Samples, Calculations – SKC 526-200_201 Analysis Instructions Using the Chromotropic Acid Assay Method User Manual
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SAMPLES:
Samples from Formaldehyde Sampler Catalog No. 526-100 are color-developed inside the 526-100 vial, but the 526-200 and 526-201 samples require the adsorp-
tion disc to be removed from the sampler and placed inside a 13 x 100 mm test tube for color development.
Formaldehyde Sampler, Catalog No. 526-100
Add 2.00 ml of DI water to each sample, vortex for 5 seconds, cover with plastic and let sit for 30 minutes.
Add 0.10 ml of chromotropic acid.
Add 3.00 ml of sulfuric acid slowly and with care, using appropriate protective measures, vortex for 5 seconds, cap with vented caps and place in the hot
water bath for 15 minutes.
Cool the samples for 30 minutes in air or more quickly in a cold water bath, and vortex for 5 seconds and decant into clean 13 x 100 mm test tubes
(centrifuge tubes).
Centrifuge decanted solutions for 10 minutes and read values at 580 nm.
Formaldehyde Samplers, Catalog No. 526-200 (STEL) and 526-201 (PEL)
Cut the samplers open to expose the fi lter discs.
Using clean tweezers extract the absorbent disc and the 2 polypropylene discs on either side of the absorbent disc.
Place the 3 discs at the bottom of a 13 x 100 mm test tube.
Add 2.00 ml of DI water, vortex 5 seconds, cover with plastic and let sit for 30 minutes.
Add 0.10 ml of chromotropic acid.
Add 3.00 ml of sulfuric acid slowly and with care, using appropriate protective measures, vortex for 5 seconds, cap with vented caps and place in the hot
water bath for 15 minutes.
Cool the samples for 30 minutes in air or more quickly in a cold water bath and vortex for 5 seconds and decant into clean 13 x 100 mm test tubes (cen-
trifuge tubes).
Centrifuge the decanted solutions for 10 minutes and read values at 580 nm.
CALCULATIONS:
Calculate the μg and ppm formaldehyde with the values given to you by SKC according to the following calculations:
μg = 2 (A580 - Intercept)/Slope (Note: The calibration curve is in terms of concentration (μg/ml), but 2 ml of each standard is used.)
ppm = (Sample μg - Blank μg)/(Diffusion Constant) (Exposure Hr)
The diffusion constant (uptake rate) of the 526-100 is 0.310 μg/ppm/hr.
The diffusion constants (uptake rates) of the 526-200 and 526-201 are individually calibrated and the information is printed on the package. If this is lost, contact
SKC Customer Service at 724-941-9701 with the serial number (not the lot number) of the sampler.
Publication #1344 Rev 1102
Formaldehyle Samplers manufactured for SKC by Air Quality Research Inc.
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