新型硝酸鹽分析儀之研究

Abstract

摘要 本研究發展了一套新型硝酸鹽分析儀。它結合了流動注入分析法（Flow injection analysis）和氣泡中隔流動分析法（Gas segmented continuous flow analysis）的優點，並去除注入一段樣品來產生波形（Peak）的判斷濃度方式，改以不斷注入樣水產生穩定的最大吸光值。製作方式為先移去舊有注入一段樣品的上樣裝置，變成以蠕動幫浦（Pump）不斷的注入樣水，並於鎘銅還原管前加裝氣泡去除裝置（Debubbler），最終透過最佳化調整即可。完成後的儀器不需要任何的注入閥或自動汲樣器（Autosampler）幫助上樣，只要將鐵弗龍管插入裝樣水的瓶中，加上使用不具記錄波形的分光光度計就可輕鬆測量。以本研究建議的裝置對自然樣品進行測試時，結果和流動注入分析法所測得的一樣，除此之外，操作的精確度（Precision）可小於1%，每個樣品的偵測時間（Detection time）約2分鐘。遇到淡水樣品時，適用範圍為0∼100uM，偵測下限（Detection limit）為0.159uM，解析度（Resolution）約為0.053uM；而海水的適用範圍則為0∼50uM，偵測下限為0.204uM，解析度約為0.068uM。若測量污染的河水或一般海水時，鎘銅還原管的還原率每測十個樣品約降2%，本研究建議每測3∼5個樣品測一次標準樣品，以提高測量的準確度（Accuracy）。

Abstract This research combined the flow injection analysis and gas segmented continuous flow analysis to develop a new type of nitrate analyzer. Steps to build the device are as following. First, an autosampler or injection valve is replaced by a pump to continuously inject the sample. Second, a debubbler is added in front of the cadmium reductor to prevent air interference and to maintain stable reduction efficiency of the reductor. Last, flow rates and detection time is adjusted to optimize the analyzer. Continuous and stable signals can be produced and consequently a spectrophotometer without the time scan function can still be used as the recorder. There is no significant difference between measurements of natural waters made by this new method and by traditional flow injection method. Moreover, the operation precision is lower than 1%, and the detection time is about 2 minutes. For the analysis of fresh water samples, the detection range is from 0 to 100uM, the detection limit ca. 0.159uM, and the resolution 0.053uM. For seawater analysis, the detection range is from 0 to 50uM, the detection limit is ca. 0.204uM, and the resolution is 0.068uM. The efficiency of cadmium reductor drops 2% every 10 samples while seawater or polluted fresh water is measured. Therefore, this thesis suggests that measuring a reference material every 3 to 5 samples in order to monitor the decay rate so that the accuracy of the measurements can be improved.