The LockSpray™ dual electrospray ion source optimizes the co-introduction of analyte and lock mass compound directly into the ion source, providing authenticated exact mass measurement in MS and MS/MS modes to within 5 ppm RMS mass accuracy (3 ppm for Xevo QTof MS and 1 ppm for Xevo G2 Tof series, Xevo G2 QTof series and SYNAPT G2 series).
The increased specificity associated with exact mass measurement provides you with improved efficacy in compound or fragment identification in metabolite profiling and proteomics applications.
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 the 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 LockSpray source design overcomes these limitations.
LockSpray Source Operation
With the LockSpray source, the conventional electrospray inlet is replaced by a new outer source housing containing an additional pneumatically assisted electrospray probe for the introduction of the lock mass reference.
An oscillating baffle driven by a programmable stepper motor samples the two electrospray streams separately. The reference spray is sampled at pre-defined intervals so that the acquisition duty cycle favors the analyte liquid stream.
The sampling baffle position is monitored in real time to allow the two liquid inlets to be indexed and the reference and sample data stored in separate files. The LockSpray source design eliminates cross-talk between the analyte and reference channels, ensuring the integrity of the exact mass data.
The LockSpray Interface/Ionization Source is available for the following MS instruments:
Equipment and Installation
The LockSpray interface/source enclosure includes an electrospray source inlet assembly with additional low flow (~10 µl/min) reference supply probe and indexed stepper motor control of the spray selection rotor. The interface is operated in conjunction with the standard co-axial electrospray probe. A separate ESI probe is included with the Xevo QTof, Xevo G2 Tof, Xevo G2 QTof, Xevo G2-S QTof, Xevo G2-S Tof, SYNAPT G2, and SYNAPT G2-S series LockSpray source enclosures.
The exact mass source assembly requires installation and operation training by a Waters Field Service Engineer.
Exact mass MS measurement enables compounds to be more easily identified, significantly increasing confidence in assigning elemental composition