The NanoLockSpray dual electrospray ion source provides authenticated exact mass measurement in both NanoFlow LC-MS and LC-MS/MS modes of operation. It features the optimized co-introduction of analyte and lock mass compounds directly into the ion source offering a superior alternative for the acquisition of exact mass data.
The increased specificity associated with exact mass measurement improves efficacy in compound or fragment identification with metabolite profiling and proteomics applications.
Exact mass measurement is typically within 5 ppm RMS mass accuracy except for LCT Premier/LCT Premier XE, Xevo QTof MS, (MALDI) Synapt MS, (MALDI) Synapt HDMS & (MALDI) Q-Tof Premier instruments where 3 ppm RMS mass accuracy can be expected.
For (MALDI) Synapt G2 MS/HDMS series, Xevo G2 Tof, and Xevo G2 QTof series instruments, typically, 1 ppm mass accuracy is seen.
Traditionally, to obtain valid exact mass measurement, an internal reference or ‘lock mass' was used to correct for changes in environment or experimental conditions over the course of an analysis. This was achieved by ‘teeing in' a suitable reference compound to the main analyte flow. However, this approach often suffered from ionization suppression, potential mass interferences and solvent gradient effects.
The NanoLockSpray source design overcomes these limitations.
NanoLockSpray Source Operation
In the NanoLockSpray source variant, the conventional electrospray inlet is augmented with a new outer source housing containing an additional pneumatically assisted electrospray probe for the introduction of the lock mass reference.
The two electrosprays are sampled exclusively using an oscillating baffle driven by a programmable stepper motor. The reference spray is sampled at pre-defined intervals ensuring the acquisition duty cycle favors the analyte liquid stream.
Positioning of the sampling baffle is monitored in real time, enabling the two liquid inlets to be indexed and the reference and sample data stored in separate files. The source's design eliminates cross-talk between the analyte and reference channels, ensuring the integrity of the exact mass data.
As a result of these design features the NanoLockSpray dual electrospray source is optimized for exact mass data acquisition with NanoFlow LC-MS/MS and is ideal for proteomics studies or low-level metabolite identification.
Equipment and Installation
The NanoLockSpray source assembly/enclosure includes a low flow (<1 µl/min) electrospray NanoFlow probe inlet to supply the reference compound, together with the indexed stepper motor control of the spray selection baffles. An adjuster assembly and endoscope viewer is also provided to assist the positioning the analyte Nanospray device.
The NanoLockSpray source for Xevo Tof/QTof series, SYNAPT series and Q-Tof Premier instruments also incorporates an additional universal NanoFlow sprayer, together with a camera assembly and LED light source, in place of the endoscope viewer. An image of the analyte spray is displayed on the instrument PC workstation.
The Nanoflow exact mass source assembly requires installation and operation training by a Waters Field Service Engineer.
The NanoLockSpray Interface/Ionization Source is available for the following MS instruments: