Lactobionic Acid

C12H22O12 (acid form) 358.3 [96-82-2].
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C12H20O11 (-lactone) 340.3 [5965-65-1].
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4-O--Galactopyranosyl-d-gluconic acid.    
Lactobionic Acid is a mixture in variable proportions of 4-O--d-galactopyranosyl-d-gluconic acid and 4-O--d-galactopyranosyl-d-glucono-1,5-lactone. It contains NLT 98.0% and NMT 102.0%, on the anhydrous basis.
•  A. Infrared Absorption 197K: [Note—If the spectra obtained show differences, dissolve the test substance and USP Lactobionic Acid RS separately in water, dry at 105, and record new spectra using the residues. ]
•  B. Thin-Layer Chromatography 621
Standard solution:  10 mg/mL of USP Lactobionic Acid RS
Sample solution:  10 mg/mL of Lactobionic Acid
Adsorbent:  Chromatographic silica gel mixture with an average particle size of 10–15 µm (TLC plates)
Developing solvent:  Methanol, ethyl acetate, ammonium hydroxide, and water (2:1:1:1)
Application volume:  5 µL
Spray reagent:  Slowly add 10 mL of sulfuric acid to about 40 mL of water. Mix, and allow to cool. Dilute with water to 100 mL, and mix. Add 2.5 g of ammonium molybdate and 1 g of ceric sulfate, and shake for 15 min to dissolve.
Analysis:  Develop the chromatograms until the solvent front has moved about three-fourths the length of the plate, and allow to dry. Spray the plate with Spray reagent, and allow to dry. Repeat two more times, heat at 110 for 15 min, and examine.
Acceptance criteria:  The principal spot from the Sample solution is similar in position and color to the principal spot from the Standard solution.
Change to read:
•  Procedure
Sample:  NF30 0.350 g of Lactobionic Acid NF30
Analysis:  Dissolve the Sample in 50 mL of carbon dioxide-free water, previously heated to 30.NF30 Immediately titrate with 0.1 NNF30 sodium hydroxide, and determine the two equivalence points potentiometrically. (See Titrimetry 541.)
Each mL of 0.1 N sodium hydroxide consumed to the first equivalency point is equivalent to 35.83 mg of C12H22O12 (corresponds to the acid form), and each mL of 0.1 N sodium hydroxide consumed between the first and second equivalency points is equivalent to 34.03 mg of C12H20O11 (corresponds to the -lactone form).
Calculate the content, expressed as a percentage, of the lactobionic acid as the sum of both results.NF30
Acceptance criteria:  98.0%–102.0% on the anhydrous basis
•  Heavy Metals 231
Thioacetamide reagent:  To 0.2 mL of thioacetamide TS add 1 mL of a mixture of 5 mL of water, 15 mL of 1 M sodium hydroxide, and 20 mL of glycerin. Heat in a water bath for 20 s. [Note—Prepare immediately before use. ]
Lead nitrate stock solution:  Prepare as directed for Special Reagents in Heavy Metals 231.
Standard solution:  On the day of use, dilute 2.0 mL of the Lead nitrate stock solution (10 ppm Pb) in water to 30 mL.
Sample solution:  Dissolve 1 g of Lactobionic Acid in water to 30 mL.
Prepare the filtration apparatus by adapting the barrel of a 50-mL syringe without its piston to a support containing, on the plate, a membrane filter of 3-µm pore size, and above it a prefilter.
Transfer the Sample solution into the syringe barrel, put the piston in place, and then apply an even pressure on it until the whole of the liquid has been filtered. When opening the support and removing the prefilter, check that the membrane filter remains uncontaminated with impurities. If this is not the case, replace it with another membrane filter, and repeat the operation under the same conditions.
Analysis:  To the prefiltrate, add 2 mL of pH 3.5 Acetate Buffer. Mix, and add 1.2 mL of Thioacetamide reagent. Mix immediately, allow to stand for 10 min, and again filter as described above, but inverting the order of the filters, the liquid passing first through the membrane filter before passing through the prefilter. The filtration must be carried out slowly and uniformly by applying moderate and constant pressure to the piston of the syringe. After complete filtration, open the support, remove the membrane filter, and dry using filter paper. In parallel, treat the Standard solution in the same manner as the Sample solution.
Acceptance criteria:  The color of the spot from the Sample solution is not more intense than that from the Standard solution (NMT 20 ppm).
•  Water Determination, Method Ia 921
Sample solution: 
0.50 g in a mixture of methanol and formamide (2:1)
Acceptance criteria:  NMT 5.0%
•  Appearance of Solution
Sample solution:  120 mg/mL of Lactobionic Acid
Standard stock solution:  Pipet 24.0 mL of ferric chloride CS and 6.0 mL of cobaltous chloride CS into a 100-mL volumetric flask. Dilute with 1% (w/v) hydrochloric acid to volume.
Reference solution:  Pipet 12.5 mL of the Standard stock solution into a 100-mL volumetric flask. Dilute with 1% (w/v) hydrochloric acid to volume.
Acceptance criteria:  The Sample solution is clear and not more intensely colored than the Reference solution.
•  Optical Rotation, Specific Rotation 781S
Sample solution:  10 mg/mL of Lactobionic Acid. Allow to stand for 24 h.
Acceptance criteria:  +23.0 to +29.0 (anhydrous substance)
•  Reducing Sugars
Sample solution:  Dissolve 5.0 g of Lactobionic Acid in 25 mL of water with the aid of gentle heat, and cool.
Analysis:  To the Sample solution add 20 mL of cupric citrate TS and a few glass beads. Heat so that boiling begins after 4 min, and maintain boiling for 3 min. Cool rapidly, and add 100 mL of a 2.4% solution of glacial acetic acid and 20.0 mL of 0.025 M iodine VS. With continuous shaking, add 25 mL of a mixture of 6 mL of hydrochloric acid and 94 mL of water. When the precipitate has dissolved, titrate the excess iodine with 0.05 M sodium thiosulfate VS using 1 mL of starch TS, added toward the end of the titration as an indicator.
Acceptance criteria:  NLT 12.8 mL of 0.05 M sodium thiosulfate VS is required, corresponding to NMT 0.2% of reducing sugars, as glucose.
•  Packaging and Storage: Preserve in well-closed containers.
•  USP Reference Standards 11
USP Lactobionic Acid RS
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Topic/Question Contact Expert Committee
Monograph Robert H. Lafaver, M.S.
Scientific Liaison
(EXC2010) Monographs - Excipients
Reference Standards RS Technical Services
USP35–NF30 Page 1837
Pharmacopeial Forum: Volume No. 37(1)