lonen, U.P. Karjalainen: Advances in Mass

B.V., Amsterdam

pounds by LR and ass Spectrometry

Jrgen H. Gross*eld 270, 69120 Heidelberg, Germany

49 6221/54-4205

session

nobenzenes and s-triazine aromaticse substitution of halogen atoms by

representing the structural types ofe been examined.

E.J. Karjalainen, A.E. Hesso, J.E. JaSpectrometry, Volume 14© 1998 Elsevier Science Publishers

POSTER B07 WEPO039

Analysis of Ferrocenyl ComHR Field Desorption M

Fred Siegler, Jens J. Wolff, Organisch-Chemisches Institut, Im Neuenheimer F

Tel.: +49 6221/54-8409, Fax: +

* present at poster

AbstractTris-ferrocenyl-substituted benzenes, s-tricyacompounds have been synthesized by stepwiferrocenylethinyl groups.

For this FD-MS study seven compounds ferrocenyl compounds under investigation hav

g., in case of extremelyhave been determined.ing spectra.

developed. Despite itsass values within a 5Ð

a successful synthesis,mental composition. to be the method ofthese ferrocenyl com-

MS, Mixture Analysis

eat interest because ofne, s-tricyanobenzene

tepwise substitution of

MS) [1], MALDI [2] andethods. During recent

s lost much popularity

In order to know about the limitations of the method, e.low solubility of potential analytes, the detection limits They were found to be in the low nanogram range for scann

A procedure for scanning mode HR-FD-MS has beeninherent difÞculties, HR-FD-MS turned out to yield reliable m7 mmu error range.

FD-MS was employed starting from a Þrst evidence for reaching to control of purity and to the establishment of ele

Field desorption mass spectrometry (FD-MS) provedchoice for the mass spectrometric characterization of pounds.

KeywordsField Desorption, Ferrocenyl Compounds, High Resolution

1 IntroductionTris-ferrocenyl-substituted aromatic compounds are of grtheir potential non-linear optical activity. Based on benzeand s-triazine such systems have been synthesized by shalogen atoms by ferrocenylethinyl groups (Fig. 1).

Matrix or solvent dependent techniques like FAB (LSIESI [3] are currently the most widespread soft ionization myears, Þeld desorption mass spectrometry (FD-MS) [4] ha

more demanding tech-

an background, FD-MStric characterization ofr a successful synthe-

emental composition. the different structuralig. 2, Table 1). The aim get an estimate of its

olubility in all solvents.nzyl alcohol or glyceroloor FAB spectra and inows FAB spectra of 4pectively.

00 to m/z 1500, LR-FD-Examples are the spec-selectively formed radi-

lly observed isotopic

because it is generally assumed to be an experimentally nique [5].

Nevertheless, due to its good sensitivity and its cleproved to be the method of choice for the mass spectromethe ferrocenyl compounds starting from a Þrst evidence fosis, reaching to control of purity and to establishment of el

For this FD-MS study seven compounds representingtypes under investigation have been examined in detail (Fwas to optimize the mass spectrometric procedure and tolimitations.

2 Results and discussion

2.1 Comparison to FAB-MSThe ferrocenyl compounds of interest are usually of low sEspecially, typical matrices used for FAB-MS like 3-nitrobeare not suited for this purpose. This gave rise to relatively pseveral cases even prevented the use of FAB-MS. Fig. 3 shand 6 which represent a relatively good and a bad case, res

2.2 LR-FD-MS scanning spectraBy scanning the instrument over a mass range from m/z 1MS yielded the basic information about reaction products. tra of 2 and 5 (Fig. 4 and Fig. 5, respectively). All samples cal cations, M+., under FD conditions. The experimenta

ic patterns are clearly

alitative level. Unfortu-fferences in desorptioncial mixtures under vir-ratios of these compo-

D-MS spectra, the qual-ot could be made downved to be useful for the of 1 + 2 + 4 in the ratiotopic patterns are fullys worth to compare this

hat it is helpful to knowimits have been deter- repeated on differentund 4 can be detectedan 10. In Fig. 9 two lev-

tative reproducibility ofge. But nevertheless,

patterns perfectly match the calculated ones. The isotopreproduced in the weak M2+ signals.

2.3 Mixture analysisFD-MS did only allow for the analysis of mixtures on a qunately, quantitative results could not be obtained due to dibehavior. It turned out that repeated measurements of artiÞtually identical conditions yielded signiÞcantly different nents for different runs (Table 2).

While quantitative results could not be obtained from Fitative decission whether another compound is present or nto the 1% level. Especially the clean background of FD prodetection of impurities. Fig. 6 shows the mixture consisting15:15:1000. The minor components may be identiÞed; isoresolved. Fig. 7 gives an example of a Òreal-lifeÓ mixture. It iwith the corresponding FAB spectrum (Fig. 3b).

2.4 Detection limitsIn unfortunate cases, the solubility might become so low tabout the detection limits of the method. The detection lmined using compound 4. The measurements have beendays. The graph of Fig. 8 clearly demonstrates that compoeven at the 0.1 ng level with a signal-to-noise (S/N) better thels of S/N are visualized. According to the moderate quantithe measurements, S/N varies over a relatively wide ran

ram range for scanning

has been developed.que [6], this approachnalyte. By use of poly-

shows a portion of theinly caused by the low

alues within a 5Ð7 mmulerating voltage scans

apan) of BE geometry,

µL of theses solutions (Linden Chromaspec,easurements, the emit-d been completely des-ll as emitter damage bys reduced when a good

detections limits may be considered to be in the low nanogspectra in any case.

2.5 High-resolution FD-MSA procedure for HR-FD-MS of the ferrocenyl compoundsWhile older approaches used the peak matching technimakes use of the co-desorption of internal standard and aethylen glykols, scanning spectra can be obtained. Fig. 10FD-HR-MS of 1. Despite its inherent difÞculties that are maion currents, HR-FD-MS turned out to yield reliable mass verror range. Both, medium range magnet scans and accehave been tested for this purpose.

3 ExperimentalWe used a Jeol JMS-700 sector instrument (Jeol, Tokyo, Jequipped with an FD/FI ion source.

For FD-MS the analytes were dissolved in CH2Cl2. 1Ð2were applied to the activated 13 µm tungsten emittersLeeste, Germany) using a microliter syringe. During the mters were heated at a rate of 4Ð8 mA/min until the analyte haorbed. To prevent thermal degradation of the analyte as weÞeld-induced discharge, sometimes the rate of heating walevel of desorption/ionization had been reached.

uning the instrument inwas scanned from m/z

ed. At R=1000 the mag-

e way. The scan range lowered. Alternatively,d. internal calibration. Forther with the analyte to obtain signals of simi-eadjustment of the sig-rbing PEG close to the

tion process, not only

ed into the mass refer-

sents the only desorp-yte without interference

For routine LR-FD-MS resolution was set to R=1500 by tthe FI mode on the molecular ion of toluene. The magnet 100Ð1500 in about 10 s.

For sensitivity determinations compound 4 has been usnet was scanned from m/z 100Ð1000 in about 10 s.

For HR-FD-MS resolution was set to R=5000 in the samwas reduced to about M±200 u and the scanning rate wasHV scanning with comparable scanning rates was employe

Polyethylene glycol (PEG 400 or PEG 600) was used forthis purpose, a solution of PEG in ethanol was applied togethe Þeld emitters. The analyte/PEG ratio was adjusted as tolar intensity for both compounds. Between measurements rnal was achieved by Þne tuning on peaks from Þeld desoexpected molecular mass.

Due to the changing PEG spectrum during the desorp[PEG+Na]+ but also [PEG+H]+ signals had to be incorporatence Þle.

4 ConclusionFD-MS is still a very valuable ionization method. FD repretion/ionization technique that allows desorption of the analwith any matrix compound or solvent effects.

Soc., Chem. Commun. 324,N. Tyler, Anal. Chem. 654A,ersley, M. Morris, L. Tetler,

, Org. Mass Spectrom. 805,

. Chem. 805, 101, 1989. b) 1991. c) R. C. Beavis, Org.ard, M. W. Duncan, Rapid.

seth, Anal. Chem., 882, 62,

n Mass Spectrometry, Per-metry, Marcel Decker, New

ley, Chichester, 1993.

1973. b) H.-R. Schulten, D.. D. Lehmann, Anal. Chim.

References[1] Liquid matrix for FAB: a) D. J. Surman, J. C. Vickerman, J. Chem.

1981. b) M. Barber, R. S. Bordoli, G. C. Elliot, R. D. Sedgwick, A. 54, 1982. 3-NBA as versatile matrix: M. Barber, D. Bell, M. EckRapid Commun Mass Spectrom. 18, 2, 1988. Review: J. Sunner28, 1993.

[2] General: a) M. Karas, U. Bahr, A. Ingendoh, F. Hillenkamp, AngewM. Karas, U. Bahr, U. Gie§mann, Mass Spectrom. Rev. 225, 10,Mass Spectrom. 653, 27, 1992. Low molecular weight: R. LidgCommun. Mass Spectrom. 128, 9, 1995.

[3] R. D. Smith, J. A. Loo, C. E. Edmonds, C. G. Barinaga, H. R. Ud1990.

[4] a) H. D. Beckey, Principles of Field Ionization and Field Desorptiogamon, Oxford, 1977. L. Prokai, Field Desorption Mass SpectroYork, 1990.

[5] J. R. Chapman, Practical Organic Mass Spectrometry, p. 211, Wi

[6] a) H.-R. Schulten, H. D. Beckey, Org. Mass Spectrom. 861, 7, Kmmler, Anal. Chim. Acta 153, 113, 1980. c) H.-R. Schulten, WActa 19, 93, 1976.

f 1Ð7.

Average isotopic mass

444.0

573.1

620.1

702.2

777.3

705.2

633.1

Table 1: Elemental composition and molecular weight o

Sample FormulaBasepeak of

isotopic pattern

1 C18H12FeBr2 443.8637

2 C30H21Fe2Br 571.9529

3 C30H21Fe2I 619.9388

4 C42H30Fe3 702.0398

5 C45H27Fe3N3 777.0256

6 C39H27Fe3N3 705.0256

7 C33H37F3N3 633.0255

artiÞcial mixtures.

Ratio exp.

2/4

1/3.7

1/12

1/1.5

1/1.2

1/2.6

1/1

1/3

1/11

1/3.6

1/1.2

1/2.9

1/3.9

1.64/1

Table 2: Theoretical and experimental ratios found from

Mixture Ratio theor.

2+4 2/4

1/10

1/10

1/2

1/2

1/1

1/1

1+3 1/3

1/10

1/2

1/1

1/1

1/1

2/1

Figure 1

Synthesis by Hagihara reaction.

Figure 2

The ferrocenyl compounds used in this study.

Figure 3

FAB spectra of 4 and 6 which is badly soluble in 3-NBA.

(Continues)

Figure 3. (cont.)

Figure 4

FD spectrum of 2.

Figure 5

FD spectrum of 5.

Figure 6

FD spectrum of an artiÞcial mixture consisting of 1, 2 and 4.

Figure 7

FD spectrum of a Òreal-lifeÓ mixture from a reaction that was intended to yield 6.

Figure 8

Plot of signal-to-noise ratio vs. amount of sample.

Figure 9

Visualization of two S/N ratios (cf. preceeding page for part 1).

(Continues)

Figure 9

(cont.)

Figure 10

HR-FD-MS scanning spectrum of 1.

Poster B07 WePo039Analysis of Ferrocenyl Compounds by LR and HR Field Desorption Mass SpectrometryFred Siegler, Jens J. Wolff, Jürgen H. Gross*1 Introduction2 Results and discussion2.1 Comparison to FAB-MS2.2 LR-FD-MS scanning spectra2.3 Mixture analysis2.4 Detection limits2.5 High-resolution FD-MS

3 Experimental4 Conclusion