Acrolein – a potent irritant for sure. A multi-blog series on airborne carbonyls, part IV.

After a brief summertime hiatus, it is time to get back to the carbonyls issueS (yes, that S was intentionally capitalized). So acrolein is extremely acrid and irritating to mucous membranes. At one point in time or another, we non-smokers have experienced the eye burning sensation of environmental tobacco smoke (ETS). Nothing like a good waft of a cigarette straight to the cornea!? Several researchers have attributed a large part of ETS’s irritating qualities to acrolein. Well… acrolein is more than just irritating to your eyes and lungs. In fact, sampling for acrolein is a royal pain in the you know what!

There are multiple widespread issues associated with sampling airborne acrolein with 2,4-dinitrophenylhydrazine (DNPH)-coated solid sorbents (i.e., U.S. Environmental Protection Agency (EPA) Compendium Method TO-11A) (U.S. EPA, 1999A). In 1986, Tejada first explained the loss of the acrolein-DNP-hydrazone (with time) concurrent with the appearance of an unknown chromatogram peak he termed “x-acrolein”. Over the next 15 years, researchers attributed poor acrolein recoveries due to any one or combination of the following:  the formation of an acrolein dimer (2-formyl-3,4-dihydro-2H-pyran) prior to derivatization; decomposition in presence of excess acid and excess DNPH; coelution of the acetone- and acrolein-DNPH derivatives; and the list goes on ad infinitum.

It was not until 2001 where Schulte-Ladbeck et al. (2001) properly described the artifact associated with the acrolein-DNPH derivatives. Essentially, they found that the acrolein-DNP-hydrazone reacts further with DNPH to form acrolein-(x) (Tejada’s aforementioned observation of x-acrolein) and that acrolein-(x) reacts again with acrolein-DNP-hydrazone to form acrolein-(y). Note that Uchiyama et al. (2010) confirmed this observation referring to the acrolein-DNP-hydrazone as ACR-D and the adduct isomer structures as AD1 and AD2 (see figure below adopted from Uchiyama et al. 2010). In short, everyone was looking at ACR-D in their chromatograms (except Tejada observed AD1, which he referred to as x-acrolein); and no one was looking at AD2 (what Shulte-Ladbeck referred to was acrolein-(y)). Over the past 15 years everyone was just watching ACR-D “disappear”, “decompose” etc… Oddly enough, Uchiyama et al. 2010 even refers to this reaction mechanism as “decomposition” of ACR-D, which I personally disagree with. Nothing is “decomposing”; the reaction is simply going to completion. In any event, I made the same observations back in 2005 for the DNSH (another hydrazine reagent with similar chemistry as DNPH) I was using in my passive sampler (see Herrington et al. (2005)).

 

Adopted from Uchiyama et al. 2010

Of course… it gets better! In October of 2000 (nearly 15 years after the problem was first discovered by Tejada), Compendium Method TO-11A was finally amended to remove acrolein from the list of applicable target analytes due to the aforementioned concerns (U.S. EPA, 2000). However, somewhere along the line the U.S. EPA was scrambling for a solution. Amidst the haste, and based on very limited evidence (my personal opinion) it was decided that canister sampling was the best approach for measuring airborne acrolein. My gut (better known within Restek for its insatiable appetite) must have been right about the limited evidence on canister sampling for acrolein, because in in 2010 the U.S. EPA released guidelines indicating that recent studies have demonstrated an increase in acrolein concentrations in “clean” canisters (U.S. EPA, 2010). The guidelines are not very detailed; however, the take-away message is that depending on the canister cleaning conditions (i.e., gas, relative humidity, temperature, etc…) acrolein concentrations may increase over time in “clean” canisters. This “growth” of acrolein in canister blanks can cause an inadvertent bias in acrolein concentrations.

So where does this leave us!? Well… for now it is highly advised that you do not use Method TO-11A for acrolein. In the meantime, canister based sampling is still probably your best approach; however, you will have to be cognizant of your canister cleaning procedures and blank canisters concentrations. Here at Restek we are investigating the cleaning of our SilcoCans and TOCans to make recommendations for the optimum cleaning procedures/conditions to limit acrolein “growth”. So keep an eye out for up-coming blogs...

References

Schulte-Ladbeck R., Lindahl R., Levin J.O., Karst U., 2001. Characterization of Chemical Interferences in the Determination of Unsaturated Aldehydes Using Aromatic Hydrazine Reagents and Liquid Chromatography. Journal of Environmental Monitoring, 3, 306-10.

Tejada S.B., 1986. Evaluation of Silica-Gel Cartridges Coated Insitu with Acidified 2,4-Dinitrophenylhydrazine for Sampling Aldehydes and Ketones in Air. International Journal of Environmental Analytical Chemistry, 26, 167-185.

Uchiyama S., Inaba Y., Kunugita N., 2010. Determination of Acrolein and Other Carbonyls in Cigarette Smoke Using Coupled Silica Cartridges Impregnated with Hydroquinone and 2,4-Dinitrophenylhydrazine. Journal of Chromatography A, 1217, 4383-8.

U.S. EPA, 1999A. Determination of Formaldehyde in Ambient Air Using Adsorbent Cartridge Followed by High Performance Liquid Chromatography (HPLC) [Active Sampling Methodology]: Compendium Method TO-11A in Compedium of Methods for the Determination of Toxic Organic Compounds in Ambient Air. U.S. Environmental Protection Agency. Washington, DC.

U.S. EPA, 1999B. Determination Of Volatile Organic compounds (VOCs) In Air Collected IN Specially-Prepared Canisters And Analyzed By Gas Chromatography/Mass Spectrometry (GC/MS): Compendium Method TO-15 in Compdium of Methods for the Determination of Toxic Organic compounds in Ambient Air. U.S. Environmental Protection Agency. Washington, DC.

U.S. EPA, 2000. Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air - Second Edition: ADDENDUM. U.S. Environmental Protection Agency. Washington, D.C.

U.S. EPA, 2010. Data Quality Evaluation Guidelines for Ambient Air Acrolein Measurements. Available at http://www.epa.gov/ttnamti1/files/ambient/airtox/20101217acroleindataqualityeval.pdf. U.S. Environmental Protection Agency.