1. Introduction

Wavelength dispersive X-ray fluorescence(WDXRF) analysis methods permit rapid, high-precision analysis of quantities of samples at a lowcost. Consequently, WDXRF allows automation ofprocess control and quality control analyses.

The recent popularity of this method has led torequests for enhanced accuracy for ultralight ele-mental analysis and for the analysis of extremelysmall areas or extremely small samples.

To meet these new requirements, Rigaku hasintroduced a new version of the RIX series, the“RIX3100". The new system features high sensitivityand the quantitative analysis capability for limitedareas, as small as 1 mm in diameter. Also, a user-friendly, high-performance data processing system isintegral for expanding applications.

2. Features

(1) High Power

A high-frequency X-ray generator is standardlyprovided to accommodate a 4 kW Rh-target X-ray

tube and a 150 mA current. When compared with theconventional 3 kW unit, the RIX3100 achieved about1.5 times greater sensitivity for heavy elements andmore than two times for light elements. (Fig. 1)

(2) Analysis of Very Small Areas [1 mm dia.]

A unique optical system allows qualitative andquantitative analysis for limited areas as small as1 mm in diameter. This makes it possible to conductqualitative and quantitative analysis of contaminantson the sample surface as well as of exceedingly smallsamples, analyses up until now regarded as impos-sible. Thus the scope of applications has broadenedsignificantly.

(3) Perfect Scan

Perfect scan is a newly developed technique toperform an upgraded SCAN QUANT by incorpora-tion optimum conditions for each element as standardconditions. In the conventional SCAN QUANT, thestandard condition is typically 50kV-50mA coveringthe whole element range. In the perfect scan, optimum kV-mA for each specific element is set as themeasuring condition. As a result, the 4kW power can

The Rigaku Journal

Vol. 14/ number 1/ 1997

Product Information

Fully Automated SequentialX-ray Spectrometer System RIX3100

Vol. 14 No. 1 1997 38

Fig. 1High-power 4 kW X-ray tube.

P.S.: Perfect scan

C.M.: Conventional method

Fig. 2Effectiveness of perfect scan (1).

Fig. 3Effectiveness of perfect scan (2).In trace Si analysis, the effect of high-order rays of Zn, a major

component, can be reduced.

be optimized to enable greater sensitivity andcorrespondingly better delectability for tracecomponents. Examples are shown in Figs. 2 and 3.

(4) Excellent Angular Resolution and S/N Ratio

The RIX3100 has also reached the highest levelever in terms of angular resolution and signal-to-noise ratio.

The optical system with a design emphasis onangular resolution allows elements in close proximityto one another to be analyzed separately. Examples of

the RIX3100's excellent angular resolution are shownin Figs. 4 and 5.

Signal-to-noise ratio is imperative forhighprecision, stable analysis of trace components.Therefore design emphasis of the optical system wasplaced 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 andwithout a Cu primary beam X-ray filter.

(5) Optimal Analysis Conditions with a Dual TargetX-ray Tube

A dual target X-ray tube can also be mounted onthe RIX3100.

The dual target tube is available in two types:Rh/Cu and Rh/W. By using two types of targetsthrough automatic switching device, highly sensitiveanalysis can be performed over the entire elementrange. When the Rh target lacks sensitivity in a certain elements range, the other target, having highersensitivity in that specific range, can take over.

The Rh/Cr dual X-ray tube is particularly usefulfor trace element analysis in polymers because the Crtarget excels in the excitation' of the K-rays of Ti, Ca,K, and Cl, and also the Lrays of Ba, Sn and Sb. TheRh/W dual X-ray tube incorporates the W targetwhich is especially good for the excitation oftransition elements and rare earth elements. A typicalexample is the analysis of very small quantities of rare earth contained in rocks.

39 The Rigaku Journal

Fig. 4 Excellent angular resolution (Ti-Kβ1, V-Kαseparation).

Fig. 5 Excellent angular resolution (S-Kα, Mo-Lα separation).

3. Applications

Table 1 shows many applications that theRIX3100 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 wavelengthscharacteristic 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 afixed spectral angle. For qualitative analysis,counting is made while scanning under interlockingoperation of the analyzing crystal and detector.

A microcomputer controls sample replacement,goniometer movement and the operation of countingcircuits, etc., while a personal computer handles dataanalysis and calculations.

Vol. 14 No. 1 1997 40

Applications

ChemicalsCatalyst, Polymer, Medicine, Pigment, Oil & Fat, detergent, Cosmetics, Toner material,Coating paper

Electronics and Magnetic materialsSemiconductor device, Memory disk, Magnetic head, Ferrite, Secondary batterymaterial, Solar battery material

SteelIron ore, Slag, Ferroalloy, Special steel, Cast steel, Cast sand, Surface treatment steelplate

Non-ferrous metalsCopper alloy, Nickel alloy, Aluminum alloy, Precious metals, Ores, Aluminum canmaterial, Shape memory alloy

CeramicsCement, Glass, Silica sand, Alumina, Silicon nitride, New ceramics, refractories,Enamel

Petroleum, Coal Grease, Lubricant, Cutting oil, Kerosene, Gas oil, Heavy oil, Coal, Coke, Coal ash

Agricultural produce, Foodstuffs Soil, Fertilizer, Plant, Pasturage, Feed, foodstuffs, Seasoning

Tasting, Research Rock, Mineral, volcanic ash, Organisms, Archaeological materials

Environmental research Industrial wastes, Sludge, River water, Air-borne dust

Table 1

Fig. 6 Enhanced S/N ratio (effectiveness of primary beam X-ray filter) (Sample: JG-1a powder)

41 The Rigaku Journal

Fig. 7 Hardware system configuration

SFP method: A method to obtain a matrix correction coefficient by applying the FP method Semi-FP Method)

EC method: A method to obtain a matrix correction coefficient based on the measured intensity (EmpiricalCalibration Method)

Fig. 8 Concept of data processing software.

4.2 Upgraded Data Processing System

A variety of analytical techniques areincorporated in the data processing system for theRIX3100. This system makes the most of the FP(Fundamental Parameter) method so that analysis canbe performed even when the content of a sample isquite unknown or when standard reference samplesare unavailable. (Fig. 8)

In particular, SCAN QUANT features thecapability of obtaining rough quantitative values(semiquantitative values) of elements in a sample, and thus it is used widely. To meet current demands forever higher accuracy of analysis, a matching libraryfunction 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 (commonlibrary) for the analysis of every type of sample. Butanalysis of light elements, and that of ultralightelements in particular, still pose problems inherent for

the samples themselves. For instance, errors occurdue to the unevenness of powder samples and due tothermal hysteresis among different metallic samples.Such errors are still unresolved. To handle them, astandard sample which resembles a sample foranalysis can now be registered in a matching libraryand after using the search operation, a computation ismade based on the standard sample. Analysisaccuracy can be improved in this way. (Fig. 9)

Also, for SCAN QUANT of a liquid sample, aprotective film (polymer film, etc.) for the sample haspreviously been corrected for requiring thepreparation of a sensitivity library dedicated to thatprotective film. Now, by automatic correction of X-ray absorption due to varied protective films(polypropylene, polyester), the common library canbe used easily for SCAN QUANT. (Fig, 10)

The impurity effect due to the protective film(polypropylene, polyester) poses a problem in traceelement analysis, however. It can be corrected for by

Vol. 14 No. 1 1997 42

Fig. 9 Polished-up SCAN QUANT.

using the 'impurity eliminating" function based onregistered data obtained from a blank samplemeasurement.

5. Application Examples

(1) Ultralight Elemental Analysis

The frontier technique in light element analysisutilizing the new optical system with a newlydeveloped synthetic lattice has resulted in 4 to 5 timeshigher sensitivity for beryllium compared withconventionally obtainable intensities. (Fig. 1 1) Thedetection limit is also improved by two times. As anexample, the analysis of Be in Be copper is shown inFig. 12.

The analytical precision has been improvedfurther for boron contained in glass. (Fig. 13)

This achievement of higher-sensitivity forultralight elements, analysis is expected to handlenew applications such as the analysis of low alloysteel in a very small area, carbon in cast iron, and trace element analysis of oxygen in fluoride which wasconsidered difficult.

43 The Rigaku Journal

Fig. 11 Sensitivity enhancement in Be analysis

Fig. 12 Be analysis in Be copper. - with 4 kW X-raytube mounted RIX3100 -

Fig. 10 Corrections for sample protecting film, atmosphere and impurity (blank)

(2) Exceedingly Small Area [1 mm dia.] Analysis

Figure 14 shows the use of SCAN QUANT over a1 mm dia. area on a tiny fragment of stainless steel. Asis shown from this example, satisfactory analysisresults are obtained even in the case of exceedinglysmall areas. For sample positioning, a portion of asample to be measured can be simply and securely

specified by using Rigaku's Y mask for positioning(patent pending), as shown in Fig. 15.

An example of a practical application is shown inFig. 16, SCAN QUANT of a triple ring preciousmetal (yellow, pink, white). Differences incomposition are obvious even when dealing with aprecious metal with small surface areas. Differencesin composition due to the color can be determined aswell.

(3) The Effect of Primary Beam X-ray Filter

Figure 17 shows an example of the analysis of Vin heavy oil. The analysis was performed with anupgraded S/N condition using an Al primary beam X-ray filter, resulting in a better detection limit thanwithout using such a filter.

(4) Quantitative Analysis with the RHIW Dual X-rayTube

Figure 8 shows an example of the analysis oftrace Ce in rock. This example clearly displays higher sensitivity with the W target than with the Rh target.

Vol. 14 No. 1 1997 44

Fig. 13 High sensitivity analysis of boron in glass.

Fig. 15 1 mm dia. area analysis

Fig. 14 1 mm dia. area analysis

Fig 16.Example of SCAN QUANT of preciousmetal ring.

Fig. 17 Analysis of V in heavy oil

Fig. 18Analysis example of trace Ce in rock. -- with a dual targetX-ray tube [Rh/W] -