Precision is the degree of variability of results, without considering the sample variability. The CV% values obtained were below 3% (0.91–2.99%), thus fulfilling the required criteria for applicable analytical method. The spiking recoveries for all analyte toxic elements and As species were in the range of 94.5–107% which further confirmed that there was no significant loss or gain for each analyte during the digestion/extraction procedures (p > 0.05; Table 2). For the analysed CRM (NMIJ CRM 7405-a), the recovery percentage was in the range of: 96.7–102.3%, (Table 3). Importantly the recovery value means of the analytes for the CRM was found to be within the interval of confidence (p < 0.05) calculated for the values certified, confirming the applicability of the analytical method (Khan et al., 2013). Based on these results for the quality parameters analysed, the analytical methods followed in this research were found very efficient to apply for determination of the analyte toxic metals and As species in edible seaweed samples.