SKC 520-02A Inorganic Mercury Passive Sampler - Manual (Page 3)

• Always replace the used foam disk in the back cap with a clean disk aft er cleaning the housing.
• This sampler only samples elemental mercury (Hg) in the vapor phase and does not sample
organic mercury compounds or particulate matt er.
• Take precautions when sampling for mercuric chloride. It can collect on the face of the badge and
interfere with sampling.
Interferences During Sampling
Ambient Temperature
The sampling rate will vary with ambient temperature changes which aff ect the
diff usion co-effi
cient. This eff ect is small but may be signifi cant if sampling at un-
usually high or low temperatures. The diff usion coeffi cient (D) is a function of the
absolute temperature (T) by the relation D T 1.5 . This factor is taken into account
in the calculation used in the OSHA method (see page 4).
Wind Velocity
The sampling rate will remain substantially constant over a range of wind velocity
from 25 to 750 ft /min. In very still air conditions (below 25 ft /min), the sampling
rate will drop by up to 30%. If very high wind velocities (in excess of 750 ft /min)
are expected, passive samplers should not be used.
Ambient Pressure Changes
The sampling rate varies with ambient pressure changes which aff ect the diff usion
co-effi
cient. The diff usion coeffi cient is inversely proportional to the ambient pres-
sure. This factor is taken into account in the calculation used in the OSHA method
(see page 4).
Presence of Other Gases
The sampling of mercury on the sorbent has been shown to be unaff ected by the
presence of other gases, including chlorine. Note, however, that complex interac-
tions in the atmosphere may reduce the total free elemental mercury present to be
sampled.
Analysis
Consult OSHA Method ID 140 and MDHS 16 for detailed analytical procedures.
Preparation of Samples
Open the sorbent capsule and carefully pour the sorbent into a 50-ml volumetric
fl ask. Add 5 ml of concentrated nitric acid followed by 5 ml of concentrated hydro-
chloric acid. Allow to stand for approximately 30 minutes or until the sorbent is
fully dissolved. Stir gently if necessary. Add approximately 15 ml of distilled water
to bring total liquid quantity up to 25 ml.
When Anasorb C300 is dissolved, a milky suspension results. This is an insoluble
residue and must be removed by fi ltration or centrifugation before analysis.
Take aliquots from this solution and analyze at 253.7 nm by cold vapor atomic
absorption.
Prepare several “blanks” by dissolving fresh, unexposed capsules of the same lot
number as the test specimen. These “blank” values represent the background level
of mercury in the sorbent and should be subtracted from all readings.
Mercury Desorption
The basic mechanism of desorption consists of adding an excess of stannous chloride
to the aliquot of sample solution. This causes the mercury to be released as elemental
mercury which is swept into the analyzer by an air or nitrogen stream.
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