An intercomparison of measurement systems for vapor and particulate phase concentrations of formic and acetic acids

Abstract

During June 1986, eight systems for measuring vapor phase and four for measuring particulate phase concentrations of formic acid (HCOOH) and acetic acid (CH3COOH) were intercompared in central Virginia. HCOOH and CH3COOH vapors were sampled by condensate, mist, Chromosorb 103 GC resin, NaOH-coated annular denuders, NaOH impregnated quartz filters, K2CO3 and Na2CO3 impregnated cellulose filters, and Nylasorb membranes. Atmospheric aerosol was collected on Teflon and Nuclepore filters using both hi-vol and 10-vol systems to measure particulate phase concentrations. Samples were collected during 31 discrete day and night intervals of 0.5-2 hour duration over a 4-day period. Performance of the mist chamber and K2CO3 impregnated filter techniques were also evaluated using zero air and ambient air spiked with HCOOHg, CH3COOHg , and formaldehyde (CH2Og) from permeation sources. Results of this intercomparison show significant systematic and episodic artifacts among many currently deployed measurement systems for HCOOHg and CH3COOHg. The spiking experiments revealed no significant interferences for the mist chamber technique and results generated by the mist chamber and denuder techniques were statistically indistinguishable. The condensate technique showed general agreement with the mist chamber and denuder methods, but episodic bias between these systems was inferred from large and significant differences observed during the first day of sampling. Nylasorb membranes are unacceptable for collecting carboxylic acid vapors as they did not retain HCOOHg and CH3COOHg quantitatively.Strong base impregnated filter and GC resin sampling techniques are prone to large positive interferences apparently resulting, in part, from reactions involving CH2Og to generate HCOOH and CH3COOH subsequent to collection. Significant bias presumably associated with differences in postcollection handling was observed for particulate phase measurements by participating groups. Analytical bias did not contribute significantly to differences in vapor and particulate phase measurements.

Budget of organic carbon in a polluted atmosphere: Results from the New England Air Quality Study in 2002

“…Gas-phase mixing ratios were calculated based on the corresponding volumes of air sampled. Performance characteristics of standard mist chamber samplers for carboxylic acids have been critically evaluated [Keene et al, 1989]. Collection efficiencies were greater than 95%, precision averaged about ±15%, and detection limits averaged about 12 pptv.…”

Carboxylic acids in the rural continental atmosphere over the eastern United States during the Shenandoah Cloud and Photochemistry Experiment

“…The mist chamber technique was used to collect and concentrate gas phase carboxylic acids from the atmosphere [Talbot et al, 1988;Keene et al, 1989]. The mist chamber sampler was mounted on the tower at a location about 2 m above the forest canopy.…”

Determinação de Ácidos Carboxílicos na Atmosfera Urbana de São Paulo: uma abordagem analítica e ambiental

“…A formação de artefatos de coleta por filtro impregnado com solução básica tem sido discutida na literatura 24,25 . As seguintes considerações sobre reações químicas podem justificar a ocorrência do artefato: a) nitrato de peroxiacetila (PAN) atmosférico se decompõe em meio fortemente alcalino, formando o íon acetato; b) acetaldeído e ésteres encontrados na atmosfera podem sofrer oxidação e hidrólise alcalina, respectivamente, dando origem aos correpondentes ácidos orgâni-cos 24,26 ; c) sais de amônio, como por exemplo, acetato de amônio, presentes no material particulado e portanto coletado no filtro superior, podem eventualmente reagir com espécies ácidas gasosas e formar o ácido volátil correspondente.…”

“…De modo geral, os ânions provenientes dos ácidos orgânicos apresentaram concentrações baixas, quando comparados com os inorgânicos. Níveis ambientais entre 0,08 e 0,86 µg/ mfluxo de ar é maior 25 . Por outro lado, é sugerido na literatura que a volatilização do ácido acético proveniente de sais de acetato depende da velocidade de conversão de fase partícula-gás e da acidez atmosférica 25 , reforçando o comprometimento entre a formação de artefato e o tempo de coleta.…”