Study on the loss of nucleoside mono-, di- and triphosphates and phosphorylated peptides to a metal-free LC-MS hardware

In our earlier LC-MS experiments on the analysis of phosphocompounds like nucleotides (mono-, di- and triphosphate) and phosphopeptides and in literature, low sensitivity and severe losses of analyte to the instrumental setup were observed. Since we noticed that the stainless steel parts of the setup (e.g., the electrospray needle) adsorbed important quantities of the phosphorylated analytes, we made a LC-ESI setup without metallic surfaces. The first results were disappointing since also the fused silica surface of the LC-ESI coupler adsorbed part of the nucleotides and phosphopeptides injected in flow analysis experiments. We present experiments documenting the contribution of the different components of the setup. A number of potential solutions to the adsorption problem are proposed and tested. Only dimethyldichlorosilane deactivation of fused silica capillaries gave satisfactory results as adsorption of nucleotides and phosphopeptide was minimised. (C) 2010 Elsevier B.V. All rights reserved.