The main difficulty in analyzing proteomic samples is related to the presence of thousands of proteins occurring in a wide concentration range.The complexity of such samples becomes even greater after enzymatic digestion to peptides prior to LC analysis.As a result it is crucial to develop technologies with extremely good resolving power and with extraordinary sensitivity to tackle such a task.Two dimensional nano liquid chromatography has dramatically reduced the requirement for loading large amounts of samples, which is important for the analysis of low-abundance compounds or available in limited quantities.In addition, ESI interface is compatible with low flow rates used in nanoLC, thus leading to an increase in sensitivity.