利用毛細管電泳檢測不同沖泡方式的咖啡中之化合物成分   免費試閱

The Detection of Compounds in the Different Brewing Coffee by Capillary Electrophoresis

本研究開發利用毛細管電泳結合紫外可見光吸收偵測器（簡稱CE-UV）搭配MEKC 分離機制的方法，以快速偵測咖啡中的五種化合物（咖啡因、綠原酸、阿魏酸、咖啡酸及菸鹼酸）。本實驗分別針對緩衝溶液濃度、pH 值、SDS濃度和甲醇在背景電解質所占的比例進行探討。使用的毛細管總長為60 公分，有效長度為48 公分。最佳分離條件為15 mM 磷酸鹽緩衝溶液（pH 8.0）並添加40 mM SDS、10% 甲醇（v/v）作為電泳緩衝溶液；估算本方法最低偵測極限（LOD）可以達到2.5 μM（阿魏酸），且5 種分析物的R2 值皆大於.995；比較同一天及不同天偵測的RSD 值皆小於5.65%。本方法應用在不同沖泡方式的咖啡上，經過簡單的前處理步驟，可以偵測咖啡中的五種化合物。比較實驗結果顯示，咖啡中化合物的含量與沖泡咖啡的粉水比例有正相關影響。其中義式沖泡咖啡所含的咖啡因含量最高為4.761 mg/mL，比其他沖泡方法所測得的含量高出1.87 ～ 7.21 倍。此方法的回收率介於84.33% ～ 98.21% 之間，驗證此分析方法可以應用在不同沖泡咖啡成品中化合物的定量。

In this study, we used capillary electrophoresis with UV-visible absorption detector (CE-UV) to detect the five compounds (caffeine, chlorogenic acid, ferulic acid, caffeic acid, nicotinic acid) in coffee with various brew methods. We investigated some factors including the concentration of buffer solution, pH value, SDS concentration and methanol in the background electrolyte. The optimum separation conditions were 15 mM phosphate buffer solution (pH 8.0) with 40 mM SDS, 10% methanol (v/v) as the electrophoresis buffer solution. The limit of detection (LOD) of our method was 2.5 μM (ferulic acid) with R2 values greater than 0.995 for five analytes. The RSD of intraday and interday were all less than 5.65%. This method could be applied to detect the real sample coffee with simple pre-treatment process steps. The experimental results exhibit that the Italian style brewing method was the highest caffeine content (4.761 mg/mL), as well as the other compounds were content higher 1.87-7.21 fold than the other methods. Recovery of this method ranged from 84.33% to 98.21%, this analysis method can be applied quantitatively in different brewing coffee compound.