A new approach to calibration and determination of selected trace elements in food contact polymers by LA-ICP-MS

A calibration strategy using porous nylon disks and reference solutions is proposed for the first time for matrix matching and determination of As, Ba, Cd, Cr, Pb, Sr and Zn in polymers by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS). Polymer samples commonly used in contact with food were analyzed. The procedure consists on the use of porous nylon disks as support for a dried droplet reference solution. Calibration in the range of 0.50–190μgg−1 for Ba, Cd, Cr, Pb, Sr and Zn and from 0.30–9.0μgg−1 for As was used. Laser and ICP-MS instrument conditions were evaluated in order to achieve the best signal-to-background ratio. The radiofrequency power and carrier gas flow rate were fixed at 1300W and 1.25Lmin−1, respectively. Spot size, repetition rate, scan line speed and laser fluency were set to 100µm, 20Hz, 100µms−1 and 17.9Jcm−2, respectively, as the established conditions for analysis of standards and samples. By using these conditions, limits of detection, estimated considering B+3s (where B is the value of the blank and s is the standard deviation of 10 measurements of the blank), ranged from 0.09μgg−1 (208Pb) to 1.09 (53Cr) and 0.05μgg−1 (208Pb) to 2.10 (53Cr) for calibration with and without 13C as internal standard (IS). In spite to the use of nylon for matrix matching of different polymeric matrices, the normalization with 13C as IS was also evaluated. The precision of the method is relatively good (RSD