Matrix effects of iron-based solution on instrumental working parameters of inductively coupled plasma atomic emission spectrometry (ICP-AES) were studied. Multielement water solutions containing Cd, Cr, Ni and Pb in matrix that consisted of zero-valent iron nanoparticles (nZVI) were analysed. Changes in emission intensities for Cd, Cr, Ni and Pb spectral lines were determined for iron matrix solutions in comparison with solutions without addition of nano zero valent iron particles (nZVI). From the experimental results, limits of detection (LOD) and signal to background ratio (SBR) were determined, as well as the impact of iron matrix concentration, RF generator power and carrier gas flow on emission intensity lines measured in axial position. The optimal instrumental working parameters for simultaneous multielement analysis were found at RF generator power higher than 1.3 kW and carrier gas flow velocities lower than 0.8 L / min. Best LOD's were achieved at RF generator power values of 1.3 – 1.4 kW and carrier gas flow velocities greater than 0.6 L / min. Highest SBR ratios for majority of elements were achieved for the RF generator power value at 1.3 kW. For optimisation of instrumental working parameters Mermet magnesium line ratio Mg II (280.270 nm) / Mg I (285.213 nm) was used. It was determined that the best stability and plasma robustness is achieved at RF generator power values of 1.3 – 1.4 kW and carrier gas flow velocities of 0.6 – 0.8 L / min.