Environmental Engineering Reference
In-Depth Information
There are disadvantages of ICP-OES, which make other atomic absorption
spectrometers still competitive under certain circumstances. These include: (a) ICP
spectra from plasma are often made up of hundred, or even thousands, of lines.
This requires higher resolution and more sophisticated optical equipment than is
needed for atomic absorption methods. This explains why ICP has much higher
instrument capital cost. (b) Higher operating cost due to the consumption of
significant amount of argon gas (5 20 L/min). (c) Need for skilled operators to
develop methods. (d) Often less precise than with atomic absorption. (e) For B, P,
N, S, and C, a vacuum UV spectrometer is necessary since emission of these
elements lie at wavelengths below 180 nm where components of the atmosphere
absorb. (f) Limited use for alkali metals (Li, K, Rb, and Cs) since the most
prominent lines are located at near-infrared wavelengths which lead to the detection
problems.
9.4 PRACTICAL TIPS TO SAMPLING, SAMPLE
PREPARATION, AND METAL ANALYSIS
In Chapter 7 (Section 7.2), we have discussed the principles and some practical tips
of sample preparation for metal analysis. In the following discussions, we further
introduce several practical guides that are essential to beginners during sample
running, calibration, and results calculation for metal analysis. For procedure
details, the reader can refer to Csuros and Csuros (2002).
Correction for Sample Moisture and Dilution
Oftentimes, beginners forget to keep a subsample for the measurement of moisture
content (w, %) of solid samples and improperly report the analytical results. It is
essential to record the mass m (to an accurate 0.0001 g) of a solid sample used for
digestion and the final volume after digestate is diluted (V, mL). If sample is a liquid,
record the original sample volume (V 1 ) and the final volume (V 2 ) if digestion or
dilution has been performed. In both cases, if the concentration from the instrument
analysis is c mg/L, then the concentration of the original sample can be calculated
as follows:
cðmg
LÞVðmLÞ100
mðgÞð100wÞ
=
Cðmg
=
kgÞ¼
ðsolid sampleÞ
ð9
:
V 2 ð mL Þ
V 1 ðmLÞ ðliquid sampleÞ
Cðmg
=
LÞ¼cðmg
=
ð9
:
Instrumental Drift and Run Sequence QA/QC
Instrumental drifting is a common problem in atomic spectrometry. Inexperienced
analysts are often frustrated by the broad variations of results for the same sample
 
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