Short name:
Vapor wall loss : Formic Acid, HMHP, and H2O2

Full name:
Vapor wall loss : Formic Acid, HMHP, and H2O2 using the Seinfeld Triple CF3O- CIMS

What is being measured:

Sampling Protocol:
Online

Manufacturer:
Custom

Model:
Custom

Instrument year :
None specified

Data recording software:
Varian Workstation

Data analysis software:
Matlab

Raw data time resolution:
1/8th seconds

Analysis data averaging:
4 minutes

Detection limit:
100 ppt

Sensitivity to temperature (and correction method, if applicable): :
Sensitive to temperature is not noted

Sensitivity to relative humidity (and correction method, if applicable): :
Sensitive to RH, correction is done by measuring the RH-dependent sensitivities and using the appropriate sensitivity factor for the chamber RH condition

Sampling method:
Direct sampling

Sample preparation method:
No sample preparation

Sample residence time (chamber to instrument) (seconds):

Length of tubing (cm):
0.03

Instrument flow rate:
2

Tubing inner diameter:

Tubing material:
FEP Teflon

Chemical identification method:
The chemicals are identified by their signature masses in CF3O- CIMS

Data analysis method:
Analyzed by taking the raw counts at each m/z, dividing by total reagent ions

Quantification method:
Quantification by applying an RH-dependent sensitivity curve for each analyte of interest

Calibration method:
Calibration is not necessary for wall loss

Calibration drift estimate:

Calibration schedule:

Uncertainty estimation method:
Uncertainties are determined from the trendline of loss rate vs. RH

Known interferences:

Link to supplemental information:
See Figure 2 in http://www.rsc.org/suppdata/c6/cp/c6cp00053c/c6cp00053c1.pdf

Additional notes:
Alpha-hydroxy hydroperoxides like HMHP have a propensity to participate in heterogeneous reactions on humid surfaces.27 Thus, we measured wall loss rates for HMHP, HCOOH, and H2O2 as a function of RH to correct for this effect. HMHP was synthesized via an alternative method to the one described in Section 2.2: a gaseous mixture of formaldehyde/N2 (produced by flowing dry N2 past heated paraformaldehyde solid) was bubbled into an aqueous H2O2 solution (50% v/v). The outflow of the bubbler (containing HCHO, HMHP, HCOOH, and H2O2) was introduced into the chamber until the signal of HMHP in CIMS was adequate, after which the flow was stopped and the wall loss was monitored for 8–10 hours. The production of HCOOH from HMHP conversion may obscure the HCOOH wall loss to a degree. However, by virtue of the synthesis method (high water content in the H2O2 bubbler), the HCOOH mixing ratio in the chamber was more abundant than HMHP by a factor of 100, so that even if all of the HMHP were converted to HCOOH, the production yield signal would impact kwall of HCOOH by only 1%. We did not observe noticeable wall loss of HMHP, HCOOH, or H2O2 under dry conditions (Fig. S2, ESI†); however, the wall loss rates become non-negligible at the highest RH investigated (72%), where HMHP was removed at a rate of approximately 0.1% per minute. The humidity-dependent wall loss rates (kwall_HMHP = −1.4 × 10−5 × RH min−1, kwall_H2O2 = −9.6 × 10−6 × RH min−1, and kwall_HCOOH = −2.2 × 10−6 × RH min−1) were used to correct the CIMS data.

Measurement uncertainty:

Measurement units: