Specifications of Lactobionic Acid USP NF Grade:
C12H22O12 (acid form) --- 358.30 --- CAS 96-82-2.
C12H20O11 (δ-lactone) 340.28 CAS 5965-65-1
4-O-β-Galactopyranosyl-d-gluconic acid.

Water Determination Acceptance criteria: 5.0% maximum.
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 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 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 is required, corresponding to NMT 0.2% of reducing sugars, as glucose.
Articles of Botanical Origin: 0.2% maximum.

Specifications of Lactobionic Acid BP Ph Eur Grade
Ph Eur
C12H22O12 (acid form) -- 358.3 -- CAS 96-82-2
C12H20O11 (d-lactone) -- 340.3 -- CAS 5965-65-1

DEFINITION
Mixture in variable proportions of 4-O-b-D-galactopyranosyl-D-gluconic acid and 4-O-b-Dgalactopyranosyl-D-glucono-1,5-lactone.
Content: 98.0 per cent to 102.0 per cent (anhydrous substance).

CHARACTERS
Appearance: White or almost white powder.
Solubility: Freely soluble in water, slightly soluble in glacial acetic acid, in anhydrous ethanol and in methanol.
mp: About 125C with decomposition.

IDENTIFICATION
A. Infrared absorption spectrophotometry.
If the spectra obtained show differences, dissolve the substance to be examined and the reference substance separately in water, dry at 105C and record new spectra using the residues.
B. Thin-layer chromatography.

Test solution: Dissolve 10 mg of the substance to be examined in water and dilute to 1 ml with the same solvent.
Reference solution: Dissolve 10 mg of lactobionic acid CRS in water and dilute to 1 ml with the same solvent.
Plate TLC silica gel plate.
Mobile phase concentrated ammonia, ethyl acetate, water, methanol.
Application: 5 μl.
Development: Over 3/4 of the plate.
Detection: Spray 3 times with ammonium molybdate solution and heat in an oven at 110C for 15 min.
Results: The principal spot in the chromatogram obtained with the test solution is similar in position and colour to the principal spot in the chromatogram obtained with the reference solution.

DEFINITION
Mixture in variable proportions of 4-O-b-D-galactopyranosyl-D-gluconic acid and 4-O-b-Dgalactopyranosyl-D-glucono-1,5-lactone.
Content: 98.0 per cent to 102.0 per cent (anhydrous substance).