紫外線発光ダイオードを光源とする可搬型蛍光光度計の開発及びそのCOD推定への応用

摘要

海水や河川水試料の化学的酸素要求量を簡便な方法で推定するため，光源に紫外線発光ダイオード(UV-LED),検出器に光電子増倍管モジュールを使用する可搬型蛍光光度計を開発した.試料水の蛍光強度(励起波長340nm.蛍光波長450nm)を測定し，公定法により得られた100℃における過マンガン酸カリウムによる酸素消費量(COD_(Mn))の値との相関を求めた.試料の採取地点ごとに蛍光強度とCOD_(Mn)の相関式の傾きは異なったが，同一地点における蛍光強度とCOD_(Mn)の時間変化はよく一致した.伊勢湾にて複数か所から採取した海水の蛍光強度とCOD_(Mn)も，河川水の影響を受けていない地点では良好な相関があり，蛍光強度からCOD_(Mn)を推定できることが分かった.また，工場排水では，操業状態の変化が少なければ本法により推定が可能であった.付加機能としてLEDを光源に用いる吸光度検出により，蛍光強度と同時に色度と濁度を測定できるようにした.%A portable fluorometer using an ultraviolet LED (UV-LED) and a photomultiplier tube module as a light source and a detector, respectively, has been developed to estimate the chemical oxygen demand (COD) value of river-water, seawater and industrial wastewater samples. The fluorescence intensities of samples (excitation wavelength, 340 nm; emission wavelength, 450 nm) were measured by this fluorometer. Their correlation to the COD values obtained by the official titration method using permanganate as an oxidant (COD_(Mn)) was studied. The equations for the correlation at different sampling points were not identical; therefore, it should be built for every sampling point. When the sample was taken from a specific point, the time course of its fluorescence intensity versus the COD_(Mn) value showed a good correlation. In the case of multi-point sampling from Ise Bay, their correlation was good, if the sampling point was not nearby an estuary. For industrial waste-water, the COD_(Mn) of the sample from a factory whose operational condition did not change drastically, can be estimated. This flurometer has additional functions to measure the color unit and turbidity of the sample by an absorbance measurement.