矽磷同步分析儀之設計與海域環境之應用

Design of a new-type flow analysis for the simultaneous determination of silicate and phosphate and its application to ocean environmental studies

丁建豪(Chien-Hao Ting)

指導教授 ： 白書禎

國立臺灣大學/理學院/海洋研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.00454

摘要

本研究設計一套矽磷同步分析系統，可精確且快速的測到水體中磷酸鹽及矽酸鹽。該系統雖源自於過去本實驗室所發展的Trident-223三同步分析儀，但做了以下的數點改進：(1)只測定磷酸鹽及矽酸鹽，不必為亞硝酸鹽的條件所牽制。(2)過去矽酸鹽測定過程中有一個加遮蔽劑的步驟，以去除磷酸鹽干擾，該系統改以扣除法解決磷干擾的問題，大幅增進了穩定度並縮短了測定時間。(3)採用一公分或五公分光徑的流動槽，但使用長光徑時必須用窄孔光槽同時使用停流技術(stop-flow)，在波長410nm下直接測定訊號為

AbsSi+P = eSi*b*[Si]*Vs/Vf + eP*b*[P]*Vs/Vf。
其中eSi及eP為矽鉬黃及磷鉬黃在波長410nm下的吸光係數，b為光徑，[Si]及[P]為矽酸鹽與磷酸鹽的原始濃度，因此矽酸鹽的濃度應為

[Si] = (AbsSi+P-eP*b*[P]*Vs/Vf)/(eSi*b*Vs/Vf)。
計算的困難度在於上式中，矽鉬黃吸光係數(eSi)為鹽度(S)的函數，磷鉬黃吸光係數(eP)為溫度(T)及鹽度(S)的函數，本文在波長410nm下，將此兩係數明確定義為

eSi(S)=-2.28*S+1800，鹽度適用範圍為0-35 psu。

eP(T, S) = (0.00108*S^2-0.0981*S+16.47)*T+(0.266*S^2-17.823*S+506)。
溫度(T)適用範圍為15-40℃、鹽度(S)適用範圍為0-35 psu。
因此只要明確得到樣水之鹽度數據、磷酸鹽的濃度及測定系統水槽的溫度，即可算出矽酸鹽的濃度，如此可將矽酸鹽的測定時間由傳統的三分鐘以上縮短為60秒以內。本研究將以上原理實際製造了一台同步分析儀進行測試，證實在自然海水最大濃度([Si]=150 uM, [P]=3 uM)時，測定樣品的相對誤差在1%以內，平均每小時可完成40-60個樣品。使用五公分長光徑矽頻道量測矽酸鹽的最小解析度為0.12 uM，線性範圍0-150 uM；磷酸鹽的最小解析度為0.01 uM，線性範圍在0-20 uM。

關鍵字

矽酸鹽 ； 磷酸鹽 ； 流動分析 ； 矽磷同步儀 ； 營養鹽測定

並列摘要

An automated flow analyzer for the simultaneous determination of phosphate and silicate has been developed. The system in principle is similar to that of the previous Trident-223 system, but improvements are made on the Si-channel which does not involve the addition of a masking reagent. The results for silicate are compensated for the phosphate interference according to the results measurement from the other P-channel. In a manual procedure, the raw absorbance (at 410nm) obtained for silicate should comprise of both silicate and phosphate signals:

AbsSi+P = eSi*b*[Si]*Vs/Vf + eP*b*[P]*Vs/Vf
Where eSi and eP are molar extinction coefficients of silicomolybdic acid and phosphomolybdic acid at a wavelength of 410 nm, b the path length, [Si] and [P] the concentrations for silicate and phosphate, respectively. Symbols Vs and Vf represent the sample volume and the final volume. The actual silicate concentration should be:

[Si] = (AbsSi+P-eP*b*[P]*Vs/Vf)/(eSi*b*Vs/Vf)
The process looks easy but it was found that eSi and eP are not constant but subject to change at different salinities. The latter is also affected by temperature. Empirical equations have been proposed for quick estimation:

eSi (S) = -2.28*S +1800, 0

並列關鍵字

Phosphate ； Silicate ； Simultaneous determination of phosphate and silicate

參考文獻

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