MASS SPECTROMETRY RESOURCE

    Nanospray-ESI is a development of ESI for spraying very low amounts of very low concentration samples (nmol/mL). The technique has an increased tolerance to high aqueous solvents and salt contamination. Spectra can be obtained from pg of material with very little clean up being required. This increased performance is the result of lowering the inner diameter of the spray needle and reducing potentials normally used in ESI. Standard nanospray uses disposable tips, but has problems with signal reproducibility between tips.

Fig 1: The Advion Biosciences Nanomate® chip system. Images © Advion Biosciences (adapted and used with permission)

The nanospray system we have here at Bristol is an automated system that uses chips (arrays) of 100 or 400 uniform nanospray needles (see figure 1) which are each used once. The analyte solution is sprayed from a non-conducting pipette tip pressed against the rear of the chip. A small gas pressure is then used to create the spray. In this way it is possible to spray for over 20 mins from just a few µl of solution. Concentrations can also be considerably reduced. The nanospray chip system (nanomate®) was developed by Advion Biosciences as an add-on to most commercial ESI sources. The array of needles is approximately the same size as a postage stamp - fig 1(a). Each needle is just a few µm long - fig 1(c). In the example spectrum below, the sample is Leucine Enkephalin (a peptide of mass 555 Da) at a concentration of 0.4µg/mL. This was sprayed for 30 mins, but only an 8 second acquisition was required to record the spectrum on the Bruker Daltonics Apex 4 FT-MS. This is equivalent to a sample consumption of about 30 pg (30x10-12g) of sample. Fig 2: An example of a nanomate-FT-MS spectrum.