Method Development for the Quantitative Analysis of Multivitamin Supplements by Laser Ablation–Inductively Coupled Plasma–Mass Spectrometry (LA-ICP-MS)

Abstract

We present the development and optimization of an analytical method based on Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) for the analysis of multivitamin dietary supplements. Samples were ground and mixed with a cellulose powder containing internal standard elements; the resulting powder was pressed into pellets. Two calibration strategies were compared: (1) using increasing mass fractions of cellulose powder forti ed with multiple elements of interest, and (2) matrix matching using a multivitamin reference material in addition to the multielement cellulose powder. Laser and ICP-MS parameters were closely monitored to produce the best signal while reducing the variability between replicate measurements. An energy output of 0.5 J/cm 2 , a repetition rate of 30 Hz, and a He carrier gas ow rate of 800 mL/min provided the best compromise between sensitivity and reproducibility. These parameters produced the most similar ablation behavior between cellulose and a matrixmatched calibration strategy. The dissimilarities in ablation yield due to differences in focal points were successfully corrected after normalizing to an internal standard, resulting in relative differences of less than 10%. The results from the two different calibration approaches were compared to those obtained from solution ICP-MS and Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) analyses. For most multivitamins, both calibration methods (i.e., cellulose and matrix-matched calibrations) performed adequately for As, B, Co, Cr, Cu, Mg, Ni, Na, Pb, and Zn. Matrixmatched calibration additionally resulted in better recoveries for S and Fe. Overall, matrix-matched calibration resulted in better recoveries for more multivitamins in comparison with cellulose calibration.

Atomic spectrometry update: review of advances in the analysis of clinical and biological materials, foods and beverages

“…The second paper was concerned with the matrix of multivitamin supplements and strived to develop a rapid and automated method that didn’t require acid digestion. 81 Matrix matched calibrators prepared using a multivitamin reference material together with a multi-element fortified cellulose powder were compared to those composed of the multi-element cellulose powder alone. Normalisation of the results to an IS was essential to correct for different ablation yields arising from differences in focus on the surface of the samples and the best choice of IS varied between the two calibration strategies.…”