SKC 500-200 UMEx 200 Passive Sampler for Sulfur Dioxide - Manual (Page 3)

Diffusion plate
Reactive tape (sample)
Collar clip
Body
Sliding
cover
Reactive tape
(blank/correction)
4. Pipett e 1 ml of extract into a vial and dilute
with 1 ml of 0.15% hydrogen peroxide. Shake
well for analysis of sulfur dioxide.
5. If also analyzing for NO
2
, § transfer the
remaining 1 ml of extract to an auto-sampler
vial for analysis of nitrogen dioxide.
§ Sampling rate for NO
2
is 17.3 ml/min.
Sulfur Dioxide Sample Analysis
1. The sample extracts are analyzed for sulfate by ion chromatography with
conductivity detection.
2. A 20 microliter portion of the extract is injected onto a Dionex 4 x 250 mm AS14A
column and with an 8.0/1.0 mM sodium carbonate/sodium bicarbonate eluent.
3. Calculate the sulfate results by comparing against a standard calibration curve.
4. Convert the results from sulfate to sulfur dioxide using the following formula:
Concentration μg/ml sulfur dioxide = Concentration μg/ml sulfate x (64.1/96.1)
Where 64.1 is the molecular weight of sulfur dioxide and
Where 96.1 is the molecular weight of sulfate
5. Total mass of sulfur dioxide is calculated below:
Concentration sulfur dioxide (μg/ml) x Desorption volume (2 ml)
6. The sulfur dioxide of the blank/correction tape must always be subtracted from
the sample tape when calculating air concentrations.
7. Calculate the air concentration in ppm using the following equations:
Volume of air (liters) = Time (minutes) x Sampling rate (15.2 ml/min)
1000
Concentration (ppm) = Mass (mg) x 24450
Air volume (L) x Molecular weight (64.1)