MALACHITE Green, also known as Aniline Green or Basic Green 4, is banned in foodstuffs in most western countries, including the USA and the UK. The compound is legitimately used as a dye in the tanning of leather, but is also used in some Asian countries as an anti-parasite and anti-fungal treatment in aquaculture.
Now the US Department of Agriculture (USDA) has published its recommended method for screening fish and crustaceans for Malachite Green. The USDA Chemistry Laboratory Guidebook, which includes tests used by the Food Safety and Inspection Service (FSIS) Laboratories, identifies as Method R44a the use of the MaxSignal Malachite Green Elisa from Bioo Scientific.
MaxSignal is a Leucomalachite Green Enzyme-linked immunosorbent assay (LMG/Elisa) said to be capable of detecting concentrations of just 0.1ppb (parts per billion) in fish and shellfish samples, and is currently the only method recommended by USDA for the detection of Malachite Green and Gentian Violet (Crystal Violet or Methyl Violet 10b) in foods.
Bioo Scientific says the Elisa offers improved extraction for recovery rates as high as 80-95%.
It is worth noting that Malachite Green is not derived from the mineral malachite, but is named for the similarity of colour it produces. Its IUPAC name is 4-[(4-dimethylaminophenyl)phenyl-methyl]-N,N-dimethylaniline.