Emitters and ion sources for ES MS

In nano-electrospray MS, optimal performance generally requires flow rates from 10 nL/min to 300 nL/min. To obtain such low flow rates requires emitters with a very narrow orifice (1 - 30 µm) and handling such small emitters requires ion sources with special manipulation and visualization features.

Nano ES products from Proxeon facilitate using the lowest possible flow rate, thereby conserving sample while still obtaining a strong signal. Their design takes advantage of the fact that the signal intensity observed in ES-MS is concentration dependent and not a function of the total sample consumption.

For busy laboratories analyzing large numbers of samples, online nano-electrospray analysis, using stainless steel emitters, is the first choice, facilitating automation and ensuring a higher throughput.

Offline analysis has several advantages when needing to extract the maximum information from very limited amounts of sample. Data can be averaged extensively to improve the S/N-ratio and conditions optimized for MS/MS experiments. Other technical advantages include:

Work at low flow rates of 10-40 nL/min.
Utilize nearly 100 % of sample
Work effectively with sample volumes down to 300 nL.
Minimize instrument contamination.
Avoid cross contamination by using disposable emitters
Spray from purely aqueous as well as purely organic solvents
Work with stable sprays over a wide pH range and in high buffer concentrations

Spectrum showing fragmentation of a doubly charged tryptic peptide at m/z 582.33 from 25 fmol loaded on a polyacrylamide gel. After in-gel digestion, the peptides were purified on a micro-column in a purification capillary (ES385) and eluted into a Nano ES emitter (ES380).