TOF-ICP

Hieftje and co-workers first reported a design for ICP-ToF mass spectrometric systems with both orthogonal acceleration (oa) and axial acceleration (aa) geometry.39 11 The different experimental setups of ICP-ToF mass spectrometers with orthogonal and axial acceleration are compared in Figures 5.10 and 5.11. Both instruments possess a time-of-flight analyzer with a reflectron to improve the mass resolution. 

Figure 5.10 Schematic of ICP-ToF-MS OptiMass 8000 (CBCScientific Equipment). (R. E. Sturgeon etai., j. Anal. At. Spectrom., 15, 607 (2000). Reproduced by permission of the Royal Society of Chemistry.)...

The axial time-of-flight ICP-MS was introduced in 1998 by LECO (Renaissance, LECO, St. Joseph, MI) and has been commercially available for several years. A schematic of the ICP-ToF-mass spectrometer is shown in Figure 5.11. The analytical performance of this mass spectrometer, which allows 25 000 spectra to be measured per second and is thus faster than a quadrupole ICP-MS,... 

With LA-ICP-ToF-MS, using the 193 nm ArF laser (laser energy lOOmJ at 120(xm laser beam diameter), a depth resolution of 200 nm per laser shot was measured.121 LA-ICP-MS was utilized for depth profiling of copper coatings on steel with certified copper coating thicknesses from about... 

For efficient removal, these plates should ideally be placed at the point at which ions attain their tightest temporal and spatial focus prior to detection. Although deflection of this type would be challenging with a swept-beam geometry, the space focus plane of the two-stage acceleration design offers an excellent opportunity to deflect the maximum number of ions over the shortest distance in the shortest time. This placement also ensures the most resolution of mass deflection. For an ICP-TOF-MS, the efficiency of removal for this parallel-plate scheme was promising [24]. 

Figure 7 Quadrupole lens system tested for inductively coupled plasma time-of-flight mass spectrometry (ICP-TOF-MS). L1-L4, cylinder lenses Qx, x dimension poles, Qy, y dimension poles rO, radius of quadrupole open aperture (0.5 cm) SI, second-stage extraction optic C, Faraday cup Gl, grounded entry grid G2 acceleration grid Yl, Y2, steering plates. (From Ref. 28.)...

In the first instrument, sensitivity and limits of detection were constrained by the total ion beam current measured after the extraction region of the TOF-MS [42]. Although pulser circuitry limited the repetition rate to 7.1 kHz and a duty factor of 3.5%, detection limits ranged from 0.03 to 3 ppb using ultrasonic nebuliza-tion [16]. Mahoney et al. later reported on improvements to the same orthogonal ICP-TOF-MS [29]. The use of a commercial skimmer cone and quadrupole doublet in the extraction optics led to an increase in primary ion current from 2 nA to 50 nA [29]. This, along with electronic improvements allowing a 16-kHz spectral-repetition rate, dropped limits of detection to 1-10 ppt when ultrasonic nebuliza-tion was utilized. 

Allen et al. have also reported the coupling of a laser ablation sample introduction to a commercial ICP-TOF-MS [48]. The authors illustrated the true multielemental capability of such a system when equipped with an improved data-ac-... 

Figure 5.11 Setup of ICP-ToF mass spectrometer Renaissance, LECO (Reproduced by permission of LECO Co.).

The application of LA-ICP-ToF-MS and LA-ICP-QMS for depth profiling of various titanium based coatings on steel and tungsten carbide and Ti based single layers is discussed in references respectively. Thickness determination was performed by LA-ICP-QMS with 5% RSD, a laser ablation rate of < 100 nm per laser shot (Nd-YAG laser at wavelength 266 nm using a laser energy of 1.5 ml at 120 p,m laser spot size), and a depth resolution of 2.5 p-m was observed. ... 

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