What is a Flame Photometer?
It is a device used in inorganic chemical analysis to determine the
concentration of certain metal ions including Sodium (Na) - Potassium
(K) - Lithium (Li) - Calcium (Ca) - Barium (Ba).
In principle, it is a controlled flame test with the intensity of
the flame colour quantified by photoelectric circuitry. The sample is
introduced to the flame at a constant rate. Filters select which
colours the photometer detects and exclude the influence of other ions.
Source: Wikipedia