Short name:
modified PTR3

Full name:
Harvard NH4+/H+ chemical ionization mass spectrometer

What is being measured:
oxidized gas-phase organic species

Sampling Protocol:
Online

Manufacturer:
Custom

Model:
PTR3

Instrument year :
None specified

Data recording software:

Data analysis software:

Raw data time resolution:
1 second

Analysis data averaging:
Variable

Detection limit:
Variable (likely < 1 ppt for some compounds)

Sensitivity to temperature (and correction method, if applicable): :

Sensitivity to relative humidity (and correction method, if applicable): :

Sampling method:
direct

Sample preparation method:

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

Length of tubing (cm):
2000

Instrument flow rate:

Tubing inner diameter:

Tubing material:
PFA Teflon

Chemical identification method:
Mass spectral peaks assigned based on best fit to high resolution mass data, taking into account possible molecular formulas based on precursor structure.

Data analysis method:
Data processed with PTRwid

Quantification method:
Quantification performed using voltage scanning and mixture of gases used for calibration, as described in Zaytsev et al., AMT, 2019

Calibration method:

Calibration drift estimate:

Calibration schedule:

Uncertainty estimation method:
Total uncertainty arises mainly from uncertainty associated with the sensitivity of the instrument to each ion. Sensitivity is highly variable depending on chemical structure. Voltage scanning is used to estimate sensitivity based on Zaytsev et al., AMT, 2019, but may be off by an order of magnitude in some cases. These errors likely cancel out to some degree when considering the total concentration of all species detected by the instrument, but concentrations for each ion are likely relatively uncertain. In rare cases, a compound may be directly calibrated using a standard calibration gas or a liquid calibration unit (Ionicon Analytik).

Known interferences:

Link to supplemental information:

Additional notes:

Measurement uncertainty:
~50%

Measurement units:
ppb