1
1
De elopmen o a sensi i e me hodology o he
2
Analysis o Chlo obenzenes in Ai by
3
Combina ion o Solid-Phase Ex ac ion and
4
Headspace Solid-Phase Mic oex ac ion
5
6
Ru h Ba o, Se gio A es, Ca men Ga cia-Ja es*, Ma ia Llompa and Ra ael Cela
7
8
Depa amen o de Química Analí ica, Nu ición y B oma ología, Facul ad de Química,
9
Ins i u o de In es igación y Análisis Alimen a io, Uni e sidad de San iago de
10
Compos ela, E-15782 San iago de Compos ela, Spain.
11
12
13
14
15
Co esponding au ho :
16
* Ca men Ga cia-Ja es
17
E-mail: qncg[email p o ec ed]
18
19
2
1
Abs ac
2
In his s udy, a combina ion o solid-phase ex ac ion and solid-phase mic oex ac ion
3
has been used o de e mine chlo obenzenes in ai . Analy es we e sampled by pumping a
4
known olume o ai h ough a po ous polyme (Tenax TA). Then, he adso ben was
5
ans e ed in o a glass ial and SPME was pe o med. The quan i ica ion was ca ied
6
ou using GC-ECD o GC-MS. Se e al SPME coa ings (100m PDMS, 75m
7
CAR/PDMS, 65m PDMS/DVB, 65m CW/DVB and 85m PA) we e e alua ed,
8
ob aining he highes esponses wi h CAR/PDMS o he mos ola ile chlo obenzenes,
9
and wi h PDMS/DVB o CW/DVB ibe s o he semi ola ile compounds. To op imize
10
some o he ac o s ha could a ec he SPME s ep, a ac o ial design was used. Kine ic
11
s udies o he SPME p ocess we e also pe o med. Conce ning he SPE s ep,
12
b eak h ough was s udied, showing ha 2.5 m3o ai could be p ocessed wi hou losses
13
o he mos ola ile compounds. The pe o mance o he me hod was e alua ed.
14
Ex e nal calib a ion, which does no equi e he comple e sampling p ocess,
15
demons a ed o be sui able, ob aining good linea i y (R2>0.99) o all chlo obenzenes.
16
Reco e y s udies we e pe o med a wo concen a ion le els (4 ng/m3and 40 ng/m3),
17
ob aining quan i a i e eco e ies (>80%). Limi s o de ec ion a he sub ng/m3we e
18
achie ed o all he a ge compounds.
19
20
Key wo ds
21
Ai analysis, chlo obenzenes, gas ch oma og aphy-mass spec ome y, Solid-phase
22
mic oex ac ion, solid-phase ex ac ion, ac o ial design, ola ile compounds.
23
3
In oduc ion
1
Chlo obenzenes a e a amily o en i onmen al pollu an s ha a e p oduced in huge
2
quan i ies in indus ial p ocesses o be used as in e media es in he syn hesis o o he
3
o ganic chemicals and in he p oduc ion o a wide ange o consume and comme cial
4
p oduc s. The less chlo ina ed benzenes a e widely used in cleaning and deg easing o
5
me al, lea he , wool and pape , in d y cleaning and ex ile dyeing ope a ions, as wood-
6
p ese ing compounds, in o ganic syn hesis o pes icides and he bicides, as deodo izing
7
agen s o ga bage and sewage, as ai eshene s, as hea ans e mediums in
8
main enance equipmen , and as magne ic coil coolan s o he elec ical and elec onics
9
indus ies. They a e also used in applica ion o emo al o su ace coa ings as sol en s
10
o o ganic ma e ials, waxes, esins, ubbe s, oils and asphal s. Pen achlo obenzene is
11
used o make pen achlo oni obenzene, a ungicide and i is cu en ly used as i e
12
e a dan . Hexachlo obenzene was used, among o he applica ions, as ungicide, in he
13
p oduc ion o py o echnic composi ions o he mili a y, as a plas icize agen o
14
poly inyl chlo ide (PVC), al hough in many coun ies i s p oduc ion and use ha e
15
ceased[1].
16
Release o chlobenzenes o he en i onmen occu s p ima y du ing manu ac u e, and
17
incine a ion o chlo obenzenes may lead o he emission o polychlo ina ed dibenzo-p-
18
dioxins and dibenzo u ans. Vola ile chlo obenzenes a e ex ensi ely used as sol en s, so
19
la ge quan i ies a e eleased o he ai . Howe e , a mosphe ic concen a ions a e usually
20
e y low, o en much less han a ew g/m3. Ne e heless, indoo ai concen a ions
21
may be om one o h ee o de s o magni ude highe whe e hey a e used [2]. Risks o
22
human exposu e a ising om con amina ed indoo ai a e linked o he use o hese
23
compounds as mo h epellen s and ai eshene s [1].
24
4
Hexachlo obenzene and 1,4-dichlo obenzene we e he i s compounds included in he
1
Thi d and Fi h ( epec i ely) Annual Repo on Ca cinogens in he U. S. Depa men o
2
Heal h and Human Se ices as easonably an icipa ed o be a human ca cinogens based
3
on su icien e idence o ca cinogenici y in expe imen al animals [2]. The Clean Ai
4
Ac Amendmen s o 1990 lis some chlo obenzenes as Haza dous Ai Pollu an s
5
(HAPs), so ede al agencies and g oups may de elop ecommenda ions o assis in
6
con olling exposu e [3].
7
Chlo obenzenes a e equen ly ound in ai a e y low concen a ions, so a
8
p econcen a ion s ep be o e he analysis is necessa y. Mos ola ile chlo obenzenes a e
9
usually analyzed ollowing gene al p ocedu es de eloped o he analysis o ola ile
10
o ganic compounds (VOCs). In mos p ocedu es, once he analy es a e ex ac ed om
11
ai o an app op ia e so ben by solid-phase ex ac ion, a he mal o sol en deso p ion
12
s ep is ca ied ou o ans e he a ge compounds in o a s anda d gas ch oma og aph.
13
Fo apping VOCs, a wide a ie y o so ben s ha e been applied, such as ca bon-based
14
ma e ial [4], Tenax [5] o mix u es o Tenax wi h o he so ben s [6, 7]. Some o he
15
apping ma e ials can also be used [8]. To e ain he less ola ile chlo obenzenes, he
16
use o mo e adso ben ma e ials such as expanded polyu e hane oam (PUF), bo h used
17
as monoso ben o mix u ed wi h o he polyme ic so ben s in mul ibed ca idges, we e
18
s udied, and he e ained compounds we e ex ac ed using Soxhle sol en deso p ion
19
du ing 12 hou s [9, 10]. Howe e , he e is cu en ly an inc easing demand o simple
20
and cos -e ec i e sampling and analy ical me hods capable o achie ing e y low
21
de ec ion limi s in eal o almos eal- ime [11]. Bene i s o solid-phase mic oex ac ion
22
(SPME) in he analysis o ai samples include he use o simple ins umen a ion like
23
ligh weigh and compac de ices, so expensi e c yo aps o he mal deso be s a e no
24
equi ed, dange ous and oxic o ganic sol en s o eagen s a e no used, and sho
25
5
ex ac ion imes a e usually employed [12]. SPME is an equilib ium echnique and in
1
consequence, analy es a e no quan i a i ely ex ac ed. The e o e, he main p oblem in
2
SPME analysis, especially in he case o ai , is calib a ion. Up o now, di e en
3
s a egies ha e been s udied o o e come his d awback o he echnique [13-19]. In
4
addi ion, he wo king concen a ion le els o ai analysis by SPME a e usually in he
5
ange o g/m3and mg/m3[20, 21]. These le els a e sui able o he de e mina ion o
6
ola ile compounds ha can be ound a ela i ely high concen a ions in ai .
7
Ne e heless, some haza dous ai pollu an s need o be moni o ed a e y low
8
concen a ions and he le els achie ed by SPME migh be insu icien .
9
In he p esen pape , a me hod based in he combina ion o SPE and SPME echniques
10
is p oposed o de e mine chlo obenzenes (including he less ola ile in he amily) in ai
11
samples. The op imiza ion o he me hod was pe o med using an expe imen al design
12
app oach. Ex e nal calib a ion, which does no equi e he comple e sampling p ocess,
13
demons a es o be sui able. Limi s o de ec ion a he sub ng/m3we e achie ed o all
14
he a ge compounds.
15
Up o now, he combina ion o bo h echniques has only been applied o he analysis o
16
wo high ola ile o ganic compounds ( oluene and benzene) in ai samples [22, 23].
17
18
Expe imen al
19
Reagen s
20
1,3-dichlo obenzene (1,3-DCB), 1,4-dichlo obenzene (1,4-DCB) and 1,2,4-
21
ichlo obenzene (1,2,4-TCB) we e supplied by Fluka (CH, Swi ze land), 1,2-
22
dichlo obenzene (1,2-DCB) and 1,2,3- ichlo obenzene (1,2,3-TCB) we e pu chased
23
om Ald ich Chemie (S einheim, Ge many), 1,2,3,4- e achlo obenzene (1,2,3,4-
24
TeCB), 1,2,3,5- e achlo obenzene (1,2,3,5-TeCB) and 1,2,4,5- e achlo obenzene
25
6
(1,2,4,5-TeCB) we e ob ained om Riedel-de Haën (Seelze, Ge many),
1
pen achlo obenzene (PeCB) and hexachlo obenzene (HCB) we e supplied by Supelco
2
(Belle on e, PA, USA). All o ganic sol en s (isooc ane, ace one, me hanol and hexane)
3
we e o pes icide g ade and we e ob ained om Me ck (Molle del Vallés, Ba celona,
4
Spain).
5
S anda d s ock solu ions o 2000-4000 mg/mL o indi iduals we e p epa ed in ace one
6
o isooc ane, and wo king solu ions we e ob ained by app op ia e dilu ion. All solu ions
7
we e s o ed in ambe colo ed ials and s o ed a –20ºC.
8
9
Ai sampling and ex ac ion o chlo obenzenes
10
Using a acuum pump wo king a 100 L/min, a known olume o ai was pumped
11
h ough a glass ube con aining 25 mg o Tenax TA adso ben (mesh size 60/80)
12
e ained by glass wool (Ald ich, Mad id, Spain). Fo eco e y expe imen s, he pump
13
was placed in a clean oom p o ided o a lamina low sys em, and a V-shaped ube was
14
inse ed be o e he collec ing Tenax ube. A solu ion o he a ge analy es in hexane
15
was hen ca e ully placed in he V-shaped ube, and a selec ed olume o ai was
16
pumped h oughou he sys em (Figu e 1). Thus, he ai was en iched in he analy es
17
be o e eaching he Tenax ube. Only Te lon (PTFE) ubing was used o connec ions.
18
The adso ben was hen pou ed in o a glass ial sealed wi h an aluminum cap u nished
19
wi h a PTFE- aced sep um. The ial was placed in o a wa e ba h a 50 o 100 °C.
20
Compounds e ained by he adso ben we e analyzed by exposing a SPME ibe o he
21
headspace o he ial (HS-SPME). Once inished he SPME p ocess, he ibe was
22
immedia ely inse ed in o he injec ion po o he ch oma og aph and chlo obenzenes
23
we e deso bed o he GC o 4 min. I necessa y, ials con aining chlo obenzenes
24
adso bed on Tenax can be s o ed a –20ºC du ing a ew days o u he analysis. SPME
25
7
manual holde s and ibe s we e ob ained om Supelco. Fibe s used in his wo k we e:
1
100 m polydime hylsiloxane (PDMS), 65 m polydime hylsiloxane-di inylbenzene
2
(PDMS/DVB), 75 m ca boxen-polydime hylsiloxane (CAR/PDMS), 65 m ca bowax-
3
di inylbenzene (CW/DVB) and 85 m polyac yla e (PA).
4
5
Gas Ch oma og aphic Analysis
6
Gas ch oma og aphy-mass spec ome y (GC-MS) analysis was pe o med in a Va ian
7
3400 GC sys em, equipped wi h a Sa u n 3 ion ap mass de ec o , ope a ed by Sa u n
8
e sion 5.4 so wa e. A Va ian VA-5MS o CP-Sil8 CB Lowbleed/MS (25 m x 0.25
9
mm i.d. x 0.25 m) column was used o he sepa a ion o chlo obenzenes. Wo king
10
GC-MS pa ame e s a e summa ized in Table 1. Mass acquisi ion anges we e
11
p og ammed by ime segmen s and cen e ed on he ions cha ac e is ic o each g oup o
12
compounds (Table 2).
13
Gas ch oma og aphy wi h ECD analysis was pe o med in a Hewle Packa d 5890
14
Se ies II-Plus GC sys em, equipped wi h an elec on cap u e de ec o and a
15
spli /spli less injec o , ope a ed by HP Chems a ion so wa e. A SE-54 (30 m x 0.25 mm
16
i.d. x 0.25 m) column (All ech, Dee ield, IL) was used o sepa a e he a ge analy es.
17
The expe imen al GC-ECD pa ame e s a e shown in Table 1.
18
19
Resul s and discussion
20
One o he mos ele an s eps in he sample p epa a ion me hod is he ans e o he
21
chlo obenzenes om he adso ben o he SPME ibe . This clea ly a ec s he amoun
22
o compound adso bed by he ibe and hence, he limi s o de ec ion and quan i ica ion
23
o he me hod. The e o e, he SPME p ocess was s udied be o e op imiza ion o he
24
sampling s ep.
25
8
Di e en SPME ibe coa ings (85 m PA, 65 m CW/DVB, 65 m PDMS/DVB, 100
1
m PDMS and 75 m CAR/PDMS) we e e alua ed using he same expe imen al
2
p ocedu e: 100 mg o clean Tenax we e placed in a glass ial and spiked wi h a s anda d
3
solu ion o chlo obenzenes in hexane o ob ain 10 ng o each a ge compound pe mg
4
o adso ben . Tenax TA was he adso ben selec ed o he SPE s ep. Due o i s as
5
deso p ion kine ics i is sui able o combine wi h SPME [8]. Sol en is le o e apo a e
6
a oom empe a u e and hen, ials a e closed and imme sed in a wa e ba h a high
7
empe a u e (100ºC) o a o deso p ion o he analy es. A SPME ibe is exposed o he
8
headspace o e he spiked adso ben o 15 min. In Figu e 2, he ch oma og aphic
9
esponses ob ained o some ep esen a i e compounds wi h each ibe a e shown. Wi h
10
PA and PDMS ibe s, he ex ac ion e iciency was e y poo o all compounds.
11
CAR/PDMS ibe was he mos e icien in ex ac ing he wo and h ee chlo ine
12
subs i u ed compounds, while PDMS/DVB and CW/DVB ibe s p o ided he mos
13
e icien ex ac ion o he semi ola ile chlo obenzenes ( e a-, pen a- and hexa- chlo o-
14
benzenes). The e o e, CAR/PDMS and PDMS/DVB ibe s we e conside ed o u he
15
op imiza ion wi h o he expe imen al pa ame e s using an expe imen al design
16
app oach. CW/DVB was disca ded due o he low s abili y o i s coa ing.
17
To simul aneously op imize he expe imen al ac o s and o e alua e he pa ame e s ha
18
can mainly a ec he mass ans e o he SPME ibe , a ac o ial design was un [24].
19
Fou ac o s we e s udied a wo le els (ex ac ion empe a u e, ibe coa ing, addi ion
20
o wa e o he solid, and s i ing o he sample) (see Table 3). The design selec ed was a
21
mul i ac o sc eening 3*2(3-1) mixed le el ac ion, which in ol es 12 expe imen s.
22
Ex ac ion ime was ixed a 15 min in all cases.
23
The analysis o he esul s p oduced he s anda dized Pa e o cha s show in Figu e 3.
24
The leng h o each ba in he g aphs is p opo ional o he absolu e alue o i s
25
9
associa ed s anda dized e ec . The s anda dized e ec is ob ained by di iding he
1
es ima ed e ec o each ac o o in e ac ion by i s s anda d e o . The e ec s a e
2
displayed in dec easing o de o impo ance, which allows easy iden i ica ion o he
3
mos impo an ac o s. Ve ical lines indica e he s a is ical signi icance o he e ec s a
4
a con idence le el o 95%. A ac o is no signi ican o a pa icula chlo obenzene
5
when i s ba does no each he c i ical line [24]. Figu e 4 shows he main e ec plo s
6
o wo selec ed chlo obenzenes. These plo s show he main e ec s wi h a line d awn
7
be ween he low and he high le el o he co esponding ac o s. The leng h o he lines
8
is p opo ional o he magni ude o he e ec o each ac o in he mic oex ac ion
9
p ocess, and he sign o he slope indica es he le el o he ac o ha p oduces he
10
highes esponse.
11
As can be seen in Figu es 3 and 4, he empe a u e o ex ac ion and he ype o ibe
12
coa ing we e he mos ele an ac o s o he ex ac ion o all chlo obenzenes.
13
Tempe a u e g ea ly a ec s he kine ics o ex ac ion. The Pa e o cha s in igu e 3
14
show ha empe a u e was signi ican in he ex ac ion o all chlo obenzenes, bu o
15
dichlo obenzenes he empe a u e ba leng h only sligh ly exceed he c i ical alue,
16
while he ba s leng h o mo e chlo ina ed benzenes exceeds o a g ea ex en he c i ical
17
alue. Figu e 4 shows ha in all cases he bes ex ac ion empe a u e was he maximum
18
(100ºC).
19
Fo highly ola ile compounds, bes esul s we e achie ed wi h CAR/PDMS coa ing
20
(labeled as low le el in Table 3, and in he main e ec s g aph shown in Figu e 4), while
21
semi ola ile compounds showed highe a ini y o he PDMS/DVB ibe ( he high
22
le el o his ac o in Table 3 and in Figu e 4). Ne e heless, he esponses o
23
semi ola ile compounds we e lowe han he esponses o he ola ile ones, ega dless
24
o he ibe used. As he aim o his wo k was o de elop a me hod o de e mine bo h
25
16
[19] G. Xiong, Y. Chen, J. Pawliszyn, J. Ch oma og . A 999 (2003) 43.
1
[20] J. Namieśnik, A. Jas zębska, B. Zygmun , J. Ch oma og . A 1016 (2003) 1.
2
[21] J.A. Koziel, P.A. Ma os, J. Pawliszyn, J. Ch oma og . A 1025 (2004) 3.
3
[22] A. Saba, A. Ra aelli, S. Pucci, P. Sal ado i, Rapid Commun. Mass Spec om. 13
4
(1999) 1899.
5
[23] A. Saba, A. Cuzzola, A. Ra aelli, S. Pucci, P. Sal ado i, Rapid Commun. Mass
6
Spec om. 15 (2001) 2404.
7
[24] S a g aphics-Plus, Expe imen al design, Appendix C, Manugis ics Inc., Rock ille,
8
Ma yland, 1996.
9
[25] D.T. Bu ns, K. Danze , A. Townshend, Recommenda ions o he Use o he Te m
10
“Reco e y” in Analy ical P ocedu es, IUPAC Recommenda ions 2001 (see
11
h p://www.iupac.o g/ epo s/p o isional/ abs ac 01/bu ns_p s.pd ).
12
[26] D.W.-M. Sin, Y.-C. Wong,W.-C. Sham, D. Wang, Analys 126 (2001) 310.
13
14
17
Figu e cap ions
1
2
Figu e 1. Schema ic diag am o he ai -sampling de ice. 1: acuum pump, 2: PTFE
3
connec o s, 3: low me e , 4: Tenax TA, 5: glass wool, 6: V-shaped glass ube o con ain
4
he analy es in he eco e y expe imen s.
5
6
Figu e 2. Compa ison o di e en ibe coa ings on he ex ac ion o some
7
ep esen a i e chlo obenzenes.
8
9
Figu e 3. Pa e o cha s o main e ec s. Ve ical lines indica e he s a is ical
10
signi icance o he e ec s (95% con idence le el).
11
12
Figu e 4. G aphics showing he in luence o main e ec s on he ex ac ion o wo
13
chlo obenzenes: low le el (-), high le el (+).
14
15
Figu e 5. Ex ac ion ime p o iles ob ained in he op imal SPME condi ions.
16
17
Figu e 6. Va ia ion o he esponse (exp essed as a ea coun s) wi h he olume o ai
18
sampled o wo selec ed chlo obenzenes.
19
20
Figu e 7. Va ia ion o he esponse (exp essed as a ea coun s) wi h he amoun o
21
adso ben o chlo obenzenes.
22
23
Figu e 8. Mass ch oma og ams ob ained by a) SPME ex ac ion a he op imal
24
expe imen al condi ions, and b) 2 L injec ion o a 1 mL n-hexane ex ac ion o he
25
18
a ge chlo obenzenes adso bed on o Tenax. The concen a ion o each compound in he
1
ai samples was 40 ng/m3.
2
3
Table 1. Expe imen al GC-MS and GC-ECD condi ions
GC-MS
O en empe a u e p og am
60ºC (2 min)
100ºC (10ºC/min)
120ºC (3ºC/min)
210ºC (10ºC/min, 2 min))
Injec ion
Spli less mode (2 min)
260-300ºC (depending on he ibe used)
T ans e line
260ºC
Ca ie gas
He, 8 psi a 60ºC
Ioniza ion mode
EI (70eV)
Mani old empe a u e
200ºC
GC-ECD
O en empe a u e p og am
50ºC (1 min)
250ºC (10ºC/min, 5 min)
Injec ion
Spli less mode (1 min)
260ºC
De ec o empe a u e
250ºC
Ca ie gas
Ni ogen, 1 mL/min
Make-up gas
Ni ogen, 40 mL/min
Table 2. Quan i ica ion ions, mass acquisi ion anges, and ime segmen s selec ed o
he de e mina ion o each g oup o chlo obenzenes using an ion ap mass de ec o .
Compound
Quan i ica ion
ions
Mass
acquisi ion
ange (m/z)
Time (min)
Segmen ime
leng h (min)
DCBs
146
144-148
0.00 o 8.00
8.00
TCBs
180+182
178-184
8.00 o 13.00
5.00
TeCBs
216
214-218
13.00 o 16.50
3.50
PeCB
248+250
246-252
16.50 o 19.00
2.50
HCB
280-288
280-290
19.00 o 22.66
3.66
Table 3. Fac o s and le els conside ed in he expe imen al design.
Fac o
Low le el
High le el
Con inuous
Wa e (L)
0
300
Yes
Tempe a u e (ºC)
50
100
Yes
Fibe
CAR/PDMS
PDMS/DVB
No
Agi a ion
No
Yes
No
Table 4. Collec ion e iciency o chlo obenzenes a wo concen a ion le els.
4 ng/m3
40 ng/m3
Appa en eco e y (%)
%RSD
Appa en eco e y (%)
%RSD
1,3-DCB
86
6
84
5
1,4-DCB
133
4
97
4
1,2-DCB
99
7
77
5
1,2,4-TCB
100
9
118
11
1,2,3-TCB
95
11
97
11
1,2,3,5-
TeCB
98
9
88
8
1,2,4,5-
TeCB
100
7
89
6
1,2,3,4-
TeCB
105
9
82
7
PeCB
126
10
87
9
HCB
-
-
116
-
Table 5. Linea i y, epea abili y (%RSD), and limi s o de ec ion and quan i ica ion o he me hod (see ex o mo e de ails).
Compound
Linea i y
Repea abili y (%RSD)
De ec ion limi s
(S/N=3, ng/m3)
Quan i ica ion limi s
(S/N=10, ng/m3)
Co ela ion
coe icien (R2)
F- es
P- alue
SPME o
spiked
Tenax
(n=6)
SPE-SPME
(n= 4)
1,3-DCB
0.9973
1.52
0.3256
12
10
0.022
0.062
1,4-DCB
0.9962
1.84
0.2582
13
10
0.012
0.033
1,2-DCB
0.9971
2.10
0.2187
13
12
0.011
0.029
1,2,4-TCB
0.9968
0.66
0.6434
11
9
0.007
0.018
1,2,3-TCB
0.9970
0.56
0.7025
11
9
0.004
0.012
1,2,3,5-TeCB
0.9971
0.34
0.8407
9
11
0.019
0.042
1,2,4,5-TeCB
0.9986
0.21
0.9249
6
10
0.005
0.011
1,2,3,4-TeCB
0.9983
0.64
0.6549
8
11
0.015
0.041
PeCB
0.9920
0.41
0.7989
8
8
0.035
0.075
HCB
0.9980
0.25
0.8987
9
8
0.108
0.238
FIG. 1
1
2
3
4
5
6
ai
FIG. 2
0
100000
0
200000
0
300000
0
400000
0
500000
0
1,2-DCB
0
50000
0
100000
0
150000
0
200000
0
250000
0
1,2,4,5-TCB
0
100000
0
200000
0
300000
0
400000
0
500000
0
1,2,4-TCB
0
100000
0
200000
0
300000
0
400000
0
500000
0
600000
0
700000
0
PeCB
PA
CW/DVB
PDMS/DV
B
PDMS
CAR/PDM
S
esponse (a ea c s)
FIG. 8b
HCB
PeCB
1,2,3,4-TeCB
1,2,3,5-TeCB
+
1,2,4,5-TeCB
1,2,3-TCB
1,2,4-TCB
1,2-DCB
1,4-DCB
1,3-DCB
5
10
15
20
(min)
kCoun s
0
1
2
3
4
0
0.5
1
1.5
0
1
2
3
0
2
4
0
1
2
3
Ions: 146+148
Ions: 180+182
Ions: 214+216+218
Ions: 248+250+252
Ions: 284+286+288
Segmen 1
Segmen 2
Segmen 3
Segm 4
Segmen 5
