Electrothermal vaporisation

Verrept P, Dams R, Kurfurst U 1993) Electrothermal vaporisation inductively coupled plasma atomic emission spectrometry for the analysis of solid samples contribution to instrumentation and methodology. Fresenius 2 Anal Chem 345 1035-1041. 

In ICP-AES and ICP-MS, sample mineralisation is the Achilles heel. Sample introduction systems for ICP-AES are numerous gas-phase introduction, pneumatic nebulisation (PN), direct-injection nebulisation (DIN), thermal spray, ultrasonic nebulisation (USN), electrothermal vaporisation (ETV) (furnace, cup, filament), hydride generation, electroerosion, laser ablation and direct sample insertion. Atomisation is an essential process in many fields where a dispersion of liquid particles in a gas is required. Pneumatic nebulisation is most commonly used in conjunction with a spray chamber that serves as a droplet separator, allowing droplets with average diameters of typically <10 xm to pass and enter the ICP. Spray chambers, which reduce solvent load and deal with coarse aerosols, should be as small as possible (micro-nebulisation [177]). Direct injection in the plasma torch is feasible [178]. Ultrasonic atomisers are designed to specifically operate from a vibrational energy source [179]. 

Liu et al. [955] developed an electrothermal vaporisation istope dilution -ICP-MS method for determining cadmium, mercury, and lead in seawater at 2, 5, and 1 ng/1 detection limits, respectively. 

Chappie and Byrne [743] applied an electrothermal vaporisation inductively coupled plasma technique to the determination of copper, cobalt, manganese, nickel, and vanadium in seawater in amounts down to 3-140 ppt. 

Olson, L.K., Vela, N.P. and Caruso, J.A. (1995) Hydride generation, electrothermal vaporisation and liquid-chromatography as sample introduction techniques for inductively-coupled plasma-mass spectrometry. Spectrochim. Acta B, 50, 1095-1108. 

Nebulisation is inefficient and therefore not appropriate for very small liquid samples. Introducing samples into the plasma in liquid form reduces the potential sensitivity because the analyte flux is limited by the amount of solvent that the plasma will tolerate. To circumvent these problems a variety of thermal and electrothermal vaporisation devices have been investigated. Two basic approaches are in use. The first involves indirect vaporisation of the sample in an electrothermal vaporiser, eg a carbon rod or tube furnace or heated metal filament as commonly used in atomic absorption spectrometry [41-43], The second involves inserting the sample into the base of the inductively coupled plasma on a carbon rod or metal filament support [44,45], Instrumentation is available from Perkin-Elmer, Thermoelectron, Phillips, Baird and Spectroanalytical Ltd. 

Vanhaecke, F., Resano, M., Moens, L. Electrothermal vaporisation ICP-mass spectrometry (ETV-ICP-MS) for the determination and speciation of trace elements in solid samples - a review of real-life applications from the author s lab. Anal. Bioanal. Chem. 375, 188-195 (2002)... 

Hulmston, P. and Hutton, R.C., Analytical capabilities of electrothermal vaporisation-inductively coupled plasma-mass spectrometry. Spectroscopy, 6(1) (1991) 35. 

Shizhong, C. Lu Dengh, Hu Zhixong and Wang Zhan (2005) The use of electrothermal vaporisation with ICP-OES for the determination of trace elements in human hair using the slurry sample technique and PTF as a modifier, International Journal of Environmental Analytical Chemistry, 85(7), pp493-501. 

Dittrich K., Berndt H., Broekaert J. A. C., Schaldach G. and Tolg G. (1988) Comparative study of injection into a pneumatic nebuliser and tungsten coil electrothermal vaporisation for the determination of rare earth elements by inductively coupled plasma optical emission spectrometry, J Anal At Spectrom 3 1105—1110. 

Boomer D. W. and Powell M. (1988) Relative merits of two methods of sample introduction in ICP-MS electrothermal vaporisation and direct sample insertion, ] Anal At Spectrom 3 791-797. 

Park C. J. and Hall G. E. M. (1988) Analysis of geological materials by ICP-MS with sample introduction by electrothermal vaporisation, J Anal At Spectrom 3 355-361. 

Electrothermal vaporisation Electrothermal vaporisation, analogous to the approach utilised in AAS, can be performed by resistive heating of sample devices such as boats, ribbons, rods, or tubes from graphite or a refractory element [46]. 

VG Isotopes Ltd., is another leading manufacturer of ICP-MS equipment. The special features of their VG Plasmaquad PQ2 includes a multi-channel analyser which ensures rapid data acquisition over the whole mass range. The multi-channel analyser facilities include 4096 channels, 300 m facility for spectral analysis, user-definable number of measurements per peak in peak jumping mode, and the ability to monitor data as they are acquired. A multi-channel analyser is imperative for acquiring short-lived signals from accessories such as flow injection, electrothermal vaporisation, laser ablation, and so on, or for fast multi-element survey scans (typically 1 minute). 

Figure 1.14 Transient signals for and produced by an electrothermal vaporisation device and detected with (a) a quadrupole-based ICP-MS instrument and (b) a ICP-TOFMS instrument, when five isotopes were measured simultaneously.

Becker, S., and Hirner,A.V. (1994). Coupling of inductively coupled plasma mass spectrometry (1CP-/V1S) with electrothermal vaporisation (ETV). Fresenius J. Anal. Chem. 350(4/5), 260. 

Shen,W-L., Caruso,J.A., Fricke, E L.,and Satzger,R.D. (1990). Electrothermal vaporisation interface for sample introduction in inductively coupled plasma mass spectrometry. J. Anal. At. Spectrom. 5(6), 451. 

U erud, H.T., and Lund, W. (1999). Modifier effects from palladium and iridium in the determination of arsenic and antimony using electrothermal vaporisation inductively coupled plasma mass spectrometry. Spectrochim.Acta, Part B 54(11), 1625. 

The potential of the most commonly used mass spectrometers (quadrupoles and magnetic sector-field single collectors) for elemental analysis has been discussed in detail in Parts 2.1 and 2.2.1 of this chapter. However, some intrinsic limitations still remain with these sequentially scanned systems, particularly when transient or time-dependent signals (such as those produced by laser ablation (LA), electrothermal vaporisation (ETV), flow injection (FI) and chromatography) are used to analyse a large number of isotopes. These scan-based systems can measure only a single m/z at a unit of time. Hence, truly simultaneous determination of multiple isotopes, particularly when fast transient signals are analysed, is not possible without the introduction of spectral skew . ... 

Results on the evaluation of the analytical and isotope ratio performance of ICP-TOF-MS measurements in steady-state signals"" " were discussed earlier in this chapter. However, the major application field of ICP-TOF-MS involves the multi-element and multiisotope analysis of rapid transient signals such as those commonly encountered in flow injection, 27,28,29-35 electrothermal vaporisation, laser ablation, "" capillary electrophoresis, (CE)" and chromatography.From the number of references related to the coupling of ICP-TOF-MS with a separation system, TOF-MS seems to be an attractive alternative to scanning-based systems for hyphenated speciation analysis. Leach et have recently reviewed the different hyphenated speciation systems that employ ICP-TOF-MS. 

Mahoney, P. P., Ray, S. J., Li, G., and Hieftje, G. M. (1999) Preliminary investigation of electrothermal vaporisation sample introduction for inductively coupled plasma time-of-flight mass spectrometry. Anal. Chem., 71,1378. 

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