A suitable solution for reconstitution of the lyophilized digests is a mixture of 30% acetonitrile (HPLC Grade or better) with 70% water containing 0.1% formic acid. The acetonitrile concentration can be critical, since the sample should not be injected into an HPLC system in a solvent matrix that has better solvent properties than the weak solvent of the gradient run due to the risk of peak broadening. However, acetonitrile concentrations below 30% may result in inadequate dissolution and the reconstitution should be checked if solutions very low in organic solvents are used.

Each vial contains the digest of 500 pico-moles of protein. The peptide concentration will therefore be 1pmol/µl if 0.5ml of Acetonitrile mixture is used to dissolve the contents. After reconstitution, the samples are ready for immediate use, but can also be further diluted:

Initial Concentration	µl Stock Solution	µl Solvent	Working Solvent
1pmol/µl	10	90	100fmol/µl
100fmol/µl	10	90	10fmol/µl