Waters Sep-Pak DNPH-Silica Cartridges - Manual (Page 2)

[ Care and Use ManUal ]
Waters Sep-Pak DNPH-Silica Cartridge
2
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.
• The gold-colored aluminum compression ring on the Sep-Pak
DNPH-Silica cartridge allows for easy identification.
Figure 1: Cutaway View
Table 1: Physical/Chemical Properties
* Evaluate cartridge performance for individual high-temperature
methods.
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
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
hydrazone derivatives
1,2,3 . The derivitization reaction (Figure 2) takes
place during sample collection. The derivatives are later eluted and
analyzed. Analysis should take place within two weeks.
Figure 2: Derivitization Reaction
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.
Polyethylene Filter
DNPH-Silica
Polyethylene Filter
Luer Connector
Aluminum
Compression Ring
Luer Connector