Flame photometry is an atomic emission method for the
routine detection of metal salts,
principally Na, K, Li and Ca. Quantitative analysis of
these species is performed by measuring the
flame emission of solutions containing the metal salts.
Solutions are aspirated into the flame. The hot
flame evaporates the solvent, atomizes the metal, and
excites a valence electron to an upper state.
Light is emitted at characteristic wavelengths for each
metal as the electron returns to the ground
state. Optical filters are used to select the emission
wavelength monitored for the analyte species.
Comparison of emission intensities of unknowns to either
that of standard solutions, or to those of an
internal standard, allows quantitative analysis of the
analyte
metal in the sample solution.
Flame photometry is a simple, relatively inexpensive, high
sample throughput method used for
clinical, biological, and environmental analysis. The low
temperature of the natural gas and air flame,
compared to other excitation methods such as arcs, sparks,
and rare gas plasmas, limit the method to
easily ionized metals. Since the temperature isn't high
enough to excite transition metals, the method
is selective toward detection of alkaline and alkali earth
metals. On the other hand, the low
temperatures renders this method susceptible to certain
disadvantages, most of them related to
interference and the stability (or lack thereof) of the
flame and aspiration conditions. Fuel and oxidant
flow rates and purity, aspiration rates, solution
viscosity, concomitants in the samples, etc affect these.
It is therefore very important to measure the emission of
the standard and unknown solutions under
conditions that are as nearly identical as possible.
Flame photometry is still one of the most demanded
analytical techniques by chemists working in
various industrial, agricultural and clinical fields. It is
a low-cost alternative to the Ion Selective
measurement method and provides the chemist with an
acceptable detection limit when measuring
Sodium, Potassium, Lithium and Calcium in aqueous samples.
Sedico Ltd. propose two instruments,
the AFP 45 flame photometer and the multi-channel automatic AFP 100 for the simultaneous analysis of Sodium, Potassium, Lithium and
Calcium in one sample aspiration. The details are in the
relevant sections of this page. |
