Superfund Innovative Technology Evaluation (SITE)
Note: EPA no longer updates this information, but it may be useful as a reference or resource.
ITRV: XRF Technologies for Measuring Soil
The Rigaku ZSX Mini II (ZSX Mini II) XRF Services x-ray fluorescence (XRF) analyzer was demonstrated under the U.S. Environmental Protection Agency (EPA) Superfund Innovative Technology Evaluation (SITE) Program. The field portion of the demonstration was conducted in January 2005 at the Kennedy Athletic, Recreational and Social Park (KARS) at Kennedy Space Center on Merritt Island, Florida. The demonstration was designed to collect reliable performance and cost data for the ZSX Mini II analyzer and seven other commercially available XRF instruments for measuring trace elements in soil and sediment. The performance and cost data were evaluated to document the relative performance of each XRF instrument.
This innovative technology verification report describes the objectives and the results of that evaluation and serves to verify the performance and cost of the ZSX Mini II analyzer. Separate reports have been prepared for the other XRF instruments that were evaluated as part of the demonstration. The objectives of the evaluation included determining each XRF instrument’s accuracy, precision, sample throughput, and tendency for matrix effects. To fulfill these objectives, the field demonstration incorporated the analysis of 326 prepared samples of soil and sediment that contained 13 target elements.
The prepared samples included blends of environmental samples from nine different sample collection sites as well as spiked samples with certified element concentrations. Accuracy was assessed by comparing the XRF instrument’s results with data generated by a fixed laboratory (the reference laboratory). The reference laboratory performed element analysis using acid digestion and inductively coupled plasma – atomic emission spectrometry (ICP-AES), in accordance with EPA Method 3050B/6010B, and using cold vapor atomic absorption (CVAA) spectroscopy for mercury only, in accordance with EPA Method 7471A.
The ZSX Mini II is a “wavelength-dispersive” XRF analyzer that can analyze for elements ranging in mass from fluorine to uranium. The ZSX Mini II differentiates the x-ray energies emitted from a sample by dispersing the x-rays into different wavelength ranges using crystals. By contrast, more common “energy-dispersive” XRF analyzers differentiate between x-ray energies based on voltages measured by the detector. For some applications, wavelength-dispersive XRF analyzers can achieve high resolutions and very good sensitivity through the reduction of interelement interferences.
Wavelength-dispersive XRFs have historically been large, laboratory-bound instruments with significant requirements for power and cooling. The ZSX Mini II is a smaller, transportable unit that can operate without additional cooling fluids on standard 110-volt circuits. The unit can employ an economical gas proportional counter as a detector rather than a diode detector with a multi-channel analyzer (common in energy-dispersive instruments) because wavelength resolution is achieved with the crystals. This report describes the results of the evaluation of the ZSX Mini II analyzer based on the data obtained during the demonstration. The method detection limits, accuracy, and precision of the instrument for each of the 13 target analytes are presented and discussed. The cost of element analysis using the ZSX Mini II analyzer is compiled and compared to both fixed laboratory costs and average XRF instrument costs.