Determination of partial solubility parameters of lactose by gas-solid chromatography.

On the basis of the Snyder/Karger-Hansen interaction model, where delta EA = Vi(delta di delta dj + delta pi delta pi + delta hi delta nj), the partial solubility parameters of a solid used as the stationary phase may be determined through gas-solid chromatography by null-injection of solutes with known solubility parameters. Using n-decane, acetonitrile, and 1-propanol as molecular probes, the values found for unhydrated lactose were 9.6, 12.8, 11.3, and 19.5 (cal1/2/cm3/2) for delta d, delta p, delta h, and delta t, respectively; relative standard errors were better than 3%. The choice and the minimum number of the best molecular probes were determined by optimization of the experimental matrix according to the D-criterion, which permits considerable reduction of experimental time yet enhances total precision.