Rice husk as an adsorbent: A new analytical approach to determine aflatoxins in milk

Aflatoxins determinations are usually expensive and employ environmentally unfriendly procedures, thus, the search for new materials and technologies, that are both ecologically safe, inexpensive and able to fulfill its role with little pre-processing is growing. One interesting approach is employing by-products as adsorbents during the extraction step of aflatoxins especially in products such as milk and dairy that are so important in basic dietary. Thus, a method to use rice husk, an agroindustry residue that is a promising material to adsorb aflatoxins to enable further analysis steps, is proposed by applying a Plackett-Burman design followed by 2(2) central composite rotational design. Rice husks were prepared by washing the husk with a solvents sequence. The washed particles were analysed by scanning electron microscopy, characterized by an elemental analyser and analysed for the presence of pesticides and mycotoxins. The rice husks contained 41% carbon, 4.3% hydrogen and 0.2% nitrogen, without mycotoxins and pesticides. The adsorptions were conducted using 0.5 g of rice husk, with 42 mesh, and 10 mL of milk contaminated with several know levels of aflatoxins M1 and B1. The solution was filtrated trough the adsorbent layer using a pressure of 10 in. Hg. The adsorbed mycotoxins were removed with 6 mL of methanol:chloroform (80:20). This condition achieved recovery of around 100% for both mycotoxins, with the average quantity of mycotoxin adsorbed equal 0.0150 µg g(-1) of afla B1 and 0.0174 µg g(-1) of afla M1.