Comparison of Sample Treatment Methods for Bismuth and Tellurium Determination in Yogurt

Background: Dairy products are rich in nutrients that are essential for a high bone mineral density. Furthermore, several studies relate additional health benefits to the regular consumption of fermented milk products such as yogurt. However, Te and Bi have been determined in milk samples but there is not available information about Te and Bi determination in yogurt samples. Methods: Three sample treatment approaches including: i) microwave-assisted digestion, ii) ultrasoundassisted extraction at room temperature, and iii) microwave assisted extraction have been investigated for the determination of bismuth and tellurium in yogurt by hydride generation atomic fluorescence spectrometry. Results: Highest levels of Bi and Te found in a variety of commercially available samples were 10.0 ± 0.8 ng mL-1 and 0.91 ± 0.05 ng mL-1, respectively. These results are on the same order or at lower concentration than in milk indicating that these two elements are not modified in a significant way throughout the technological process involved in yogurt manufacture. Conclusion: All three methods gave coincident results in samples elaborated with skimmed or partially skimmed milk, nevertheless sonication gave lower values for samples with major fat content. The use of microwave-assisted extraction is recommended because it offers a less time consuming methodology.