Identification of impurities and statistical classification of methamphetamine

ForensicScienceInternational182(2008)13–19

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ForensicScienceInternational

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Identi cationofimpuritiesandstatisticalclassi cationofmethamphetaminehydrochloridedrugsseizedinChina

JianXinZhanga,*,DaMingZhanga,XuGuangHanb

ab

ForensicMedicalExaminationCenterofBeijingPublicSecurityBureau,Beijing,ChinaTheMinistryofPublicSecurityofthePeople’sRepublicofChina,China

ARTICLEINFOABSTRACT

Articlehistory:

Received27May2008

Receivedinrevisedform12September2008Accepted22September2008Keywords:

MethamphetaminehydrochloridePro lingofimpuritiesClusteranalysis

Atotalof48methamphetaminehydrochloridesamplesfromeightseizureswereanalyzedusinggaschromatography–massspectrometry(GC–MS)andgaschromatographywitha ameionizationdetector(GC–FID).

Majorimpuritiesdetectedinclude1,2-dimethyl-3-phenylaziridine,ephedrine/pseudoephedrine,1,3-dimethyl-2-phenylnaphthalene,1-benzyl-3-methylnaphthalene.Thesedataaresuggestiveofephe-drine/pseudoephedrineasthemainprecursorofthemethamphetaminehydrochloridesamplesseizedduring2006–2007.Additionallythepresenceof1,3-dimethyl-2-phenylnaphthalene,1-benzyl-3-methylnaphthaleneisindicativethatsixseizuresweresynthesizedviathemorespeci cephedrine/hydriodicacid/redphosphorusmethod.

Inaddition, veimpuritieswerefoundforthe rsttimeinmethamphetaminehydrochloridesamples.SeventeenimpuritypeakswereselectedfromtheGC–FIDchromatograms.Thepeakareasoftheselectedpeakswerethengroupedforclusteranalysis.

ß2008ElsevierIrelandLtd.Allrightsreserved.

1.Introduction

Duetotheincreasingnumberofdrugcases,aswellasthewideningglobalizationofillicitdrugs,lawenforcementagenciesworldwidehaveadoptedthestrategyofpro lingofdrugimpu-rities.DetailedimpurityinformationhasbeenreportedonthemethamphetaminedrugsseizedincountriessuchastheEuropeanCommission[1],Japan[2,3],Thailand[4],Korea[5,6],thePhilippines[7]andAustralia[8,9],wheremethamphetamineabuseisoneofthemostseriousdrugissues.

Theinformationobtainedcanbeusedtoestablishdrugtra-f ckingpatternsanddistributionnetworks,andtoidentifymethodsusedinthemanufactureofillicitdrugs.Methampheta-minehydrochlorideiscurrentlyoneofthemostwidelyusedillicitdrugsintheChina.However,intheopenliteraturestherehasbeenlittleinformationavailableonimpuritycharacteristicsorpro lingofmethamphetaminedrugseizuresinChina.

Themainobjectiveofthisworkistoobtainimpuritycharac-teristicsofthemethamphetaminehydrochloridedrugsandtoidentifysyntheticroutesandthetrendinrecentyearsproviding

forensicintelligenceproducttotheBeijingPublicSecurityBureau(BPSB)intelligencegroup.2.Materialsandmethods2.1.Samplepreparation

Methamphetaminehydrochloridecrystalsweregroundandhomogenized.Fiftymilligramsweredissolvedin1mLofbuffersolution(fourparts0.1MphosphatebufferofpH7.0andonepart10%,w/v,Na2CO3).Thesolutionwasextractedbyvibratingfor5minwith0.5mLofethylacetatecontainingfourn-alkanes(C10,C15,C20andC28)asinternalstandardsat0.02mg/L.Aftercentrifugingthesolutionfor5minat3000rpm,theorganiclayerwastransferredintoaglassinsertofGCmicrovialforautomaticsampling,and1mLwasinjectedontheGC–FIDandGC–MSanalysis.

2.2.Reagentsandchemicals

Bufferchemicals,sodiumdihydrogenphosphatedihydrate(NaH2PO4Á2H2O),disodiumhydrogenphosphatedodecahydrate(Na2HPO4Á12H2O)andsodiumcarbonate(Na2CO3),wereanalyticalgrade,sourcedfromBeijingChemicalReagentLtd.(China).HPLC

*Correspondingauthor.Tel.:+861062908966.

E-mailaddress:zhangjianxin7292000@(J.X.Zhang).

0379-0738/$–seefrontmatterß2008ElsevierIrelandLtd.Allrightsreserved.doi:10.1016/j.forsciint.2008.09.012

14J.X.Zhangetal./ForensicScienceInternational182(2008)13–19

gradeethylacetatesolventwassourcedfromTediaCompany,Inc.(USA).Internalstandards,n-alkanes(C10,C15,C20andC28),weresourcedfromFluka(USA).2.3.Dataanalysis

ProcessingofGC–FIDpeakareaswereperformedinGCChemstation(AgilentTechnologiesCo.)andExcel2003(MicrosoftCo.).ClusteranalysisandotherstatisticalcalculationswerecarriedoutinSPSS13.0(SPSS,Inc.).EachpeakareawascalculatedrelativetoIS3andcommonlogarithmsof1000timestheirrelativeareaswereusedforthecalculationofEuclideandistancebetweenthesamples,andtheclassi cationofthesampleswasvisualizedbyhierarchicalclusteranalysisviatheWardmethod.2.4.GCconditions

GCconditionsoftheGC–FIDandGC–MSwerethesame.Theoventemperaturewasprogrammedasfollows:initialtemperaturewas508Cheldfor1min,followedbyanincreaseof108C/minto3008C,andthenheldfor10min.Theinjectoranddetector(transferline)temperaturesweresetat230and3008C,res-pectively.Nitrogenwasusedasacarriergasataconstantcolumn owrateof2mL/min.Onemicroliteroftheextractswasinjectedinthepulsedsplitless(PS/L)mode.2.5.Instruments

MS2vibratingshaker(IKACo.,Chinamanufactory)wasusedforextractionoforganicimpurities,anda2420centrifuge(KUBOTACo.,Japan)wasusedforcentrifugation.Gaschromatographic(GC)analysiswascarriedoutonaHewlett-PackardHP6890NGCequippedwithanFIDandanHP7683automaticsampler.GC–MSanalysiswascarriedoutonaTraceGCUltraequippedwith

Table1

poundno.1234567891011121314151617181920212223242526272829

ab

aPolarisQmassselectivedetector(MSD)andanAS3000auto-maticsampler.TheMSDwasoperatedintheelectronimpact(EI)modeat70eV.Scanmodewasusedasanacquisitionmode,andthemassrangeswere35–450(m/z).TheGC–FIDandGC–MSwereequippedwithaDB-5capillarycolumn(30mÂ0.32mmÂ1.0mm lmthickness)(AgilentTechnologiesCo.,USA).3.Results

EightseizuresofmethamphetaminehydrochloridefromBPSBcapturedbetween2006and2007wereanalyzed.Typicallytheseizureswerecrystalsandhadapurityofmorethan95%.Eachofseizuresweighedover400gandbelongedtoabag.Thecontentsofeachselectedbag(seizure)weredividedintosixsamples.Thus,atotalof48sampleswereobtained.10gwereweighedoutfromeachsampleandcrushed.Fiftymilligramsweretakenforanalysis.Theeachsamplewasanalyzedthreetimestodeterminethevariabilitywithineachsampleandwhetherthesamplesfromthesamebag(seizure)belongtothesamebatch.Table1liststhemainimpuritiesfound,andtheircharacteristicMSionsfoundasaresultofGC–MSanalysis.ThenumbersassociatedwiththecompoundscorrespondwiththeannotatedpeaksinFig.1.

Theresultsshowthatgenerallyimpuritypro lesofmetham-phetaminesamplesinthesameseizureshowmoresimilaritiesthanthatindifferentseizures,

TypicalgaschromatogramsoftheethylacetateextractsofmethamphetaminesamplesareshowinFig.1.Peaks#1,#2,#4,#5,#7,#8,#9,#12,#15,#16,#18,#19,#21,#22and#23werecon rmedtobetoluene,benzaldehyde,cis-1,2-dimethyl-3-pheny-laziridine,1-phenyl-2-propanone/amphetamine,N-ethylampheta-mine,N,N-dimethylamphetamine,ephedrine/pseudoephedrine,N-acetylephedrine,3,4-diphenyl-3-buten-2-one,N,N-di-(b-phenyli-sopropyl)amine(twostereoisomers),1,3-dimethyl-2-phenyl-naphthalene,1-benzyl-3-methylnaphthalene,Me(a-Me-

Name

Toluene

BenzaldehydebIS1(C10)

cis-1,2-Dimethyl-3-phenylaziridineb1-Phenyl-2-propanone/amphetaminebUnknown

N-Ethylamphetamineb

N,N-DimethylamphetaminebEphedrine/pseudoephedrinebIS2(C15)Unknown

N-AcetylephedrinebUnknownUnknown

3,4-Diphenyl-3-buten-2-oneb

N,N-di-(b-Phenylisopropyl)amine(twostereoisomers)bIS3(C20)

1,3-Dimethyl-2-phenylnaphthaleneb1-Benzyl-3-methylnaphthalenebUnknown

Me(a-Me-Ph)amino-1-Ph-2-propanone(twostereoisomers)bBenzoylmethamphetamineb

N,N-di-(b-Phenylisopropyl)formamidebUnknownbUnknownbUnknownbUnknownbUnknownbIS4(C20)

RRta4.3278.5689.13411.32411.47213.32913.40813.74815.32316.43417.73317.92818.07918.79020.79721.39221.87122.93423.13523.28423.29023.38024.32225.17625.32226.29026.51326.60929.227

Majorions91,92

105,77,51,106146,146,44,72,72,58,91,58,117,70,178,91,217,217,91,91,105,91,115,58,168,168,168,

105,132105

150,72,9144,9191

77,105162,100118,128,179,162,

119,449144,91

221,222,152119,44

232,202,232,202

159,131,115

120,105,190,238,146162,77,91190,162,119249,178,26491,190

167,91,126167,91,126167,91,126

Relativeretentiontime.

TheseimpuritiesarementionedinRef.[8]for2,4,5,7–9,12,Ref.[1]for15,21,22,Ref.[9]for16,23,Ref.[5]for18,19,24–28.

J.X.Zhangetal./ForensicScienceInternational182(2008)13–1915

Fig.1.TypicalGC–FIDchromatogramsofthesamples.

16J.X.Zhangetal./ForensicScienceInternational182(2008)13–19

Table2

poundno.1467891112151618192425262728

Name

Toluene

cis-1,2-Dimethyl-3-phenylaziridineUnknown

N-Ethylamphetamine

N,N-DimethylamphetamineEphedrine/pseudoephedrineUnknown

N-Acetylephedrine

3,4-Diphenyl-3-buten-2-one

N,N-di-(b-Phenylisopropyl)amine1,3-Dimethyl-2-phenylnaphthalene1-Benzyl-3-methylnaphthaleneUnknownUnknownUnknownUnknownUnknown

Ph)amino-1-Ph-2-propanone(twostereoisomers),benzoyl-methamphetamineandN,N-di-(b-phenylisopropyl)formamidebyGC–MS,respectively,fromthecomparativeanalysisofrespectivepeakretentiontimeandmassspectraldatawiththoseofauthenticcompoundsorliteratures.Fig.2showsEImassspectraofpeaks#6,#11,#13,#14and#20,whicharenewimpuritiesfound.

Amphetamine,#2and#8areimpuritiesproducedintheprocessofextraction[10]orthepyrolysisproductsunderthehightemperatureofGCinjector[11,12].The1-phenyl-2-propanone(P2P)co-elutedwithamphetamine.

Afterexcludingtroublesomeandnon-characteristicpeaks,the17peaks(inTable2)wereselectedandwereappliedforclusteranalysis.Similarityand/ordissimilarityofthechromatographicpro lesbetweensampleswereevaluatedusingtheEuclideandistancesof17relativepeakareasaftercommon-logarithmictransformation.Fig.3showsthedistributionofdistancesbetweenthepro lesobtainedfromthesameseizure,aswellasthosefromdifferentseizures.Outof120pairsofintra-seizuredistances,noneoverlappedwiththerangeofinter-seizuredistances.Adendro-gramobtainedfromahierarchicalclusteranalysisof48samplepro lesalsoshowsthatthesameseizurepro leswerewellgrouped(Fig.4).Thesamplesfromthesamebag(seizure)possiblybelongtothesamebatch.Intra-andinter-laboratoryreproduci-bilityisnowinprogress.Itiswellknownthatthereareseveralstatisticalindicesforcomputerizedcomparison.Furtherstatisticalanalysesarecurrentlyunderinvestigation.4.Discussion

4.1.Optimizationofanalyticalprocedure

ThevalidityanduseofGCandGC–MSmethodologiesfortheanalysisofmethamphetaminedrugshavebeenwellcoveredinthe

literatureswithconsiderablemethodsdevelopmentandoptimi-zationreported.Theuseofthemediumborecolumnwith1mm lmthicknesswasjusti edbyInoueetal.[13].

Preliminaryexperimentswereperformedtooptimizetheanalyticalprocedure.TherearemanyartifactimpuritiesarisingfromthepreparationofsamplesandconditionsofGC.Moreover,someartifactsposeabarriertothestatisticalprocessingofmathamphetaminepro ling.SasakiandMakino[3]investigatedcapillaryGCanalysisusingpulsedsplitless(PS/L)injectiontominimizethethermaldecompositionofimpuritiesattheinjectionportandimprovethetransferofsamplesintothecolumn.TheeffectiveconditionsforPS/L-modewerecon rmedtobe2308Cand50psi.Thehighreproducibilityofthisanalyticalmethodthusenablesthereliabilityofstatisticalanalysistobeenhanced.

Fig.2.Massspectraofnewlyfoundimpurities:(a)peak6;(b)peak11;(c)peak13;(d)peak14;(e)peak20.

J.X.Zhangetal./ForensicScienceInternational182(2008)13–1917

Fig.2.(Continued

).

4.2.Identi cationofimpurities

Forimpuritieswithcerti edstandardsavailable,identi cationwasbasedonthematchofboththeretentiontimeandmassspectrumofanunknownpeakwiththatofthestandard.Thisapproachallowedtoluenetobeidenti edintheseizedsamples.Otherimpuritieswereidenti edviacomparisonwithknownliteraturesreports.Thus,themassspectrumandretentiontimeassociatedwith#2,#4,#5,#7,#8,#9,#12,#16and#23areconsistentwithdatareportedbyQietal.[8,9].Themassspectrumandretentiontimeassociatedwith#15,#21and#22areconsistentwithdatareportedbyDujourdyetal.[1].

Compounds#18and#19correlatewellwith1,3-dimethyl-2-phenylnaphthaleneand1-benzyl-3-methylnaphthalene,synthe-sizedbyLeeetal.[5]usinga-acetylphenylacetonitrilewithhydriodicacid/redphosphorus.Thecompounds#24,#25,#26,#27and#28werealsoobservedbyLeeetal.[5]

.

Fig.3.Distributionofdistancesbetweensamplepro lesfromintra-seizure(left)andbetweensamplepro lesfrominter-seizure(right),asmeasuredbyEuclideandistance.

18J.X.Zhangetal./ForensicScienceInternational182(2008)13–19

Fig.4.Dendrogramobtainedfromaclusteranalysisof48methamphetaminesampleimpuritypro lesfromeightdifferentseizures.

Exhaustiveliteraturessearchingandspectralanalysisfailedtoidentifycompoundsassociatedwithpeaks#6,#11,#13,#14and#20.Noevidenceofsimilarspectrawasfoundassociatedwithimpuritiesinmethamphetamineoranyothercommonillicitdrugs.Interestinglycompound#11hasthesamemajorionsas#16.

4.3.Routeidenti cation

Thesamplesareexpectedtoprovideimportantinformationtohelpwiththeidenti cationofsyntheticroutes.Determinationofthesyntheticrouteinmethamphetaminepro lingreliesontheidenti cationofkey,routespeci cmarkerimpuritycompounds.LeuckartreactionandreductiveaminationofP2Pandvariousroutesstartingfromephedrineorpseudoephedrinearethemostcommonlyusedmethodsinclandestinelaboratories[14–15].Characteristicsofimpuritiesinmethamphetamineovertheyearshavebeenutilizedtoidentifysyntheticroute.Whilethepresenceofephedrine/pseudoephedrinemayindicateasyntheticrouteviaephedrine,P2Pisanon-speci cmarkerforbothreductiveaminationandtheLeuckartreactionsinceitisalsoaby-productoftheephedrineroute[16].EvidentiallyP2Phasbeenfoundinmethamphetaminesynthesizedfromephedrine[17,18].Ephe-drine/pseudoephedrineappearedinFig.1(a),whichpresumablyindicatesanephedrineoriginofthissample.

Impuritiesconsistentwiththeephedrinerouteincluded1,2-dimethyl-3-phenylaziridine,1,3-dimethyl-2-phenylnaphthaleneand1-benzyl-3-methylnaphthalene.Thetwonaphthalenesareconsideredspeci coftheephedrine/hydriodicacid/redphos-phorusroute.

The1,2-dimethyl-3-phenylaziridinesareconsideredmarkercompoundsoftheephedrinerouteastheyarefoundonlyinmetha-mphetaminesynthesizedfromephedrine/pseudoephedrineandtheirformationiscloselyrelatedtoephedrineorpseudoephedrine.Itisproposedthatduringthesynthesis,thehaloephedrineinter-mediates(chloroephedrine,ifviatheEmderoute,oriodoephedrine,whenusinghydriodicacid/redphosphorus)undergoaninternalsubstitutionreaction,orringclosure,losingchlorineoriodinetoproducethecis-and/ortrans-aziridines[9,16,17].Thechromato-gramshowninFig.1(a)illustratesatypicalpro leofephedrineprecursorwithcis-1,2-dimethyl-3-phenylaziridinepresent.

Furthermore,accordingtoCantrelletal.[16],undertheacidicconditionsassociatedwiththehydriodicacid/redphosphorusmethod,theaziridinesundergoringopeningproducingtheP2Pintermediate,withsubsequentself-condensationanddehydrationoftwoP2Pmoleculesaffording1,3-dimethyl-2-phenylnaphtha-leneand1-benzyl-3-methylnaphthalene.GiventhattheP2P

intermediatedoesnotoccurundernon-acidicconditions,suchastheephedrinerouteviachloroephedrine,thenaphthalenesareconsideredcharacteristicsofthehydriodicacid/redphosphorusephedrineroute[16,17].Fig.1(a–cande)showsthepro leofamethamphetaminesamplessynthesizedviathisroute.

#16and#23areamongthemostcommonimpuritiesarisingviatheLeuckartrouteand/orreductiveamination[19].However,theyareidenti edinmethamphetaminecontainingexplicitephedrineroutemarkerssuchasaziridinesandnaphthalenes#18and#19.Itisinteresting,asshowninFig.1(a–cande),thatthepeakintensitiesofthenaphthalenes#18and#19increaseasthatofthe#16decreaseandviceversa.Thisvariationisparticularlysigni cant,foritseemsthatthetwotypesofimpuritiesaregeneratedfromcompetitiveprocesses[9].

Tosummarize,exceptfortwoseizureswehavebeenunabletoidentifythesyntheticroute,allotherseizurescontainevidencetheywereproducedviaephedrine/pseudoephedrine.Fromtheresultswecandeducetheconclusionthatephedrine/pseudoephe-drineistheprimarychemicalprecursorofmethamphetamineseizedinrecentyearsinchina.5.Conclusion

Thepresentmethodofferssuperiorseparationofimpuritiesinmethamphetaminehydrochloridecrystalsusingchromatographictechniques.The17peaksselectedwerecharacteristicanddiagnosticfortheclassi cationandcomparisonofchromatograms.TheEuclideandistanceof17relativepeakareasafterlogarithmictransformationwaseffectivefortheevaluationofsimilarityand/ordissimilarityofimpuritypro les.Thepreliminaryworkshowsthatitisveryusefulforgettingintelligencefrommethamphetamineimpuritypro ling.

Informationabouttheimpuritiesinmethamphetamineallowedidenti cationofthedrugsyntheticroutes.Inthedrugsmanufacturedviatheephedrineroutewherethemarkercompounds,theaziridinesornaphthalenes,werepresentdistinc-tively.However,insomecasesforthehighpuritymethamphe-tamine,thisinformationaloneisinsuf cienttoindicateanyspeci cclandestinemanufacturingroute.Weareactivelypursuingtheidentitiesoftheunknownimpuritiesviasyntheticapproachandwillreporttheoutcomesofoureffortsinduecourse.References

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