Analysis of Potentially Toxic Bioaccessible Elements in Locally Available Bread Using Continuous On-Line Leaching Coupled to Inductively Coupled Plasma Mass Spectrometry
Lamsal, Ram Prasad
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A previously developed, efficient and simple on-line leaching method was used to assess the bioaccessible fraction of potentially toxic elements (Cr, As, Pb and Cd) in whole wheat brown and white bread samples. Artificial saliva, gastric juice and intestinal juice were successively pumped into a mini-column, packed with bread (maintained at 37°C) connected on-line to the nebulizer of an inductively coupled plasma mass spectrometry (ICP-MS) instrument equipped with a collision-reaction interface (CRI) to mitigate the impact of polyatomic interferences. In contrast to the conventional batch method to which it was compared, this approach provides real-time monitoring of potentially toxic elements that are continuously leached with 3 artificial gastro-intestinal reagents. Mass balance for both methods was verified at the 95% confidence level. Results obtained from the whole wheat brown and white bread showed that the majority of Cr, Pb and Cd was leached by gastric juice but, in contrast, the majority of As was leached by saliva. Results showed a higher total content for elements in whole wheat bread than in white bread but in contrast, there was a higher percentage of bioaccessible elements in white bread than in whole wheat bread. This difference may be attributed to the several food processing steps involved for white bread compared to whole wheat bread. Both the on-line and batch methods showed that 40% -98% of toxic elements in bread samples are bioaccessible. Hydrogen as the CRI gas was efficient at minimizing carbon- and chlorine-based polyatomic interferences.