Peak Parking: A meaningful technology in gaining Instrument Time and Sensitivity

Peak parking is a useful technique for target peptide identification purposes. If properly carried out, it provides the analyst much more time to perform the wished experiments, like e.g. adjustment of collision energy. In addition the sensitivity of the analysis may be significantly improved. NanoSeparations' peak parking system (fig 1) is simple to implement, reliable and easy to use. The hardware comprises of a second, lower back pressure restrictor and an additional 4 port switching valve. At the event of a raising signal of  interest, the 4-port valve is switched, resulting in sudden decrease of the column head pressure and likewise flow-rate through the column. Using our 5 umID ES emitter, the lowest flow rate yielding a stable spray amounts approx 20 nL/min, or ~20 % of the normal flow rate through a 50 umID column.

Fig 2 shows an overlay of  the analysis of a standard peptide mixture (2 fmol consumed)  without (white) and with (yellow) peak parking. Parking was performed on one peptide for 70 s allowing an increase of MS/MS scanning time across the peak from 10 to over 70 sec. Notice that the performance for later eluting peaks is not affected, indicating that migration velocity through the column during peak parking is negligible. Data obtained on a  Micromass QToF Ultima