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dvances in th nalysisofPersistent Halogenated organicCompoundsEric J. Reiner, Ad rien ne R. Bod en, Tony Chen, Karen A. M acPherson a nd A l ina M . Musc alu,Ontario Ministry of the Environment, Laboratory Services Branch, Toronto, Ontario Canada,

Persistent halogenated organic pollutants are chemical compounds of anthropogen ic o rigin tha tresist degradation and accumulate in the food-chain. The analysis of these compounds requirescomplex sample preparation and analytical procedures using sensitive and selective state-of-the-artinstrumentation to achieve the desired selec tivity, accuracy and detection limits . This article reviewsadvances in the analysis of persistent halogenated organic compounds over the last century.An important goal in the fieid of analytical chemistry is toachieve continual improvement in the analysis of persistenttoxic pollutants. Halogenated organic compoundsrepresent an important group of pollutants. They are usedin a wide variety of applications such as flame retardants,fire suppressants, heat-transfer agents, surfactants andpesticides, mainly be cause of their chemical inertnessand sfability. As a result of this stabiiity, many of thesehalogenated organic c omp ounds are persistent in theenvironment, toxic and bioaccum ulative in the food chain,and are consequentiy associated with adverse effects onhuman health and the environment.

The Stockholm Convention on Persistent Organic Pollutants(POPs) (2001) is an international treaty that focuses on theelimination or reduction of a number of these com pounds orgroups of compounds, which include pesticides, industrialchemicals and unintentionally produced POPs. The list ofthe original twelve compounds or groups of compoundsand seco nd gro up of nine is summarized in Table 1,alongwith an additional g roup of three comp ounds currently beingreviewed for addition. The persistence and toxicity of thesecompounds as weil as many thousands of others^^ hasdriven the discovery and development of new a nalyticalequipment and techniques in the interest of protec tinghumans and wildlife. Sensitivity, selectivity, speed of analysisand cost (four key method attributes) need to be co nsideredwhen selecting the most appropriate method of analysis. Theproper extraction, preparation and instrumental techniquesmust be s elected to ensure that the uncertainty of the

technique meets the required data quality objectives andthe m ethod is fit for the purpose for which it was intended. Continuai improvement should be the prime considerationof any analytical laboratory with the key method attributesoptimized for the test at hand.Halogenated organics have been prod uced by humansintentionally and unintentionally tor hundreds of years. Thegreatest challenge through the years has been findinganalytical methods that are sensitive and selective e noughto determine concentrations at levis low enough to protechumans a nd wildlife. The current standard for an alysisof organohalogens is gas chromatography (GC) with an

appropriate detector thai meets the required selectivity[e.g.,mass spectrometry (MS) or electron capture detectio(ECD)].Unfortunately, methods capable of determiningconcentrations to meet the above criteria have only beenavailable for the last few decad es.Early Non-chromatographic MethodsHaiogenated organic compounds such as polychlorinatedbiphenyls (PCBs)^ and polychiorinated naphthalenes(PCNs)^ have been used for more than 100 years. PCNs, fsynthesized in 1833 were not used extensively until the ear1900s when they found applications as flame retardants infabrics, dielectric fluids and anti-fungal agents for gas masMethods of analysis for these halogena ted POPs atthat time were not sensitive or selective. The Ca riusme thod (pre-1900) determined organic halidesby boiling samples with nitric acid in the presence


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Reiner et alof silver nitrate followed by gravimetric etermination ofthe silver halides that precipitate from solution. In theStepanovv^ or Bacon^ method (early 1900s) the organichalide was reacted with sodium in the presence of ethanoland the chloride was determined using a Volhard titration(silver nitrate was a dded in excess which reacts with thechloride produced). The excess silver was back titrated withthiocyanate in the presence ofFe^ ^,which forms a brightred com plex with the thiocyanate when the excess silverwas complexed. The Stepanow and Bacon titration methodsredu ced de tection limits to the part-per-thousand range fromthe (ow perc ent levis previously a chieved by the Cariusmethod.

Oc cupa tional exposure of industrial workers toorganohalogens accelerated the need for new analyticaltechniques . Chloracne , first reported in 1899, is a diseasecaused by extensive exposure to halogenated organicsJ^Chloracne resulting from PCN contamination was firstreported by Wauer in 1918.^ Factory workers pro ducingand using H alowaxes a nd other PCN formulations alsoexhibited nausea, anorexia, vertigo, jaundice and dea th.Substitutes, such as PCBs. were considered less toxic andreplace d PCNs in many applications. However, by 1937 Itwas reco gnized that PCBs also caused similar effects andthat factory workers often exhibited chloracne as well as theother effects listed above for PCN s. During the early part ofthe previous century occupational exposure was common.Warren Crummett in Decades of Dioxin^^writes about hisobservations in 1943 on the first days at work as a chemist ina chem ical plant saying: I was scared. It appeared obviousto me that this is a high-risk place to work. Chlorine andnitrosyl chlorid e leaks into the plant occurred frequently.One day I unwittingly s tepped into a pocket of such g as. Thechokin g impac t knocke d me to the floor and I had to report tothe health departm ent for oxygen inhalation treatment. Almostall the procedure s on this job were hazardous.

Dichlorodiphenylthchloroethane (DDT) was first synthesizedin 1874, but its insecticidal prope rties were not discovered until1939. DDT was used to control mosquitoes for maiaria andlice for typhus during the Second World War.' -^sJ^^Q ^gg QDDT and other organochlorine (OC) pesticides skyrocketedin 1940s and 50s to control pests and increase crop yields.During that time DDT was analysed using a colorimetricmethod developed by Schechter etal.^^where DDT anddegradation products dichlorodiphenyldichloroethylene (DDE)and dichlorodiphenyldichloroethane (DDD) were subjectedto fuming nitric acid to produce a tetranitro-DDT complexthat is reacted with a sodium methylate-methanol reagen t.The resulting compound can be determined with maximum

adsorption al around 600nm.Levels down to 10 pg (-1 0 ppm)could be detected.The Advent of Gas ChromatographyAlthough not used for quantitative trace level analysis until the1950s, the concept of chromatography had been reportedmany yearsearlier by Tswett^'' and Day''^w oreported thatdyes and crude oil fractions were selectively retained on solidsubstrates respectively. Other observations of selective gasadsorption and separation onc^bonand silicageP^were alsoreported in literature during the first half of the 20th century. In1941,fviartin and Synge,^'^who performed research onliquid-liquid partitioning experiments, reported that, themobile phase need not be a liquid but may be a vapour, andthat, very refined separations of volatile substances should

Figu re 1 : The first published gas ch romatog ram. R eproduce dwith permission, from James and Martin,Biochem J 35,679-690 (1952). Copyright: the Biochemical Society (http://'AT'.vw bioc he m j org )

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U1 y g 1 m

1 120 30Time (mtn)

Figure 2: Unknown peaks m a GC-ECD organochlorinepesticide sc an. Copyright (1972) Royal Swedish Academ y ofScience from AMBIO. by Sren JensenRepublished by permission of Royal Swedish Academy ofSciences/Allen Press Publishing S ervices.


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Reiner et al.therefore be possible in a column in which permanent gas ismade to flow over gel impregnated with a non-volati le solvent."The pract ical development of gas chromatography (GC) wasnot realized until 1952^'"^^ when Martin and James were ableto separate an d quantify four organic ac ids on a 4 ft x 4 mmcolum n p acked with DC-si l icone oi l containing 10% stearic acidusing N2 as the carrier ga s. Figure 1 shows the first publish edgas chro matogra m. The eluants were detected by t it rat ion withsodium hydroxide and phenol red indicator. The detection limitwas 20 pg an d the colum n ha d 700 plates with a peak capacityof 5 to 6 peak (i.e.,5 to 6 pea ks cou ld be basel ine separated inan analytical run).

Using GC, chemists could now separate chemicalcompounds at trace levels, but the challenge was to find anaccurate, sensitive and non-discriminating detector. A number

Figure 3 : PCBs in a GC-E CD organochiorine peslicicle scanfrom various biological sam ples in Swe den. Copy right (1972)Royal Swedish Academ y of Sciences from AMBIO. by SrenJensen. Republished by permission of Royal SwedishAcade my of Sciences/Allen Press Publishing Services.

p,o -DOTl OIELDRIN

BpDOE

White-tailed eagle tO

d p p DDE

ks

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of di f ferent detectors were developed including the thermalcondu ctivi ty detector (TCD). coulome tric detector and themost imp ortant for determination of OC pesticides, the electrocapture detector (ECD), The ECD. developed in 1960, wasvery sensit ive towards halogenated compounds and coulddetect as l itt le as 10"''^moles. It was also very selective forelectronegative compounds making i t ideal for halogenatedorganics and organochtorine pest icides.^ ' 'Silent SpringThe amou nts of pest icides used in the late 1950s a nd early1960s was excessive. OC pesticides could signi f icant lyincrease crop yields by 40% or more. The use of pest icide swas see n as posit ive even though they were highly toxic a ndpersistent. In 1954 and 1956, the reproduction of salmon inthe Miramichi River of New Brunswick, Canada, was almosteliminated by the spraying of nearby forests with DDT to contspruce bud worm. In 1962, 350 mil l ion pounds of pest icideswere used in the US- One of every 12 acres was treated with

Table 1: Stockholm convention POPs.C ategory C om po und sPesticides Aldrin

ChiordarwDieldrinDDTEndrinHeptachlorHexachlorobenzene (HCB)M i rexToxaphene

Industrial chem icals Polychlorinated Biphenyls (PCBs)Unintentional Polychlorinated Dibenzo dioxinsproduction (PCDD) and Dibenzofurans (PCDF)

PCBsHC B

A dd ed (M ay 2009) C hiordeconea-hexach lorocyctohexane-hexachlorocyclohexaneHexabromobiphenylHexabromodtpheny eiher andheptabromodiphenyl etherLindane (gamma-hexachlorocyclohexane)PentachlorobenzenePerfluorooctanesulfonic acid (PFOS),its salts and perfluorooctanesulphonylfluorideTetrabromodiphenyl ether andpentabromodiphenyl ether

Compoundsunder reviewNominated foraddition (Oct 2009)

Short-chain chlorinated paraffin(SCCPs)Endosulphan


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Reiner et al.chroma tograms for a variety of wdlife from different food weblevels. The interfering com pounds identified as PCBs werepresent in every sam ple. Many early OC results were probab lybiased due to contribution from PCBs.

Samp le extracts had to be split into fractions to eliminatebias from PCB an d OC pesticide overlapping peaks inpacked column chromatograms. Extracts were cleaned andfractionated using open column chromatograpfiy. Rorisil is themost common Chromatographie adsorbent, but silica gel andalumina are alsoused.The majority of the PCBs an d a few OCs(typically A idrin) elute in the first fraction whiie the remainingOCs and some PCBs (typically the non-ortho substitutedPCBs) elute in the seco nd fraction.Chromatographie and Column TechnologyAnalyses were performed mainly on packed columnsuntil the early 1980s. Analytical run times were hours long;peaks were up to 10 min wide with many coelutions due tolow resolving powers (typically in the order of a thousand).The capillary column, a wall-coated open tubular coiumn,was developed in 1958,-^ but due io issues with inertness(metal supports) and fragility (glass supp orts), it was not usedroutinely until the invention of fused silica in 1979.3'' Fused-silica columns based on optical fibre technology, are inert,flexible and durable.

Stationary phases coat the inner column wall andcolumn lengths can be much greater than packed columnsbecause there are no back pressure issues from particles.Initial column bleed problems were solved by crosslinkingstationary phase s to the columns. Peak capa cities wereincreased by an order of magnitude from pac ked columns (toabout 50). Capillary columns use much lower gas flows and,therefore, can be directly coupled with mass spectrometers.The separating power of GC and the selectivity of massspectrometry make GC-MS the universal analyticaltechnique.^^'^^ Although the mass spectrometer candistinguish between most chemical compounds by mass, itcannot distinguish isomers (which have the same m ass) fromone another for groups of compounds such as PCBs, PCNsand dioxins. Complete separation of the toxic compoundsfrom the non-toxic ones is a very important consideration

Figure 6:Schematic for a GC x GC analyt icalsystem.Reproducedwith perm ission from Focant etal..Talanta63 1231-12402004,Co py righ i 2004 Elsevier_

Table3(a ): Summ ary of methods for anaiys isof halogenated organic s (1800s -1980s).MethodDaterangeAnalytesSelectivitySensitivitySpeedCost persampie(SUSD)Equipmentcost(SUSD)

GravimetricCarius1800sHalo-organicsHalo-organics% levelHours 10

< 1 0 0

TitrationStepanowBacon1900to 1940sHalo-organicsHalo-organicsMilligrammesHours 1 0s

SiOO s

PhotometricSchechter1940sto 1950DDTand metabolitesDD Ta nd relatedcompoundsMicrogrammesHours 10's

1000

ChromatograpiiicThinLayer1950to 1970OCpesticidesOCpesticidesMicrogrammesHours 10

1OOs

ChromatographiePackedGC1950to 1980sPCB O C pesticidesN= 1 0 0 0n^=5Microgrammestonanogrammes(ECD)2-3 days 1OOs

100000


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Reinerta l .when the degree of toxicity varies significantly betweenisomers and congeners of a group of compounds.Modern Chromatographie MethodsG C- M S is required tc detect dioxins. Dioxins are one ofthe most toxic chemica l groups known to man . They wereinitially identified as highly toxic by-products of phenoxy-acidherbicides, 3,4,5,-T an d 2,4-D, use d to control weeds andexcess foliage Dioxins and structural ly related com pound s,furans, are a group of 210 pianar co m pou nds with two chiorinesubsti tuted benzene r ings co nnec ted by one (furan) or two(dioxin) oxygen atom s as shown in Figure 4, Con generswith chlorines in the 2,3,7,8 ring positions (17 congeners)react with the mam malian aryl hydroc arbon receptor (AhR)promoting a number of toxic effects including cancer, immuneimpairment, as well as developm ental and reprcductivedisorders,-^'' Conge ners without a chlorine in one or more ofthe 2,3,7,8-positions {193 congeners) are not toxic and do notbioaccumulate in f ish and mam mals. The LD 50 (m edian lethaldose) for 2,3,7,8-TCDD can be as low as ~1 pg/kg of bodyweight (guinea pig) while the NOEL (No Observable EffectLevel) for 1,3.6,8-TCDD is 3 g/kg body weight. These twocom poun ds are the main dioxin by -produ cts in the formation ofthe phenoxy acid herbicide: Agent Orange. Compounds thatare planar, can be positioned in a rectangle with dimensions ofapproxim ately 0.3 x 1.0 nm (10"^ m) with chlorines p ositionednear the corners of the rectangle, have a higher probability ofbinding to the AhR and exhibiting dioxin-like characteristics.Some PCBs and P CNs also have significant dioxin-l ikecharacter.

A six-year study (1972-1977) show ed that humanmiscarriages were three times greater in areas where AgentOrange w as used^^-^^ and as s uch, it was ban ned in theUS in 1979. In 1970 a group of scientists determined that adetection limit of 1 ppt w ould be requ ired to minimize risk todioxin exposure. This was much lower than the 50 ppb levelachievable at that time and would require a very sensitive andselect ive analyt ical proce dure with concen trat ion factors of10^-10^ to meet detect ion l imits. Gas ch romatograph y highresolut ion mass spectrcmetry (GC-HRMS) would potential lybe the only technique that co uld m eet these very str ingent d ata

qual i ty objec t ives. The analysis of dioxins is on e of the m ostchal lenging pursuits in analyt ioal chemistry and a benchmarfor the analysis o other organo haiogens.^ ' ' '^^ The analytesof interest must b e quanti tat ively e xtracted from the s am ple.Interfering compounds must be removed using a series ofcoiumn Chromatographie procedures such as si l ica, aluminaFlorisi l or carbon. The extract must then be concentrated tominute volumes to detect sub-pic ogra mm e (10"^^ g) levels insamples. Interfering compounds including non-toxic isomersand congeners must be separated and the toxic c om pone ntdetected using high resolut ion mass spectrometry (HRMS).

The use of capi l lary chromatography with ECD orMS detect ion has been the standard for the analysis oforganohalogens since the early 1980s. Capi l lary columnsare produced in a variety of dimensions. The most commondimensions are 60 m or 30 m columns with 0.25 mm innerdiameter (i.d,), 0.25 [}m f i lm thicknes s (f. t.) and non-p olar(dimethylsi loxane) or sl ight ly polar (5% diphenlym ethylsi loxancoatings. Most analysts attem pt to run all of their analy ses onthese phases because they provide good separation for themajori ty of compounds and the phases are inert to the majorof organohaiogens and other matrix coextractables. Analyt icruns typical ly are 30-60 minutes in length.Advancing Chromatographie MethodsMic robo re colu mn s i.c . < 0.18 an d f,t, < 0-2) can sign ifican tredu ce a nalysis times. If the pha se ratio (the ratio of i.d. to f.t,is kept constant, the chromatog raphy (refative elut ion orde r)and area under the peaks theoret ical ly remain the same.Reducing i.d. and f.t, results in shorter retention times andtal ler and narrower Chromatographie peaks. This technique,cal led fast GC, can reduce analysis t imes by 50% or more aincrease signal-to-noise S/N) by up to a factor of f ive,^ ^'^^ Tmajor l imitation of this technique is finding a detector that canscan fast enoug h in order to accurately de fine a peak (obtaina minim um of 7 to 10 sam pling points across a GC peak), ' '^Figure 5(a) shows the GC t ime-of-f l ight mass spectrometric(GC-TOF-M S) separat ion o f 117 com poun ds a mixture ofPCBs, OCs, chorobenzenes (CBs) and po lycycl ic aromat ichydrocarbons (PAHs) achieved in about 7 min. Peaks areabout 2 s wide a nd, therefore, at least 5 scans p er se co nd a

Table 3(b): Summary of methods for analysis of halogenated organics (1980 -prese ni)MethodDate rangeAnalytesSelectivitySensitivitySpeedCost persample (SUSD)Equipmentcost ( USD)

ChromatographieGC~ECD1980 to presentStockholm List

n = 5 0Picogrammes tofemtogrammes (ECD)2-3 days$100s

$100000

ChromatographieG C- M S1960 to presentStockholmListN= 1 0 'n.=50Picogrammes2-3 days$1OOs

$200000

ChromatographieGC - H R MS1970 to presentStockholm ListN=3X1O*n.=100Picogrammes tofemtogrammes2-3 daysS500-$1000

$500000

Ch romatog raph icGCxGC2000 to presentStockholm List plus manyadditional organohalogenN,=10-, Nj=1000n ^ =5 0 x2 0 - 1 0 0 0Picogrammes tofemtogrammes2-3 days$500-31000

$150000 (ECD)$40000 0 (TOF)


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Reiner et alrequired to obtain the minimum number of sampling points.The time-of-flight (TOF) mass spectrometer was the firstto be com bined with a gas Chromatograph. ^ Early m odelshad unit mass resolution and were not controlled via a datasystem.New configurations c an scan much faster and havereflectron designs that increase resolution significantty.^

Some data systems now enable d econvolution ofoverlapping peaks. As shown for the peaks plotted inFigure 5{c), the slope of the tangent of alt ions at a specifictime can be determined and grouped. Compounds withvaried differentials can be deconvo luted from one another.Figure 5(b) shows the total ion chromatogram (TIC) over a 10s section of a standard containing over 100 OC pesticides.PCBs and PAH, There appears to be five peaks in the

Figure 7:GC < GC-ECD chromatograms of sludge andsediment samples containing a variety of different halogenatedorganics (CBZ = chlorobenzenes, PCDEs = polychlorinateddiphenylethers, BDEs = brominated diphenylethers)

1 Drmension{s

Figure 5(b) chrom atogram, however, after deconv olution ofthe peaks is performed, nine peaks can be detected.Table 2 describes the potential time savings using fast GC.Additional time savings can be realized with analyte-specificcolumns. Columns for a variety of compoun ds includingdioxins [DB-Dioxin (Agilent Technologies. Santa Clara,California, USA), Rtx-Dioxin2 (Restek, Bellafonte, PennsylvanUSA)],SP-2331 (Supeioo. Bellafonte, Pennsylvania, USA) anBPX-DXN,(SGE, Austin, Texas, USA)]; PCBs [HT-8 (SGE)and Rtx-PCB (Restek)]; and OC Pesticides [Rtx-C LPestiddes(Restek)] have been developed.

These columns have been designed to separate critical paiof coeluting analytes and minimize the number of coelutionsseen on dimethyl s iioxane or 5% diphenylmethylsJioxanecolumns. In past years, the adoption of fast GC has beensluggish as older GC ovens couid not heat at high enoughramp rates, coiumns were not readily avaiiable in fast GCdimensions(i.d.< 0.18 and f.t. < 0.2) and some regulatorymethods were not flexible enough to allow the use of m icrobocoiumns. The number and phases of columns availablein dimensions capable of doing fast GC has increasedsignificantly in the past few years and newer GCs are allcapable of fast oven heating.Analytical ChallengesCoelution of analytes for the analysis of all groups ofhalogenated organics presents a significant analyticalchallenge. There currently is no single GC column that canseparate all the components of compound groups such asPCBs. PCNs. dioxins/furans, or OC pesticides in a singleanalyticalrun.GC -MS or GC-HR MS is currently the methodof choice for dioxins/furans, dioxin-like PCBs and PCNs. OCpesticides and PCBs are also routinely determined usingdual column analysis with BCD detection. Multidimensional orcomprehensive two-dimensional chromatography (GCxGC)is a relatively new technique that can analyze samples on twodifferent GC phases in the same analysis. ^ ^^ In GC xG C, twodifferent Chromatographie colum ns are connected in seriesthrough a m odulator, which traps the analytes eluting fromthe primary column and re-injects them in small compressedpackets onto the secondary columns. Figure 6 shows twocoeluting peaks eluting from the primary column [6(a)], theresulting modulated packets eluting from the secondary colum[6{b)] and the corresponding two-dimensional colour intensityplot or three-dimensional contour plot [6(c)] illustrating the dataGC xG C has a number of advantages over single columntechniques. When orthogonal columns are coupled in serie(coiumns that provide separation through different physicaland chemical properties, e.g.. boiling point/polarity versusshape selection) se parations are ordered in Chromatographspace. Thus, different compound groups tend to separateinto distinct ordered bands of peaks eluting at about a45''angle relative to each other. This spatial ordering ofcompound class peaks aids in the separation, identificationand classification of multi-component compound groups(e.g.,PCBs. PCNs, dioxins). As indicated earlier, massspectrometers cannot separate isomers. congeners orhomologues with identical mass to charge ratios. GCxGCprovides muc h greater Chromatographie resolution and peacapacity than single column systems. The GCx GC peakcapacity is the product of the individual peak capacities of


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Reiner et alorder of 1000 peaks or more. With such great s eparatingefficiency, a simple detector such as ECD can be used.Figure 7 shows the G CxG C chromatogram of a numberof halogenated organics. GCx GC can also be used asscreening method for variety of haiogenated compounds.

Polychlorinated alkanes (PCAs) includ ing short chainchlorinated paraffins (SCCPs) are a very challenging group ofcom pounds to analyse. ^ They have replaced PCBs in manyapplications. There are many thousands of congeners andPCAs often appear as a plethora of indistinct peaks creatinganunresolved hump in one-dimensional chromatograms(similar to that seen for complex hydrocarbon mixtures). In two-dimensional chromatograms, they appear as structured bandsand can easily be identified and quantified. Polychlorinatedterphenyls (PCTs) manufactured as Aroclors where used insimilar applications as PCBs, but also as synergistic agentsfor the application of Lindane.^ Not normally detected inconventional analyses, PCTs are often observed in GCxGCchromatogram s of sludges and sedim ents. [See Figure 7(c)and as confirmed using GCxG C-TO F-MS in Figure 8.]

The majority of the halogenated organic compoundslisted in Table are lypophilic and have similar physical andchemical properties. They can be extracted together and theextract can be cleaned using common procedures.^^'^^ Silica,alumina and Florisii are classical procedures used to removeiipids and other polar matrix compounds .^'' This results inEheability to collect similar compounds (halogenated POPs) inthe same ex tract and creates the potential for one analyticalsystem to identify and quantify them in a single analytical run.Hytylinen^^ has reviewed a series of novel sample extractionand Chromatographie techniques that can be used to simplifyand sp eed up analyses.Advancing into the Next CenturyOver the last century, sensitivity and selectivity for thedetermination of halogenated organics has increasedsignificantly. Current analytical m ethods, in most cases,are selective and sensitive e nough to inform scientistso the presenc e and levels of distinct organohalogens insam ples. This helps us in our endeavour to protect humanlife and w ildlife from exposures to toxic persistent organiccompounds. The current challenge is to chromatographicallyseparate, detect and quantify as many persistent organicpollutants as possible within the same sample extract.Multidimensional chromatography provides the bestChromatographie separation. The mass spectrometer iscurrently the m ost selective an d sensitive detector possible.Unfortunately, there currently is no mass s pectrometer thatcan scan and detect compounds at the low femtogrammelevel at rates of 20 s per decade with resolutions of 10000orbetter The ultimate instrument would use GCxGC forseparation, with the sca n speeds of TOF mass spectrometers(>25 per second) and the selectivity {resolution >10000)and sensitivity (10 fg) of a high resolution magn etic sectorinstrument- Jensen's 1972 Ambio paper The PCBStory^^ends w ith a compelling moral:

The accumulationo fPCBin nature was discoveredaccidentally as was mercurycontamination What conclusionscan bedrawn from these findings Similar discoverieso ftheaccumulationofother chemicals arequitelikely tooccurat

It isnecessary that responsible authorities invest in manpowan dequipmenttofacilitate an unbiased searchf orpollutantsan early stagebysystematicanalysis.These are the measures that shouldbetaken ifthe damaan dperhaps irremediable effectso fa substance areto bediscovered beforeand not afterithas entered theenvironmeThisappliesespecially to substances that accumulateand ahighlypersistent as we have learnt from the historyofPCBsUnfortunately, since 1972 there have been num eroustroubling discoveries of other chemicals in the environment,in humans and in wildlife. These include brominatedcompounds^^^*-' (polybrominaed diphenylethers,hexabrom ocyclododecane), ch lorinated compounds^^ ^-(chlorinated diphenyl ethers, Dechlorane Rus and otherDechlorane compounds) and fluorinated compou nds^^ '^(PFOS, PFOA).Regulations such as EU No 850/2004 and the StockholmAgreement have been d eveloped to reduce or eliminate theuse of toxic, persistent and bioaccumulative com pound sand redu ce levels of these com pounds in the environment.

Many countries have drafted or are in the process of dra ftingregulations directed toward the virtual elimination of thesecom pound s in the environment. Even so, the number ofchemicals used in commerce and industry increasesexponentially everyyear Many of these compounds andtheir degradation products find their way into the environmentenabling them to weave their way into every living thing.The ultimate goal wou ld be to develop analytical methodsthat can analyse all POPs in a single sample extract as well

Figure 8:GC - GC-TOF confirmation of terpherryts in abiosolid sample.


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as separateanddetect the toxic components at the lowfemtogramme levis.

Over the last century, the advancesinanalytical methodshave been extensive [Table 3{a) and Table 3(b)]. Single toxiccomponents canbe isolated from an indefinite numberofotherchemically similar compunds and accurately quantifiedat tracelevels. Detection limits have decreasedby over 10 ordersofmagnitude. Methods have become more sensitive and selective.Unfortunately, this has also resultedinanalysts often beingtoofocusedat looking for only their specific compoundsof interest.The newer methods: GCxGC and fast scanning detectorsshould enable ustolook atmany more compoundsin cur sampleextracts. We must develop these techniquesas an analyticaltriageto assess what hazardous compunds may be present inthe sample. There are many thousandsofhalogenated organicchemicals usedby man and many others that are producedasunintentional by-productsordegradation products that couldpotentiallybe more toxic than the parent compound. Consideringhow complex the environmental chemistry, fate and transportof these compounds are/^ it is vitaifriat we continuetoadvanceouranalytical methodstobetter enableus toscan theenvironment for persistent toxic organic compounds.

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Dr Eric Reiner is a senior mass spectrometry researchscientist at the Ontario Ministry of the Environment, CanadaHe also serves as an adjunct professor at the University ofToronto and at the University of Waterloo. He has over 20years experience in the analysis of halogenated persistentorganics.Dr Adrienne BodenIs a dioxin and toxic organics scientistat the Ontario Ministry of the Environment. Canada. Sheperformed her PhD studies in chemistry with a focus onenvironmental analysis at McMaster University. Her currentwork focuses on the GCxGC analysis of persistent toxicorganics,Tony Chens a senior toxics organic scientist at the OntarioMinistry of the Environment with 20 years experience in theanalysis of OC pesticides. PCBs and PAH.Karen MacPhersonis a senior dioxin scientist at the OntarMinistry of the Environment with more than 20 years ofexperience in the analysis of Dioxin-like compounds andbrominated flame retardants.Alina Muscatu MASc. is a toxic organics technologist at theOntario Ministry of Environment. She has 7 years experiencein the analysis of PCBs. OC Pesticides. She has been workin


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