Lexikon
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X-ray fluorescence spectrometric analysis
XRF (X-ray fluorescence spectrometry) is a non-destructive analytical technique used to identify and determine the concentrations of elements present in solid, powdered and liquid samples. The atoms of the analyte are illuminated by X-ray and the excited atoms discharge fluorescent radiation. The energy (wavelength) of the emitted radiation is characteristic to the element, the intensity is proportional to the abundance (concentration) of the element. The analysis is based on a calibration with samples containing known elements. XRF is capable of measuring elements from beryllium (Be) to uranium (U) and beyond at trace levels often below one part per million and up to 100%. The concentration measurement is influenced by the matrix (matrix effect). The XRF spectrometer measures the individual component wavelengths of the fluorescent emission produced by a sample when irradiated with X-rays. Typical environmental applications: at wood treating facilities determination of chromium, arsenic and pentachlorophenol; in numerous other sites toxic metals such as lead, mercury, arsenic and cadmium. XRF is commonly used as a screening tool to identify contaminated areas that must be remedied. Smaller instruments, even hand held devices might be used on site, while higher end instruments are used in the lab. (Source: www.panalytical.com)
xenobiotic
xenobiotics are substances foreign to an entire biological system. They are artificial substances, which did not exist in nature before their synthesis by humans. The term originates from Greek, meaning foreigner, stranger.
xenoestrogen
xenobiotic that have estrogenic effect is named xenoestrogen. Their effect is based on their ability to bound to human (or animal) estrogen-receptors. Amongst xenoestrogens pesticides, industrial chemicals and additives as well as pharmaceutical substances can be found.