Isomerization of lactose in solid-state by mechanical stress during grinding.
Isomerization during grinding of solid-state alpha-monohydrate, alpha-anhydrate and beta-anhydrate of lactose was investigated. Samples were ground in an agate centrifugal ball-mill at 270 rev min-1 at room temperature (20 degrees C). The crystallinity of ground lactose was measured by Hermans' method from the powder X-ray diffraction profiles. The alpha- and beta-lactose content of the ground lactose was obtained from the specific rotation measured by using angular rotation spectrophotometry. The crystalline lactose samples were transformed into non-crystalline solids by mechanical stress during grinding. After grinding, the water content of all ground lactose samples increased, and the samples had about 2 mol water per lactose after 10 h grinding. After 10 h grinding of alpha-monohydrate and alpha-anhydrate, 10 and 15%, respectively, of alpha-lactose was transformed into beta-lactose by the mechanical treatment. After 10 h grinding of beta-lactose, 20% of beta-lactose was transformed into alpha-lactose. The results suggest that crystalline lactose was transformed into a non-crystalline solid, and water was adsorbed on the non-crystalline lactose. The non-crystalline solids of alpha- or beta-lactose were then transformed into their counterparts by the mechanochemical effects of grinding.
Kobe Women's College of Pharmacy, Japan.
M
M
Otsuka
H
H
Ohtani
N
N
Kaneniwa
S
S
Higuchi
D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003460:Crystallization; D004055:Differential Thermal Analysis; D004339:Drug Compounding; D007536:Isomerism; D007785:Lactose / Q000032:analysis / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013818:Thermogravimetry; D014867:Water / Q000032:analysis; D014961:X-Ray Diffraction
D014867:Water; D007785:Lactose