly, adding the washing to the first filtrate. Using a suitable ionization chamber, measure the radioactivity in the filtrate and on each filter. Calculate the percentage of radioactivity retained on the 5.0-µm filter taken by the formula: in which F is the radioactivity on the filter, and T is the total radioactivity of each filter and filtrate: not more than 7.5% of the total radioactivity is retained on the 5.0-µm filter. Calculate the percentage of radioactivity retained on the 0.1-µm filter by the same formula: not less than 82.5% of the total radioactivity is retained, and not more than 10.0% of the total radioactivity passes through the 0.1-µm membrane.

100(A/B)

Procedure—

Acetate buffer— Transfer 20.0 mL of 0.2 M acetic acid and 30.0 mL of 0.2 M sodium acetate to a 100-mL volumetric flask, dilute with water to volume, and mix. Adjust by the addition, if necessary, of 0.2 M acetic acid or 0.2 M sodium acetate to a pH of 4.9 ± 0.1.

Basic acetate buffer— Transfer 50 mL of 1 N sodium hydroxide to a 500-mL volumetric flask. Dilute with Acetate buffer to volume, and mix.

Standard preparation— Using a “To contain” pipet, transfer 2.0 mL of 7 Percent Bovine Serum Albumin Certified Standard (see under Reagents in the section Reagents, Indicators, and Solutions), to a 250-mL volumetric flask. Rinse the pipet with Basic acetate buffer collecting the rinse in the volumetric flask. Dilute with Basic acetate buffer to volume, and mix.

Standard solutions— Into 5 separate graduated test tubes pipet 1, 2, 3, 4, and 5 mL of the Standard preparation. Dilute the first four with Basic acetate buffer to a final volume of 5.0 mL. Pipet 5 mL of Biuret Reagent TS into each tube, and mix. Incubate each at 37 ± 1 for 30 minutes. Allow to cool to room temperature. Determine the absorbances of the solutions in 1-cm cells at the wavelength of maximum absorbance at about 555 nm using a mixture of Basic acetate buffer and Biuret Reagent TS (1:1) as the blank. Plot the concentration, in mg per mL, versus the absorbance of each Standard solution and draw the best straight line through the points to obtain the standard curve.

Test preparation— Constitute the contents of each of 2 containers with 2.0 mL of Acetate buffer and allow to stand for 30 minutes. Transfer the contents of both containers to a centrifuge tube rinsing the containers with four 1-mL portions of Acetate buffer. Collect all the washings in the same centrifuge tube. Centrifuge the tube for 15 minutes at 4 at a force of 86,400 g (gravity). Quantitatively transfer the supernatant to a 50-mL volumetric flask. Add 5.0 mL of 1 N sodium hydroxide, dilute with Acetate buffer to volume, and mix. Pipet 5 mL of this solution into a test tube to obtain the Soluble albumin test solution. Dissolve the residue from the centrifugation in 5.0 mL of Basic acetate buffer to obtain the Insoluble albumin test solution. Treat each solution in the same manner as described under Standard solutions, beginning with “Pipet 5 mL of Biuret Reagent TS” and determine the absorbance of each solution as directed for Standard solutions. From the observed absorbance of each Test preparation, determine the concentration of total albumin from the standard curve. Multiply the concentration obtained for the Soluble albumin test solution by 25 to obtain the mg of soluble albumin per container. Multiply the concentration obtained for the Insoluble albumin test solution by 2.5 to obtain the mg of insoluble albumin per container.