The LOQ was based on the trueness and precision data, obtained by recovery determination and was defined as the lowest validated spiked level meeting the requirements of a recovery within the range 70–120% and an RSD 6 20%. Measurement uncertainty (MU) was established according to ISO (International Organization for Standardization)/TS 21748:2004 (International Organization for Standardization, 2004) and EURACHEM guide (Eurachem, 2000).