INNOVATIVE TECHNOLOGY VERIFICATION REPORT XRF TECHNOLOGIES FOR MEASURING TRACE ELEMENTS IN SOIL AND SEDIMENT RONTEC PICOTAX XRF ANALYZER
The Rontec PicoTAX 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 PicoTAX 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 PicoTAX 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 PicoTAX is a transportable bench-top device that provides quantitative and semi-quantitative multi-element microanalysis of soils and sediments using total reflection XRF spectroscopy. The spectrometer includes a 40-watt metal-ceramic x-ray tube excitation source and a thermoelectrically cooled silicon drift (Si Drift) x-ray detector. The PicoTAX is capable of detecting up to 75 elements from aluminum to yttrium and from palladium to uranium. The PicoTAX uses an internal standard for instrument calibration; thus, initial calibration is not required. A solution of internal standard that contains a project-specific element is added to each sample to establish response factors (determined by the software). Element quantitation is determined by comparing the response to the unknown element to the response of the internal standard with a known concentration. A laptop computer is used to monitor and control all aspects of PicoTAX system operation. Rontec’s Quantum software, which is loaded into the laptop computer, calibrates the instrument, handles measurement data and methods, controls all hardware functions, and provides statistical functions, reporting functions, and data and spectra export. This report describes the results of the evaluation of the PicoTAX 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 PicoTAX analyzer is compiled and compared to both fixed laboratory costs and average XRF instrument costs.