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

9.4 Blank Correction - Measure the absorbance of the unexposed reagent and
subtract the value from the absorbance of the sample.
9.5 Calibration and Standardization
9.5.1 Calibrating solutions are made up to 10 ml to facilitate the calculations:
9.5.2 Obtain a range of calibration points containing from 1 µl to 10 µl of ozone
equivalent per 10.0 ml of solution. Prepare by individually adding 1.0, 2.0, 4.0,
6.0, 8.0 and 10.0 mL of the calibrating iodine solution (Section 9.4.2) to 10.0 ml
volumetric flasks. Bring each to the calibration mark with absorbing reagent.
9.5.3 Read the absorbance of each of the prepared calibration solutions as described
in Section 10.3 and 10.4.
9.5.4 Plot the absorbance of the obtained colors against the concentration of O3 in
µl/10 ml absorbing reagent. The plot follows Beer's law. Draw the straight line
through the origina giving the best fit, or fit by least squares. Do not extrapolate
beyond the highest concentration.
10.0 CALCULATIONS
10.1 Standard conditions are taken as 101.3 kPa and 25 o C, at which the molar gas
volume is 24.47 liters.
10.2 Record the volume of sample collected in liters. Generally the correction of the
sample volume to standard conditions is slight and may be omitted. However, for
greater accuracy corrections may be calculated by means of the perfect gas
laws.
10.3 The total µl of O3/10 ml of reagent are read from the calibration curve.
10.4 The concentration of O3 in the gas phase in µl/l or ppm is given by :
Total µl ozone per 10 ml
O3 ppm = -------------------------------
Volume of air sample, L
10.5 The concentration of O3 in terms of µg/m 3 at 101.3 kPa and 25 o C is obtained
when desired from the value of µl/l (Section 11.4) by :
ppm x 48.00
µg O3/m3 = ------------------ x 10 3
24.47
= 1962 x ppm
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