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

(ii) The absorbance of the reagent blank, which is temperature
sensitive to the extent of 0.015 absorbance unit/ o C, should not
exceed 0.170 absorbance unit at 22 o C with a 1 cm optical path
length, when the blank is prepared according to the prescribed
analytical procedure and to the specified concentration of the dye.
(iii) The calibration curve, section 8.5.2 should have a slope of 0.030 +
0.002 absorbance unit/µg SO2 at this path length when the dye is
pure and the sulphite solution is properly standardized.
7.2.10.2 Pararosaniline Stock Solution – Dissolve 0.5 gm of specially purified
Para rosaniline (PRA) in 100 ml distilled water. Keep it for 2 days and filter
the solution. The solution is stable for 3 months if stored in a refrigerator.
7.2.10.4 Pararosaniline Working Solution - 10 ml of stock PRA is taken in a 250
ml volumetric flask. Add 15 ml conc. HCL and make up to volume with
distilled water.
8.0 PROCEDURE
8.1 Sampling and Analysis
8.1.1 Sampling - Procedures are described for short-term (30 minutes, 1 hour, 4 hours
long-term (24 hours) sampling. One can select different combinations of
sampling rate and time to meet special needs. Sample volumes should be
adjusted, so that linearity is maintained between absorbance and concentration
over the range in question.
8.1.2 30 Minutes, 1 Hour and 4 Hours Sampling - Insert a midget impinger into the
sampling system (Figure 1). Add 10 ml TCM solution to the impinger (30 ml
TCM solution for 4 hours sampling). Collect sample at 1 litre/ minute for 30
minutes, 1 hour or 4 hours using either a rotameter, as shown in Figure 1, or a
critical orifice, as shown in Figure 2, to control flow. Shield the absorbing reagent
from direct sunlight during and after sampling by covering the impinger with
aluminum foil to prevent deterioration. Determine the volume of air sampled by
multiplying the flow rate by the time in minutes and record the atmospheric
pressure and temperature. Remove and stopper the impinger. If, the sample
must be stored for more than a day before analysis, keep it at 5 o C in a
refrigerator; see section 10.1 during hot weather, sampling is not recommended
unless it is possible to refrigerate the samples as taken.
8.1.3 24 Hours Sampling - Place 50 ml TCM solution in a large absorber and collect
the sample at 0.2 litre/minute for 24 hours. Make sure no entrainment of solution
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