Experiment #4
Determination of Nicotine and Aldehydes in Indoor Air
Purpose
The purpose of this experiment is to determine the concentrations of nicotine and several
aldehydes in indoor air.
Theoretical Background
Your water supply can be clean, even if your neighbor's is contaminated. The soil you
grow your vegetables in may be clean, even though there are some very contaminated
sites on the surface of the Earth. However, species are very mobile in the atmosphere.
You are familiar with this if you have sat in a bar or restaurant where there are smokers.
Even with the installation of smoke reduction equipment, you can smell cigarette smoke
anywhere in the establishment. This is of concern due to modern research linking secondhand smoke to various physical ailments.
Methods
You will be supplied with a personal air pumping system and four adsorbent cartridges.
Using this apparatus, you will take samples for nicotine and aldehydes in each of two
locations - the location of interest (e.g. a bar, a restaurant, or even your own home) and a
control location. The cartridges are then eluted with a small volume or organic solvent,
and the eluate is analyzed by GC and HPLC.
Experimental
Field Sampling
Each student will go into the field to sample environmental tobacco smoke (ETS) with a
personal air monitoring pump. In one sampling, you will attach a 2,4dinitrophenylhydrazine (DNPH) impregnated solid phase extraction (SPE) cartridge and
in the other an XAD-2 cartridge. The former will simultaneously derivatize and adsorb
aldehydes as they are pulled through the cartridge while the latter will adsorb nicotine.
The procedure is then repeated in control locations. The targets of interest are nicotine,
formaldehyde and any other aldehydes that can be resolved and detected. HPLC will be
used to separate the formaldehyde hydrazone from other interfering compounds and
capillary GC to isolate and quantify nicotine.
Methodology
Air sampling. The nominal sampling rates for the two cartridges are 500 ml/min for the
DNPH SPE cartridge and 1 liter/min for the XAD-2 cartridge. You will need to calibrate
the air pump, in the laboratory, both before and after you gather your sample by using a
bubble meter. This must be done for EACH type of tube, i.e. you will calibrate four
times. The TA will demonstrate how to do this and will also give you some indication as
to the total amount of air needed for the available detection limits attainable with the
instruments in the lab; typically a sampling time of 1-2 hours at the above flow rates
yields detectable signals. Below is a plot of flow rate versus pump setting when no tube
or a DNPH tube is connected to the pump inlet. Note how different the two lines are.
Connecting the tube imposes a significant pressure drop on the system, causing the air
flow to be smaller. The flow will be different again using one of the XAD tubes. Note
that the temperature and atmospheric pressure during calibration and during sampling
MUST be recorded to properly assess the volume of air collected.
The diagram below shows how the tube is configured. Note that the air sample is drawn
in through the narrow end, but that elution of the adsorbed/derivatized compounds is in
the OPPOSITE direction. That is the purpose of the reservoir above the adsorbent - to
allow for a few mL of eluent. Use the self-adhesive bar code labels to identify your
samples, and stick the corresponding labels in your lab notebook.
Location. The purpose of this is for you to carry out the sampling of polluted air at a
location of your choice. Each student will have to consider carefully the QA/QC issues
involved in obtaining a representative sample, having appropriate blanks and controls,
and maintaining sample integrity. The sampling site should be chosen carefully to
illustrate some hypothesis that is being made. For example, if a smoke-filled bar is
chosen for sampling, perhaps the control site would be a smoke-free restaurant. Although
tobacco smoke is likely the only source of nicotine it should be remembered that there are
innumerable sources of formaldehyde. Make sure to note as much about the sample
location as possible for later data analysis.
Analysis. Set aside a lab period to extract the two analytes from their respective sorbents
and measure each using the two chromatographic systems. The SPE cartridge will be
eluted with acetonitrile (~5 ml) and diluted to the mark in a volumetric flask. The XAD
tube will require a bit more work as there are two sections to the tube. The first and
largest amount of XAD is the primary sorbent and you'll need to carefully remove this
from the tube into an appropriate container containing the extracting solvent (ethyl
acetate); be precise about the final volume of extracting solvent. The shorter section of
XAD is the back-up sorbent and is there to indicate whether there was any
"breakthrough" of nicotine during the air sampling. Isolate this separately from the
primary sorbent as it will represent a check on the sampling methodology. There, of
course, should also have two DNPH cartridges attached to each other to provide the same
assurance of no breakthrough but at this time we will not due to cost considerations.
The nicotine will be quantified using GC/TSD in room 437. The aldehydes will be
analyzed using HPLC in the CHEM 3305 lab.