Short name:
PTRMS

Full name:
Quadrupole Proton Transfer Reaction Mass Spectrometer

What is being measured:
VOCs, OVOCs

Sampling Protocol:
Online

Manufacturer:
Ionicon

Model:
1

Instrument year :
None specified

Data recording software:

Data analysis software:

Raw data time resolution:
10 s

Analysis data averaging:

Detection limit:
100 pptv

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

Sensitivity to relative humidity (and correction method, if applicable): :
As relative humidity increases, the ratio of protonated water dimer:protonated water increases. Sensitivities of VOCs with a proton affinity lower than the water dimer (i.e. benzene) decrease with an increase in relative humidity, and sensitivities of VOCs with a proton affinity higher than the water dimer (i.e. acetone) increase with relative humidity, due to the higher total count of water ions present.

Sampling method:
Direct sampling from chamber

Sample preparation method:

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

Length of tubing (cm):

Instrument flow rate:

Tubing inner diameter:

Tubing material:

Chemical identification method:
Protonated parent ion from proton transfer of H3O+ to VOCs, and in some cases some neutral losses based on chemical ionization literature.

Data analysis method:

Quantification method:
Raw signal at each mass is normalized by reagent ion signal, and multiplied by a calibration factor to obtain the concentration data in ppb.

Calibration method:
Calibration of analytes performed usually a gravimetrically prepared cylinder of VOCs in air or N2, where the calibration flow is mixed with clean air, and the calibration flow is modified. The normalized signal is plotted against concentration of standards to determine sensitivity for individual compounds. Compounds not directly quantified are estimated by the average of VOC sensitivities.

Calibration drift estimate:
Medium (on the order of days)

Calibration schedule:

Uncertainty estimation method:
The uncertainty for directly calibrated VOCs is +/- 20 %, propagated from uncertainties in standard cylinder concentrations, changes in ion transmission, uncertainties in the flow rate of zero air and calibration air. The uncertainty for compounds without a direct calibration is +/- 50% based on the range of measured sensitivities.

Known interferences:

Link to supplemental information:

Additional notes:

Measurement uncertainty:
+/- 20% for directly calibrated compounds.

Measurement units:
All measurements from this instrument are converted to ppb