Determination of volatile bases in seafood using the ammonia ion selective electrode: collaborative study.
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.
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Rhode Island Department of Health Laboratories, Providence 02904, USA.
Pivarnik
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Thiam
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Pivarnik
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D000641:Ammonia / Q000032:analysis*; D000643:Ammonium Chloride / Q000032:analysis; D000818:Animals; D002170:Canada; D049832:Decapodiformes; D004284:Dogfish; D005412:Flatfishes; D017736:Ion-Selective Electrodes; D008744:Methylamines / Q000032:analysis; D011786:Quality Control; D015203:Reproducibility of Results; D017747:Seafood / Q000032:analysis*; D013048:Specimen Handling; D014481:United States; D014835:Volatilization
D008744:Methylamines; D000643:Ammonium Chloride; D000641:Ammonia; C023336:trimethylamine