direct detection of c 2 h 2 in air and human breath by cw-crds florian schmidt, olavi vaittinen,...
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![Page 1: Direct detection of C 2 H 2 in air and human breath by cw-CRDS Florian Schmidt, Olavi Vaittinen, Markus Metsälä and Lauri Halonen Laboratory of Physical](https://reader036.vdocument.in/reader036/viewer/2022062407/56649cbb5503460f949834fd/html5/thumbnails/1.jpg)
Direct detection of C2H2 in air and human breath by cw-CRDS
Florian Schmidt, Olavi Vaittinen, Markus Metsälä and Lauri Halonen
Laboratory of Physical Chemistry, University of Helsinki, Finland
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2June 21, 2010
Cavity ring-down spectroscopy (CRDS)
Absorption enhancement due to cavity: 103 to 105
CRDS independent of laser power fluctuations
No calibration needed
int0
1 1 1Sn
c
Laser
Scan
Detector
0
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3June 21, 2010
Experimental CRDS setup - schematic
Tuning range: 1520-1575 nm (6350-6575 cm-1)
Cavity Finesse: 390 000
Sensitivity: 7×10-11 cm-1
Acquisition time: 1 s - 20 min
Detected at ppt level: C2H2, NH3, HCN
Other detectable species: CH4, N2O, CO, CO2, H2O
ECDL = external cavity diode laserOI = optical isolatorAOM = acousto-optic modulatorMFC = mass flow controller
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4June 21, 2010
Experimental CRDS setup
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5June 21, 2010
Motivation to measure acetylene
One of the most common hydrocarbons in the troposphere Mostly anthropogenic sources (fossil- and biofuels, biomass burning) Correlates with other combustions gases and VOCs
Trace pollution and exposure to combustion gases (exhausts, smoking) Baseline of breath C2H2 in the healthy population? Is C2H2 a biomarker for
a medical condition (e.g. Proteus mirabilis bacterial infection)?
Not previously detected in ambient air with high time resolution and without pre-concentration.
Not previously quantified in breath GC-MS slow and expensive Not measurable with PTR-MS and SIFT-MS with standard pre-cursors
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6June 21, 2010
Spectra from breath and ambient air
Air acetylene concentration 0.93 ppbv; Scan time 20 min; Detection limit 120 ppt
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7June 21, 2010
System response to C2H2 absorption
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8June 21, 2010
Outdoor air – continuous flow
F. M. Schmidt, O. Vaittinen, M. Metsälä, P. Kraus, L. Halonen, Appl. Phys. B (2010)
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9June 21, 2010
Day – Night comparison
F. M. Schmidt, O. Vaittinen, M. Metsälä, P. Kraus, L. Halonen, Appl. Phys. B (2010)
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10June 21, 2010
Indoor – outdoor air comparison
F. M. Schmidt, O. Vaittinen, M. Metsälä, P. Kraus, L. Halonen, Appl. Phys. B (2010)
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11June 21, 2010
Breath collection and sample handling
No adsorption/desorption phenomena in the bags, the gas system tubing and the quartz-coated ring-down cavity
Acetylene can be collected and stored in aluminum breath bags (statistical error for 10 bags: 0.4 ppb)
Acetylene concentration stays within 0.4 ppb for 5 days in the bag
No quantitative difference between alveolar/full breath samples and nose/mouth breathing (non-smokers)
Thus: static measurements were possible
Spectrometer temperature: 22 degrees (room temperature)
Sample pressure in the cavity: 0.1 bar
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12June 21, 2010
Study - Background level of C2H2 in breath
40 healthy volunteers
22 male, 18 female, 20 to 63 years old, 31 non-smokers, 9 smokers
Subjects requested to have stayed at sampling location for 30 min prior to breath collection
One full breath sample collected to a breath bag
At the same time: one ambient air sample collected to a second bag
Samples were analyzed on the same day or at least within 48 hours.
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13June 21, 2010
Results – Breath acetylene minus air acetylene
Breath C2H2 baseline = Ambient air C2H2 level
Smokers could be identified with a sensitivity and specifity of 100 %
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14June 21, 2010
Timer after smoking
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15June 21, 2010
Exposure studies
Subject smokes a cigarette or takes a puff
Continuous breathing into CRDS system for up to 30 min
C2H2 decay recorded standing on peak of absorption profile (3 points per second)
For long-term decay: bag samples or shorter intervals of continuous breathing
Fit exponential functions to decay
Simple 3-compartment model (respiratory tract, blood, tissue)
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16June 21, 2010
Breath cycles
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17June 21, 2010
Acetylene residence times
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18June 21, 2010
Summary
CRDS suitable for fast and direct detection of C2H2 in air and breath
Mean C2H2 mixing ratio in Helsinki outdoor air of ~1 ppbv
C2H2 correlates with CO, human activity and temperature
Strong fluctuations (up to 60 ppbv on a minute time scale) in urban outdoor air during daytime. Single bag measurements unreliable.
Breath C2H2 baseline is equal to ambient air C2H2 level
Smokers were identified with 100 % sensitivity and specifity
Breath acetylene returns to baseline level around 3 hours after exposure. Urban air pollution could impair smoking status assessment
High-time resolution decay measurements could improve knowledge about residence times of gases and related physiological processes
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19June 21, 2010
Acknowledgements
Dr Olavi Vaittinen
Dr Markus Metsälä
Peter Kraus
Mirva Skyttä
Prof Lauri Halonen
Academy of Finland