Interferences and Their Elimination in the Determination of Cadmium in Infant Complementary Foods by Inductively Coupled Plasma Triple Quadrupole Mass Spectrometry

An inductively coupled plasma triple quadrupole mass spectrometric (ICP-QQQ-MS) method was established for the determination of cadmium (Cd) in cereal-based complementary foods for infants and young children. In different collision/reaction modes, namely single quadrupole-helium collision (SQ-He), double quadrupole-helium collision (QQQHe) and double quadrupole-oxygen reaction (QQQ-O₂), various possible interferences in the MS measurement process were analyzed and several methods to eliminate them were proposed. The results showed that the decreasing order of the ability to resist matrix, oxide and multiatomic ion interferences was QQQ-O₂ > QQQ-He > SQ-He. QQQ-O₂ combined with the standard addition method showed a better ability to eliminate interference. By introducing interference correction equations, the problem of inconsistency between Cd isotope abundance ratio and natural abundance ratio caused by interference from stannum (Sn) isotopes was effectively solved. The results of Cd determination by isotope dilution mass spectrometry (IDMS) in the QQQ-O₂ mode were consistent with those obtained using the standard addition method, indicating effective elimination of both matrix effect and MS interference. The proposed ICP-QQQ-MS method allows the accuracy determination of Cd in complex matrix samples.