Parallel reactions in open chip-based nanovials with continuous compensation for solvent evaporation

In an earlier report (Litborn, E., Emmer,,Angstrom., Roeraade, J., Anal. Ch im. Acta 1999, 401, 11-19, we described a technique for performing chemistr y in chip-based vials. A major problem, solvent evaporation, was partially remedied by using a closed humidity chamber. in this paper we report an imp roved technique for performing parallel reactions in open, 15 nL volume, ch ip-based vials. The evaporation of solvent from the reaction fluid was cont inuously compensated by addition of solvent via an array of microcapillarie s. The suitability of the method was demonstrated by performing eight separ ate peptide maps of myoglobin in parallel, using the three enzymes trypsin, alpha-chymotrypsin and endoproteinase Glu-C. The total amount of myoglobin utilized to perform the eight digests was less than 100 pmol. The correspo nding amount of enzymes was ca. 0.1 pmol per reaction. In order to evaluate the operating limits of the technique, a study of the evaporation of solve nts from a series of vials with proportionally smaller volumes operated at different temperatures was performed. The results showed that the concept f or continuous compensation of solvent evaporation should be applicable to r eaction volumes down to 30 pL.