Determination of histamine in fish sauce from Thailand using a solid phase extraction and high-performance liquid chromatography

A clean-up procedure using a solid phase extraction technique and a high-pressure liquid chromatography (HPLC) method for the determination of histamine in fish sauce from Thailand is introduced. The method was tested on fish sauce samples by adding various concentrations of histamine standards: 50-1000 mg/L of fish sauce, five replicates for each concentration. The samples were mixed with methanol and shaken for 1 min, applied to Bond But strong cation exchanger, then eluted with a mixed buffer solution of 0.5 M KH2PO4 (pH 6.5): methanol (1 : 1, v/v). Analysis was carried out by using HPLC with a post-column reaction with o-phthalaldehyde to form a fluorescent derivative. The recovery from fish sauce ranged from 90.5 to 95.5% with the limit of detection at 5 ng of histamine. The analysis of 549 commercial fish sauce samples showed that the samples contained histamine at various levels with the majority in the range of 200-600 mg/L.