Chapter 3: Bulk Analysis

3.1.1 Fundamentals

Atomic spectroscopy is actually not one technique but three (Willard et al., 1974): atomic absorption, atomic emission, and atomic fluorescence. Of these, atomic absorption (AA) and atomic emission are the most widely used. Our discussion will deal with them and an affiliated technique, inductively coupled plasma (ICP)-mass spectrometry.

• Atomic absorption. Atomic absorption (Willard et al., 1974) is the process that occurs when a ground-state atom absorbs energy in the formoflight ofa specific wavelength and is elevated to an excited state. The amount of light energy absorbed at this wavelength will increase as the number of atoms of the selected element in the light path increases. The relationship between the amount of light absorbed and the concentration of an analyte present in known standards can be used to determine unknown concentrations by measuring the amount of light they absorb. Instrument readouts can be calibrated to display concentrations directly.

  The basic instrumentation for atomic absorption requires a primary light source, an atom source, a monochromator to isolate the specific wavelength of light to be used, a detector to measure the light accurately, electronics to treat the signal, and a data display or a logging device to show the results. The atom source used must produce free analyte atoms from the sample. The source of energy for free atom production is heat, the most common source being an air-acetylene or nitrous oxide-acetylene flame. The sample is introduced as an aerosol into the flame. The flame...