24 Spectroscopy Europe 10/3 (1998)

TONY DAVIES COLUMN

IntroductionThis column has not dealt with mass

spectrometric issues since 1991–3.1

This five year lapse needs to beredressed and the recent release of theNIST’98 mass spectral library seemed agood opportunity.

At a recent meeting at NIST inWashington I had the pleasure ofmeeting with Gary Mallard and SteveStein who are amongst the staff respon-sible for the new NIST’98 release ofthe NIST/EPA/NIH Mass SpectralLibrary.2 The new release has beenextensively updated, quality controlledand is far larger than earlier versions.There is now a series of helpful utilitiesshipped with the package amongstwhich is a powerful program called theAutomated Mass SpectrometryDeconvolution and IdentificationSystem (AMDIS) written for analysingGas Chromatography (GC) or LiquidChromatography (LC) ElectronIonisation Mass Spectral data sets.

This new program has been devel-oped using US government funds overa two year period to provide a badlyneeded resource for policing theChemical Weapons Convention.3 Theaim of the development was to providebetter analysis interfaces for GC/MSand LC/MS data sets. An additionalmodule was provided by the Ministryof Defense of Israel which providesadditional “match factors” for makingchemical identifications.

Six speciality target libraries areinstalled which consist of selected spec-tra from the 130,000 in the fullNIST/EPA/NIH library:

NISTCW is 62 chemical-weaponsrelated data sets,NISTDRUG is 778 drug analysisspectra,NISTEPA is 1106 EnvironmentalProtection Agency (EPA) targetcompounds,NISTFDA 419 for Food andDrug Administration (FDA) analy-ses,

NISTTOX 1251 spectra toxico-logical library,NISTFF 993 flavours and fra-grances

How it worksThe program analyses individual sin-

gle ion chromatograms to identifyautomatically possible componentpeaks within the GC/MS data set. Allof the masses which are identified ashaving the same chromatographic char-acteristics are then put forward as theunknown spectrum for a spectral searchwithin a selected target library (Figure1).

The chromatographic trace at thetop if the figure has a number of smallmarkings along the upper border(Figure 2.) The “▼” shapes indicatecomponents located and the “T” abovethese components indicates that one ormore substances in the target library fitthe component mass spectrum. By

clicking on either the component ortarget symbol it is possible to see the

The new Automated MassSpectrometry Deconvolution andIdentification System (AMDIS)

Antony N. DaviesISAS, Institut für Spektrochemie und Angewandte Spektroskopie, Dortmund, Germany.

Figure 1. This is the AMDIS user interface. The data set is a GC/MSanalysis of a round-robin sample of milk powder contaminated witheight chlor-organic pesticides at a concentration of 4 ng mL –1. Thetarget database is the EPA.

Figure 2. A cut out of Figure 1showing the four chromatogra-phy peaks around 17 minutesand the symbols indicating thatAMDIS has located components“ ▼▼” and has hits from the targetdatabase “T”.

relevant mass spectral data sets. Theactive symbol then turns red.

The mixture of black and whitepeaks are the scan data and the extract-ed spectrum (white) and secondly(lower trace) the target database hit andthe extracted spectrum (white) (Figure3).

The complete result report can beviewed within another component ofthe package (Figure 4) and printed outin Analysis Reports complete with rel-evant QA/QC data (Figure 5).

The test data set shown in Figure 1 isfrom a GC/MS round-robin experi-ment into the analysis of contaminatedmilk powder. Eight organo-chlorinepesticides were in the samples at con-centration around 4 µg µL–1. Using the

EPA target library and the standard set-tings 10 different components werefound, however, for the chromatogra-phy peaks at 16.0 and 30.7 minutestwo different components were locatedwithin each peak but were identified asthe same compound.

A peak was identified at 24.4 min-utes as a plasticiser contaminant and theEndrin peak at 31.84 minutes waslocated but as Endrin was missing fromthe target library and as no similar

compounds were found no hit was reg-istered.

Figure 6 is a report constructed byexporting text via the clipboard into aword processing package. Informationin the AMDIS reports view relating tothe first hits and their synonyms iscombined with the chromatographicpeak retention time along with thecorrect pesticide identification provid-ed by the user.

AMDIS had succeeded in identifyinga component spectra at 31.78 minutesbut unable to identify it. The next stepwas to take the unknown componentspectrum extracted by AMDIS and,having added it to a search list, transferit to the full NIST’98 database. Thiswas singularly unsuccessful with Endrinonly appearing at rank 12 in the hit list.However, using the hybrid searchoption combining the standard similari-ty search with a neutral loss search pro-moted Endrin to third in the hit list.This unspectacular performance onEndrin is apparently (according to ourmass spectroscopists) down to the poornature of the mass spectrum recordedhere with little isotopic informationessential to achieving good databasesearch results.

To give AMDIS a better chance offinding all our substances, a new targetdatabase was created combining theEPA and FDA libraries and the Endrinspectrum exported from the NIST’98database.

This proved the old adage that if“you know beforehand what you arelooking for you are sure to find it” inmass spectrometry and as can be seenin Figure 7 the missing peak is now

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TONY DAVIES COLUMN

Figure 3. A cut out of Figure 1showing the original scan datain black and the extracted com-ponent spectral data based onthe AMDIS analysis.

Figure 4. The AMDIS results interface. The text windows can becopied using windows clipboard which helps in making up userreport sheets such as shown in Figure 6.

AMDIS GC/MS Analysis Report - Data:D:\DATA\MAMPE13.FIN Page 001AMDIS GC/MS Analysis ReportOrganization: ISAS DortmundDivision: Organic AnalysisData: MAMPE13.DLibrary: D:\Programme\AMDIS32\LIB\Nistepa.mslNumber of Identifications: 10RT(min) Hits Chemical Name16.014 4 ??? Cyclohexane, 1,2,3,4,5,6-hexachloro-, (1.alpha.,2.

??? Cyclohexane, 1,2,3,4,5,6-hexachloro-, (1.alpha.,2.??? Cyclohexane, 1,2,3,4,5,6-hexachloro-???Cyclohexane, 1,2,3,4,5,6-hexachloro-, (1.alpha.,2.

16.025 2 ??? Cyclohexane, 1,2,3,4,5,6-hexachloro-, (1.alpha.,2.??? Cyclohexane, 1,2,3,4,5,6-hexachloro-, (1.alpha.,2.

16.401 ? Benzene, hexachloro-17.700 5 ? Cyclohexane, 1,2,3,4,5,6-hexachloro-, (1.alpha.,2.

? Cyclohexane, 1,2,3,4,5,6-hexachloro-, (1.alpha.,2.??? Cyclohexane, 1,2,3,4,5,6-hexachloro-???Cyclohexane, 1,2,3,4,5,6-hexachloro-, (1.alpha.,2.??? Cyclohexane, 1,2,3,4,5,6-hexachloro-, (1.alpha.,2.

18.002 5 ? Cyclohexane, 1,2,3,4,5,6-hexachloro-, (1.alpha.,2.?? Cyclohexane, 1,2,3,4,5,6-hexachloro-, (1.alpha.,2.??? Cyclohexane, 1,2,3,4,5,6-hexachloro-???Cyclohexane, 1,2,3,4,5,6-hexachloro-, (1.alpha.,2.??? Cyclohexane, 1,2,3,4,5,6-hexachloro-, (1.alpha.,2.

24.391 ??? Di-n-butyl phthalate30.541 ??? Dieldrin30.778 Benzene, 1,1’-(dichloroethenylidene)bis[4-chloro-30.789 Benzene, 1,1’-(dichloroethenylidene)bis[4-chloro-35.419 2 ??? Benzene, 1,1’-(2,2-dichloroethylidene)bis[4-chloro

??? Benzene, 1-chloro-2-[2,2,2-trichloro-1-(4-chloroph

Figure 5. A section taken from the results report printout. This clearlyshows the problems of identifying various hexachlorocyclohexaneisomers by mass spectral data alone!

correctly identified. Even thoughAMDIS identifies our “mystery peak”it shows it is not happy by writing“???Endrin” as the hit identification. InAMDIS speak it doesn’t come muchlower down the hit rankings and stillget shown!

ConclusionsThis has been a short article on one

of the features which have appeared in

the NIST’98 new release of theNIST/EPA/NIH Mass SpectralLibrary. Here we fed some very toughsample data into the program whichwas not set up to identify most of thecompounds we were interested in. Alater test using phenoxy alkanoic acidpesticides from spiked drinking watersamples was even less successful untilwe expanded our target library afterwhich all of our compounds werelocated and identified by AMDIS evenwhere co-elution was taking place.

The best testers of new software sys-tems are the people who work in thelabs and who have to use them on aregular basis. The constant commentcoming back from the people testingthis installation was “why couldn’t wehave had this system last year when......”! The 32 bit system running underWindows NT4 was completely stableand quick, the 16 bit version runningunder Windows 3.11 failed to readonly one of the data sets we presented.

We are still only starting to play withthis tool but I think the number of fea-tures which are being discovered dailyand acclaimed by our staff places this asone of their firm favourites.

Readers may be interested in a newspectrum viewer/plugin that will short-ly be available under:

http://www.labcontrol.com/ViewP.htm

although at the time of going to pressthe page was still under construction!

We would be grateful to receive anyexperiences you may have had usingspectroscopic data standards especiallywith web software. E-mail todavies@isas-dortmund.de

References1. Kurt Varmuza and Antony N.

Davies, “A Software Tool forRecognising Hidden Relationshipsbetween Mass Spectra andChemical Structures”, SpectroscopyInternational 3(4), 14–17 (1991).and A.N. Davies, “MassSpectrometric Data Systems”,Spectroscopy Europe 5(1), 34–38(1993).

2. NIST’98 Release of theNIST/EPA/NIH Mass SpectralLibrary is significantly expandedover previous versions with129,136 spectra and almost com-plete coverage with chemicalstructures. For more general infor-mation please contact: StandardReference Data Program, NationalInstitute of Standards andTechnology, Bldg 820, Rm 113, Gaithersburg, MD 20899-0001, USA. Te:l +1-301-975-2208,Fax: +1-301-926-0416, E-mail:srdata@nist.gov. The scientificcontact for the database is: StephenE. Stein, Mass Spectrometry DataCenter, National Institute ofStandards and Technology,Gaithersburg, MD 20899-0001,USA. Tel: +1-301-975-2505, Fax:+1-301-975-3670, E-mail:steve.stein@nist.gov or W. Gary Mallard, A111/221Chemical Reference Data andModelling Group NIST,Gaithersburg, MD 20899, USA.

26 Spectroscopy Europe 10/3 (1998)

TONY DAVIES COLUMN

PEAK 1 (16.014) alpha-HCH.alpha.-Lindane------------------------- Synonyms ------------------------- Cyclohexane, 1,2,3,4,5,6-hexachloro-,(1.alpha.,2.alpha.,3.beta.,4.alpha.,5.beta.,6.beta.)- Cyclohexane, 1,2,3,4,5,6-hexachloro-, .alpha.- .alpha.-Benzene hexachloridePEAK 2 (16.0254).alpha.-Lindane------------------------- Synonyms ------------------------- Cyclohexane, 1,2,3,4,5,6-hexachloro-,(1.alpha.,2.alpha.,3.beta.,4.alpha.,5.beta.,6.beta.)- Cyclohexane, 1,2,3,4,5,6-hexachloro-, .alpha.- .alpha.-Benzene hexachloridePEAK 3 (16.401) HCBBenzene, hexachloro-------------------------- Synonyms ------------------------- Amatin; Anticarie; Bunt-cure; Bunt-no-more; Co-op Hexa; Hexachlorobenzene; HCB; Julin's Carbon chloride; No Bunt;

PEAK 4 (17.700) beta-HCH.delta.-Lindane ------------------------- Synonyms ------------------------- Cyclohexane, 1,2,3,4,5,6-hexachloro,(1.alpha.,2.alpha.,3.alpha.,4.beta.,5.alpha.,6.beta.)- Cyclohexane, 1,2,3,4,5,6-hexachloro-, .delta.- .delta.-(Aeeee)-1,2,3,4,5,6-Hexachlorocyclohexane .delta.-Benzene hexachloride; .delta.-BHC .delta.-Hexachlorocyclohexane .delta.-HCH; .delta.,1,2,3,4,5,6-Hexachlorocyclohexane Cyclohexane, .delta.,1,2,3,4,5,6-hexachloro-PEAK 5 (18.002) gamma-HCH.delta.-Lindane------------------------ Synonyms ------------------------- Cyclohexane, 1,2,3,4,5,6-hexachloro-,(1.alpha.,2.alpha.,3.alpha.,4.beta.,5.alpha.,6.beta.)- Cyclohexane, 1,2,3,4,5,6-hexachloro-, .delta.- .delta.-(Aeeee)-1,2,3,4,5,6-Hexachlorocyclohexane .delta.-Benzene hexachloride; .delta.-BHC .delta.-Hexachlorocyclohexane .delta.-HCH; .delta.,1,2,3,4,5,6-Hexachlorocyclohexane Cyclohexane, .delta.,1,2,3,4,5,6-hexachloro-

PEAK 6 (24.391) plasticiser contaminationDibutyl phthalate ------------------------- Synonyms ------------------------- 1,2-Benzenedicarboxylic acid, dibutyl ester Phthalic acid, dibutyl ester n-Butyl phthalate; Butyl phthalate; Celluflex DPB Elaol; Genoplast B; Hexaplas M/B; Palatinol CPEAK 7 (30.541) dieldrinDieldrin ------------------------- Synonyms ------------------------- 2,7:3,6-Dimethanonaphth[2,3-b]oxirene, 3,4,5,6,9,9-hexachloro- 1a,2,2a,3,6,6a,7,7a-octahydro-,(1a.alpha.,2.beta.,2a.alpha.,3. Beta.,6.beta.,6a.alpha.,7.beta.,7a.alpha.)- 1,4:5,8-Dimethanonaphthalene, 1,2,3,4,10,10-hexachloro-6,7- epoxy-1,4,4a,5,6,7,8,8a-octahydro-, endo,exo- exo-Dieldrin; Aldrin epoxide; Alvit 55; Dieldrex Dielmoth; Dildrin; DorytoxPEAK 8 (30.778) p,p'-DDEp,p'-DDE ------------------------- Synonyms ------------------------- Benzene, 1,1'-(dichloroethenylidene)bis[4-chloro- Ethylene, 1,1-dichloro-2,2-bis(p-chlorophenyl)- p,p'-(Dichlorodiphenyl)dichloroethylene DDE; 1,1-Dichloro-2,2-Bis(p-chlorophenyl)ethylene 1,1-Dichloro-2,2-di(p-chlorophenyl)ethylene 2,2-Bis(4-chlorophenyl)-1,1-dichloroethylene 4,4'-DDE ; 2,2-Bis(p-chlorophenyl)-1,1-dichloroethylenePEAK 9 (30.789)p,p'-DDE ------------------------- Synonyms ------------------------- Benzene, 1,1'-(dichloroethenylidene)bis[4-chloro- Ethylene, 1,1-dichloro-2,2-bis(p-chlorophenyl)- p,p'-(Dichlorodiphenyl)dichloroethylene; DDE 1,1-Dichloro-2,2-Bis(p-chlorophenyl)ethylene 1,1-Dichloro-2,2-di(p-chlorophenyl)ethylene 2,2-Bis(4-chlorophenyl)-1,1-dichloroethylene 4,4'-DDE; 2,2-Bis(p-chlorophenyl)-1,1-dichloroethylenePEAK 10 (35.419) p,p'-DDT1,1-Dichloro-2,2-bis(p-chlorophenyl)ethane------------------------- Synonyms -------------------------Benzene, 1,1'-(2,2-dichloroethylidene)bis[4-chloro-Ethane, 1,1-dichloro-2,2-bis(p-chlorophenyl)-p,p'-(Dichlorodiphenyl)dichloroethanep,p'-DDD; p,p'-TDE; DichlorodiphenyldichloroethaneDilene; DDD; ME1700

Figure 6. The retention times reference substance identification andsynonyms for the proposed best hits in the target EPA library.

Figure 7. The hits results improve when the Endrin spectrum expect-ed around 31.7 minutes is actually represented in the target database!

Tel : +1-301-975-2564, Fax:+1-301-975-3670, E-mai l :gary.mallard@nist.gov.

3. The Chemical WeaponsConvention Website is athttp://www.opcw.nl/ The web-site is run by the TechnicalSecretariat of the Organisation forthe Prohibition of ChemicalWeapons and provides not onlyinformation on the ChemicalWeapons Convention but also onother issues relating to toxic chem-icals and chemical protection.

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