Z-spray

The Z-spray inlet/ionization source sends the ions on a different trajectory that resembles a flattened Z-shape (Figure 10.1b), hence the name Z-spray. The shape of the trajectory is controlled by the presence of a final skimmer set off to one side of the spray instead of being in-line. This configuration facilitates the transport of neutral species to the vacuum pumps, thus greatly reducing the buildup of deposits and blockages. 

The Z-spray inlet causes ions and neutrals to follow different paths after they have been formed from the electrically charged spray produced from a narrow inlet tube. The ions can be drawn into a mass analyzer after most of the solvent has evaporated away. The inlet derives its name from the Z-shaped trajectory taken by the ions, which ensures that there is little buildup of products on the narrow skimmer entrance into the mass spectrometer analyzer region. Consequently, in contrast to a conventional electrospray source, the skimmer does not need to be cleaned frequently and the sensitivity and performance of the instrument remain constant for long periods of time. 

This chapter provides brief descriptions of analyzer layouts for three hybrid instruments. More extensive treatments of sector/TOF (AutoSpec-TOF), liquid chromatography/TOF (LCT or LC/TOF with Z-spray), and quadrupole/TOF (Q/TOF), are provided in Chapters 23, 22, and 21, respectively. 

A liquid chromatograph (LC) is combined with a TOF instrument through a Z-SPRAY ion source. Two hexapoles are used to focus the ion beam before it is examined by a TOF analyzer, as described in Figure 20.3. 

Z-spray is a novel kind of electrospray that functions as a combined inlet and ion source. Chapter 8 ( Electrospray Ionization ) should be consulted for comparison. 

The Z-spray source utilizes exactly these same principles, except that the trajectory taken by the ions before entering the analyzer region is not a straight line but is approximately Z-shaped. This trajectory deflects many neutral molecules so that they diffuse away toward the vacuum pumps. 

The Z-trajectory ensures excellent separation of ions from neutral molecules at atmospheric pressure. In line-of-sight or conventional electrospray sources, the skimmer is soon blocked by ions and molecules sticking around the edges of the orifice. In Z-spray sources, the final skimmer, being set off to one side, is not subjected to this buildup of material. 

Z-spray sources require much less frequent maintenance than do conventional electrospray sources. 

The Z-spray inlet/ion source is a particularly efficient adaptation of the normal in-line electrospray source and gets its name from the approximate shape of the trajectory taken by the ions between their formation and their entrance into the analyzer region of the mass spectrometer. A Z-spray source requires much less maintenance downtime for cleaning. 

Z-spray. Z refers to the approximate shape of the trajectory of particles formed by electrospray ionization... 

Figure 2.2 Schematics of (a) in-line and (b) Z-spray electrospray interfaces. From applications literature published by Micromass UK Ltd, Manchester, UK, and reproduced with permission.

Z-spray An electrospray source in which ions are extracted into the mass spectrometer at 90° to the direction in which the spray is produced. 

In the case of carbamate insecticides, both ESI and APCI can be used. However, in this study, the sensitivity of APCI was 3-5-fold less than that of ESI. In this case, the Z-spray configuration was used with APCI, which gives a lower efficiency of ions reaching the mass analyzer than is achieved with other instrumental configurations. 

Figure 11.2 A schematic of the electrospray process, showing the release of charged droplets from the Taylor cone and the Z-spray arrangement with respect to the sample inlet, sample cone, and the subsequent path of the ions into the analyzer.

Fig. 19.14. Accumulation of phosphate salts in the atmospheric pressure ionization chamber. Note the large accumulation of salts on the striker plate. Additional accumulation of salts can be seen on the back walls of the chamber. The general dustiness in the chamber is salt accumulation. This source is a z-spray ionization source chamber of a Micromass Quattro Ultima mass spectrometer system.

Fig. 11.9. Micromass z-spray interface, (a) Photograph of the actual spray, (b) schematic drawing. By courtesy of Waters Corporation, MS Technologies, Manchester, UK.

Mccomb, M. E., and Perreault, H. (2000). Design of a sheathless capillary electrophoresis-mass spectrometry probe for operation with a Z-Spray ionization source. Electrophoresis 21, 1354-1362. 

Fig. 5.7 AChE-catalyzed hydrolysis of the fluorescent substrate AMQI in volatile buffer monitored by mass spectromet. Line 1 Start of the substrate pump delivering AMQI. Line 2 Start of the enzyme pump delivering AChE. Peak 3 Injection of 0.1 pM galanthamine. Peak 4 Injection of 1.0 pM galanthamine. MS instrument Q-ToF2 (Waters) equipped with a Waters Z-spray electrospray (ESI) source, (a) Mass chromatogram of m/z 288 (galanthamine) (b) mass chromatogram of m/z 104...

Fig. s.n On-line continuous-flow monitoring of biochemical interaction with (a) fluorescence and (b) MS SIM (m/z 390) detection. Fluorescein-biotin (96 nM), streptavidin (32 nM), 20-pL loop injections of 1000 nM biotin (n = 3). MS instrument Q-ToF2 (Waters) equipped with a Waters Z-spray electrospray (ESI) source. Point 1 Carrier pump, protein and reporter ligand pumps... 

---