Thin-layer chromatographic screening methods for histamine in tuna fish.

Twelve solvent systems were tested for their ability to separate histamine and histidine on a variety of thin-layer coatings. The best solvent-adsorbent systems were: chloroform-methanol-ammonia (2:2:1), methanol-ammonia (20:1), acetone-ammonia (95:5), and double development with (a) n-butanol-acetone-water (2:2:1) and (b) chloroform-methanol-ammonia (12:7:1), all on silica-gel layers. Ninhydrin was used as the visualization reagent. These four systems were then evaluated for their potential use as rapid screening procedures in the detection of possibly deleterious levels of histamine in tuna fish. Successful separation of histamine from the other ninhydrin-positive components of methanolic tuna fish extracts was achieved with all four systems. A sample from a lot of tuna implicated in human illness was found to have a histamine level considerably higher than tuna purchased from a local retail outlet or an extract spiked to a histamine level considered to be a threshold value for toxicity symptoms. The methanol-ammonia (20:1) and chloroform-methanol-ammonia (2:2:1) systems, used with silica-gel plates, are the most promising for rapid preliminary screening of tuna fish extracts for histamine.