Flame PhotometryThe principles

Introduction

• Many determinations made in the clinical laboratory are based on measurements of radiant energy • emitted, transmitted, absorbed, scattered, or reflected under controlled

conditions.

Introduction

• Flame emission spectrophotometry• based on the characteristic emission of light by atoms of many metallic

elements when given sufficient energy, such as that supplied by a hot flame.

• Photometry• is defined as the measurement of light

• Spectrophotometry• is defined as the measurement of the intensity of light at selected

wavelengths.• For example,

• Lithium produces a red, sodium a yellow, potassium a violet, and magnesium a blue color in a flame.

• the light intensity of the characteristic wavelength produced by each of the atoms is directly proportional to the number of atoms that are emitting energy, which in turn is directly proportional to the concentration of the substance of interest in the sample.

Instrumentation of flame emission spectroscopy (FES)

• 1)Vaporization:• The solvent is vaporized leaving particles of solid salt.

• 2) Atomization:• The salt is converted into free neutral gaseous atoms or radicals

• 3) Excitation:• Some of these atoms are excited by the thermal energy of the flame to

higher

• Excited Metal atoms• Ground State atoms

• Emission spectrum-H

• Emission spectrum-Fe (Iron)

Application of FES

• Qualitative analysis and Quantitative analysis of Alkali and alkaline earth metals• Na,K,Ca,Mg.

• Quantitative Analysis • Calibration Curve

• Emission intensity vs concentration is plotted

Quantitative Analysis: External Standard Method

Quantitative Analysis: Internal Standard Method

Limitation of FES

• The number of excited atoms in flame is very small. • It is the alkaline and alkaline earth metals that can be practically determined.

• It needs perfect control of flame temperature.• Interference by other elements is not easy to be eliminated• Heavy and transition metals

• the number of emission lines is enormous and the spectra are complex• respond linearly to ion concentrations over a rather narrow

concentration range so suitable dilutions usually have to be prepared