Determination of technetium-99 using electrothermal vaporization inductively coupled plasma-mass spectrometry (ETV-ICP-MS) and NH4OH as chemical modifier

In recent years, developments in ICP-MS have led to improved methods for determination of long-lived radionuclides. This paper reports the use of NH4OH as a matrix modifier and ETV sample introduction for the determination of technetium-99 (99Tc) in a variety of environmental and biological samples, using Re as carrier and 99mTc as yield monitor in the chemical separation method. Addition of an excess of NH4OH led to a stable 99Tc signal, reduced memory effect, better reproducibility and reduced detection limits. Following radiochemical separation of 99Tc from the sample matrix, detection limits in the order of a few μBq have been achieved. ETV has also proved applicable for rapid, direct analysis of a number of environmental samples having relatively high concentrations of 99Tc (sediment extracts and river water close to nuclear installations). However, in this case, control of matrix effects (signal reduction and enhancement) using standard additions is necessary.