Determination of chromium, cadmium and lead in food-packaging materials by axial inductively coupled plasma time-of-flight mass spectrometry Original Research Article

Inductively coupled plasma mass spectrometry (ICP-MS) with a time-of-flight (TOF) analyser was used for the determination of chromium, cadmium and lead in six food-packaging materials (paper and paper board). The samples (0.20–0.25 g) were digested in concentrated nitric acid in a high pressure microwave oven at 180 °C within 15 min. Two different plasma conditions were applied: cool plasma conditions (0.76 kW; 0.85, 0.89 and 15.5 l min−1 nebuliser, auxiliary and plasma gas flow rate, respectively) for the determination of chromium and normal plasma conditions (1.21 kW; 0.66, 0.68 and 13.6 l min−1 nebuliser, auxiliary and plasma gas flow rate, respectively) for the determination of cadmium and lead. External calibration was used in combination with rhodium (40 ng g−1) as an internal standard. The detection limits (DL = 3S.D./sensitivity) under the conditions used corresponded to 0.01 ng g−1 (52Cr), 0.06 ng g−1 (53Cr), 0.07 ng g−1 (111Cd), 0.03 ng g−1 (114Cd) and 0.02 ng g−1 (206Pb and 208Pb). The precision (R.S.D.) for six replicate determinations (10 s integration time) of 1 and 10 ng g−1 of each analyte varied from 0.72% (206Pb) to 4.43% (111Cd). The contents of chromium, cadmium and lead in the examined materials were evaluated using the signals of 52Cr, 114Cd and 208Pb. They were in the range: 0.25–0.50 μg g−1 for Cr, not detected (nd) to 0.12 μg g−1 for Cd and 0.28–0.35 μg g−1 for Pb in paper and 0.50–0.64 μg g−1 for Cr, nd to 0.09 μg g−1 for Cd and 0.67–0.99 μg g−1 for Pb in paper board.