Encyclopedia of Environmental Science and Engineering, Volume I and II

558 INSTRUMENTATION: WATER AND WASTEWATER ANALYSIS

in a fluorometer (see Figure 14) or a spectrofluorometer (see

Figure 15).

(b) Atomic 33,34

Atomic fluorescence is a fairly new instrumental

method that has been used for environmental samples. The

instrumental arrangement is given in Figure 4C. Because

of the dearth of commercial sources of the instrument and

no large benefits compared to other atomic spectroscopic

instruments there is a small number of literature citations

for its use.

(c) X-ray^35

X-ray fluorescence spectroscopic instrumentation uti-

lizes an x-ray source, i.e., x-ray tube or radioactive source,

to energize electrons of the inner orbitals of atoms which on

Power

supply

Motor

Fuel

Sample

Oxygen

Flame

Rotating

chopper

Hollow

cathode

tube

Monochromator Detector amplifier Read-out

a–c

FIGURE 12 Components of an atomic absorption spectrophotometer. The flame may be

replaced by a furnace. (Reprinted from Ref. (176), p. 464 by permission of Prentice Hall,

Inc., Englewoods Cliffs, NJ.)

Rowland circle

Photomultiplier tubes

Mirror –1000 V dc

power supply

Integrating

capacitor

Measuring

electronics

Microprocessor

A/D

Quartz

Lens window

Aperture

Pivoted mirror

Mirror

Moveable slit

Stepper

motor

Concave

diffraction

grating

Mercury lamp

Source

Lens

Prealigned

exit slit

Computer

FIGURE 13 A plasma multichannel spectrometer based upon Rowland circle optics. (Courtesy of Baird Corp./

IMC Bedford, MA.)

C009_005_r03.indd 558C009_005_r03.indd 558 11/23/2005 11:12:22 AM11/23/2005 11:12:22