Z-spray source

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. 

A heated countercurrent gas flow is applied in a number of other sources, e.g., in the initial Fenn ESI source (Figure 5.3) and in sources based on this design (Figure 5.5). The gas also assists in droplet evaporation. A cone gas is applied in a recent design of the Z-spray source from Waters (Figure 5.7). 

Z-Spray Source with a Quadrupole Mass Filter for Gas-Phase Investigations at FELIX... 

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. 

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. 

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. 

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.

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... 

Taylor and colleagues [98] at the Mayo Clinic published a method for the simultaneous analysis of urinary cortisol and cortisone. They used 2H4 cortisol as an internal standard and took a 0.5-ml urine sample. An API 2000 with Turboion-spray source was used in the positive-ion mode. Chromatography was conducted on a standard-bore C18 column with Q8 precolumn filter. MRM was conducted in the positive-ion mode monitoring m/z 363—>121 for cortisol, 367—>121 for 2TL, cortisol, and 361— -121 for cortisone. Cortisol and cortisone were separated and both were eluted within 2 min. Inter- and intra-assay variation for both compounds was < 9% for amounts above 2 pig/dl. The values obtained agree well with those of other studies, such as ours (Table 5.3.2) [62]. They found a range for cortisol for adult males of 4.2-60 pg/24 h and for adult females 3.0-43 pg/24 h. In summary, the 3-min run time of their method has allowed the Mayo group to completely transfer their cortisol and cortisone workload from RIA and HPLC to MS/MS. 

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