Grantee Research Project Results

Final Report: Novel Method for Measurement of Acrolein in Aerosols

EPA Grant Number: R827352C010
Subproject: this is subproject number 010 , established and managed by the Center Director under grant R827352
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Southern California Children's Environmental Health Center
Center Director: McConnell, Rob Scot
Title: Novel Method for Measurement of Acrolein in Aerosols
Investigators: Charles, Judith M.
Institution: University of California - Davis
EPA Project Officer: Chung, Serena
Project Period: June 1, 1999 through May 31, 2005 (Extended to May 31, 2006)
RFA: Airborne Particulate Matter (PM) Centers (1999) RFA Text |  Recipients Lists
Research Category: Particulate Matter , Air Quality and Air Toxics , Air

Objective:

Hypothesis

The overall objective of the project is to develop a method to measure acrolein, and other carbonyls that either are directly emitted from motor vehicles or are photooxidation products of hydrocarbons in motor vehicle exhaust (e.g., crotonaldehyde, hydroxyl acetone, glycolaldehyde, methyl glyoxal, glyoxal) that is accurate and precise, and that affords a short sampling time.

Objectives

The objective of this project was to develop a new method to measure acrolein and other toxic carbonyls in air that affords part-per-trillion detection limits and short sampling times (10 minutes). The proposed method relies on using a mist chamber to sample carbonyls, followed by detection of the compounds by using derivatization along with gas chromatography/mass spectrometry (GC/MS).

Summary/Accomplishments (Outputs/Outcomes):

Initial work was conducted to explore whether carbonyls could be sampled into a mist chamber by using an aqueous bisulfite solution, and whether the carbonyls could be analyzed by releasing the carbonyl-bisulfite adduct and then derivatizing the “free” carbonyl with 0-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine (PFBHA) prior to detection by using GC/MS. Specifically, experiments were conducted to: 1) establish the formation of carbonyl-bisulfite adducts by measuring the formation constants (k_f) for formaldehyde, methyl glyoxal, acrolein, glyoxal, methacrolein, crotonaldehyde, hydroxy acetone and glycolaldehyde, 2) investigate the effect of pH on PFBHA derivatization of the carbonyls in the presences and absence of bisulfite, and 3) investigate the effect of bisulfite concentration on PFBHA derivatization. Once optimum conditions were determined for formation and derivatization of the carbonyls, we compared the collection efficiency (CE) in the mist chamber using an aqueous solution, a 0.001M bisulfite solution, a 2mM PFBHA solution and a 2mM pentafluorophenylhydrazine (PFPH) solution. The collection efficiency is a measure of the efficiency of the mist chamber to capture the carbonyls is the first mist chamber, using 2 mist chambers in series.

The k_f of the carbonyls were determined at pH=5.0 using pseudo-first order kinetics. The k_f for fomaldehyde was 15.15 ± 1.36 M^-1s^-1 which is in close agreement with the literature value of 12.83 M^-1s^-1, thereby validating the analytical approach. The formation constant for acrolein was 0.73 ± 0.10 M^-1s^-1 with a 96% yield in 10 minutes. These k_f and the k_f obtained for the other compounds establish the formation of carbonyl-bisulfite adducts at pH=5.0 with >80% yields in 10 minutes. Since samples will be collected in the field, and then prepared for analysis in the laboratory, we also explored the stability of the bisulfite adducts over a 6 day period. The effect of pH on PFBHA derivatization was explored at pH=1, 5 and 12 in the absence of bisulfite. The results were consistent with previous data that demonstrate that PFBHA derivatization occurs at neutral and acidic, but not basic pH. The experiment was repeated at pH=5.0 in the presence of 0.05 M bisulfite. The concentration of the PFBHA derivatives was lower in the presence of bisulfite than in the absence of bisulfite, indicating that the bisulfite hinders PFBHA derivatization of the carbonyls. Further experiments established that derivatization was also compromised at 0.005 M and 0.001 M bisulfite concentrations, with higher concentrations of derivatives being formed at the lowest bisulfite concentration. The finding that bisulfite hinders or interferes with PFBHA derivatization was significant and may be a deterrent to using an aqueous solution bisulfite as the collecting medium in the mist chamber. Comparison of the collection efficiency for acrolein, methacrolein, methyl vinyl ketone, crotonaldehyde, glyoxal and methyl glyoxal using water, a 0.001 M bisulfite solution, a 2 mM PFBHA solution and a 2 mM PFPH solution demonstrated this occurrence. Overall the collection efficiency followed the order of water < PFBHA solution < 0.00 1M bisulfite solution < PFPH solution. For example for acrolein, the collection efficiency in water, a 0.001 M bisulfite solution, a 2 mM PFBHA solution and a 2 mM PFPH solution was 0.18±0.04, 0.448±0.13, 0.19±0.07, and 0.89±0.07, respectively. The reason that the collection efficiency for PFPH is higher than PFBHA is not clear, but may be due to greater water solubility and lower volatility of the hydrazone derivatives, and faster and more expedient derivatization of the carbonyls using PFBHA compared to PFPH (see Figure 1).

Figure 1. Comparison of Collection Efficiencies of Acrolein and Other Carbonyls Using Different Solutions in a Mist Chamber

In view of the established k_f for the carbonyls, and the water-solubility and stability of the carbonyl-bisulfite adducts, the lower collection efficiency in the presence of the bisulfite solution compared to using PFPH is likely a result of poor derivatization of the carbonyls with PFBHA in the presence of bisulfite. The difference between the collection efficiency when water is used as the collection media vs. an aqueous solution of PFPH indicates that formation of the derivatives is critical to efficiently capturing the carbonyls.

Previous research conducted in our laboratory demonstrates the ability of a 2 mM solution in a mist chamber to sample carbonyls with Henry’s law constants < 10³. To sample less polar carbonyls, such as acrolein, a 0.001 M bisulfite or a 2 mM PFPH solution can be used. Although the use of the bisulfite solution to collect the carbonyls and form carbonyl-bisulfite adducts is an attractive approach due to the water solubility of carbonyl-bisulfite adducts, PFBHA derivatization of the carbonyls is hindered in the presence of S(IV). For this reason, if bisulfite is used in the mist chamber to collect the carbonyls, we suggest that further research be conducted to investigate the direct detection of the carbonyl-bisulfite adducts. The high collection efficiencies for acrolein (CE=8.0), and overall good collection efficiency (CE > ~6.0) for methacrolein, methyl vinyl ketone, crotonaldehyde, glyoxal and methyl glyoxal using a 2 mM PFPH solution in the mist chamber indicates that use of PFPH along with detection by using GC/MS will afford sensitive detection of acrolein and other toxic carbonyls.

Supplemental Keywords:

RFA, Health, Air, Scientific Discipline, HUMAN HEALTH, Risk Assessments, particulate matter, Environmental Chemistry, Atmospheric Sciences, Biochemistry, Health Effects, Air Pollutants, aerosols, toxicity, ambient aerosol, asthma, particle concentrator, atmospheric chemistry, human exposure, aerosol composition, quinones, particulate exposure, particulates, allergens, toxicology, particle transport, morphometric analyses, particle size measurement, air pollution, human health effects, human health risk, PAH, airborne urban contaminants, airway disease

Relevant Websites:

http://www.scpcs.ucla.edu Exit

Progress and Final Reports:

Original Abstract

1999

2000

2001

2002 Progress Report

2003 Progress Report

2004

Main Center Abstract and Reports:

R827352    Southern California Children's Environmental Health Center

Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R827352C001 The Chemical Toxicology of Particulate Matter
R827352C002 Pro-inflammatory and the Pro-oxidative Effects of Diesel Exhaust Particulate in Vivo and in Vitro
R827352C003 Measurement of the “Effective” Surface Area of Ultrafine and Accumulation Mode PM (Pilot Project)
R827352C004 Effect of Exposure to Freeways with Heavy Diesel Traffic and Gasoline Traffic on Asthma Mouse Model
R827352C005 Effects of Exposure to Fine and Ultrafine Concentrated Ambient Particles near a Heavily Trafficked Freeway in Geriatric Rats (Pilot Project)
R827352C006 Relationship Between Ultrafine Particle Size Distribution and Distance From Highways
R827352C007 Exposure to Vehicular Pollutants and Respiratory Health
R827352C008 Traffic Density and Human Reproductive Health
R827352C009 The Role of Quinones, Aldehydes, Polycyclic Aromatic Hydrocarbons, and other Atmospheric Transformation Products on Chronic Health Effects in Children
R827352C010 Novel Method for Measurement of Acrolein in Aerosols
R827352C011 Off-Line Sampling of Exhaled Nitric Oxide in Respiratory Health Surveys
R827352C012 Controlled Human Exposure Studies with Concentrated PM
R827352C013 Particle Size Distributions of Polycyclic Aromatic Hydrocarbons in the LAB
R827352C014 Physical and Chemical Characteristics of PM in the LAB (Source Receptor Study)
R827352C015 Exposure Assessment and Airshed Modeling Applications in Support of SCPC and CHS Projects
R827352C016 Particle Dosimetry
R827352C017 Conduct Research and Monitoring That Contributes to a Better Understanding of the Measurement, Sources, Size Distribution, Chemical Composition, Physical State, Spatial and Temporal Variability, and Health Effects of Suspended PM in the Los Angeles Basin (LAB)