The potential effect of spectral interference on the accurate measurement of the cadmium (Cd) mass fraction in nutraceutical materials using inductively coupled plasma quadrupole mass spectrometry was studied. The materials were two new Standard Reference Materials (SRMs): SRM 3233 Fortified Breakfast Cereal and SRM 3532 Calcium Dietary Supplement, as well as several existing materials: SRM 3258 Bitter Orange Fruit, SRM 3259 Bitter Orange Extract, SRM 3260 Bitter Orange Oral Dosage, and SRM 3280 Multivitamin/Multielement Tablets. Samples were prepared for analysis using the method of isotope dilution and measured using standard mode, collision cell with kinetic energy discrimination (CC/KED) mode, and standard mode with sample introduction via a desolvating nebulizer system. Three isotope pairs, 112Cd/111Cd, 113Cd/111Cd, and 114Cd/111Cd were measured. Cadmium mass fraction results for unseparated samples of each material were compared to results obtained after the matrix was removed via chemical separation. In four of the six materials studied, measurements using the standard mode, with sample introduction via the desolvating nebulizer gave results for unseparated samples quantified with the 112Cd/111Cd isotope pair that showed a positive bias relative to matrix-separated samples. Similarly, use of the standard mode without the desolvating nebulizer gave results that showed a positive bias for unseparated samples quantified with the 112Cd/111Cd isotope pair. Collision cell/KED mode, however, was very effective for reducing spectral interference for Cd in all of the materials and isotope pairs studied, except in the multivitamin /multielement matrix (SRM 3280), where the large corrections for known isobaric interferences or unidentified interferences compromised the accuracy. For SRM 3280, matrix separation provides the best method to achieve accurate measurement of Cd.
Citation: Analytical and Bioanalytical Chemistry
Pub Type: Journals
Cadmium, ICP-MS, interference, collision cell, desolvating nebulizer, nutraceutical, food, dietary supplement, reference material