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

9.1.3.2 Solution B - Pipet 25 ml of solution A into a 250 volumetric flask and
dilute to volume with absorbing solution. This contains 1 µg NO - 2/ml. Prepare
fresh daily.
9.2 Calibration
9.2.1 Flowmeter - Calibrate the flowmeter against a calibrated flow measurement
standard, such as a wet test meter, bubble flowmeter, or other reliable volume
measurement standard. Calibrate in units of standard cm 3 /min (i.e., corrected to
25 o C and 760 torr).
9.2.2 Absorber - Calibrate the polypropylene absorber (see 8.1.2) by pipeting 50 ml of
water or absorbing reagent into the absorber. Scribe the level of the meniscus
with a sharp object, mark over the area with a felt-tip marking pen, and rub off the
excess.
9.2.3 Spectrophotometer
9.2.3.1 Prepare calibration curve using 1 µg/ml working standards (see 9.1.3.2).
9.2.3.2 In accordance with the analytical procedure given in 9.4, measure and
record the absorbance for each calibration standard (0, 1, 2, 3, 4, 5, 6, 7,
8, 9, 10, 12, 15, 20 µg NO2.
9.2.3.3 Plot absorbance (y-axis) versus the corresponding concentration in µg
NO - 2/50 ml final solution (x-axis). Draw or compute the straight line best
fitting the data to obtain the calibration curve.
9.3 Sample Collection
9.3.1 4-Hourly Sampling
9.3.1.1 Assemble the sampling apparatus (Figure 1) at the sampling site.
Components upstream from the absorber may be connected, where
required, with Teflon tubing; glass tubing with dry ball joints; or glass
tubing with butt-to-butt joints with Teflon or polypropylene.
9.3.1.2 Add exactly 30 ml of absorbing reagent to the calibrated absorber.
9.3.1.3 Disconnect the funnel, connect the calibrated flowmeter, measure the flow
rate before sampling and record as F1. If, the flow rate before sampling is
not 1 Lpm, replace the flow control device and/or check the system for
leaks. Start sampling only after obtaining an initial flow rate of 1 Lpm.
9.3.1.4 Sample for 4 hrs. Record the exact sampling time in minutes at ts.
124