Introduction
The flame photometry is a technique that presents good sensitivity, and is used mainly for the determination and on of alkali metals. The equipment consists of a flame normally produced by mixing oil liquefied air-gas, a monochromator and a detector. The solvent for the preparation of the sample solution and reference solutions should preferably be aqueous. The organic solvents may be used, provided that they do not interfere with the stability of the flame.
Interferences
The interferences that occur in flame photometry are very similar to those observed in Atomic absorption spectrometry. However spectrum interferences may occur caused by the emission of molecular rotation- vibration bands such as OH (310-330 nm), NH (around 340nm), N2+ (around 390nm), C2 (around 450nm), etc
Solvents
The solvent must be selected with caution. If there is a significant difference of surface tension or viscosity between the sample and reference solution, variations will occur in aspiration and nebulization rates and as a consequence, significant differences in signals produced. Thus, the solvent applied in the preparation of sample and references should be as similar as possible.
Procedure
The equipment must be operated according to the manufacturer’s instructions and in the wave length specified. Adjust the zero with the solvent. Then, inject the concentrated reference solution and adjust the sensitivity desired. The determinations are made by comparison with reference solutions containing known analyte concentrations. The measurements can be carried out by the Direct calibration method or by Standard addition method
Flame photometry, direct calibration method, standard addition method
