食品中螢光增白劑分離鑑定方法之研討

SEPARATION AND IDENTIFICATION OF FLUORESCENT WHITENING AGENTS IN FOOD

螢光增白劑（Fluorescent Whitening Agents）為一種染料，主要用於纖維或木漿以增加白度，雖其毒性低，但基於其應用性不以添加至食品為目的，故不准許使用於食品。本研究之目的提針對食品中可能使用之螢光增白劑作分離及鑑定。結果顯示：由市售之25件白蘿蔔檢體中，共計7件檢體具螢光性，以五種溶劑萃取，顯示以二甲醯胺（dimethylformamide）之萃取效果較好。以薄層層析法鑑別，自6種展開溶媒系中發現有4種可將螢光增白劑展開，但無充分分離效果，故僅能判別檢體是否含螢光增白劑，而無法用於螢光增白劑之鑑別。以二種高效液相層析法鑑別，顯示以離子配對層析法（ion - pair chromatography）分離效果較佳，其分析條件為：層析管： LiChrosorb RF—18（25cm × 4mm i.d., 5μm），移動相：甲醇：水（43：57）含有0.005M氯化三乙銨、0.0025M醋酸鈉及0.0025M醋酸，流速為1.5ml/min，溫度為60℃，以螢光檢測器於激發波長340nm、放射波長440nm檢測。以此條件分析7件含螢光增白劑檢體，發現其中6件檢體所含之螢光增白劑均為4 ,4'-bis[4-3-anilino-6-hydroxyethy lamino-1,3,5 triazin-2-yl）amino] stilbene-2,2'-disulfonic acid disodium salt，另1件檢體所含之螢光增白劑為4,4'-bis[4- anilino-6-methoxy-1,3,5 triazin-2-yl）amino] stilbene - 2,2'-disulfonic acid disodium salt。

Fluorescent whitening agents (FWA) are a group of dyes low in toxicity and often used in fiber and wood pulp, however they are not permited to be used in food. The present study was aimed to separate and identify FWA in food, after detecting seven samples out of twentyfive radish collected from local markets contained fluorescence. Five solvents were tested for extraction of FWA from fluorescence–containing radish, the result showed that dimethylformamide was the most effective solvent. The thin layer chromatography was used to separate and identify FWA. Four out of six tested developing solvents resulted in appropriate Rf values by spotting standard FWA on plates, however the TLC Could only be used to indentify the present of FWA, but it was not sufficient enough to separate FWA for identification. Two methods of high performance liquid chromatography were also compared for the separation and identification of FWA. It was shown that the ion–pair chromatography gave a better separation effect of FWA. The conditions of HPLC were as follows: column, LiChrosorb RP – 18 (25cm x 4mm i.d., 5µm); mobile phase, methanol: water (43:57) ontaining 0.005M trimethylammonium chloride, 0.0025M sodium acetate and 0.0025M acetic acid; flow rate, 1.5ml/min; temperature, 60℃; fluorescent detector, excitation wavelength 340nm and emission wavelength 440nm. By applying the HPLC method to seven FWA – containing samlpes, the testing identified that a FWA, 4,4’ – his [ 4 – 3 – anilino – 6– hydroxyethy la mino – 1,3,5 triazin – 2 – yl) amino]stilbene – 2,2’ – disulfonic acid disodium salt, was present in six samples, while 4,4’–bis[4 – aniline – 6 – methoxy – 1,3,5 triazin – 2 – yl) amino]stilbene – 2,2‘– disulfonic acid disodium salt was detected only in a sample.