Spark-ablation ICP

Tab. 6. Analytical precision of spark ablation ICP-OES for a BAS 410/1 steel sample, ccu = 3.6 mg/g. Line pair leu 324.7 nm/lfe 238.2 nm- 400 Hz medium voltage spark, 1.5 kW argon ICP, transport gas flow 1.2 L/min, 0.5 m Paschen-Runge spectrometer, measurement time 10 s [213],...

A comparative study of spark-ablation ICP-MS and GD-MS in the case of steel has been reported by Jakubowski and coworkers [536, 613], The RSFs for a number of trace elements and the measurement precision are very similar in both cases. Steel analysis by GD-MS benefits from the addition of 1% of H2 to the Ar discharge gas [614], the explanation for which is certainly complex. For certified reference steels, including superalloys, reliable analysis results can be obtained. The determination of Mo, Nb and Zr in steels by GD-MS was found to be affected by the formation of multiply-charged cluster ions (metal argides) [615]. A correction based on the assumption that the rate of formation of the singly-charged argide is the same for all analytes and coincident with that of FeAr+ was used. The capabilities of low resolution GD-MS were shown by the example of steel analysis [616], where detection limits were down to 1 ng/g and up to 30 elements could be determined. 

To analyze metals and alloys directly without dissolution, both spark ablation [349] and laser ablation [61,211] dry aerosol generation systems have been used to introduce samples into an ICP-MS. These approaches often require matrix-matched standards, although several active research groups are focusing on techniques to reduce that requirement. The amount of material ablated depends on the sample type. Fractionation of elements can also be a problem, depending on the sample, the laser fluence, the laser wavelength, and the number of laser pulses used to sample from a fixed location. Volatile elements that are segregated in the samples appear to be most prone to fractionation problems [61],... 

Fig. 100. The analysis of Al and AlSi alloys by spark ablation coupled with ICP-OES. 3 kW argon-nitrogen I CP, Spectrovac 1000 and 1 kV spark at 25 Hz. (Reprinted with permission from Ref. [100].)...

Kehden A., Flock J., Vogel W. and Broekaert J. A. C. (2000) Direct solids atomic spectrometric analysis of metal samples by laser induced argon spark ablation coupled to ICP-OES, Appl Spectrosc, in press. 

Jakubowski N., Feldmann I., Sack B. and Stuwer D. (1992) Analysis of conducting solids by ICP-MS with spark ablation, J Anal At Spectrom 7 121-125. 

Spark ablation. Spark ablation solid sampling uses the same type of spark source already described. The function of the spark in this case is to vaporize the solid sample the ICP plasma can atomize any nonatomic vapor reaching it. Spark ablation is limited to the analysis of solids that conduct electricity. It is very useful for metals and alloys because it eliminates time-consuming sample dissolution and costly high-purity acids. 

Laser ablation Laser ablation (LA) in combination with the ICP atomiser has become a powerful and flexible techniqvie for solid sample introduction [47]. LA-AES has found its niche primarily as a bulk sampling technique for the analysis of bulk solid materials with a large focal spot (500—1000 pm). It offers comparable detection capability to spark ablation/emission but is not dependent on the sample being conductive. The experimental set-up, revealed in Fig. 12.32, consists in its simplest form of a pulsed laser (excimer- or Nd YAG-laser) with a defined pulse energy, some focusing optics, and a sample cell with a continuous Ar flow con-... 

ICP emission spectroscopy is used primarily for the qualitative and quantitative analysis of samples that are dissolved or suspended in aqueous or organic liquids. The techniques for preparation of such solutions are similar to those described in Section 9D-1 for flame absorption methods. With plasma emission, however, it is possible to analyze solid samples directly. These procedures include incorporating electrothermal vaporization, laser and spark ablation, and glow-discharge vaporization, all of which were described in Section 8C-2, Suspensions of solids in solutions can... 

In spark ablation, a spark at constant density is obtained in a matter of seconds, and thus, particularly in the case of small spark chambers, prebum times are accordingly low. In plasma emission as well as in plasma mass spectrometry a linear dynamic range of more than four orders of magnitude can be obtained and RSDs are a few percent in the case of absolute measurements. However, as shown by the results in Table 6, they can easily fall to below 1%, when using an internal standard element (Fe in the case of steel samples). The matrix effects from the sampling source are low, as will be shown in combination with ICP-OES (see Refs. [242, 248]). They are lower than in arc ablation, as here differences stemming from the thermal volatility of the elements and their compounds play a lesser role. The... 

With advanced Nd YAG lasers at atmospheric pressure, as utilized when coupling with ICP-OES or MS, selective volatilization is moderate. However, in the case of brass, it is as high as in spark ablation and causes problems in calibration [257]. In recent work, favorable working conditions in laser ablation studies were also shown to apply at reduced pressures of around 10-100 mbar [255, 258, 259]. In a number of cases, analytes in very different matrices were found to give signals which fitted astonishly well with the same calibration curves from OES, and a nearly matrix-independent calibration could be applied. This would be very welcome in the analysis of compact ceramics, for which no other direct analysis methods exist. By careful optimization of the laser working conditions, it is now possible to obtain very reproducible sample material from plastics, as shown by Hemmerlin and Mermet [260]. 

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