Fluorometric analysis

A general term for analytical methods in which a sample is irradiated with excitation light and the resulting fluorescence is measured to perform qualitative and quantitative analysis. UV light, X-rays, α (alpha) rays, electron beams, etc. can be used as excitation light. Fluorescence caused by X-ray irradiation is called fluorescent X-rays, and analytical methods that use this are called X-ray fluorescence analysis, while the light emitted when gaseous atoms absorb a resonance line, become excited, and then return to the ground state is called atomic fluorescence, and analytical methods that use this are called atomic fluorescence analysis. Each analytical method has its own characteristics, but when simply called fluorescence analysis, it refers to the case where a liquid or solid sample is excited with UV light. Fluorescence can be measured with the naked eye, but generally a fluorescence measuring device is used. The device consists of a light source, an excitation light selection unit, a sample chamber, a fluorescence selection unit, a photoelectric photometer, and an indicator, and is called a fluorometer, a fluorescence spectrophotometer, a spectrofluorometer, etc. depending on the optical configuration. Xenon lamps and mercury lamps are widely used as ultraviolet light sources, and this light is usually irradiated from one side of a rectangular or round container with four transparent sides containing a sample, and the generated fluorescence is usually measured at a right angle to the light. The measured fluorescence energy is related to various factors, but under certain measurement conditions it is proportional to the sample concentration, and is used to detect and quantify various organic compounds and metal elements. This method can be applied directly to compounds that emit fluorescence, but in the case of compounds that are not fluorescent, they are converted into fluorescent compounds by reacting them with an appropriate reagent and then measured. The phenomenon in which fluorescence intensity decreases due to coexisting substances is called quenching, and there is a method that utilizes this to quantify quenching substances, which is called quenching fluorescence quantification or fluorescence quenching quantification.

[Takada Takeo]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

試料に励起光を照射し、その結果放射される蛍光を測定して定性、定量を行う分析方法の総称。励起光としては紫外線、X線、α(アルファ)線、電子線などが使われるが、X線照射による蛍光を蛍光X線とよび、これを利用する分析法を蛍光X線分析法、また気体状態の原子が共鳴線を吸収して励起し、ふたたび基底状態に戻るときに発する光を原子蛍光とよび、これを利用する分析法を原子蛍光分析法という。それぞれ特長ある分析法であるが、単に蛍光分析という場合には液体または固体試料を紫外線で励起する場合をいう。蛍光の測定は肉眼で行うこともあるが、一般には蛍光測定装置を用いる。装置は、光源部、励起光選択部、試料室、蛍光選択部、光電測光部、指示部からなり、光学計の構成によって蛍光光度計、蛍光分光光度計、分光蛍光光度計などに分けられてよばれている。紫外線光源としてはキセノンランプや水銀ランプが広く用いられ、この光を、試料を入れた四面が透明な角形または丸形容器の一方から照射し、発生した蛍光はこれと直角方向で測定するのが普通である。測定される蛍光エネルギーは種々の因子に関係するが、一定の測定条件下では試料濃度に比例し、各種の有機化合物や金属元素の検出や定量に使われる。蛍光を発する化合物には直接本法を適用できるが、蛍光性でない化合物の場合には適当な試薬と反応させて蛍光性化合物に変えて測定する。また共存する他物質などによって蛍光強度が低下する現象を消光といい、これを利用して消光物質の定量を行う方法があり、これを消蛍光定量法あるいは蛍光消失定量法とよんでいる。

［高田健夫］

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