Ozone oxidation of antidepressants in wastewater -Treatment evaluation and characterization of new by-products by LC-QToFMS.

1.1 MB·English

by  Lajeunesse, Andre

Lajeunesseetal.ChemistryCentralJournal2013,7:15
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RESEARCH ARTICLE Open Access
Ozone oxidation of antidepressants in
–
wastewater Treatment evaluation and
characterization of new by-products by
LC-QToFMS
André Lajeunesse1, Mireille Blais2, Benoît Barbeau2, Sébastien Sauvé3 and Christian Gagnon1*
Abstract
Background: The fate of14 antidepressants along withtheirrespectiveN-desmethyl metabolites and the
anticonvulsive drug carbamazepine was examinedin a primary sewage treatment plant (STP) and following
advanced treatments with ozone (O ).The concentrations ofeach pharmaceuticalcompound were determined in
3
raw sewage, effluent and sewage sludge samples by LC-MS/MS analysis.The occurrence of antidepressant
by-products formedin treated effluent after ozonationwas also investigated.
Results: Currentprimarytreatmentsusingphysicalandchemicalprocessesremovedlittleofthecompounds(mean
removalefficiency:19%).Experimentalsorptioncoefficients(K )ofeachstudiedcompoundswerealsocalculated.
d
Sorptionofvenlafaxine,desmethylvenlafaxine,andcarbamazepineonsludgewasassumedtobenegligible(logK ≤2),
d
buthighersorptionbehaviorcanbeexpectedforsertraline(logK ≥4).OzonationtreatmentwithO (5mg/L)ledtoa
d 3
satisfactorymeanremovalefficiencyof88%ofthecompounds.Screeningofthefinalozone-treatedeffluentsamplesby
highresolution-massspectrometry(LC-QqToFMS)didconfirmthepresenceofrelatedN-oxideby-products.
Conclusion:Effluentozonationledtohighermeanremovalefficienciesthancurrentprimarytreatment,andtherefore
representedapromisingstrategyfortheeliminationofantidepressantsinurbanwastewaters.However,theuseofO
3
producedby-productswithunknowntoxicity.
Keywords:Antidepressants,Ozone,LC-MS/MS,Sewagetreatmentplants,Biosolids,Side-products
Background antidepressants and the antiepileptic drug carbamaze-
Urban wastewaters are one of the major sources of pine (CAR) frequently used for treating schizophrenia
pharmaceutically-active compounds (PhACs) into aquatic and bipolar disorder [7,8]. The persistent drug CAR
environments [1,2]. The elimination of many pharmaceu- largely sold in Canada is currently prescribed in combi-
ticals in sewage treatment plants (STPs) being often nationtoantidepressantsallovertheworldduringtherapy.
incomplete[3-5],effluentsfromSTPsthuscontributetoa Therefore, a monitoring of CAR is also required to better
significantloadofpharmaceuticalresiduesinthereceiving assess its environmental fate in different matrices. Toxicity
waters [6]. Little is however known on the potential studies of these neuroactive compounds provided evidence
release of transformation by-products following advanced forbiologicaleffectsonaquaticorganisms[9-13].Although
wastewatertreatments. the occurrence of antidepressants in sewage effluents
Among the most prescribed PhACs throughout the [6,14-17] and wastewater sludge [18-20] has been demon-
world are the psychiatric drugs that include the strated, the fate of these substances following different
treatments in STPs has not been extensively documented.
*Correspondence:[email protected] A previous study indicated that a primary treatment
1EnvironmentCanada,WastewaterandEffluentsSection,WaterScienceand process has limited capability to remove and/or degrade
TechnologyDirectorate,105McGillStreet,Montreal,QuebecH2Y2E7,
antidepressantsresiduesinwastewater[15].Further results
Canada
Fulllistofauthorinformationisavailableattheendofthearticle
©2013Lajeunesseetal.;licenseeChemistryCentralLtd.ThisisanOpenAccessarticledistributedunderthetermsofthe
CreativeCommonsAttributionLicense(http://creativecommons.org/licenses/by/2.0),whichpermitsunrestricteduse,
distribution,andreproductioninanymedium,providedtheoriginalworkisproperlycited.
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obtained for STPs operating different biological processes investigate the occurrence of antidepressant by-products
(e.g. secondary treatment with activated sludge) revealed formedintreatedeffluentafterozonation.
moderate potential (mean removal efficiency ≤ 30%) to
degrade antidepressants from wastewater [20]. Therefore, Experimental
alternative treatment technologies may have to be imple- Chemicalsandmaterials
mented or combined to achieve high removal of com- All certified standards were > 98% purity grade. Fluoxetine
pounds in STPs [21]. As such, experimental evidence (FLU), norfluoxetine (NFLU), paroxetine (PAR), sertraline
reported elsewhere clearly demonstrates that existing (SER), (S)-citalopram (CIT), fluvoxamine (FLUVO), des-
limitations in primary and secondary processes can be methylfluvoxamine (DFLUVO), mirtazapine (MIR), and
overcome with more advanced treatment strategies inclu- desmethylmirtazepine (DMIR) were provided by Toronto
ding chemical oxidation with ozone or the use of high Research Chemicals Inc. (North York, Ontario, Canada).
pressuremembranetechnologies[22-24]. Desmethylsertraline (DSER), venlafaxine (VEN), O-desme-
While conventional activated sludge treatments were thylvenlafaxine (DVEN), and the surrogate standard
shown to degrade pharmaceuticals to varying extent [25], bupropion-d were obtained from Nanjing Jinglong
9
ozone (O ) treatments showed promising results in terms PharmaTech (Nanjing, China). Amitriptyline (AMI), nor-
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of removal efficiencies as an efficient oxidizer to remove triptyline (NTRI), carbamazepine (CAR), and surrogate
endocrine disruptors compounds and pharmaceuticals standard 10,11-dihydrocarbamazepine were purchased
products in wastewater [26,27]. Generally, O reacts with from Sigma-Aldrich Co. (St. Louis, Missouri, USA),
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organic molecules through either the direct reaction with whileinternalstandardcis-tramadol13C-d waspurchased
3
molecular O (via 1–3 dipolar cyclo addition reaction on from Cerilliant Corp. (Round Rock, Texas, USA). The
3
unsaturated bonds, and electrophilic reaction on aromatics high-performance liquid chromatography–grade solvents
havingelectrondonorgroupse.g.OH,NH )orbydecom- (methanol and acetonitrile) and ammonium hydroxide
2
position through the formation of chain intermediate free wereprovidedbyCaledonLaboratoriesLtd.(Georgetown,
radicals, including the hydroxyl radical OH(cid:129) (less selective Ontario, Canada). Reagent-grade hydrochloric acid, acetic
reaction on saturated aliphatic molecules) [26,28]. The acid,ammoniumbicarbonate,andACSgradeethylacetate
stability of dissolved ozone is readily affected by pH, ultra- were provided by American Chemicals Ltd. (Montreal,
violet (UV) light, ozone concentration, and the concentra- Quebec, Canada). Solid-phase extraction (SPE) cartridges
tion of radical scavengers such carbonate – bicarbonate of 6 mL, 200 mg Strata™ X-C were purchased from Phe-
species, the dissolved organic carbon and humic acids nomenex (Torrance, California, USA). Stock solutions of
[28,29].Exceptforfewexperimentscompletedwithfluoxe- 100 mg/L of each substance were prepared in methanol
tine (FLU), the number of studies dedicated to the elimi- and stored at 4°C in amber glass bottles that were previ-
nation of antidepressants by oxidation processes (e.g. TiO ously washed with methanol. The chemical structures of
2
membrane reactor, O with UVactivation, O with H O ) theselectedcompoundsareprovidedinFigure1.
3 3 2 2
has been rather limited [22-24]. Since molecular O is a
3
selective electrophile that reacts quickly with amine and Instrumentation
double bounds moieties [26], ozonation should be efficient Liquidchromatography(LC)
todegradeantidepressantsmostlyconstitutedofsecondary Liquid chromatography (LC) was performed using an
or tertiary amine and conjugated rings. However, as Agilent 1200 Series LC system equipped with binary
reportedforβ-Lactamantibacterialagents(e.g.penicillinG, pumps, degasser, and a thermostated autosampler main-
cephalexin) spiked in wastewater, O reaction leads to the tained at 4°C. The antidepressants were separated on a
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formation of biologically active sulfoxides analogues [30]. KinetexW XB-C18 column (100 mm × 2.10 mm, 1.7 μm)
For antidepressants, no study on the transformation using a binary gradient made of (A) ammonium bicarbo-
products following an O treatment in wastewater is nate (5 mM) pH 7.8, and (B) acetonitrile at a flow rate of
3
currently available. As yet, no data is reported neither on 400 μL/min. The volume of injection was 15 μL for
by-products toxicity. Nevertheless, formation of N-oxide, influent, effluent, and sludge extracts. The gradient used
amide, aldehyde, and carboxylic acid by-products is was(%B):0min(10%),6min(80%),10min(80%),12min
expected after ozonation of secondary and tertiary amine (90%), 14 min (10%), and 16 min (10%). An equilibration
compoundsinaqueoussolutions[31,32]. time of 4 min was used resulting in a total run time of
Inthepresentwork,theeffectivenessofozonetreatments 20min.Thecolumntemperaturewasmaintainedat40°C.
in terms of removal efficiency is tested at three different
concentrations for the oxidation of 14 antidepressants Tandem-massspectrometry(QqQMS,QqToFMS)
along with their direct N-desmethyl metabolites and the For quantitative analysis, the LC system was coupled to a
anticonvulsive drug carbamazepine during ozonation of a 6410 triple quadrupole mass spectrometer (QqQMS)
primary-treated effluent. The goal of the study was also to manufactured by Agilent Technologies (Santa Clara, CA,
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N N O HN O NH2
OH OH
F3C F3C N
O HO O NH2
Venlafaxine (VEN) Desmethylvenlafaxine (DVEN) Fluoxetine (FLU) Norfluoxetine (NFLU) Carbamazepine (CAR)
MW 277.41 g/mol MW 263.38 g/mol MW 309.33 g/mol MW 295.30 g/mol MW 236.27 g/mol
HN
O O
O N N
N
N
N N
NH F NH
Amitriptyline (AMI) Nortriptyline (NTRI) Paroxetine (PAR) Mirtazepine (MIR) Desmethylmirtazepine (DMIR)
MW 277.40 g/mol MW 263.38 g/mol MW 329.37 g/mol MW 265.35 g/mol MW 251.33 g/mol
HN NH2
O OH N
O
F3C F3C
N O N O
Cl Cl
Cl Cl NH2 NH2 F
Sertraline (SER) Desmethylsertraline (DSER) Fluvoxamine (FLUVO) Desmethylfluvoxamine (DFLUVO) Citalopram (CIT)
MW 306.23 g/mol MW 291.06 g/mol MW 318.33 g/mol MW 304.31 g/mol MW 324.40 g/mol
Figure1Chemicalstructuresofthestudiedcompounds.
USA) equipped with an electrospray ionization (ESI) collision energies varying between 0 and 10 V. For both
source. The capillary was maintained at 4000 V, and the detection systems, the MassHunter software from Agilent
cone voltage was optimized for each compound in the Technologies was used for data acquisition and proces-
positive-ion mode (ESI+). Additional detector parameters sing. Optimized parameters for QqQMS are listed in a
wereheldconstantforallantidepressants:gastemperature table(Additionalfile1).
325°C;gasflow10L/min;nebulizer35psiand dwelltime
50 ms. For qualitative by-products analysis, a 6530 quad- Samplelocationandcollection
rupole time-of-flight mass spectrometer (QqToFMS) also Samplelocation
manufactured by Agilent Technologies, was utilized. The All samples were collected onsite at the sewage treatment
QqToFMSwasequippedwithathermalgradientfocusing plant(STP)ofthecityofRepentigny(30kmNorth-Eastof
ESI source (Jet Stream technology). Source parameters Montreal, Qc, Canada) in amber glass bottles previously
consisted of the following: gas temperature 325°C; sheath washed with methanol during an ozonation pilot-study
gas temperature 350°C; sheath gas flow 11 L/min; drying performed in June 2011. The Repentigny STP typically
gasflow5L/min;nebulizer35psig,fragmentor100Vand treats 25 000 m3 of raw sewage daily for a population of
capillary voltage 4000 V. The QqToFMS was operated in approximately 60 000 persons. Wastewater is primary-
the 4 GHz High Resolution mode with a low mass range treated using both physical and chemical treatments
(1700m/z). Purine (121.050873m/z) and Hexakis (e.g. flocculation of suspended matters with alum and/or
(922.009798m/z) were used as internal reference masses FeCl ). For the purpose of this study, treated wastewater
3
toimprovemassaccuracy.Initialtestswereperformedon was further experimentally ozone-oxidized on site. Main
treated effluent extracts in high resolution tandem MS characteristics of the Repentigny STP are reported in
mode using a mass range of m/z 100–400 (specific Table 1. Ozonation of the effluent consisted of an ozone
collisionenergy:0V)atarateof5spectra/stoscreenthe (O ) generator (Ozone Solution, Model: TG10–Ozone
3
exact [M+H]+ masses of the precursor ions. Identified Solution) fed with ultra-pure oxygen (99.9999%). Gaseous
compounds were then fragmented with different specific ozone was bubbled in a ceramic diffuser located inside a
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Table1MainwatercharacteristicsoftheRepentignysewagetreatmentplant
Wastewater Temperature(°C) pH Alkalinity(mg/L)CaCO TSS(mg/L) BOD (mg/L) COD(mg/L)
3 5
Rawsewage(Influent) 17 7.3 189 146 136 227
Effluent – 7.2 165 12 36 59
TSS:TotalSuspendedSolids,BOD:BiochemicalOxygenDemand,COD:ChemicalOxygenDemand.
5
vertical column (6.3 m, 5.08 internal diameter) where both Sampleextraction
gastransferandcontacttimeoccurredsimultaneously.The Sewagesamples
water flow wasmaintained at 1.2 L/min while the O flow Extraction method for raw sewage and effluent samples to
, 3
rate injection was kept around 75 to 110 N mL/min beanalyzedfor variousclassesofantidepressantswasdone
(head pressure: 10 psi). Contact time of O with treated as previously described [15]. The decision to incorporate
3
effluent was 10 min. Ozone transfer was monitored by the neutral drug carbamazepine (CAR) amongst the basic
measuringoff-gasozoneconcentrationsusingthestandard antidepressants forced us to modify the protocol by
KI procedure [33]. Applied ozone dosages were then replacingthestrongcationexchange cartridgeby amixed-
corrected for ozone transfer efficiency which varied from mode cartridge for sample purification (Strata X-C,
75 to 80%. Total and residual dissolved O concentrations Phenomenex)[20].
3
were determined following the standard indigo trisulfonate The validated extraction protocol used here was simi-
colorimetricmethod[34]. lar to that described in Lajeunesse et al. [20]. Each
250 mL of filtered sewage sample were spiked with
100 μL of a surrogate standard solution prepared in
Samplecollection methanol (bupropion-d / 10,11-dihydrocarbamazepine,
9
Typically,water samplesofinfluent (raw sewage), primary- 2.5 mg/L) and addition of 2.5 mL of methanol before
treated effluent, and ozone treated effluent were collected lowering the pH to around 3 with 100 μL of phosphoric
between 10:00 and 14:00 in polyethylene containers and acid (85%). The mixed-mode solid phase extraction
stored on ice. Samples of wet primary sewage sludge (SPE) cartridges were conditioned with 4 mL of metha-
(biosolids)werealsocollectedonthesamedaysandimme- nol followed by at least 8 mL of Milli-Q water. SPE was
diately stored on ice in polyethylene bottles. In the labora- performed with a VAC ELUT SPS24 manifold (Varian)
tory, approximately 10 g of wet biosolid material was at flow rates ~10–15 mL/min. After extraction, all
filtered with a 0.7 μm glass fiber filter to get a dewatered cartridges were washed with 2 mL of HCl (0.1 M). The
sludge sample that was frozen, freeze-dried, and stored CAR molecules were eluted first with 2 × 2 mL of ethyl
at−80°Cuntiluse.Allsampleswereextractedandanalyzed acetate prior the evaporation of the solvent in the
within48haftertheircollection. tubes to dryness under a gentle stream of nitrogen.
Table2Meanconcentrationsofstudiedcompoundsextractedinwastewater(rawsewage,effluent)andbiosolid
samplesfromtheRepentignySTP
Compounds Wastewaters(n=2) Biosolids(n=2)
Rawsewage(ng/L) Effluent(ng/L) RemovalEff.(%) Sludge(ng/g) K (L/kg) logK
d d
CIT 207±12 148±16 29 172±38 1.2×103 3.1
SER 13±1 9.4±0.1 28 43±5 4.6×103 3.7
DSER 23±1 19±3 17 31±6 1.6×103 3.2
AMI 223±21 195±11 13 58±22 2.9×102 2.5
NTRI 21±3 19±4 6.8 9.0±1.1 4.7×102 2.7
VEN 4061±153 3144±107 23 227±49 7.2×101 1.9
DVEN 4185±133 3448±279 18 73±2 2.1×101 1.3
CAR 747±14 714±13 4.4 26±12 3.6×101 1.6
FLU 11±1 9.5±0.6 16 15±1 1.6×103 3.2
NFLU 7.0±0.4 6.5±0.2 7.1 3.8±0.6 5.8×102 2.8
PAR 15±1 13±4 9.0 5.6±3.6 4.2×102 2.6
MIR 171±20 109±3 36 27±6 2.5×102 2.4
DMIR 41±1 25±1 38 13±1 5.4×102 2.7
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Venlafaxine (VEN)
Citalopram (CIT)
Paroxetine (PAR)
Fluoxetine (FLU)
Figure2RepresentativeLC-QqQMSchromatogramsofselectedantidepressantsdetectedinprimary-treatedeffluentsampleextract.
Meanwhile, all SPE cartridges were washed with 2 mL of of ammonium bicarbonate (5 mM) pH 7.8 – acetonitrile
methanol. The antidepressants retained onto the sorbent (1:1 v/v) in injection vials and later injected in
were then eluted with 2 × 2 mL of a solution of 5% (v/v) LC-QqQMSorLC-QqToFMSforanalysis.
NH OH in methanol. The combined fractions (e.g. CAR
4
and antidepressants) were mixed with 100 μL of a solu- Sewagesludgesamples
tion of cis-tramadol13-d in methanol (5 mg/L) as the The simultaneous extraction of CAR and antidepressants
3
internal standard and the solvent in tubes was evapo- in biosolid samples was completed using the validated
rated to dryness with nitrogen. The dried extracts were protocolreportedinLajeunesseetal. [20].Briefly,0.200g
reconstituted with 0.50 mL of the mobile phase solution of freeze-dried sludge is transferred to a 16 × 150 mm
1,0
d 0,8
K
e
v 0,6
ati
el 0,4
r
0,2
0,0
Figure3RelativeK valuesofthestudiedcompounds.
d
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Table3Meanconcentrationsandremovalofantidepressantscontainedinfinaleffluentfollowingozonation
Compounds Conc.(n=2) Ozone5mg/L Conc.(n=2) Ozone9mg/L
Effluent(ng/L) Disinfectedeffluent(ng/L) RemovalEff.(%) Effluent(ng/L) Disinfectedeffluent(ng/L) RemovalEff.(%)
CIT 186±27 123±11 34 148±16 56±1 62
SER 14±2 – 100 9.4±0.1 – 100
DSER 23±1 – 100 19±3 – 100
AMI 106±5 36±1 66 195±11 15±1 92
NTRI 18±1 0.18±0.01 99 19±4 – 100
VEN 2194±191 963±43 56 3144±107 986±27 69
DVEN 2319±11 – 100 3448±279 – 100
CAR 716±4 12±1 98 714±13 – 100
FLU 6.3±0.8 – 100 9.5±0.6 – 100
NFLU 11±2 – 100 6.5±0.2 – 100
PAR 9.0±1.3 – 100 13±4 – 100
MIR 104±1 1.6±0.1 98 109±3 – 100
DMIR 41±4.1 3.3±0.4 92 25±1 – 100
Note:MeasuredresidualO concentrationsfor5,9and13mg/LofO wererespectively0.000,0.036and0.514mg/L.
3 3
borosilicate glass screw-top conical tube before adding PTFE 0.45 μm filter, and then injected in LC-QqQMS
8 mL of a solution composed of methanol / 0.1 M acetic systemforanalysis.
acid buffer solution pH 4.0 (1:1 v/v). Each tube were
spiked with 100 μL of a surrogate standard solution Results and discussion
prepared in methanol (bupropion-d / 10,11-dihydrocar- Antidepressantsinrawsewageandprimary-treated
9
bamazepine, 2.5 mg/L). Samples were then shaken vigo- effluent
rously and mixed on a rotary extractor (Caframo REAX) Outofthe15compoundsinvestigated,13weredetectedin
for 15 min. After extraction, tubes were placed in a soni- raw sewage samples and only the antidepressant FLUVO
cation bath for 15 min before adding 4 mL of Milli-Q and its direct metabolite DFLUVO were not detected.
watertoeachtube.Tubeswerethencentrifuged(320xg) Compound concentrations ranged from 6.5 ng/L (NFLU)
at room temperature for 5 min. Following the SPE proto- to4185ng/L(DVEN)(Table2).Atypicalchromatogramof
col described previously for aqueous sewage samples, thedetectedantidepressantsVEN,CIT,PAR,andFLUina
supernatants were transferred directly on mixed-mode primary-treated effluent extract is depicted in Figure 2.
cartridges.Thefinalextractswerereconstitutedin0.5mL Overall, moderate to poor removal efficiencies were ob-
of the mobile phase solution of ammonium bicarbonate tained for most antidepressants (mean removal efficiency
(5 mM) pH 7.8 – acetonitrile (1:1 v/v), filtered with a of 19%). Results showed that current enhanced primary
Primary Primary + Ozone (5 mg/L)
Primary + Ozone (9 mg/L)
100
80
)
%
al ( 60
v
o 40
m
e
R
20
0
Figure4ReductionofantidepressantsandCARinprimary-treatedeffluentbyozonedisinfectionat5and9mg/LO concentration.
3
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Figure5LC-QqToFMSchromatogramsofN-oxideby-productsdetectedindisinfectedeffluent(O concentration:5mg/L).
3
treatment using physical and chemical processes removed obtainedforthisprimarytreatmentstronglysuggeststhata
little of the studied compounds (Table 2). The substances mechanism other than chemical adsorption would be
with lowest removal efficiencies were CAR (4.4%), along required to effectively remove antidepressants from urban
with the antidepressant metabolites NTRI (6.8%) and wastewater.
NFLU (7.1%). Similar low removal rates were previously
reportedforantidepressants[15]andCAR[35]inprimary- Antidepressantsinsewagesludge
treated effluents. Despite a noteworthy reduction of to- Primary sludge samples consistently displayed quantifiable
tal suspended solids – TSS (Table 1), the weak removal amountsofthestudied compounds (exceptedFLUVOand
(a) 0 V collision energy
(b) 10 V collision energy
Figure6LC-QqToFMSmassspectraofN-oxideVENindisinfectedeffluent(O concentration:5mg/L):productionsat0Vcollision
3
energy(a)and10Vcollisionenergy(b).
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DFLUVO) (Table 2). Highest mean concentrations in sorption behaviour is expected for SER, DSER, FLU, and
biosolid samples were found for VEN (227 ng/g), CIT CITwhichhavehigherrelativeK values(Figure3).
d
(172 ng/g), DVEN (70 ng/g), AMI (58 ng/g), and SER
(43ng/g).Ourresultsareconsistentwiththemeanconcen- Antidepressantsintreatedeffluent-ozonation
trations for the antidepressants FLU (123 ng/g) and PAR Ozonation of the primary-treated effluent did degrade
(41 ng/g) reported by Radjenović et al. [18] in primary antidepressants with higher efficiency, yielding a mean
sludge samples. Interestingly, among reported concentra- removal efficiency of 88% when 5 mg/L of ozone was
tions, less antidepressant metabolites were detected in applied (Table 3). Ten (10) of the 13 compounds initially
sewage sludge samples for N-desmethyl metabolites in present in the effluent had removal efficiencies ≥ 92%
comparison to their respective parent molecules. These (Figure 4). Only three substances (CIT, AMI, and VEN)
findings suggest that more polar compounds have a lower yielded lower removal efficiencies, being 34, 66, and 56%
affinityforthesolidphaseofsewagesludgeandhencehave respectively. As discussed in background section, the
limitedremovalefficiencies. ozonation mechanism is directly affected by the ozone
In order to describe the fate and behavior of antidepres- stability. Thus, scavengers compounds (e.g. carbonate,
sants in primary STP, specific partitioning coefficient (K ) bicarbonate, dissolved organic and humic acids) present in
d
valuesforantidepressantsandmetabolitestosewagesludge effluent may have slowed down the ozone decomposition
were estimated. The K coefficients were calculated using by inhibiting the free-radical reaction chain, and conse-
d
theratio[Sludge]/[Effluent];where[Sludge]istheconcen- quently the formation of hydroxyl radicals OH(cid:129) necessary
tration of antidepressants in sewage sludge (ng/kg) and to degrade saturated aliphatic carbon chain on molecules
[Effluent] is the concentrations of antidepressants in final [28]. Since, CIT, AMI and VEN have long tertiary amine
effluent(ng/L)[36].TheobtainedK valueswereappliedto aliphatic chains on their chemical structures, steric hin-
d
evaluate the affinity of compounds to primary STP sludge. drance may have prevented ozone reactions normally
The K values were lowest for VEN, DVEN, and CAR expected at specific sites of the molecules [37]. In present
d
(Table2)withvaluesrangingfrom21to72L/kg.Withlog study,itisverydifficulttoassesstherelativeimportanceof
K values ≤ 2, sorption to solid matter for VEN, DVEN, direct ozone-mediated transformations, and thereby to
d
and CAR is therefore defined as negligible [36]. Higher draw a general conclusion about each compound and
(a) 0 V collision energy
(b) 10 V collision energy
Figure7LC-QqToFMSmassspectraofN-oxideDVENindisinfectedeffluent(O concentration:5mg/L):productionsat0Vcollision
3
energy(a)and10Vcollisionenergy(b).
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transformation during ozonation in a single matrix with decided to keep a large isolation width of the quadrupole
varyingOH(cid:129)scavengingcapacities,underacertainpHcon- (e.g. 4 m/z) to increase sensitivity. Hence, MS/MS mass
dition. Obviously, the work presented therein was not spectraofN-oxideVENandDVENlikelycontainedprod-
intended to the understanding of ozonation mechanisms. uct ions of othermolecules that may have interfered with
However, as reported by Zwiener and Frimmel [38], so- the mass spectra interpretation. According to European
calledradicalscavengerscompetewithpharmaceuticalsfor Commission Decision 2002/657/EC [40], at least 4 “iden-
theOH-radicalsandbythisdecreasethedegradationkine- tification” points are required in order to confirm the
tics of the targeted pharmaceuticals. Nevertheless, removal presenceofasubstance.Sinceonehigh-resolutionprecur-
efficiency increased to 94% for most compounds using an sor ion and one high-resolution product ion were ob-
optimal ozone dose of 9 mg/L (Figure 4). At the highest tained during experiments (total identification points: 2 +
ozone treatment tested (i.e. 13 mg/L), all antidepressants 2.5 = 4.5), the results of our study (with accurate mass
were oxidized and degraded from primary-treated effluent errors < ± 5.00 ppm) were considered sufficient to con-
samples. Current limitation of the analytical method may firmthepresenceoftheN-oxideby-products.
have lead to undetected polar compounds that would Additional LC-QqToFMS analysis performed on effluent
requiredifferentchromatographicandinstrumentaladjust- extracts previously treated with 9 mg/L of O confirmed
3
ments.However,Snyderetal.[26]havereportedverysimi- also the presence of both N-oxide by-products. When the
lar removal efficiencies for CAR (> 99%) and FLU (> 93%) concentration of O reached 13 mg/L, none of the by-
3
for comparable effluent samples treated with 3.6 mg/L of products were detected in corresponding effluent samples.
O .Undercontrolledconditionsusinga5–Lglassjacketed ThissuggeststhatanoptimalO dosagewouldberequired
3 3
reactor, Rosal et al. [39] observed high removal efficiencies to completely degrade the N-oxide by-products from trea-
forCAR(98%),CIT(93%),FLU(100%),andVEN(88%)in ted effluents. Additional tests performed on raw sewage
wastewater samples exposed to 2.4 – 6.1 mg/L of O for (influent) and primary-treated effluent confirmed the ab-
3
lessthan5min. sence of the two N-oxide by-products prior ozone treat-
ments.Toourknowledge,thepresentstudyisthefirstone
Characterizationofnewby-productsbyLC-QqToFMS toreportthecharacterizationofantidepressantby-products
In this study, the two most abundant antidepressants in municipal effluent samples after experimental ozone
detected in raw sewage were VEN and its N-desmethyl treatment.
metaboliteDVEN.Therefore,primary-treatedeffluentsam-
ples previously treated with O at different concentrations Conclusions
3
werescreenedbyLC-QqToFMStoconfirmthepresenceof This study described the fate and behavior of antidepres-
relatedby-productsofthesetwocompounds. santsandtheirN-desmethylmetabolitesinaprimarySTP
Initial tests performed on treated effluent extracts following ozone treatment. Effluent ozonation led to
(O dose: 5 mg/L) in high resolution tandem MS mode higher mean removal efficiencies than current primary
3
using a mass range of m/z 100–400 (specific collision treatment, and therefore has represented a promising
energy:0V)enabledthepositivedetectionofN-oxideby- strategy for the elimination of antidepressants in urban
product precursor ions for VEN (m/z 294.2059, accurate wastewaters. However, the use of O has produced
3
mass error: -3.40 ppm) and DVEN (m/z 280.1903, accu- N-oxideby-productswithunknowntoxicity.Ofparticular
rate mass error: -3.21 ppm). The chromatograms and concern is the potential that removal of pharmaceuticals
mass spectrums of both characterized by-products are following wastewater disinfection using advanced oxida-
depicted respectively in Figures 5, 6a, and 7a. Precursor tionprocess(i.e.ozonation)couldgenerateby-productsof
[M+ H]+ions wereisolated inthefirstquadrupoleofthe similar parent chemical structures that would need to be
QqToF and then fragmented in the collision cell at 10 V identified,quantifiedandevaluatedfortheirtoxicity.
in order to perform accurate mass measurements on the
resultingfragmentions.Isolationandfragmentationofthe Additional file
precursor ion of N-oxide VEN (m/z 294.2057, accurate
mass error: -4.08 ppm) generated a product ion at m/z Additionalfile1:OptimizedLC-(ESI+)QqQconditionsforthe
127.1125 (Figure 6b). This ion fragment corresponds to analysisofantidepressants.Thesupportingdocumentreportsthe
instrumentalLC-MS/MSparameters.
[C H O + H]+ and has an accurate mass error from
8 14
theoretical values of 1.57 ppm. As for the N-oxide DVEN
when its precursor ion at m/z 280.1910 (accurate mass Competinginterests
Theauthorsdeclarethattheyhavenocompetinginterests.
error: –0.71 ppm) was isolated and fragmented, an ion at
m/z 113.0966 was observed that could be interpreted as Authors’contributions
[C H O+H]+withanaccuratemasserrorof±0.00ppm ALperformedthemainpartoftheexperimentsanddraftedthemanuscript.
7 12 MBperformedozonetreatmentexperimentsandhelpedanalyzingthedata.
(Figure 7b). During MS/MS characterization, it was CGandSShelpedinterpretingtheresultsandcoordinatedthemanuscript
Lajeunesseetal.ChemistryCentralJournal2013,7:15 Page10of11
http://journal.chemistrycentral.com/content/7/1/15
writing.BBhelpedanalyzingthedataanddraftingthemanuscript.Allthe 15. LajeunesseA,GagnonC,SauvéS:Determinationofbasicantidepressants
authorsreadandapprovedthefinalmanuscript. andtheirN-desmethylmetabolitesinrawsewageandwastewaterusing
solid-phaseextractionandliquidchromatography-tandemmass
spectrometry.AnalChem2008,80:5325–5333.
Acknowledgements 16. SchultzMM,FurlongET:Traceanalysisofantidepressantspharmaceuticals
TheauthorsgratefullyacknowledgethecityofRepentignyforproviding andtheirselectdegradatesinaquaticmatrixesbyLC/ESI/MS/MS.AnalChem
sewageandbiosolidsamples.ThisworkwasfundedbytheChemical 2008,80:1756–1762.
ManagementPlan–HealthCanadaandtheSt.LawrenceActionPlan. 17. MetcalfeCD,ChuS,JudtC,LiH,OakesKD,ServosMR,AndrewsDM:
Antidepressantsandtheirmetabolitesinmunicipalwastewater,and
Authordetails downstreamexposureinanurbanwatershed.EnvironToxicolChem2010,
1EnvironmentCanada,WastewaterandEffluentsSection,WaterScienceand 29:79–89.
TechnologyDirectorate,105McGillStreet,Montreal,QuebecH2Y2E7, 18. RadjenovićJ,JelićA,PetrovićM,BarcelóD:Determinationof
Canada.2ÉcolePolytechniquedeMontréal,DepartmentofCivil,Geological pharmaceuticalsinsewagesludgebypressurizedliquidextraction(PLE)
andMiningEngineering,P.O.Box6079,SuccursaleCentre-ville,Montreal, coupledtoliquidchromatography-tandemmassspectrometry.Anal
QuebecH3C3A7,Canada.3DepartmentofChemistry,Universitéde BioanalChem2009,393:1685–1695.
Montréal,P.O.Box6128,SuccursaleCentre-ville,Montreal,QuebecH3C3J7, 19. HörsingM,LedinA,GrabicR,FickJ,TysklindM,laCourJansenJ,Andersen
Canada. HR:Determinationofsorptionofseventy-fivepharmaceuticalsinsewage
sludge.WaterRes2011,45:4470–4482.
Received:20September2012Accepted:22January2013
20. LajeunesseA,SmythSA,BarclayK,SauvéS,GagnonC:Distributionof
Published:25January2013
antidepressantresiduesinwastewaterandbiosolidsfollowingdifferent
treatmentprocessesbymunicipalwastewatertreatmentplantsin
Canada.WaterRes2012,46:5600–5612.
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