Principle of flame photometry

Flame photometry is a simple, quick, accurate and inexpensive method for the determination of alkali and alkaline earth elements.

The aqueous solution containing the relevant substance to be analyzed is dispersed into the nonluminous flame as a fine spray. Thereafter, the flame luminates due to the thermal excitation of the atoms. The more atoms in the measurement sample, the higher the quantity of emitted light. Thus, the concentration of the analyte can be determined by measurement of the light density. Each element has its characteristic spectral color, i.e. it emits light of characteristic wavelengths which are defined by the specific atomic structure of the element.

The radiated light of the elements is selected by optical filters, permitting only light of a defined wavelength to reach the photo-detector. The signal is amplified, undergoes analog-digital conversion and the concentration of the relevant element is calculated using an appropriate algorithm. For each element to be measured, there is a special filter and a separate photo-detector.

Flame photometry is a relative measurement technique in which the unknown sample is compared to a standard of a defined concentration.

The FP8800 can determine the concentration directly or alternatively use a spectral reference line. With this technique, all samples and standards are diluted with a solution containing a reference element. The element used as a reference is measurable with the flame photometer, but is not present in the sample. Any measurement interferences will effect the reference element and the sample element in virtually the same way, thus largely compensating possible measurement interferences.