»Anhydrous Lactose is primarily beta lactose or a mixture of alpha and beta lactose.
Labeling Where the labeling indicates the relative quantities of alpha and beta lactose,determine compliance using Content of alpha and beta anomers.
USP Reference standards á11ñ USP Anhydrous Lactose RS.USP Sucrose RS.USP Fructose RS.USP Dextrose RS.
B: Proceed as directed in Identificationtest Bunder Lactose Monohydrate,except to use USP Anhydrous Lactose RSinstead of USP Lactose Monohydrate RSin Standard solution Aand Band to use Anhydrous Lactose in the Test solution.
C: Proceed as directed in Identificationtest Cunder Lactose Monohydrate.
Loss on drying á731ñ Dry it at 80for 2hours:it loses not more than 0.5%of its weight.
Water,Method Iá921ñ: not more than 1.0%,determined on a preparation containing anhydrous lactose in a mixture of methanol and formamide (2:1).
Heavy metals,Method IIá231ñ: 5µg per g.
Content of alpha and beta anomers
Silylation reagent Prepare a mixture of pyridine and trimethylsilylimidazole (72:28).
Resolution mixture Prepare a mixture of alpha lactose monohydrate and beta lactose having an anomeric ratio of about 1:1based on the labeled anomeric contents of the alpha lactose monohydrate and the beta lactose.
Chromatographic system (see Chromatography á621ñ)The gas chromatograph is equipped with a flame-ionization detector and a 4-mm ×0.9-m glass column packed with 3%liquid phase G19on support S1A.The column temperature is maintained at about 215,and the injection port and the detector temperatures are maintained at about 275.The carrier gas is helium,flowing at a rate of about 40mLper minute.
Derivatization procedure Transfer about 1mg of Anhydrous Lactose to a 5-mLreaction vial equipped with a screw cap,add 0.45mLof dimethyl sulfoxide,seal the vial tightly with a screw cap,and mix on a vortex mixer to dissolve.Add 1.8mLof Silylation reagent,seal the vial tightly with a screw cap,and mix gently.Transfer about 1mg of Resolution mixtureto a second 5-mLreaction vial equipped with a screw cap,add 0.45mLof dimethyl sulfoxide,seal the vial tightly with a screw cap,and mix on a vortex mixer to dissolve.Add 1.8mLof Silylation reagent,seal the vial tightly with a screw cap,and mix gently.Maintain both vials at room temperature for 20minutes before using.
Procedure Inject a 2.0-µLportion of the derivatized Resolution mixtureinto the chromatograph,and record the peak areas for the major peaks:the relative retention times are about 0.7for the silyl derivative of alpha lactose and 1.0for the silyl derivative of beta lactose,and the resolution,R,between the two peaks is not less than 3.0.Similarly inject a 2.0-µLportion of the derivatized Anhydrous Lactose into the chromatograph,and record the peak areas for the major peaks.Determine the percentage of alpha anomer in the Anhydrous Lactose by the formula:
100ra/(ra+rb),in which rais the response of the alpha anomer silyl derivative peak and rbis the response of the beta anomer silyl derivative peak.Determine the percentage of beta anomer in the Anhydrous Lactose by the formula:
Auxiliary Information Staff Liaison:Justin Lane,B.S.,Scientific Associate
Expert Committee:(EMC)Excipients:Monograph Content