流動訊號在微管路中時間效應之探討

Abstract

流動注入分析法為一自動化分析技術，其紀錄訊號的波形常呈現不對稱，並且有拖尾(tailing)的現象。最近有文獻中提出時間效應的假說來解釋拖尾現象，所謂時間效應是指樣品在管路中流動時，由於樣品在管內的空間分佈狀態隨時間一直在改變，而傳統單通道偵測器收集到的訊號其實是空間波形不斷變化累積的結果，使得測量結果與樣品在管路內的空間分佈並不相同。 本研究以多通道偵測系統觀察管路中的流動訊號，它能夠獲得樣品在管路內的空間分佈狀態(空圖)，及記錄隨流析時間得到的訊號圖形(時圖)，對實驗所得波形各指標參數，包含不對稱因子、分散係數等進行比較，以及進行「空時疊圖」的波形比較，由實驗結果顯示，在二種不同管柱內徑(500μm、750μm)及不同流速(1.83~18.3cm/s)條件下，發現空圖與時圖有明顯的差異，證明時間效應確實存在，且隨著管柱內徑的增大及流速的提高，時間效應的影響更為顯著。此外，樣品在管內流動的過程中，樣品區帶的擴張程度在管路前端非常劇烈，以致於偵測器所得的訊號為一拖尾波形，波形不對稱主要是因為時間效應的貢獻程度極大，但是，隨著樣品在管內的流析時間越長，擴張效應會越來越趨緩，因此，時間效應的貢獻程度也會越來越小，並藉由偏差函數的比較，顯示記錄波形與高斯模擬波形間的差異很小，所以，最後會得到相當接近高斯的記錄波形。

Flow injection analysis (FIA) is an automatic analysis technology. The recorded signals of FIA often appear in asymmetric tailing peaks. A hypothesis of temporal effect is proposed to explain the tailing phenomenon recently. Because the spatial distribution of the sample in the flow channel changes with time, the recorded signal from a traditional single-channel detector is actually taking the accumulation result of the spatial profile variation of the sample in the channel. Accordingly, the recorded signal as a function of time is different from the true spatial distribution of the sample in the flow channel . The spatial profiles of the sample in the flow channel are recorded as a function of time using a multi-channel detection system. Under two tube diameters (500μm and 750μm) and various linear flow rates (1.83~18.3 cm/s), apparent differences are observed by comparing peak shapes between the spatial and temporal profiles. Thus the temporal effect is confirmed. This effect is found to increase as the inner diameters of the tube and flow speed become larger. The sample zone expands more pronounced in the earlier stage after sample injection. Thus, tailing peaks are obtained due to the greater temporal effect. When the sample flows in the channel for a longer time; however, the expansion of the sample zone becomes steady. Gaussian peak profiles are thus recorded due to the negligible temporal effect.