Short name:
VOCUS

Full name:
VOCUS CI-TOF

What is being measured:
VOC chemical speciation

Sampling Protocol:
Online

Manufacturer:
TOFWERK, Aerodyne Research, Inc

Model:
2R, with LTOF

Instrument year :
circa 2019

Data recording software:
TofDaq, Acquility

Data analysis software:
Tofware

Raw data time resolution:
1 s

Analysis data averaging:
None

Detection limit:
sub ppt

Sensitivity to temperature (and correction method, if applicable): :
Unknown. Not relevant for data posted since instrument was at stable laboratory temperatures.

Sensitivity to relative humidity (and correction method, if applicable): :
No dependence (since high water mixing ratios in the IMR region by design)

Sampling method:
~1-2 liters per minute through 1/4 inch OD (~1/8 inch ID) PFA Teflon 10 m tubing

Sample preparation method:
None

Sample residence time (chamber to instrument) (seconds):
2.4

Length of tubing (cm):
1000

Instrument flow rate:
~0.1 lpm (sampling inlet flowrate to instrument ~2 lpm)

Tubing inner diameter:
0.32 cm

Tubing material:
PFA Teflon

Chemical identification method:
exact mass (m/z), aided by knowledge of chemical system under study and precursors added.

Data analysis method:
Standard high-resolution fitting using Tofware software in Igor Pro (Wavemetrics)

Quantification method:
Daily calibrations with multiple VOC from calibration cylinder and sometimes known injection quantity of VOC into chamber of known volume. Relationship between ions/s and mixing ratio established.

Calibration method:
See "quantification method". Calibration cylinder air mixed with zero air or as standard addition at several concentrations levels (controlled with automated routine).

Calibration drift estimate:
No estimate

Calibration schedule:
Prior to each chamber experiment

Uncertainty estimation method:
Accuracy uncertainty primarily from uncertainty in calibration. Precision uncertainty from ion counting statistics.

Known interferences:
Compounds with same or very similar m/z.

Link to supplemental information:
https://www.tofwerk.com/products/vocus/ https://pubs.acs.org/doi/full/10.1021/acs.analchem.8b02641

Additional notes:

Measurement uncertainty:
TBD

Measurement units:
ppb?