以感應耦合電漿原子發射光譜儀的樣品直接導入裝置測定食品中重金屬含量之探討

STUDY FOR THE DETERMINATION OF HEAVY METALS IN FOODSTUFF BY INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION SPECTROMETRY WITH DIRECT SAMPLE INSERTION DEVICE

本實驗的目的在探討感應耦合電漿原子發射光譜儀的樣品導入系統──樣品直接導入裝置（Direct Sample Insertion Device DSID），能否應用於食品中重金屬的分析。首先以進步回歸分析氫氣電漿所得五項操作變數冷卻氣體流量、輔助氣體流量、施於電漿功率、觀測電漿位置及石墨杯相對於感應圈位置，對於信號背景值比有顯著的影響。其中以冷卻氣體流量及觀測電漿位置對信號背景值比的影響最大。以美國國家標準局之標準品小牛肝（SRM-1577a）、脫脂奶粉（SRM-1549）及米粉（SRM-1568），用DSID方法來測定重金屬鎘、銅及鋅之含量，三種標準品各別添加一定量之基值改良劑氟化納後，三者在重量不變下，鋅含量與鋅信號強度可以成直線線性關係，但鎘與銅則不可。以樣品直接導入方法與傳統灰化方法分析牡蠣乾中鋅及鎘之含量。樣品直接導入方法之變異係數大於傳統灰化方法。樣品直接導入方法分析鋅含量變異係數為15-24%，而鎘之變異條數為28-83%。雖然樣品直接導入方法之變異係數大，但所須檢體量少，且可縮短分析的總時程。

A method for the determination of heavy metals in foodstuff by inductively coupled plasma atomic emission spectrometry with direct sample insertion device is described. The performace of the instrument has been investigated as a function of a number of parameters associated with direct sample insertion device and plasma operation. The flow rate of cooling argon gas and observation height are the two that have the greatest effect on shingal-to-background ratio. The system was tested with three NBS standards reference materls. The analytical results of the standards have a linear correlation between signal intensity and zinc content of each standard under same weight, there are higher varietion coefficiency of the system than convention analytical methods.