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 degrees C, no appreciable loss of water could be observed over a period of 90 min. At 95 degrees 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. (C) 2000 Elsevier Science B.V. All rights reserved.