Ambient Air quality Monitoring Guidlines. - Maharashtra Pollution ...

prior to analysis. The interference of trace metals may be eliminated by the
addition of ethylenediamine tetra acetic acid (EDTA) to the absorbing solution
prior to sampling. At least 60 µg iron (III), 10 µg manganese (II), and 10 µg
chromium (III) in 10 ml absorbing reagent can be tolerated in the procedure. No
significant interference was found from 10 µg copper (II) and 22 µg vanadium
(V). Ammonium, sulphide, and aldehydes do not interfere.
6.0 APPARATUS
6.1 Sampling
6.1.1 Absorber - An all-glass midget impinger, as shown in Figure-1, is recommended
for 30 minutes, 1 hour and 4 hours samples. For 24 hours sampling, assemble
an absorber from the following parts.
6.1.3 Polypropylene Two-Port Tube Closures
6.1.3 Glass Impingers - Tubing, 6 mm OD and 15 cm long. One end is drawn to
small diameter so that a No.79 jeweller's drill bit will pass through, but a No.78
jeweller's bit will not. The other end is fire polished.
6.1.4 Polypropylene Tubes - Tubes 164 by 32 mm, 'Nalgene' or equivalent.
6.1.5 Pump - Capable of maintaining an air pressure differential greater than 0.7 atm
at the desired flow rate.
6.1.6 Air Flowmeter or Critical Orifice - A calibrated rotameter or critical orifice
capable of measuring air flow within 2%. For 30 minutes sampling, a 22 gauge
hypodermic needle 2.5 cm long may be used as a critical orifice to give a flow of
about 1 litre/minute. For 1 hour sampling, a 23 gauge hypodermic needle 1.6 cm
long may be used to give a flow of about 0.2 litre/minute. Use a membrane filter
to protect the orifice (Figure 2).
6.2 Analysis
A spectrophotometer suitable for measurement of absorbance at 560 nm with an
effective spectral band width of less than 15 nm is required. Reagent blank
problems may occur with spectrophotometer having greater spectral band
widths.
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