RIX3100. Fully Automated Sequential X-ray Spectrometer System. Product Information

Transcription

1 The Rigaku Journal Vol. 14/ number 1/ 1997 Product Information Fully Automated Sequential X-ray Spectrometer System RIX Introduction Wavelength dispersive X-ray fluorescence (WDXRF) analysis methods permit rapid, highprecision analysis of quantities of samples at a low cost. Consequently, WDXRF allows automation of process control and quality control analyses. The recent popularity of this method has led to requests for enhanced accuracy for ultralight elemental analysis and for the analysis of extremely small areas or extremely small samples. To meet these new requirements, Rigaku has introduced a new version of the RIX series, the RIX3100". The new system features high sensitivity and the quantitative analysis capability for limited areas, as small as 1 mm in diameter. Also, a userfriendly, high-performance data processing system is integral for expanding applications. 2. Features (1) High Power A high-frequency X-ray generator is standardly provided to accommodate a 4 kw Rh-target X-ray tube and a 150 ma current. When compared with the conventional 3 kw unit, the RIX3100 achieved about 1.5 times greater sensitivity for heavy elements and more than two times for light elements. (Fig. 1) (2) Analysis of Very Small Areas [1 mm dia.] A unique optical system allows qualitative and quantitative analysis for limited areas as small as 1 mm in diameter. This makes it possible to conduct qualitative and quantitative analysis of contaminants on the sample surface as well as of exceedingly small samples, analyses up until now regarded as impossible. Thus the scope of applications has broadened significantly. (3) Perfect Scan Perfect scan is a newly developed technique to perform an upgraded SCAN QUANT by incorporation optimum conditions for each element as standard conditions. In the conventional SCAN QUANT, the standard condition is typically 50kV-50mA covering the whole element range. In the perfect scan, optimum kv-ma for each specific element is set as the measuring condition. As a result, the 4kW power can

2 Fig. 1 High-power 4 kw X-ray tube. P.S.: Perfect scan C.M.: Conventional method Fig. 2 Effectiveness of perfect scan (1). In trace Si analysis, the effect of high-order rays of Zn, a major component, can be reduced. Fig. 3 Effectiveness of perfect scan (2). Vol. 14 No

3 be optimized to enable greater sensitivity and correspondingly better delectability for trace components. Examples are shown in Figs. 2 and 3. (4) Excellent Angular Resolution and S/N Ratio The RIX3100 has also reached the highest level ever in terms of angular resolution and signal-to-noise ratio. The optical system with a design emphasis on angular resolution allows elements in close proximity to one another to be analyzed separately. Examples of Fig. 4 Excellent angular resolution (Ti-Kβ 1, V-Kα separation). the RIX3100's excellent angular resolution are shown in Figs. 4 and 5. Signal-to-noise ratio is imperative for highprecision, stable analysis of trace components. Therefore design emphasis of the optical system was placed equally on the S/N ratio. In addition, five kinds of primary beam X-ray filters are provided to offer the optimum filter for each element. Figure 6 shows a rock sample analysis with and without a Cu primary beam X-ray filter. (5) Optimal Analysis Conditions with a Dual Target X-ray Tube A dual target X-ray tube can also be mounted on the RIX3100. The dual target tube is available in two types: Rh/Cu and Rh/W. By using two types of targets through automatic switching device, highly sensitive analysis can be performed over the entire element range. When the Rh target lacks sensitivity in a certain elements range, the other target, having higher sensitivity in that specific range, can take over. The Rh/Cr dual X-ray tube is particularly useful for trace element analysis in polymers because the Cr target excels in the excitation' of the K-rays of Ti, Ca, K, and Cl, and also the Lrays of Ba, Sn and Sb. The Rh/W dual X-ray tube incorporates the W target which is especially good for the excitation of transition elements and rare earth elements. A typical example is the analysis of very small quantities of rare earth contained in rocks. Fig. 5 Excellent angular resolution (S-Kα, Mo-Lα separation). 39 The Rigaku Journal

4 Fig. 6 Enhanced S/N ratio (effectiveness of primary beam X-ray filter) (Sample: JG-1a powder) Table 1 Applications Chemicals Electronics and Magnetic materials Steel Non-ferrous metals Ceramics Petroleum, Coal Agricultural produce, Foodstuffs Tasting, Research Environmental research Catalyst, Polymer, Medicine, Pigment, Oil & Fat, detergent, Cosmetics, Toner material, Coating paper Semiconductor device, Memory disk, Magnetic head, Ferrite, Secondary battery material, Solar battery material Iron ore, Slag, Ferroalloy, Special steel, Cast steel, Cast sand, Surface treatment steel plate Copper alloy, Nickel alloy, Aluminum alloy, Precious metals, Ores, Aluminum can material, Shape memory alloy Cement, Glass, Silica sand, Alumina, Silicon nitride, New ceramics, refractories, Enamel Grease, Lubricant, Cutting oil, Kerosene, Gas oil, Heavy oil, Coal, Coke, Coal ash Soil, Fertilizer, Plant, Pasturage, Feed, foodstuffs, Seasoning Rock, Mineral, volcanic ash, Organisms, Archaeological materials Industrial wastes, Sludge, River water, Air-borne dust 3. Applications Table 1 shows many applications that the RIX3100 is used for. 4. System Configuration 4.1 Hardware (Fig. 7) Irradiation a sample with a beam of primary X- rays from the X-ray tube will induce secondary X- rays, or fluorescent X-rays with wavelengths characteristic of the elements in the sample. Spectrometric analysis is performed by using an analyzing crystal and detecting the fluorescent X-rays with a detector (SC, F-PC). For quantitative analysis, counting is made at a fixed spectral angle. For qualitative analysis, counting is made while scanning under interlocking operation of the analyzing crystal and detector. A microcomputer controls sample replacement, goniometer movement and the operation of counting circuits, etc., while a personal computer handles data analysis and calculations. Vol. 14 No

5 Fig. 7 Hardware system configuration SFP method: A method to obtain a matrix correction coefficient by applying the FP method Semi-FP Me thod) EC method: A method to obtain a matrix correction coefficient based on the measured intensity (Empi rical Calibration Method) Fig. 8 Concept of data processing software. 41 The Rigaku Journal

6 4.2 Upgraded Data Processing System A variety of analytical techniques are incorporated in the data processing system for the RIX3100. This system makes the most of the FP (Fundamental Parameter) method so that analysis can be performed even when the content of a sample is quite unknown or when standard reference samples are unavailable. (Fig. 8) In particular, SCAN QUANT features the capability of obtaining rough quantitative values (semiquantitative values) of elements in a sample, and thus it is used widely. To meet current demands for ever higher accuracy of analysis, a matching library function has been added to SCAN QUANT. In conventional SCAN QUANT, oxide reagents, pure metals and the like are used as library samples. They are registered in a sensitivity library (common library) for the analysis of every type of sample. But analysis of light elements, and that of ultralight elements in particular, still pose problems inherent for the samples themselves. For instance, errors occur due to the unevenness of powder samples and due to thermal hysteresis among different metallic samples. Such errors are still unresolved. To handle them, a standard sample which resembles a sample for analysis can now be registered in a matching library and after using the search operation, a computation is made based on the standard sample. Analysis accuracy can be improved in this way. (Fig. 9) Also, for SCAN QUANT of a liquid sample, a protective film (polymer film, etc.) for the sample has previously been corrected for requiring the preparation of a sensitivity library dedicated to that protective film. Now, by automatic correction of X- ray absorption due to varied protective films (polypropylene, polyester), the common library can be used easily for SCAN QUANT. (Fig, 10) The impurity effect due to the protective film (polypropylene, polyester) poses a problem in trace element analysis, however. It can be corrected for by Fig. 9 Polished-up SCAN QUANT. Vol. 14 No

7 Fig. 10 Corrections for sample protecting film, atmosphere and impurity (blank) Fig. 11 Sensitivity enhancement in Be analysis using the 'impurity eliminating" function based on registered data obtained from a blank sample measurement. 5. Application Examples (1) Ultralight Elemental Analysis The frontier technique in light element analysis utilizing the new optical system with a newly developed synthetic lattice has resulted in 4 to 5 times higher sensitivity for beryllium compared with conventionally obtainable intensities. (Fig. 1 1) The detection limit is also improved by two times. As an example, the analysis of Be in Be copper is shown in Fig. 12. The analytical precision has been improved further for boron contained in glass. (Fig. 13) Fig. 12 Be analysis in Be copper. - with 4 kw X-ray tube mounted RIX This achievement of higher-sensitivity for ultralight elements, analysis is expected to handle new applications such as the analysis of low alloy steel in a very small area, carbon in cast iron, and trace element analysis of oxygen in fluoride which was considered difficult. 43 The Rigaku Journal

8 (2) Exceedingly Small Area [1 mm dia.] Analysis Figure 14 shows the use of SCAN QUANT over a 1 mm dia. area on a tiny fragment of stainless steel. As is shown from this example, satisfactory analysis results are obtained even in the case of exceedingly small areas. For sample positioning, a portion of a sample to be measured can be simply and securely Fig. 13 High sensitivity analysis of boron in glass. specified by using Rigaku's Y mask for positioning (patent pending), as shown in Fig. 15. An example of a practical application is shown in Fig. 16, SCAN QUANT of a triple ring precious metal (yellow, pink, white). Differences in composition are obvious even when dealing with a precious metal with small surface areas. Differences in composition due to the color can be determined as well. (3) The Effect of Primary Beam X-ray Filter Figure 17 shows an example of the analysis of V in heavy oil. The analysis was performed with an upgraded S/N condition using an Al primary beam X- ray filter, resulting in a better detection limit than without using such a filter. (4) Quantitative Analysis with the RHIW Dual X-ray Tube Figure 8 shows an example of the analysis of trace Ce in rock. This example clearly displays higher sensitivity with the W target than with the Rh target. Fig mm dia. area analysis Fig mm dia. area analysis Vol. 14 No

9 Fig 16. Example of SCAN QUANT of precious metal ring. Fig. 17 Analysis of V in heavy oil Fig. 18 Analysis example of trace Ce in rock. -- with a dual target X-ray tube [Rh/W] -