»Lactose Monohydrate is a natural disaccharide,obtained from milk,which consists of one glucose and one galactose moiety.[NOTELactose Monohydrate may be modified as to its physical characteristics.It may contain varying proportions of amorphous lactose.]
Packaging and storage Preserve in tight containers.
Labeling Where the labeling states the particle size distribution,it also indicates the d10,d50,and d90values and the range for each.For modified Lactose Monohydrate,also label it to indicate the method of modification.
USP Reference standards á11ñ USP Lactose Monohydrate RS.USP Sucrose RS.USP Fructose RS.USP Dextrose RS.
Clarity and color of solution Asolution of 1g in 10mLof boiling water is clear and nearly colorless.Determine the absorbance of this solution at a wavelength of 400nm.The absorbance divided by the path length in centimeters is not more than 0.04.
B: DiluentPrepare a mixture of methanol and water (3:2).
Developing solvent Prepare a solution consisting of a mixture of ethylene dichloride,glacial acetic acid,methanol,and water (50:25:15:10).
Standard solution A Prepare a solution of USP Lactose Monohydrate RSin Diluenthaving a known concentration of 0.5mg per mL.
Standard solution B Prepare a solution of USP Dextrose RS,USP Lactose Monohydrate RS,USP Fructose RS,and USP Sucrose RSin Diluenthaving a known concentration of 0.5mg per mLfor each Reference Standard.
Test solution Transfer about 25mg of Lactose Monohydrate to a 50-mLvolumetric flask,dissolve in and dilute with Diluentto volume,and mix.
Procedure Apply separately 2µLeach of Standard solution A,Standard solution B,and the Test solutionto a thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel.Allow the spots to dry,and develop the plate in a paper-lined chromatographic chamber equilibrated with Developing solventfor about 1hour prior to use.Allow the chromatogram to develop until the solvent front has moved about three-quarters of the length of the plate.Remove the plate from the chamber,dry in a current of warm air,and redevelop the plate in fresh Developing solvent.Remove the plate from the chamber,mark the solvent front,and dry the plate in a current of warm air.Spray the plate evenly with a solution containing 0.5g of thymol in a mixture of 95mLof alcohol and 5mLof sulfuric acid.Heat the plate at 130for 10minutes:the principal spot obtained from the Test solutioncorresponds in appearance and RFvalue to that obtained from Standard solution A.The test is not valid unless the chromatogram obtained with Standard solution Bshows four clearly discernible spots,disregarding any spots at the origin.
C: Dissolve 250mg in 5mLof water.Add 3mLof ammonium hydroxide,and heat in a water bath at 80for 10minutes:a red color develops.
Specific rotation á781ñ Dissolve 10g by heating in 80mLof water to 50.Allow to cool,and add 0.2mLof 6Nammonium hydroxide.Allow to stand for 30minutes,and dilute with water to 100mL:the specific rotation,calculated on the anhydrous basis,determined at 20,is between +54.4and +55.9.
Microbial limits á61ñ The total aerobic microbial count does not exceed 100cfu per g,the total combined molds and yeasts count does not exceed 50cfu per g,and it meets the requirements of the test for absence of Escherichia coli.
Acidity or alkalinity Dissolve 6g by heating in 25mLof carbon dioxide-free water,cool,and add 0.3mLof phenolphthalein TS:the solution is colorless,and not more than 0.4mLof 0.1Nsodium hydroxide is required to produce a red color.
Loss on drying á731ñ Dry it at 80for 2hours:the monohydrate form loses not more than 0.5%of its weight,and the modified monohydrate form loses not more than 1.0%of its weight.
Water,Method Iá921ñ: between 4.5%and 5.5%,determined on a preparation containing lactose monohydrate in a mixture of methanol and formamide (2:1).
Residue on ignition á281ñ: not more than 0.1%,determined on a specimen ignited at a temperature of 600±25.
Heavy metals á231ñ Dissolve 4g in 20mLof warm water,add 1mLof 0.1Nhydrochloric acid,and dilute with water to 25mL:the limit is 5µg per g.
Protein and light-absorbing impurities á851ñ Measure the light absorption of a 1%(w/v)solution in the range of 210to 300nm.The absorbance divided by the path length in centimeters is not more than 0.25in the range of 210to 220nm and is not more than 0.07in the range of 270to 300nm.
Auxiliary Information Staff Liaison:Justin Lane,B.S.,Scientific Associate
Expert Committee:(EMC)Excipients:Monograph Content