Waters Sep-Pak DNPH-Silica Cartridges - Manual (Page 3)

[ Care and Use ManUal ]
Waters Sep-Pak DNPH-Silica Cartridge
3
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
that this level be at least 10 times of that of the background
3 .
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
* 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 4: Range of Sample Volumes vs. Expected Concentration
Caution: Ozone (usually present in urban air) degrades the hydrazone
derivatives
4 . 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.
Figure 3: Flow Rate versus Applied Vacuum
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 -