Instrument - Formaldehyde laser-induced fluorescence (Keutsch)

Short name:

Full name:
Formaldehyde laser-induced fluorescence (Keutsch)

What is being measured:
Formaldehyde concentration

Sampling Protocol:



Instrument year :
None specified

Data recording software:
Inquire with PI

Data analysis software:
Inquire with PI

Raw data time resolution:
1 Hz

Analysis data averaging:
Inquire with PI

Detection limit:
0.05 ppbv

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

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

Sampling method:
Direct sampling

Sample preparation method:

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

Length of tubing (cm):

Instrument flow rate:

Tubing inner diameter:

Tubing material:
PFA Teflon

Chemical identification method:
Laser-induced fluorescence. HCHO is excited near 28299 cm-1, promoting a unique rotational transition that is one of the most intense features in the excitation spectrum.

Data analysis method:
Background subtraction using "online" and "offline" frequencies. See Ref for more details.

Quantification method:
An absolute absorption cross section of 4.1 × 10-19 cm2 × molecule-1 at 150 Torr is applied to the difference of the online and offline signals.

Calibration method:
Calibration of the instrument is carried out by two independent methods, both of which involve measuring the LIF signal produced by a known concentration of HCHO. The first is a precalibrated permeation tube (100-044-2300-U45, Metronics Inc.) emitting 35 ng (HCHO) /min at T ) 45 °C which is entrained in a flow of 5 standard liters per minute (slm) of UZA, controlled by an MKS Instruments mass flow controller (part no. 1179A53CS1BV). The calibrant is further diluted by the purges (total flow of 0.15 slm) resulting in a mixing ratio of 5.5 ppbv HCHO in the White cell. The second calibration method consists of bubbling UZA through a dilute aqueous solution of HCHO. A measurement of the HCHO concentration from the bubbler is obtained by performing cavity ring-down spectroscopy (CRDS) on the output of the bubbler immediately before or after taking an LIF calibration (under conditions of the same temperature and humidity).

Calibration drift estimate:

Calibration schedule:

Uncertainty estimation method:
The uncertainty in the reported measurements is a convolution of the uncertainties associated with the CRDS measurements, the pressure and flows in the White-cell, and with the observed LIF signal.

Known interferences:

Link to supplemental information:

Additional notes:

Measurement uncertainty:

Measurement units: