Excitation and Detection

X-ray tube excitation provides excellent sensitivity across the full 1-37 KeV (Na - U) analytical range. Optimum sensitivity for a particular element is achieved by selecting an X-ray tube voltage and primary beam filter which produce a band of excitation radiation just above the absorption edge of the target element. This approach has the dual effect of improving sensitivity and reducing background. A high resolution detector provides low detection limits, greater freedom from line overlaps, and better accuracy over a wide range of concentrations.

Detection limits depend on the element and the sample matrix. From sodium through calcium detection limits range from a few hundred ppm to 10 ppm. From titanium through uranium, detection limits as low as 2ppm are achieved. Analytical precision depends on the element(s) of interest the concentration, and the counting time. For most metals at 100ppm in a organic matrix, precision of 3% RSD (relative standard deviation) can be achieved with counting times of 10 minutes or less. Long-term stability of the system is better than 1% relative permitting operation without restandardization for weeks or months at a time.

Several algorithms are available for analysis of measured intensities, including linear and quadratic curves, an empirical matrix correction which uses a suite of type standards, and fundamental parameters matrix correction.

The software is designed to operate with minimal operator intervention once an analytical method has been established. Automation of analytical parameters such as voltage, current, and atmosphere (air/vacuum/helium) allow total software control of the system so that even with the tremendous flexibility of the system, operation is initiated with only two keystrokes.