食鹽中亞鐵氰化鹽之檢驗   全文下載

Determination of Ferrocyanide in Salt

依據「食品添加物使用範圍及限量暨規格標準」附表一之規定，亞鐵氰化鈉（sodium ferrocyanide）、亞鐵氰化鉀（potassium ferrocyanide）及亞鐵氰化鈣（calcium ferrocyanide）均為准用之品質改良用、釀造用及食品製造用劑，可使用於食鹽，用量以無水亞鐵氰化鈉（anhydrous sodium ferrocyanide）計為13 mg/kg以下，限於食品製造或加工必須時使用，用作抗結塊劑。本研究完成食鹽中亞鐵氰化鹽之檢驗方法確效，將食鹽檢體以去離子水溶解，其中亞鐵氰化鹽在水中解離產生之亞鐵氰酸根[Fe（CN）6-4]可與硫酸亞鐵溶液反應呈色，利用分光光度計測定720 nm之吸光值。本檢驗方法之定量極限為1.0 mg/kg（含量以無水亞鐵氰化鈉計）。以氯化鈉作為空白樣品，分別添加2.5及5.0 mg/kg之亞鐵氰酸根，回收率分別為99.9%及99.0%，同日間變異係數分別為1.35及2.24%，異日間變異係數分別為6.37及2.08%。為驗證本檢驗方法之適用性，本研究自行抽驗市售食鹽產品共計15件，其中3件產品標示有食品添加物亞鐵氰化鉀，檢驗結果顯示15件市售產品中，共計5件檢出含有亞鐵氰化鹽，含量以無水亞鐵氰化鈉計為2.2 - 5.1 mg/kg，雖均符合限量標準，但有2件於外包裝未標示含有亞鐵氰化鹽。檢驗結果均已進行後續相關處辦。

Sodium ferrocyanide, potassium ferrocyanide and calcium ferrocyanide are legal food additives. They are added to food grade salt as an anticaking agent. An analytical method for the determination of salts of ferrocyanide in food grade salt by colorimetric method was developed. The coordination complex of ferrocyanide [Fe(CN)6 -4] is yellow, but converts into a deep blue color when it combines with iron. The absorbance at 720 nm was measured using a spectrophotometer for the quantitation of ferrocyanide. The limit of quantitation (LOQ) of ferrocyanide was 1.0 mg/kg. The recoveries of ferrocyanide were between 99.0 and 99.9% at 2.5 mg/kg and 5.0 mg/kg. The coefficient of variation (CV) of intraday and interday recovery studies were 1.35-2.24% and 2.08-6.37%. A survey on the content of ferrocyanide in 15 commercial products was conducted. The results showed 5 samples were found positive for ferrocyanide.