Determination of Volatile Bases in Seafood Using the Ammonia Ion Selective Electrode: Collaborative Study

• Published in: Journal of AOAC INTERNATIONAL
• Main Authors: Ellis, P Christopher, Pivarnik, Lori F, Thiam, Mamadou, Berger, L, Field, S, Green, D, Hewes, D, Lemerise, D, Lyttle, C, Maciel, J, Soper, K
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 2000
• Subjects: Pharmacology; Agronomy and Crop Science; Environmental Chemistry; Food Science; Analytical Chemistry; atlantic cod
• Online Access: http://dx.doi.org/10.1093/jaoac/83.4.933; http://academic.oup.com/jaoac/article-pdf/83/4/933/32415131/jaoc0933.pdf

Abstract Nine collaborating laboratories tested a combination of 23 seafood samples for volatile bases using an ammonia ion selective electrode. Results were reported as mg NH3/100 g fish, but the method reflected levels of both ammonia and trimethylamine, which permeated the ammonia membrane. The 23 samples were broken down into 8 blind duplicate pairs, 2 Youden matched pairs, and 3 single samples covering fresh to spoiled product ranging from 8 to 82 mg NH3/100 g. Seven species were evaluated: Atlantic cod, squid, Atlantic halibut, gray sole, monkfish, dogfish, and Atlantic mackerel. The ammonia electrode assay was performed on an aqueous homogenate consisting of 95 mL distilled water and 5.0 g sample tissue. Alkaline ion strength adjusting solution (2 mL) was added to the homogenate to liberate ammonia that was sensed by the ion specific electrode and measured on a precalibrated portable meter. Repeatability standard deviations (RSDr) ranged from 4.2 to 17%; reproducibility standard deviations (RSDR) ranged from 8.8 to 21%. A standard ammonium chloride solution was provided to all laboratories to spike 3 different samples at 10 mg NH3/100 g. Recoveries of added ammonia as ammonium chloride for fresh, borderline, and spoiled samples were 88.6, 107, and 128%, respectively.