A laser ablation technique has been studied as a versatile method of direct solid sampling for subsequent elemental analysis. It has been successfully coupled with analytical techniques such as atomic absorption spectrometry (AAS)1-3, microwave-induced4, direct currents, and inductively coupled6,7 plasma atomic emission spectrometry (MIP-, DCP-and ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS).8-1° These tandem methods have a number of advantages such as high sensitivity, little or no sample preparation, small amount of samples required and the ability to analyze both conductive and nonconductive solids.We recently investigated laser ablation/ ICP-AES and ICP-MS in order to develop a rapid method for solid analysis. 7'8' 11,12 In these reports we showed that fractional vaporization, which limited analytical precision and accuracy, occurred during the ablation process. On the other hand, Hager10 indicated in a report on laser ablation/ ICP-MS that differences in the response factors were observed between free-running and Q-switched laser modes of operation • and that more uniform responses were obtained with the Q-switching mode. Thompson et a1.13 also showed that the matrix effect associated with an ablation event can be minimized with a maximum Q-switched laser. These results show that the magnitude of selective vaporization depends on the types of laser pulses.The present work aimed at investigating the laser dependence of selective vaporization. The use of six types of the laser pulses (three types of lasers each at two different running modes) was compared by collecting ablated particles, followed by analyzing them with solution-based ICP-AES or ICP-MS. Experimental Apparatus and operating conditionsThe operating conditions of the three types of lasers are shown in Table 1, together with the amounts of ablated

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Direct analysis of silicate samples for the rare earth elements (REEs) by inductively coupled plasma mass spectrometry (ICP-MS) has been performed. Each finely ground sample (particle size <3 µm) was dispersed in 0.1% aqueous Triton X-100 solution and nebulized into an inductively coupled plasma. The resulting ions were detected by mass spectrometry. Parameters such as particle size, slurry concentration and argon carrier flow rate exercised a great influence on sensitivity, precision and accuracy of slurry nebulization/ICP-MS. Calibration curves were constructed using aqueous standard solutions. The extended dynamic range (EDR) detection system allowed the use of matrix element as an internal standard; this procedure was effective to correct the differences in sensitivity between the solution and the slurry methods. The optimum procedure was applied to the determination of REEs in standard silicate rocks of the Geological Survey of Japan. The precision ranged from 0.8 to 6.3 (RSD, %) for REEs contents of 0.13 -38 ppm. Detection limits of REEs were excellent (0.002 -0.02 ppm at the effective integrating time of 10 s). KeywordsSlurry nebulization, inductively elements coupled plasma mass spectrometry, silicate analysis, rare earthInductively coupled plasma (ICP) is now becoming accepted as an effective ionization source for subsequent mass spectrometric measurement. Comprehensive reviews have been presented by Date', Houk2 and Kawaguchi.3 In initial works on ICP mass spectrometry (ICP-MS), samples were generally introduced into ICP as aerosols of aqueous solutions; therefore, the dissolution of solid samples was required for many applications. This process is quite labor-intensive and time-consuming, especially for the analysis of refractory ceramic or silicate rocks.

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A flow injection (FI) technique has been applied to the trace analysis of metal samples using inductively coupled plasma mass spectrometry (ICP-MS). Parameters such as carrier flow rate, injection volume and sample concentration has a great influence on the sensitivity, precision and analysis time of the FI/ ICP-MS. A small volume (240 µl) of nickel-base alloy solutions containing up to 0.75% (m/v) was introduced into an ICP-MS instrument by the flow of carrier solution. The optimized procedure was applied to the determination of Tl, Pb and Bi in standard nickel-base alloys of the National Institute of Standards and Technology. The result was compared with that of the continuous sample nebulization method. The Fl method gave improved precision as well as high sensitivity. The precision ranged from 2.0 to 8.2 (RSD, %) for the elements containing 0.25 -11.7 ppm. Detection limits were 0.001-0.04 ppm.Keywords Flow injection analysis, inductively coupled plasma mass spectrometry, nickel-base alloy, thallium, lead, bismuthInductively coupled plasma mass spectrometry (ICP-MS) has been extensively employed for trace metal analysis and metal isotopic analysis.'-3 A primary limitation of the method is the difficulty of the analysis of solutions containing high concentration of dissolved salts, so fairly dilute sample solutions (<0.1 % (m/ v)) were generally introduced into the ICP-MS instrument. The problems are mainly associated with the blockage of sampler orifice, polyatomic spectral interference and matrix induced non-spectroscopic interference (signal suppression or signal enhancement).3-6The coupling of flow injection (Fl) technique to ICP-MS is an attractive approach for the analysis of the solutions of high salt content. Advantages of the Fl method over the conventional solution introduction method have been discussed in previous papers.5-g The merit of the FI/ ICP-MS include minimal orifice blockage, minimal non-spectroscopic interference by concomitant salts, small amount of sample consumed and rapid sample throughput.In spite of a large demand for improvement of precision and rapidity in trace analysis of alloys, and of the high applicability of the Fl procedure9, the Fl method has been rarely applied in this area.5 This work was undertaken to develop the Fl procedure for ICP-MS.The analytical system was applied to the determination of thallium, lead and bismuth in nickelbase alloys by means of ICP-MS. A simple Fl system seemed to alleviate the problems associated with the high salt content and to extend significantly the capability of ICP-MS. Multi-element stock solution containing 10 µg ml-' of Tl, Pb and Bi was prepared by mixing aliquots of 1 mg ml-' of single-element stock solutions (for use in atomic absorption spectrometry, Kanto Chemical Co. Inc.). Working standards were obtained by adding the matrix solution for matrix matching and 2 ml of 2.3 M hydrofluoric acid, followed by diluting to appropriate volume with 0.7 M nitric acid. The matrix solution was prepared by dissolving pure Ni, Cr and Co metals ...