Chemical Analysis of Exhaled Human Breath Using a Terahertz
Spectroscopic Approach
Alyssa M. Fosnight, Benjamin L. Moran, and Ivan R. Medvedev 1)
Department of Physics, Wright State University, 3640 Colonel Glenn Highway, Dayton, Ohio
45435, USA
Supplemental Materials
In order to precisely quantify the dilution of ethanol, methanol, and acetone present in breath,
the preconcentration efficiency of Entech 7100A system was determined in a separate set of
experiments. This was done by injecting a Tedlar bag containing 3 L of Nitrogen (measured with
a TSI series 4100 thermal flow meter) with 0.75 μL of acetone, methanol, and ethanol. Hamilton
Company 7000 series modified MICROLITER syringes with a dispensing volume of 0.5 μL
purchased from Fisher Scientific were used to deliver a 0.75 μL of pure liquid samples into a
Tedlar bag. The reproducibility of 0.75 μL injection into a Tedlar is unlikely to be better than 5
to 10 %. Given the amount of injected sample and amount of nitrogen in the bag, the expected
chemical concentrations in the Tedlar bag was determined. Therefore, by taking the ratio of the
concentration found by a spectroscopic measurement and the expected concentration, the
preconcentration efficiency could be calculated. In separate set of measurements, 0.05 mL of
liquid water was added into the Tedlar bag to simulate moist human breath. The preconcentration
efficiency was measured as a function of sampling volume. The sampling volume was varied
from 100 cc to 500 cc in increasing and decreasing directions to assess the effects of sampling
volume and chemical history on the preconcentration efficiency of Entech 7100A.
Figure S1 shows the experimentally determined preconcentration efficiency of Entech 7100A
for ethanol, methanol, and acetone as a function of sampling volume, sample wetness (labeled
‘Wet’ and ‘Dry’ in Figure S1), and the chemical history of the preconcentrator. The chemical
history dependence was studied by sequentially increasing or decreasing (labeled ‘Up’ and
‘Down’ respectively) volumes of breath samples. No significant correlation between the
efficiency and sample wetness or chemical history was observed, but there was a noticeable
dependence on the sampling volume for methanol and ethanol. The average of all the
measurements taken at 500 cc sampling volume was used as a measure of our preconcentration
efficiency. The RMS of the preconcentration efficiency distribution at 500 cc was used as a
measure of its uncertainty.
1)
Author to whom correspondence should be addressed. Electronic mail: ivan.medvedev@wright.edu
FIG S1. Preconcentration efficiency of Entech 7100A as a function of molecular species,
samples volume, sample wetness, and the preconcentration history of the system.
TABLE SI. Spectroscopic line center-frequencies in MHz for acetone, methanol, and ethanol
used for chemical detection. Line frequencies are listed in the order they appear in the snippet
spectrum shown in Figure 1.
Acetone
226832.08
230176.70
235548.35
237751.08
238868.95
239991.07
245353.09
256259.03
258493.67
259618.37
Methanol
211803.34
227094.78
237970.44
239970.26
241267.89
241791.41
244337.99
261704.48
264325.60
265289.66
Ethanol
225660.44
230991.56
232318.69
233208.71
239478.27
242350.02
242524.40
242870.76
244634.12
259777.30
TABLE SII. Spectroscopically determined partial pressures (Psample) in Torr and least squares
signal to noise ratios (SNR) for acetone, methanol, and ethanol as a function of time after the
beginning of alcohol consumption.
Time
(min)
-107
-80
34
55
90
125
155
190
230
269
300
335
Acetone
Psample SNR
16.7
126
11.3
78
7.4
15
13.2
49
13.8
37
12.0
18
13.3
57
13.6
31
16.9
53
17.7
123
19.5
129
13.8
101
Methanol
Psample SNR
1.2
14
0.5
6
0.009
0.03
0.9
5
1.4
6
2.0
5
0.8
5
1.2
4
1.8
9
2.7
29
2.4
24
1.5
17
Ethanol
Psample
SNR
3.4
17
0.7
4
136.2
186
545.7
1378
456.8
842
469.2
490
123.5
363
171.4
262
120.4
255
64.4
305
23.8
107
6.4
32
TABLE SIII. Experimentally determined dilutions for acetone, methanol and ethanol and
corresponding breath alcohol content determined by the breathalyzer measurements and
Widmark’s formula as a function of time after the beginning of alcohol consumption.
Corresponding experimental uncertainties are listed in parenthesis. BAC is measured in grams
per 100 mL of blood volume.
Time
(min)
Acetone
(ppb)
Methanol
(ppb)
Ethanol
(ppm)
-107
-80
34
55
90
125
155
190
230
269
300
335
1042 (127)
706 (87)
462 (67)
826 (103)
864 (109)
753 (103)
831 (103)
854 (109)
1060 (132)
1105 (136)
1223 (150)
863 (106)
302 (109)
136 (55)
2 (93)
217 (91)
347 (140)
504 (215)
207 (85)
311 (137)
460 (172)
683 (241)
587 (208)
379 (135)
0.63 (0.12)
0.14 (0.05)
25 (4)
101 (17)
84 (15)
87 (15)
23 (4)
32 (5)
22 (4)
12 (2)
4.4 (0.8)
1.17 (0.21)
Breathalyzer
(BAC)
0
0
0.033
0.038
0.032
0.023
0.017
0.008
0
0
0
0
(ppm)
0
0
86.2
99.3
83.6
60.1
44.4
20.9
0
0
0
0
Widmark’s
Formula
(BAC)
(ppm)
0
0.0
0
0.0
0.0427
111.4
0.0374
97.7
0.0287
74.9
0.0199
52.0
0.0124
32.4
0.0037
9.5
0
0.0
0
0.0
0
0.0
0
0.0
TABLE SIV. Experimentally determined dilutions and spectroscopic least squares signal to noise
ratios (SNR) for acetone, methanol, and ethanol as a function of time after the beginning of
alcohol consumption. Corresponding experimental uncertainties are listed in parenthesis.
Time
/min
-107
-80
34
55
90
125
155
190
230
269
300
335
Acetone
(ppb)
1042 (127)
706 (87)
462 (67)
826 (103)
864 (109)
753 (103)
831 (103)
854 (109)
1060 (132)
1105 (136)
1223 (150)
863 (106)
SNR
126
78
15
49
37
18
57
31
53
123
129
101
Methanol
SNR
(ppb)
302 (109)
14
136 (55)
6
2 (93)
0.03
217 (91)
5
347 (140)
6
504 (215)
5
207 (85)
5
311 (137)
4
460 (172)
9
683 (241)
29
587 (208)
24
379 (135)
17
Ethanol
(ppm)
0.63 (0.12)
0.14 (0.05)
25 (4)
101 (17)
84 (15)
87 (15)
23 (4)
32 (5)
22 (4)
12 (2)
4.4 (0.8)
1.17 (0.21)
SNR
17
4
186
1378
842
490
363
262
255
305
107
32