Waters Sep-Pak XPoSure Aldehyde Sampler User Manual
[ CARE AND USE MANUAL ]
[ CARE AND USE MANUAL ]
Sep-Pak XPoSure Aldehyde Sampler
CONTENTS
I. INTRODUCTION
a. Sep-Pak DNPH-Silica Cartridge Description
II. USING THE SEP-PAK XPOSURE
ALDEHYDE SAMPLER
a. Theory of Operation
b. Preventing Contamination
c. Collecting the Sample
d. Eluting the Derivatives from the Sampler
III. ANALYZING THE DNPH DERIVATIVES
a. Theory of Operation
b. Preventing Contamination
c. Collecting the Sample
d. Calculating Results
IV. APPLICATION EXAMPLES
a. Formaldehyde in Laboratory Air - STEL
b. Glutaraldehyde in Laboratory Air – STEL
I. INTRODUCTION
Waters Sep-Pak® XPoSure™ Aldehyde Samplers are convenient,
reproducible sampling devices for quantifying formaldehyde
concentrations in the workplace and indoor air within a range of
0.001 to 5 parts per million (ppmv).
V. STORAGE AND DISPOSAL OF THE SAMPLERS
a. Storing Unused Samplers
b. Storing Exposed Samplers
c. Disposing of used cartridges
VI. TROUBLESHOOTING
VII. REFERENCES AND BIBLIOGRAPHY
VIII. ORDERING INFORMATION
IX. APPENDIC ES
a. Appendix A: Measuring Acetontrile Purity
b. Appendix B: Synthesizing the DNPH-Derivative Standards
c. Appendix C: Measuring Breakthrough
d. Appendix D: Useful Conversion Factors
d.1. Carbonyl to Hydrazone Conversion Factors
d.2. Equation for converting µg/L to ppmv
d.3. Conversion Factors: µg/L to ppmv
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a. Sep-Pak XPoSure Aldehyde Sampler Description
and Features
Sep-Pak XPoSure Aldehyde Samplers contain acidified
2,4-Dinitrophenylhydrazine(DNPH)-coated silica, packed
in Waters Sep-Pak Plus cartridges.
The samplers are constructed from high-purity and high-
density polyethylene components, triaxially-compressed
packed beds and Luer fittings equipped with end caps and
plugs.
The samplers are designed for flow rates of up to 1.5 L/min
with typical personal pumps.
The gold-colored aluminum compression ring on the
Sep-Pak XPoSure Aldehyde Sampler allows for easy
identification.
Luer Connector
Polyethylene Filter
DNPH-Silica
Aluminum
Compression Ring
Polyethylene Filter
II. USING THE SEP-PAK XPOSURE
ALDEHYDE SAMPLER
a. Theory of Operation
Sep-Pak XPoSure Aldehyde Samplers trap aldehydes in air by
reacting them with acidified 2,4-dinitrophenylhydrazine(DNPH),
forming stable hydrazone derivatives. The derivitization reaction,
as shown in Figure 2, takes place during sample collection. T he
derivatives are later eluted and analyzed using HPLC.
Figure 2. Derivitization Reaction.
b. Preventing Contamination
Contamination is most likely to occur during sample collection.
Before eluting the derivatives, clean all glassware by rinsing with
acetonitrile and heating to 60 °C in a vacuum oven for at least
30 minutes. Eluting the samples in a nitrogen-purged glove box
further reduces the risk of contamination.
Luer Connector
Figure 1. Cutaway View.
Table 1: Physical and Chemical Properties
Hold-up Volume
Collection Efficiency
Capacity
Quantity of DNPH Silica
Sampling Temperature
Dimensions
a.
Based on 50% consumption of DNPH.
b
Evaluate sampler performance for individual high-temperature method.
a
b
>95% for sampling rates up to 1.5 L/min
Approximately 70 µg formaldehyde
0.35 g/sampler (~1 mg DNPH)
0.7 mL
10 °C to 100 °C
4.3 cm total length
2.0 cm o.d. at widest point
1.0 cm i.d.
0.9 cm bed length
The acetonitrile you use to elute the DNPH derivatives can also be
a source of contamination. Even HPLC-grade acetonitrile may have
unacceptable levels of carbonyl contaminants and should be stored
in a carbonyl-free environment. A concentration of 10 µg/L of
any aldehyde or ketone contaminant will add 0.1 µg to the blank
values determined for the DNPH-derivatives per cartridge. Follow
the procedure in Appendix A, Measuring Acetonitrile Purity, to
pre-qualify your acetonitrile.
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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
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.
1,2
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.
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
Formaldehyde <0.45 <0.06
Adetaldehyde <0.75 <0.15
Acetone <1.5 <0.38
Othersa <0.75 -
a.
Individually, as acetone-DNPH.
µg DNPH Derivatives
per Sampler
µg Carbonyl Compounds
per Sampler
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.
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2.0
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1.8
1.6
1.4
1.2
1.0
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.
0.8
0.6
0.4
0.2
5
Figure 3: Typical Sampler Backpressure Profile.
15
Vacuum (inches water)
Sample Collection – PEL (0.01 to 1.0 ppmv)
To collect the PEL air sample:
1. Calibrate the sampling pump with a representative sampler in
line. Set the flow to 100 mL/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 8 hours, yielding a sample volume of 48 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 48 L air sample is sufficient for quantifying formaldehyde in the
range of 0.01 to 1 ppmv. Formaldehyde concentrations lower than
0.01 ppmv in air will require longer sampling times and a larger
air sample. Conversely, formaldehyde concentrations that exceed
1.0 ppmv will require shorter sampling times or reduced sampling
flow rates in order to avoid overloading the sampler and obtaining
nonlinear results.
d. Eluting the Derivatives from the Sampler
To elute the derivatives from the sampler:
1. Remove the sampler from the stapled pouch.
2. Elute the DNPH derivatives from the sampler with pre-qualified
25
30
acetonitrile directly into a 10 mL volumetric flask. Use a flow
rate of <3 mL/min. Higher flow rates (>3 mL/min) can result in
reduced recovery.
3. Cap the volumetric flask and mix by inverting it several times.
4. Analyze the eluate using HPLC.
Note: Since background levels may change during storage, always
compare samples to a blank sampler from the same lot, stored
under the same conditions.
III. ANALYZING THE DNPH DERIVATIVES
a. Operating Guidelines
To ensure success in your HPLC analysis:
Use a pre-column filter between the injector and column.
Use HPLC-grade water and HPLC-grade acetonitrile.
Degas the mobile phases by simultaneously applying
vacuum and ultrasound to the mobile phases for 30 seconds.
If you are using a low-pressure mixing gradient system,
sparging with helium may be necessary.
Waters Symmetry® C18 columns are shipped containing
water/acetonitrile. Before the first analysis, equilibrate the
column with mobile phase at 1.3 mL/min for 10 minutes in
mobile phase or until the baseline is stable. See Table 4 for
separation conditions.
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