Waters Sep-Pak XPoSure Aldehyde Sampler - Manual (Page 3)

[ CARE AND USE MANUAL ]
c. Collecting the Sample
Caution: Beware of unintentional exposure of the samplers and
eluted samples to aldehyde and ketone sources. Laboratory air
often holds high concentrations of acetone. Labeling inks and
adhesives as well as packaging containers (including vials with
plastic caps) are all possible sources of contamination.
Sampling methods have been developed and validated for both 15
minute short-term exposure limit (STEL), and in 8 hour personal
exposure limit (PEL) measurements following the National
Institute for Occupational Safety and Health (NIOSH) guidelines
1,2 .
XPoSure Aldehyde Samplers have been tested under controlled
laboratory conditions. Table 2 lists the equipment needed to
collect air samples using XPoSure Aldehyde Samplers. The
recommended measurement range for formaldehyde is:
STEL: 0.022 to 2 ppmv
PEL: 0.01 to 1 ppmv
Table 2: Sample Collection Equipment
Suggested Personal Pump Specifications
Operating Range 100 to 1,500 mL/min
Compensation Range 1,500 mL/min – 0 to 20 inches water
Flow Control ±5% set point constant flow
Flow Indicatora Built-in flow indicatora
a. A flow calibrator may also be required.
The background levels of aldehydes and ketones in the sampler
determine the sensitivity of the method. The volume of air passed
through the sampler must be large enough for the quantity of
DNPH derivatives formed to be several times greater than the
background level. The United States Environmental Protection
Agency (US EPA) recommends that this level be at least 10 times
the background level.
3 Table 3 lists the sampler background
specifications.
Table 3: Sampler Background Specifications
Compound
µg DNPH Derivatives
per Sampler
µg Carbonyl Compounds
per Sampler
Formaldehyde <0.45 <0.06
Adetaldehyde <0.75 <0.15
Acetone <1.5 <0.38
Othersa <0.75 -
a. Individually, as acetone-DNPH.
Sample Collection – STEL (0.02 to 2.0 ppmv)
To collect the STEL air sample:
1. 1Calibrate the sampling pump with a representative sampler
in line. Set the flow to 1.5 L/min. Figure 3 shows the flow rate
through a sampler versus applied vacuum. Once calibrated,
remove and store this representative sampler for future
calibrations.
2. Take a fresh sample from its pouch. Remove and save the end
cap and plugs.
3. Connect the sampler to a pump with flexible plastic tubing. The
sampler is bidirectional (flow can be in either direction).
4. Draw air for 15 minutes, yielding a sample volume of
22.5 liters.
5. Reseal the sampler with its end cap and plug.
6. Store the sampler in the pouch provided with appropriate
identification. Seal the pouch by folding the edge over twice
and stapling it shut. Avoid exposing the samplers to heat.
A 22.5 L air sample is sufficient for quantifying formaldehyde in
the range of 0.02 to 2 ppmv. Formaldehyde concentrations lower
than 0.02 ppmv in air will require longer sampling times and a
larger air sample. Conversely, formaldehyde concentrations that
exceed 2.0 ppmv will require shorter sampling times or reduced
sampling flow rates in order to avoid overloading the sampler and
obtaining nonlinear results.
Note: The maximum recommended sampler capacity is
2.3 µmoles total carbonyl species. This calculates to 50% of
the DNPH consumed. Contaminated air may contain significant
concentrations of other aldehydes and ketones and the total may
exceed the capacity of the sampling device. Follow the procedure in
Appendix C, Measuring Breakthrough for more information.
3
[ CARE AND USE MANUAL ]
Sep-Pak XPoSure Aldehyde Sampler