Liquid lid for biochemical reactions in chip-based nanovials

The present paper describes a new technique to suppress evaporation of solvent from very small volumes. Vials (15 nl) on a silicon microchip were filled with water, and covered with a thin, flowing film of a volatile liquid (e.g., octane). Water evaporation was greatly reduced. At 37°C, no appreciable loss of water could be observed over a period of 90 min. At 95°C, most of the water sample was left in the vial for more than 3 min. The applicability of the method is demonstrated by a tryptic digest, where the resulting peptide fragments were analyzed by capillary electrophoresis. In addition, a discussion of the possibilities and limitations of some alternative methods is included in the paper, as well as an outlook on future developments of the liquid lid concept.