Leveraging Cl-H Mass Defect Plots for the Identification of

Leveraging Cl-H Mass Defect Plots for the Identification
of Halogenated Organic Contaminants
Jonathan D. Byer1, Mehran Alaee2, Karl Jobst3, Grazina Pacepavicius2, and Joe Binkley1
1LECO Corporation, St Joseph, MI, USA; 2Environment Canada, Burlington, ON, Canada; 3Ontario Ministry of the Environment, Etobicoke, Canada
Results
Introduction
a
a
Time (s)
Cl-H Mass Defect
• Time-of-flight mass spectrometry (TOFMS) is unsurpassed for
non-target analysis because full range mass spectra are
acquired simultaneously with minimal mass bias at acquisition
rates suitable for narrow gas chromatographic peaks. This
provides a number of advantages, including the possibility of
deconvolving chromatographic interferences using modern
software, further enhancing the ability to isolate and identify a
greater number of compounds.
• Mass defect is the difference between the nominal and exact
masses of a compound or its fragments1.
• Halogenated compounds have characteristic mass defects and
isotope patterns that make them readily distinguishable from
most other compound classes2,3.
• Mass defect (Cl-H) can be calculated according to the following
equations, where the IUPAC mass is the observed mass and the
scaling factor for chlorine substituted for hydrogen equals
34/33.960479:
613.59943
PCTs
Dieldrin and DDT
breakdown products
methoxy nonachlorodiphenyl ether
PCDEs / PCHBs
Fenclorim
HCB
Fenclorim
Caliper - sample "LO No PFTBA", 937.693 s - ( 1172.32 s + 936.321 s ), Height (Abundance)
600
400
355.06977
50
75
125
100
150
175
224
200
225
1650
1660
XIC(457.7369±0.0005)
XIC(507.7293±0.0005)
1670
XIC(459.7348±0.0005)
XIC(509.7282±0.0005)
1680
1690
XIC(461.7311±0.0005)
XIC(511.7238±0.0005)
459.73479
b
100
0
M/Z
100
200
300
400
500
c
510
Cl
Cl
459
Cl
Cl
Cl
Cl
50
O
O
100
117
130
Cl
Cl
500
600
700
800
Figure 1: (a) Total ion chromatogram and (b) combined mass spectrum of a pooled
eel sample from Lake Ontario, Canada. The combined mass spectrum was
generated by expanding the caliper over the entire chromatographic run, which was
dominated by ions corresponding to siloxanes and hydrocarbons. More than 900
peaks were identified using high resolution deconvolution in the ChromaTOF-HRT
software.
0
240
220
200
180
160
140
120
(wr10) Benzene, pentachloro(2,3,4,5-tetrachloro-6-methoxyphenoxy)-
260
613.59872
390.81026
236.84047
250.85602
260.87273
271.80917
426.76896
255.77592
272.84052
350
400
280
300
320
340
360
380
166
49
60 71
95
107
400
437
420
440
380
Cl
Cl
Cl
Cl
Cl
238
460
480
500
273
Cl
131
4
343
201
212
200
220
261
240
260
Mass Accuracy Mass Defect
Mass
Formula
(ppm)
(Da)
375.7508 C8Cl8
1.288
-0.2492
377.7475 C8Cl7[37]Cl
0.434
-0.2525
379.7445 C8Cl6[37]Cl2
0.224
-0.2555
381.7408 C8Cl5[37]Cl3
-1.524
-0.2592
383.7384 C8Cl4[37]Cl4
-0.151
-0.2616
280
300
SMD
(Cl-H)
0.18195
0.18098
0.18024
0.17891
0.17878
320
340
360
380
Scaled Mass
(Cl-H)
RDBE
376.182
5
378.181
5
380.1802
5
382.1789
5
384.1788
5
400
5
 A number of legacy contaminants such as polychlorinated biphenyls (PCBs),
polybrominated diphenyl ethers (PBDEs), polychlorinated diphenyl ethers
(PCDEs), dieldrin, mirex, hexachlorobenzene (HCB) and other pesticides, as
well as a number of previously unknown compounds were tentively identified
in the pooled sample.
 Many breakdown products and metabolites were also detected such as DDD,
DDE, and methoxy nonachlorodiphenyl ether.
 Cl-H mass defect plots are a useful tool for filtering through complex data for
the identification of halogenated contaminants.
 This technique functions as a screening tool for the identification of
unknowns, and in the future, may be used as a form of fingerprinting to
compare samples.
References
229
215
395
0
300
Conclusions
439.78861
394.77248
217.86667
167.37599
125.35249
138.27276
103.07529
43.09827
55.14926
69.20698
82.07315
300
3
Figure 6: Workflow for the identification of compounds using Cl-H mass
defect plot. (1) Select and display masses of interest on chromatogram;
(2) select peak; (3) deconvoluted mass spectrum; (4) compare to NIST or
other library database; (5) verify correct chemical formula with accurate
mass data.
1700
509.72816
1640
Cl
400
84
153
104
M/Z
200
429.08863
281.05100
295.10317
207.03230
221.08423
147.06545
71.08542
83.08545
111.11677
43.05426
2500
250
308
40
60
80 100 120 140 160 180
(mainlib) Benzene, pentachloro(trichloroethenyl)-
a
2250
200
150
118
N
100
300
100
50
Figure 3: Extracted ion chromatograms, mass spectrum, and library spectrum of fenclorim, a
herbicide safener used to protect crops against damage caused by pretilachlor. It is typically used on
.
rice, so its occurrence in Lake Ontario fish was unexpected.
b
200
300
379.74447
Cl
165
100
400
0
200
400
M/Z
500
N
Cl
1300
XIC(342.7778±0.0005)
342.77783
100
189
400
500
200
600
M/Z
Cl
600
600
300
700
154
800
1250
307.80963
Cl
1000
0
XIC(309.8066±0.0005)
XIC(379.7445±0.0005)
1200
0
Library Hit - Similarity: 784 - Library: mainlib - Fenclorim, Abundance
950
960
XIC(189.0212±0.0005)
XIC(223.9903±0.0005)
1150
100
153.04438
57.14363
100.21894
105.34317
800
223.99016
1100
Caliper - sample "LO No PFTBA", 1108.97 s - ( 1113.31 s + 1105.9 s ), Height (Counts)
200
1000
700
400
XIC(307.8096±0.0005)
XIC(344.7756±0.0005)
650
189.02118
1050
237.87193
550
1000
191.83185
450
800
500
950
159.85981
m/z
350
250
940
420
400
380
340
360
Scaled m/z (Cl-H)
2
900
600
320
Chlorinated styrene fragments
C8H 6-nCln•+ (n = 2 - 6)
1000
700
300
280
Caliper - sample "LO No PFTBA", 1662.69 s - ( 1666.61 s + 1658.03 s ), Height (Abundance)
800
202.87947
215.88724
0.12
Time (s)
Time (s)
900
179.95666
0.14
a
2000
1
0.16
0
930
920
XIC(153.0446±0.0005)
XIC(191.0185±0.0005)
XIC(225.9877±0.0005)
600
0.18
Figure 2: (a) Cl-H mass defect plot of the raw mass spectral data for a pooled Lake Ontario eel
sample. (b) A zoomed-in view of the Cl-H mass defect plot highlighting the region containing
halogenated species. The colored points represent m/z values with elemental compositions including
Cl and/or Br calculated with a mass accuracy <2 ppm. The masses displayed in b were filtered from a
by mass defect, and also required at least two masses to occur within 1.9965 ±0.0005 Da or 1.9974
±0.0005 Da, corresponding to the mass difference between 37Cl -35Cl and 81Br -79Br, respectively.
Time (s)
500
0.20
C7H 3Br3Cl+
200
• A total of 10 large freshwater eels were collected from eastern
Lake Ontario, Canada in 2008.
• Sample extracts were pooled for instrumental analysis on a
LECO Pegasus GC-HRT, high resolution TOFMS.
• Extracts were injected (1 µL) using an Agilent 7693
autosampler attached to a 7890 GC fitted with a multi-mode
inlet operated in solvent vent mode.
• A Restek Rxi-guard column (5 m x 0.25 mm) with a Rxi-5MS
(30 m x 0.25 mm x 0.25 µm) was used for chromatographic
separation.
• The oven program was initially 90oC (held for 2.4 min) then
ramped to 320oC at 8.5oC/min (held for 15 min).
• The HRT was operated in EI mode with filament energy of 36
eV, a mass range from m/z 35 to 850, and an acquisition rate
of 6 spectra/s.
• Data were processed using ChromaTOF-HRT® software, which
included peak finding with mass spectral deconvolution.
400
0.22
127.88753
0.05
150
LECO Pegasus® GC-HRT
300
C5H 6-nCln•+
(n = 4 - 6)
C5H 5-nCln+
(n = 3 - 5)
Analysis
Cl
0.24
Hepta/Octachlorostyrene
C10H 6-nCln•+ (n = 3 - 5)
0.1
1:1 DCM:Hexane (v/v)
Gel Permeation Chromatography
Cl
200
95.91560
101.09589
Clean-up
Cl
0.26
Photomirex
Nonachlor
Chlordane
Mirex
C8H 5Br3•+
PCB fragments
Cl
0.28
PCBs
0.15
Cl
Caliper - sample "LO No PFTBA", 310 s to 2653.16 s
PBDEs
0.2
Cl
Br3
65.93924
Cl-H Mass Defect
DDE
0.25
Methylene chloride (DCM)
c
Standard
Figure 5: (a) XIC of an unknown in Lake Ontario pooled eel sample
and an analogue of Dechlorane 6043. (b) Mass spectrum of the
unknown in the Lake Ontario pooled sample. (c) Mass spectrum of a
Dec-604 analogue standard.
0.35
Extraction
362.74218
1000
900
800
700
600
500
400
300
200
100
0
M/Z
m/z
Siloxanes
0.3
1000
b
C7H3Br3Cl+
C13H5Br3Cl6• +
b
Homogenization
1610
Normalized(XIC(339.7915±0.0005)) Lake Ontario Pooled Eel
Normalized(XIC(339.7915±0.0005)) Dec 604 Standard
Caliper - sample "Dec 604 Standard", 1577.83 s - ( 1581.83 s + 1573.83 s ), Height (Abundance)
Methods
57.06989
1600
C5Cl5 +
0.4
1750
1590
unassigned
In this study we used non-target analysis in the form of
Cl-H mass defect plots, to identify halogenated
contaminants in eels (Anguillia rostrata) from Lake Ontario,
Canada.
1500
TIC
1580
Lake Ontario Pooled Eel
Cl-H Mass Defect = Cl-H Scaled Mass – Nominal Cl-H Scaled Mass
1250
1570
C8H5Br3 • +
Cl-H Scaled Mass = IUPAC Mass × Scaling Factor
Time- (s)
1000
Caliper
sample "LO500
No PFTBA",750
Height (Abundance)
1560
520
Figure 4: (a) Extracted ion chromatgrams (XIC) for the six most abundant
ions, as well as (b) the mass spectrum of a peak discovered from points on
the mass defect plot, and (c) Wiley 10 library mass spectrum of 6-methoxynonachlorodiphenyl ether. The accurate mass data and the library hit
suggest that the unknown compound is a methoxynonachlorodiphenyl
ether.
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2. Taguchi VY, Nieckarz RJ, Clement RE, Krolik S, Williams R. (2010); JASMS. 21(11):
1918-21
3. Jobst KJ, Shen L, Reiner EJ, Taguchi VY, Helm PA, McCrindle R, Backus S. (2013); Anal
Bioanal Chem. 405: 3289-97
4. Byer JD, Lebeuf M, Alaee M, Brown RS, Trottier S, Backus S, Keir M, Couillard CM,
Casselman J, Hodson PV. (2013); Chemosphere. 90(5): 1719-28
Contact Information: [email protected]

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