Quantitative evaluation of selenium contained in tea by high performance liquid chromatography

Area of Science:

• Analytical Chemistry
• Food Science
• Nutritional Science

Background:

• Accurate determination of selenium (Se) is crucial for biological and food analysis.
• Existing methods may lack sensitivity or require complex sample preparation.
• Understanding Se contribution from dietary sources like tea is important for public health.

Purpose of the Study:

• To develop and validate an improved, sensitive method for quantifying trace selenium in biological materials.
• To assess the selenium content in various types of tea.
• To evaluate the contribution of tea consumption to daily selenium intake in the Japanese population.

Main Methods:

• Development of a high-performance liquid chromatography (HPLC) method utilizing a fluorescent derivative of selenite with 2,3-diaminonaphthalene.
• Validation of the method using 11 biological reference materials.
• Quantification of Se concentrations in general teas and a specific "high Se tea" variety.
• Determination of Se extractability from tea leaves via infusion.

Main Results:

• The developed HPLC method demonstrated low detection limits (0.5 ng/g dried, 0.03 ng/mL fluid) and high reliability, matching certified values in reference materials.
• General tea leaves contained an average of 33 ± 19 ng/g Se, with less than 5% extractable by infusion.
• "High Se tea" exhibited significantly higher Se concentrations (455 ± 184 ng/g) with over 20% extractability.
• Tea intake generally contributes minimally to daily Se intake in Japan, but high consumption of "high Se tea" could increase intake by nearly 10%.

Conclusions:

• The improved HPLC method is reliable for determining trace selenium levels in diverse biological and food matrices.
• Typical tea consumption is unlikely to significantly contribute to selenium intake in the Japanese population.
• Consumption of specific high-selenium teas warrants consideration for potential impact on daily selenium status.