Waters Sep-Pak DNPH-Silica Cartridges User Manual

[ Care and Use ManUal ]
WAters seP-PAK dnPH-sILICA CArtrIdGe
Contents
I. IntroduCtIon
a. Sep-Pak DNPH-Silica Cartridge Description
II. usInG seP-PAK dnPH CArtrIdGes
b. Preventing Contamination c. Collecting the Sample d. Eluting the Derivatives
III. AnALYZInG tHe dnPH derIVAtIVes
a. Operating Guidelines
b. Performing HPLC Analysis c. Analyzing a Cartridge Blank
d. Selecting Separation Conditions
IV. APPLICAtIon eXAMPLes
a. Estimating Sample Volume
b. Analysis of Auto Exhaust Emissions c. Analysis of Residential Air
d. Analysis of Research Lab Air
I. IntroduCtIon
Waters Sep-Pak® DNPH-Silica cartridges are convenient, reproducible
sampling devices for quantifying aldehydes and ketones in gasses,
including air within a range of 1 to 5,000 parts per billion (ppbv).
V. storAGe And dIsPosAL oF used CArtrIdGes
VI. trouBLesHootInG
VII. reFerenCes And BIBLIoGrAPHY
VIII. orderInG InForMAtIon APPendICes
IX. APPendICes
a. Measuring Acetonitrile Purity b. Synthesizing DNPH Derivative Standards c. Measuring Sample Breakthrough
Waters Sep-Pak DNPH-Silica Cartridge
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Po lyethylene Filter
DNPH-Silica
Po lyethylene Filter
Luer Connector
Aluminum
Compression Ring
Luer Connector
a. Sep-Pak DNPH-Silica Cartridge Description
• WatersSep-PakDNPH-Silicacartridgesconsistofacidified
2,4-dinitrophenylhydrazine-coated silica packed in Waters
Sep-Pak Plus cartridges.
• WatersSep-PakPluscartridgesareconstructedofhigh-purity
polyethylene components with triaxially-compressed packed
beds and Luer fittings equipped with end caps and plugs.
• T hegold-coloredaluminumcompressionringontheSep-Pak
DNPH-Silica cartridge allows for easy identification.
II. usInG seP-PAK dnPH-sILICA CArtrIdGes
a. Theory of Operation
Waters Sep-Pak DNPH-Silica cartridges trap aldehydes and ketones in
gasses by reacting them with the DNPH in the cartridge to form stable
1,2 ,3
hydrazone derivatives
place during sample collection. The derivatives are later eluted and
analyzed. Analysis should take place within two weeks.
Figure 2: Derivitization Reaction
. The derivitization reaction (Figure 2) takes
Figure 1: Cutaway View
Table 1: Physical/Chemical Properties
Hold-Up Volume 0.7 mL
Particle Size 55 to 105 µm Collection Efficiency >95% for sampling rates up to 2 L/min Capacity Approximately 75 µg formaldehyde Quantity of DNPH-Silica 0.35 g/cartridge (1.0 mg DNPH) Operating Temperature* 10 °C to 100 °C Dimensions 4.3 cm total length
2.0 cm o.d. at widest point
1.0 cm i.d.
0.9 cm bed length
* Evaluate cartridge performance for individual high-temperature
methods.
b. Preventing Contamination
Contamination is most likely to occur during sample preparation.
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.
The acetonitrile used to elute the DNPH derivatives can also be a
source of contamination. Even HPLC-grade acetonitrile may have
unacceptable levels of carbonyl contaminants. 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 to test your acetonitrile.
c. Collecting the Sample
Caution: Beware of unintentional exposure of the cartridges 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.
Waters Sep-Pak DNPH-Silica Cartridge
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[ Care and Use ManUal ]
Caution: Ozone (usually present in urban air) degrades the hydrazone
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derivatives
. Place an Ozone Scrubber Cartridge (Waters Part
number: WAT054420) on the inlet of the Sep-Pak DNPH-Silica
cartridge.
Notice: Do not use Sep-Pak DNPH-Silica cartridges to process liquid
samples.
To collect the sample:
1. Take the cartridge from its pouch. Remove and save the end cap
and plug.
2. Connect the cartridge to a pump with flexible plastic tubing.
The cartridge is bidirectional (flow can be in either direction).
Figure 3 shows the flow rate through a cartridge versus applied
vacuum.
3. Draw the sample through the cartridge. Record the flow rate and
collection time.
4. Reseal the cartridge with its end cap and plug.
5. Store the cartridge in the provided pouch with appropriate
identification. If possible, seal the pouch using a heat sealer,
®
or store the cartridge in a glass container with a Teflon
-lined
cap. Keep the samples cool (<4 °C). Elute the cartridge within
two weeks.
The volume of air passed through the cartridge must be large
enough for the quantity of DNPH derivative formed to be several
times greater than the background level (Table 2). The United
States Environmental Protection Agency (US EPA) recommends
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that this level be at least 10 times of that of the background
.
Figure 4 shows the ranges of sample volumes to use as a function
of expected concentration. If you can not predict the concentration
of total carbonyl compounds in a sample, follow the procedure in
Appendix C, Measuring Sample Breakthrough.
Table 2: Background Levels of DNPH Derivatives
Compound µg DNPH Derivative per Cartridge µg as Carbonyl Compound per
Cartridge Formaldehyde <1.0 <0.15 Acetone <2.0 <0.50 Others* <0.75 -
* Individually, as acetone-DNPH, determined using a gradient
from 70/25/5 water/acetonitrile/tetrahydrofuran to 40/60 water/
acetonitrile. Other conditions are as in Section III, d.
Figure 3: Flow Rate versus Applied Vacuum
Waters Sep-Pak DNPH-Silica Cartridge
Figure 4: Range of Sample Volumes vs. Expected Concentration
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d. Eluting the Derivatives
There are two recommended methods for elution of the derivatives
from the cartridge:
Volumetric Method:
1. Elute the DNPH derivatives from the cartridge directly into a
5 mL volumetric flask. Use 3 mL HPLC-grade acetonitrile at a
flow rate of less than 3 mL/min. Higher flow rates (>3 mL/min)
can result in reduced recovery.
2. Dilute to volume with HPLC-grade acetonitrile.
Gravimetric Method:
1. Elute the DNPH derivatives from the cartridge directly into a
tared vessel. Weigh the eluate and divide by the density of the
acetonitrile to obtain the sample volume. Acetonitrile has a
density of 0.785 g/mL at 20 °C.
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.
b. Performing HPLC Analysis
To analyze the sample:
1. Prepare the standard solution of the DNPH derivatives that you
need to quantify. The concentrations of the standards should be
in the same range as the expected concentrations in the sample.
To synthesize DNPH derivatives, see Appendix B.
2. Prepare a cartridge blank from the same sample lot as the
c a r t r i d g e u s e d t o c o l l e c t t h e s a m p l e , u s i n g t h e s a m p l e
procedure and same bottled solvent.
3. Analyze the standard solution to determine the response
factor for each derivative. Due to the high linearity of the
detector response, a single point calibration is sufficient for
Waters detectors.
Note: Use an injection volume appropriate for your column. Inject
≤20 µL for a 3.9 x 150 mm Nova-Pak C
3.0 x 75 mm Nova-Pak C
column.
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column, and ≤10 µL for a
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4 . A n a l y z e t h e c a r t r i d g e b l a n k t o d e t e r m i n e b a c k g r o u n d l e v e l s .
Ensure that the blank values are in the normal range
(see Table 2).
5. Analyze the samples.
•  UseHPLC-gradeunstabilizedtetrahydrofuranformakingmobile
phases.
•  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Nova-Pak
C18 columns are shipped containing
water/acetonitrile. Equilibrate the column at 1.5 mL/min for
10 minutes in mobile phase before the first analysis.
Waters Sep-Pak DNPH-Silica Cartridge
6. Subtract the blank values from the sample values. Run standards
at regular intervals between samples.
c. Analyzing a Cartridge Blank
Analyze a blank to determine background levels. Figure 5 shows a
typical result from a blank cartridge extraction. Since background
levels may change during storage (see Section V), always compare
samples to blank cartridges from the same lot stored under the same
conditions.
Note: When preparing a blank sample, ensure that you use the exact
bottled reagents that were used for the preparation of the sample.
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