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Low acetaldehyde collection efficiencies for 24-hour sampling with 2,4-dinitrophenylhydrazine (DNPH)-coated solid
Jason S Herrington1, Zhi-Hua Tina Fan, Paul J Lioy
1Joint Graduate Program in Exposure Science, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School and Rutgers, The State University of New Jersey, 683 Hoes Lane West, Piscataway, New Jersey 08854, USA.
Long-term air sampling using 2,4-dinitrophenylhydrazine (DNPH) methods shows high collection efficiency (CE) for formaldehyde but poor CE for acetaldehyde. This suggests significant underestimation of acetaldehyde concentrations in many studies.
Area of Science:
- Environmental Chemistry
- Atmospheric Science
- Analytical Chemistry
Background:
- Airborne aldehyde and ketone sampling commonly uses 2,4-dinitrophenylhydrazine (DNPH)-coated solid sorbents, considered a gold standard since the 1970s.
- These methods have been extensively developed but inadequately evaluated for long-term (≥24 h) collection efficiency (CE) of carbonyls other than formaldehyde.
- Existing literature does not demonstrate acceptable CEs for long-term DNPH sampling of non-formaldehyde carbonyls, yet 100% CE is often assumed.
Purpose of the Study:
- To evaluate the long-term sampling collection efficiencies (CEs) of formaldehyde and acetaldehyde using commonly employed DNPH-coated solid sorbents.
- To assess the validity of assuming 100% CE for long-term carbonyl sampling with DNPH methods.
Main Methods:
- Laboratory experiments were conducted using a dynamic atmosphere generation system to produce known concentrations of formaldehyde and acetaldehyde.
- Several commonly used DNPH-coated solid sorbents were tested for their 24-hour sampling collection efficiency (CE).
- Post-sampling acid addition was attempted to improve acetaldehyde CEs.
Main Results:
- 24-hour formaldehyde sampling CEs ranged from 83% to 133%, consistent with previous findings.
- In contrast, 24-hour acetaldehyde sampling CEs varied significantly, ranging from 1% to 62%.
- Attempts to enhance acetaldehyde CEs by adding acid post-sampling were unsuccessful.
Conclusions:
- DNPH-coated solid sorbent methods exhibit high CE for formaldehyde but critically low CE for acetaldehyde during long-term (24-hour) air sampling.
- Assuming 100% CE for 24-hour acetaldehyde sampling with DNPH methods leads to substantial underestimation of actual concentrations.
- The findings highlight a significant limitation in current standard methods for assessing long-term exposure to non-formaldehyde carbonyls.
