Methods for simultaneous determination and identification of MS-222 and metabolites in fish tissues
By: by Charles W. Luhning. Residues of MS-222, benzocaine, and their metabolites in striped bass following anesthesia / by Charles W. Luhning
Contributors: United States. Bureau of Sport Fisheries and Wildlife; United States. Bureau of Sport Fisheries and Wildlife
Series: Investigations in fish control -- 51-52
Publisher: U.S. Dept. of the Interior, Fish and Wildlife Service, Bureau of Sport Fisheries and Wildlife
Published: 1973
Place of publication: Washington, D.C
Language: eng
Number of pages: 11
Subjects: Animal anesthesia; Testing; Fishes; Physiology; Striped bass
Other titles: Environmental Information Services Collection.; Residues of MS-222, benzocaine, and their metabolites in striped bass following anesthesia.
Description: MS-222 (methanesulfonate of meta-aminobenzoic acid ethyl ester) is a primary aromatic amine commonly used to anesthetize fish. Like all primary aromatic amines, its diazonium salt reacts with N-1-naphthylethylenediamine dihydrochloride to form a wine-red azo dye with a maximum absorbance at 545 nm. Basic carbon tetrachloride extraction separates the azo dyes of MS-222 and its acid metabolite, m-aminobenzoic acid, and quantitative determination of each compound is made colorimetrically. By this method, recoveries of 82to 110 percent for MS-222 and 84 to 117 percent for m-aminobenzoic acid were obtained from largemouth bass muscle and liver tissues spiked with 1 to 10 microgram/gram of each compound. Quantitative estimation and identification of each compound were possible from samples spiked with as little as 1 microgram/gram of MS-222 or m-aminobenzoic acid.

Striped bass (Morone saxatilis) anesthetized in a 100-mg/1 solution of MS-222 at 17.5° C contained an average of 57.9 microgram/gram of MS-222 and 23.2 microgram/gram of m-aminobenzoic acid residues in the muscle tissue immediately after a 30-minute exposure to the drug (0-hour withdrawal samples). After this tissue was homogenized and stored in a refrigerator for 1 week at 1.7° C, residues were 100 percent m-aminobenzoic acid. Fish anesthetized with benzocaine and treated in like manner still contained residues of benzocaine and a small amount of p-aminobenzoic acid (3.4 percent) after storage. The ester and acid residues of both anesthetics decreased steadily with length of recovery time. The residues were measured by a modified Bratton-Marshall colorimetric method and confirmed by thin-layer chromatography.
Notes: Includes bibliographical references.