Analysis of Musty Odors using SPME-GC/MS - Shimadzu

SHIMADZU APPLICATION NEWS
● GASCHROMATOGRAPHY MASS SPECTROMETRY
LA146-E024
No.M209
Analysis of Musty Odors using SPME-GC/MS
Japan’s tap water has a solid reputation for its safety.
However, water supplies that are taken from surface
water sources, such as dams, lakes and rivers, may
generate musty odors during the summer. As a
countermeasure, carbon treatment is being used. The
substances causing the musty odor are 2-methylisoborneol
(2-MIB) and geosmin, produced by algae
and actinomyces. The odor threshold values for these
substances are extremely low, in the order of several
ng/L, so pretreatment is required to concentrate
samples. In the Japanese goverment’s drinking water
examination, the solid phase extraction GC/MS and
the purge & trap GC/MS methods had been stipulated,
and, in 2001, the headspace GC/MS method was
added. However, the solid phase extraction GC/MS
has disadvantages such as time-consuming and
complex extraction procedures and large consumption
of organic solvents. As for the purge & trap GC/MS
method, the analysis system is expensive and
maintenance is difficult.
Solid phase microextraction (SPME) is a pretreatment
method that extracts organic compounds from the
headspace of liquid or solid samples, concentrates
them, thermally desorb them in the GC injector, and
introduces them into the column. This pretreatment
method is attracting attention because it does not
require organic solvents, is fully automated and
operation is easy.
■ Analytical Conditions
Autosampler : AOC 5000 (SHIMADZU)
SPME Fiber : PDMS/DVB 65µm(SUPELCO)
Instrument : GCMS-QP2010(SHIMADZU)
GC Column : DB-5(J&W, 30m×0.25mm I.D. df=0.25µm)
AOC-5000
sample amount
Incubat Temp.
Desorb Time
Pre Inc Time
Extract Time
GC
Injection Temp.
Column Temp.
Carrier Gas
Injection Method
MS
Interface Temp.
Ionsource Temp.
Monitor Ion
: 10mL+NaCl3g
: 80˚C
: 3min
: 5min
: 30min (headspace)
: 230˚C
: 40˚C(3min)-15˚C/min-250˚C(3.0min)
: 100kPa
: Splitless (Sampling Time : 3min)
: 250˚C
: 200˚C
: 2-MIB : 95, 107 Geosmin : 112, 182
■ Sensitivity
Fig. 1 shows the SIM chromatograms for each substance
at 0.001µg/L and 0.010µg/L. Sufficient sensitivity was
verified for a concentration of 0.001µg/L, demonstrating
that the SPME method provides sensitivity equivalent
to that of the solid phase extraction or purge & trap
method.
■ Calibration Curves
Fig. 2 shows the calibration curves for concentrations
over a range of 0.001µg/L to 0.050µg/L. Excellent
linearity was obtained for both substances, with
coefficients of correlation of 0.9995 (2-MIB) and
0.9997 (geosmin).
(1)2-MIB
(2)Geosmin
intensity
50000
45000
40000
35000
30000
25000
20000
15000
10000
5000
2-MIB
0
11.0 11.1 11.2 11.3 11.4 11.5
0.001µg/L
min
95.00
*1.00
107.00
*1.00
intensity
400000
350000
300000
250000
200000
150000
100000
50000
2-MIB
0
11.0 11.1 11.2 11.3 11.4 11.5
min
0.010µg/L
95.00
*1.00
107.00
*1.00
intensity
60000
55000
50000
45000
40000
35000
30000
25000
20000
15000
10000
5000
geosmin
0
14.5 14.6 14.7 14.8 14.9 15.0
min
0.001µg/L
112.00
*1.00
182.00
*1.00
intensity
600000
550000
500000
450000
400000
350000
300000
250000
200000
150000
100000
50000
geosmin
0
14.5 14.6 14.7 14.8 14.9 15.0
min
0.010µg/L
112.00
*1.00
182.00
*1.00
Fig.1 SIM Chromatograms

No.M209
(1) 2-MIB
ID#:1 m/z:95.00 Compound Name:2-MIB
f(x)=22364490.302279*x+5991.570697
Correlation Coefficient (R)=0.999499
[*10^6] #
1
1
2
3
4
Concentration(µg/L)
0.001
0.010
0.020
0.050
Area
26133
246730
434120
1128506
(2) Geosmin
ID#:2 m/z:112.00 Compound Name:Geosmin
f(x)=64559563.075706*x-17585.304252
Correlation Coefficient (R)=0.999714
[*10^6] #
1
3
2
3
4
Concentration(µg/L)
0.001
0.010
0.020
0.050
Area
66289
641253
1224401
3227040
5
[*10^-2]
5
[*10^-2]
Fig.2 Calibration Curves
■ Reproducibility
In order to check reproducibility, a low-concentration
sample (0.001µg/L) was analyzed five times. Table 1
shows the results. Pretreatment conditions such as the
temperature and time were controlled by the
autosampler, achieving a excellent reproducibility with
a CV value at 7%.
(1) 2-MIB
Measurement of Blank After Injecting 0.050 µg/L Sample
11 12
min
Measurement at 0.001 µg/L
95.00
*1.00
107.00
*1.00
Table 1 Reproducibility
2-MIB
Geosmin
Data 1
23993
69827
Data 2
24463
67942
Data 3
25919
68361
Data 4
21435
58156
Data 5
26133
66289
CV (%)
7.7
7.0
11 12
min
95.00
*1.00
107.00
*1.00
■ Carry Over
In order to check sample carry over, blank water was
measured after injecting a high concentration sample
(0.050µg/L). In Fig. 3, results are compared for the
blank water and low concentration sample (0.001
µg/L). The results show that the carry over is below the
lower detection limit.
(2) Geosmin
Measurement of Blank After Injecting 0.050µg/L Sample
14 15
Measurement at 0.001µg/L
min
112.00
*1.00
182.00
*1.00
■ Conclusion
In this Application News, the SPME-GC/MS method
was applied to measure the musty odor in water. The
results showed good sensitivity and quantitation
capability. Although the Drinking Water Examination
Method does not accept the SPME-GC/MS method for
analyzing musty odors, it has been confirmed that this
method is effective.
14 15
min
112.00
*1.00
182.00
*1.00
Fig.3 Data Comparison
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