A molecularly imprinted material made from polymerizing a monomer having the structural formula (OR).sub.3Si--B-A-B--Si(OR).sub.3. A is a divalent organic group, B is a saturated or unsaturated divalent hydrocarbon group or a covalent bond, and R is an independently selected saturated or unsaturated monovalent hydrocarbon group. A preconcentrator having: a container comprising in inlet and an outlet and the above material within the container. The inlet is capable of allowing a fluid to enter the container. The outlet is capable of being coupled to a sensor and of allowing the fluid to exit the container.