Determination of four aflatoxins on dark tea infusions and aflatoxin transfers evaluation during tea brewing

In daily tea drinking, little is known on aflatoxin transfers from tea-leaf to infusion during brewing and the actual intake. A verified aflatoxins analytical method on tea infusion is significant to the exposure assessment. Here, an optimal method 3 (M3) was screened and validated on four aflatoxins (B₁, B₂, G₁ and G₂) simultaneous determination. Recoveries of AFG₁ and AFB₁ were 87.37 %±1.99 %-102.03 %±8.62 %, and AFG₂ and AFB₂ were 83.99 %±8.65 %-100.14 %±1.69 %. The correlation coefficient on the fortified samples determination was > 0.99 for each aflatoxin. In accuracy and precision validation, aflatoxins recoveries in high and low fortified samples were 85.94 %-103.83 %, and RSDs were 2.20 %-9.15 %. Method applicability test showed that the M3 was qualified for six different dark tea types. Extraction rate of 30-days stored AFB₁ fortified tea-leaf by acetonitrile-water (84:16, v/v) was < 50 %; meanwhile, only 2.94 % spiked AFB₁ was released by ten times tea brewing which indicated that Puerh tea have strong adsorbability to aflatoxin.