Encyclopedia of Analytical Chemistry

Multidimensional (MD) separation is a combination of two or more separation techniques that increases peak capacity. There are two requirements or criteria in MD as suggested by Giddings. First is orthogonality, which means that the separation mechanism in each step must be based on different molecular properties such as size, charge, hydrophobicity, or chirality. Second is that the separation obtained in the first dimension must be preserved in the subsequent dimensions. There are two types of MD separation, comprehensive and heart cutting. In the first type, all compounds present in the mixture are separated and detected, while in the second, only selected fractions in the mixture are analyzed. The…