Sample pretreatment methods, such as preconcentration, are used to increase the detection sensitivity and selectivity of many analytical instruments. Conventional preconcentrators are troubled by large pressure drops, dead volumes, and high power consumptions. However, the advancement of MEMS technology has enabled the realization of miniaturized preconcentrators that overcome these shortcomings. We have microfabricated different preconcentrators providing us high surface-to-volume ratios, low thermal masses, small flow resistances, and high adsorption capacities. We have also explored different materials for adsorption including Tenax TA, electroplated gold, and DVB. In a parallel research, we have been working on the development of new SPME (solid phase microextraction) fibers that can trap higher boiling point compounds.