Optimal Offline Nanospray Offline analysis is characterized as loading a discrete sample, usually by syringe or pipette, into an emitter that is then mounted into the mass spectrometer's source. Sample flow is generated by the electrostatic attraction of the liquid inside the emitter, which has been changed by high voltage, or by the gentle pressurization of the source. Borosilicate glass and quartz PicoTips® are an improved version of the traditional nanospray ionization emitters. Their special taper makes them virtually self-filling, and their specified tip opening eliminates the need to break open the tips prior to use. The proper OD for the emitter is determined by the manufacturer of your nanospray source. The Micromass® ZSpray™ uses PicoTips with a 1 mm OD while the ABI Mariner™/QSTAR®, Bruker NanoSpray™, MDS Proteomics/Protana NanoES, and Thermo Finnigan Nanospray Ion Sources take PicoTips with a 1.2 mm OD.

Determine your target flow rate; then locate the corresponding tip size. EconoTips™ have a 1 µm ID tip and are perfect for routine sampling with a standard single-layer conductive coating. GlassTips™ are available in 2 and 4 µm tip IDs, with or without a durable, inert, multi-layer conductive coating (U.S. Patent 5,788,166) and undergo rigorous inspection by video microscopy. Select QuartzTips™ for samples that are sodium-sensitive or require an emitter with better resistance to high pH solvents.

Coating Options

In order to perform electrospray, high voltage must be supplied to the mobile phase. The electrical contact can be made in either of two methods — indirectly through a conductive coating on the emitter, or directly through a junction. Each of these methods requires different styles of emitters. Once you have determined your contact method, select the corresponding coating. Distal coatings are not available for offline emitters.

		Tip Contact Using the Standard Coating (CE) The electrical contact is made to the outside of the emitter. The emitter has a conductive coating on the tip where the voltage contacts the mobile phase. PicoTips® with a standard coating have - CE- in their stock numbers. Use primarily with PEEK™ fittings.
		Junction Contact for Uncoated Tips (N) The electrical contact is made to the fitting holding the emitter. Voltage contact is made directly to the mobile phase. PicoTips® that are uncoated have -N- in their stock numbers. Use primarily with metal fittings.