Advanced Topic 928 of 1102 Analytical, Lab & Spectroscopy
Flame Photometry
Measures emission intensity of alkali metals in flames.
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In-depth explanation of Flame Photometry
Flame photometry measures the light emitted by atoms of certain metals when a solution is sprayed into a flame and the atoms are excited thermally. Each element emits at characteristic wavelengths, and at moderate levels the emission intensity is proportional to the element's concentration. Alkali metals such as sodium, potassium and lithium emit strongly at relatively low flame temperatures, so the technique is particularly suited to them, although alkaline earth metals can also be measured. Filters or a monochromator select the wavelength of interest. The method is quick and inexpensive, and it was long the standard for sodium and potassium in clinical laboratories before ion-selective electrodes took over much of the work.
Going deeper: Flame Photometry
Key ideas: Calibrate with standards that bracket the sample, and dilute to stay in the linear range. Colours of emission: Na yellow (589 nm), K violet (767 nm), Li red (671 nm), Ca orange-red (622 nm), Ba green. Use an internal standard such as lithium to correct for flame fluctuations. Ionization suppressors such as extra caesium prevent loss of signal at high temperature.
Common mistakes and connections: Students think emission intensity is independent of flame temperature, but small temperature changes shift the excited fraction exponentially, so keep gas flow steady. Self-absorption at high concentrations bends the curve. Sodium contamination from glass and fingers causes high blanks. Related to flame tests, atomic emission, AAS and electrolyte measurements in clinical labs.
Visualization of Flame Photometry
Flame-excited sodium atoms relax from 3p to 3s, emitting 2.10 eV light at 589 nm, the yellow line used to measure sodium. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Sodium and potassium in blood serum are measured by flame photometry at about 589 nm and 767 nm.
Frequently asked questions about Flame Photometry
What is Flame Photometry?
Measures emission intensity of alkali metals in flames.
Is Flame Photometry a beginner, intermediate or advanced topic?
Flame Photometry is a advanced topic in Analytical, Lab & Spectroscopy. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Flame Photometry?
Study these earlier topics in Analytical, Lab & Spectroscopy first: 13C NMR, MRI, Atomic Absorption Spectroscopy.
What comes after Flame Photometry?
The next topics in Analytical, Lab & Spectroscopy are ICP-MS and X-ray Crystallography.
Can I practise Flame Photometry with quizzes?
Yes. The interactive lesson includes a self-check question on Flame Photometry, and the Analytical, Lab & Spectroscopy quiz draws on every topic in this area.
Where Flame Photometry fits in Analytical, Lab & Spectroscopy
Flame Photometry is topic 52 of 99 in Analytical, Lab & Spectroscopy.