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Laboratory Information Bulletin 4333 and 4334 Amendments (Malachite Green)

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Laboratory Information Bulletin

LIB No. 4333 and 4334

Determination of Leucomalachite Green and Malachite Green Residues in Catfish, Basa, Tilapia, Trout, and Shrimp


Wendy C. Andersen, Sherri B. Turnipseed, and José E. Roybal

A modified extraction was validated by LC-VIS and LC-MSn for LMG and MG residues in catfish, basa, tilapia, trout, and shrimp, and was verified in eel. To achieve high residue recoveries in these species, the following changes should be made to the salmon extraction detailed in LIB 4334 (page 7):

  1. Increase the quantity of alumina used in the initial extraction from 6 g to 10 g.
  2. In the liquid-liquid extraction step, let phases separate for a maximum of 10 minutes (salmon method states 15 minutes minimum).