Suitability of the PicoTAX total reflection X-ray fluorescence (TXRF) spectrometer was studied for determination of As and trace metals in the Haveri Au-Cu sulphide mine tailings leached with aqua regia and in water affected by acid mine drainage. Results for 12 water and 16 tailings samples were compared with accredited methods, inductively coupled plasma-atomic emission spectrometry (ICP-AES) and inductively coupled plasma-mass spectrometry (ICP-MS). Certified reference samples analysed were QC Metal LL from Eurofins A/S, and groundwater CRM 609 and lake sediment BCR-280R from the Institute for Reference Materials and Measurements (IRMM) of the European Commission. Approximate method detection limits (MDL) for water samples, based on reference sample analyses, are in the range of 20 μg l−1 for As, Cr, Pb and Zn and 5–10 μg l−1 for Co, Cu, Ni, V and Mn. MDLs for aqua regia leach, calculated using reagent blank values, were ≤20 (mg kg−1) for As, Co, Cr, Cu, Mn, Ni, V, and Zn. Random error of determination varied from 12 to 20 %. Inter-element interferences include: As and Pb on each other, and Fe on Cr and Co. Using the Mo anode of the X-ray tube excludes the determination of Cd, Mo, Nb, Tc and Zr. TXRF can be recommended merely as a preliminary technique for selecting samples.