Determination of aflatoxins in Chinese medicinal herbs by high-performance liquid chromatography using immunoaffinity column cleanup Improvement of recovery.

Although analytical methods are available for the determination of aflatoxins in medicinal herbs, none of them can be applied satisfactorily to all sample matrices. The difficulty arises from the complex chemical composition of the herbs. Recovery is generally low by using immunoaffinity column cleanup due to the acidity of the water extractive leading to a weakened binding affinity. As a solvent for dilution and neutralization, phosphate buffer saline is useful for certain herbs but not for others that have high acidity. The problem can be solved by using 0.1 M phosphate buffer, which has a higher buffering capacity and eliminates sodium chloride. The modified method was validated by the analysis of a certified reference material and shown to be useful for the determination of aflatoxins in herbal samples of high acidity.