Improved analyte detectability of proteins and peptide lysates by means of multiple large‐volume injection in LC‐MS

A ‘multiple (trapping) large‐volume injection’ approach was developed for the analysis of peptides and proteins. In this way, a maximally 10‐fold gain in sensitivity could be achieved. The system involves the use of an automated 10‐port switching valve in combination with a 1 mm i.d. trapping/guard column and a 1 mm i.d.×150 mm analytical column. The optimized multiple injection/loading procedure allows quantitative measurements of peptides and protein lysates. Linear calibration curves ( R 2 ⪈ 0.988) over a minimum of two orders of magnitude were generated for a range of peptide and protein standards with sensitivities equal to or even exceeding, those generally achieved only through increasing miniaturization (quantification limit ⪈0.5 pmol/mL).