The Fragmentation of Amine Cluster Ion Including Hcl Proton A$Nities Of

J. Mass Spectrom. Soc. Jpn. Vol. 51, No. 1, 2003

REGULAR PAPER

The Fragmentation of Amine Cluster Ion Including HClῌ ῌProton A$nities of Drugs of Abuseῌ

Shigeki M6IHJBJG6,῎a) Hideyuki T6@:O6L6,b) and Kimio IH6b)

(Received September 24, 2002; Accepted October 23, 2002)

ῌ The fragmentation of the cluster ion, [A1῎HCl῎A2῎H] of amine bases A1 and A2,isstudied by the BEBE ῌ type tandem mass spectrometer. The cluster ion, [A1῎HCl῎A2῎H] ,isgenerated by the fast atom bombard- ment (FAB) ionization of mixture of two hydrochlorides of amines. The precursor ion is selected by the ﬁrst analyzer (BE) and the product ions are scanned by the second analyzer (B/E linked scanning). The fragmentation ῌ ῌ ῌ of [A1῎HCl῎A2῎H] yields two protonated monomers, [A1῎H] ,[A2῎H] ,and protonated heterodimer, [A1῎ ῌ ῌ ῌ ῌ H῎A2] .The relative abundances of [A1῎H] and [A2῎H] from the fragmentation of [A1῎HCl῎A2῎H] are found to be related to their relative proton a$nities and are used to determine the proton a$nities (PAs) of methamphetamine and its analogs. The PA of methamphetamine is estimated to be 965 kJ/mol.

ylamines.3) However, the PAs of drugs of abuse are not 1. Introduction reported yet as far as we know. Methamphetamine is the most commonly abused of The kinetic method developed by Cooks et al.isused this class of drugs in both the United States and Japan. to determine the PA values of various compounds.3)῍10)

In some European countries there is a greater problem In the kinetic method, the relative abundance of [A1῎ ῌ ῌ with abuse of amphetamine and/or the synthetic ana- H] and [A2῎H] from the fragmentation of a proton ῌ logs: 3,4-methylenedioxyamphetamine (MDA), 3,4- bound heterodimer, [A1῎H῎A2] ,shows the PA dif- methylenedioxymethamphetamine (MDMA), and 3,4- ference between compounds A1 and A2.PAvalue of A1 methylenedioxy-N-ethylamphetamine (MDEA), they may be obtained when PA of A2 is known. are often seized by the law enforcement agencies in In the previous paper, we showed that the fragmen- Japan these days. tation of [M῎HCl῎M῎H]ῌ yields [M῎H]ῌ and [M῎H Mass spectrometry, and in particular gas chromatog- ῎M]ῌ (a HCl loss) and discussed the behavior of the raphy/mass spectrometry (GC/MS), is being ex- product ions.9) tensively used for the detection and analysis of drugs In this work, we present the fragmentation of [A1῎ ῌ of abuse and their metabolites in body fluids. The HCl῎A2῎H] and the relation between the relative ῌ ionization method for GC/MS is mostly electron ioniza- abundances of [A1῎H]῎ and [A2῎H] from the frag- ῌ tion (EI), however, chemical ionization (CI) is often used mentation of [A1῎HCl῎A2῎H] and PA di#erences to confirm the molecular weight. In recent years, liquid between A1 and A2.The PAs of methamphetamine and chromatography/mass spectrometry (LC/MS) using its analogs are also discussed. atmospheric pressure chemical ionization (APCI) or 2. Experimental electrospray ionization (ESI) method has become one of the important techniques for trace analysis of drugs 2.1 Materials of abuse. In CI, APCI, and even in ESI, analyte charging Glycerol (FAB matrix) was purchased from Kanto in the gas phase occurs through gas-phase proton- Chemical Co., Inc. Methamphetamine hydrochloride transfer reactions. Therefore, the measurements of was purchased from Dainippon Pharmaceutical Co., proton a$nity (PA) values of drugs of abuse seem to be Ltd. Amphetamine sulfate, 3,4-methylenedioxymeth- more interesting. The proton a$nities (PAs) of many amphetamine (MDMA) hydrochloride, 3,4-methylene- compounds have been measured and reported.1), 2) Car- dioxy-N-ethylamphetamine (MDEA) hydrochloride, doso et al.recently reported the PAs of some phenylalk- and dimethylamphetamine hydrochloride were sup- plied from National Research Institute of Police Sci- ῎a) 福井県警察本部科学捜査研究所 ῌῌ910῍8515 福井市大手 ence. Other chemicals were analytical grade and pur- 3῍17῍1῍ chased from Wako Pure Chemical Industries, Ltd. All Forensic Science Laboratory, Fukui Prefectural Police compounds were used without further purification. PA Headquarters (3῍17῍1Ohte, Fukui 910῍8515, Japan) values are taken from ref. 1. b) ῌῌ ῍ 福井大学教育地域科学部理科教育 910 8507 福井市文 2.2 FAB mass spectrometry 京 3῍9῍1῍ Natural Science Education Laboratory, Faculty of Educa- Mass spectrometric measurements were performed tion and Regional Studies, Fukui University (3῍9῍1 with a JEOL JMS-700T tandem mass spectrometer Bunkyo, Fukui 910῍8507, Japan) (BEBE type) operating under positive ion FAB condi-

῏ Congratulations on winning the 2002 Nobel Prize Dedicated to Dr. John B. Fenn, awarded the 2002 Nobel Prize in Chemistry, in recognition of his great contributions to mass spectrometry and development of methods for identiﬁcation and structural analyses of biological macromolecules.

ῌ196ῌ ῌ The Fragmentation of [M1ῌHClῌM2ῌH] (M1,M2῍Amines)

Fig. 1. FAB mass spectrum of the mixture of methylamine (A1)and ethylamine (A2).

ῌ Fig. 2. MI spectra (A) and CAD spectra (B) of [A1ῌHClῌA2ῌH] ions from the mixture of (a) methylamine (A1)and

ethylamine (A2), (b) ethylamine (A1)andn-butylamine (A2), (c) dimethylamine (A1)and trimethylamine (A2), and (d)

diethylamine (A1)and triethylamine (A2). tions (Xe beam of 6 keV translational energy, gun cur- experiments were obtained in the third ﬁeld-free region rent 3 mA). Collisionally activated dissociation (CAD) of the instrument. All samples (hydrochlorides unless

ῌ197ῌ S. Matsumura, H. Takezawa, and K. Isa

Table 1. Proton A$nities of Reference Bases and ῌ ῌ ln ([A1H] /[A2H] )inFragmentation of ῌ [A1HClῌA2H] from Mixture of Metham-

phetamine (A1)and Reference Bases (A2)

ῌ a) ln([A1H] / Reference bases (A2)PA(kJ/mol) ῌ [A2H] ) Methylamine 896 4.20 Ethylamine 908 3.51 n-Butylamine 914 2.85 Dimethylamine 923 3.12 N,N-Dimethylamine 935 1.41 Trimethylamine 942 1.82 Diethylamine 945 2.01 Piperidine 947 1.64 Di-n-propylamine 952 0.70 ῌ ῌ Di-n-butylamine 956 0.12 Fig. 3. ln([A1H] /[A2H] ) vs.PA(A2)forthe CAD of ῌ N,N-Dimethylisopropylamine 961 0.11 [A1ῌHClῌA2ῌH] from the mixture of meth- Triethylamine 972 ῍0.82 amphetamine (A1)and reference bases (A2). a) From ref. 1.

ῌ Fig. 4. MI spectra (A) and CAD spectra (B) of [A1ῌHClῌA2ῌH] ions from the mixture of (a) 2-phenylethylamine (A1)

and amphetamine (A2), (b) amphetamine (A1)and methamphetamine (A2), (c) methamphetamine (A1)and ephedrine

(A2), (d) ephedrine (A1)and MDMA (A2), (e) MDMA (A1)and MDEA (A2), (f) MDEA (A1)and dimethylamphetamine

(A2), and (g) dimethylamphetamine (A1)and methoxyphenamine (A2).

ῌ198ῌ ῌ The Fragmentation of [M1ῌHClῌM2ῌH] (M1,M2῎Amines) stated otherwise) were mixed with glycerol (FAB ῎896 kJ/mol) and ethylamine (PA῎908 kJ/mol) at matrix) and put on the probe tip. The ion accelerating m/z 32 and m/z 46, respectively, and the proton bound voltage was 10 kV. The resolution was 1,000. FAB heterodimer (a HCl loss) at m/z 77 are produced from ῌ mass spectra were recorded at a scan rate of m/z 2,600 the cluster ion, [A1ῌHClῌA2ῌH] ,atm/z 113. The in 10 s for the mass range m/z 0῍800. proton bound heterodimer is not observed in the both For CAD measurements, Ar was introduced into the of MI (Fig. 2-A-d) and CAD spectra (Fig. 2-B-d) from the collision cell until the intensity of the precursor ion mixture of diethylamine (PA῎945 kJ/mol) and tri- beam was reduced to about 30῏.The mass range was ethylamine (PA῎972 kJ/mol). scanned from 0 to the mass that is 5 ῏ larger than that From Fig. 2, the intensity of a proton bound hetero- ῌ of selected precursor ion at a scan rate of m/z 2,600 in dimer, [A1ῌHῌA2] ,from the fragmentation of [A1ῌ ῌ 120 s and accumulated for 5 min. Metastable ion (MI) HClῌA2ῌH] tends to decrease as the PAs of com- spectra were obtained without collision gas. pounds A1 and/or A2 have higher PA values. The ῌ ῌ relative abundances of [A1ῌH] and [A2ῌH] from the 3. Results and Discussion ῌ fragmentation of [A1ῌHClῌA2ῌH] are reasonablein 3.1 FAB mass spectra of mixture of two hydro- the results from the fragmentation of [A1ῌH ῌ chlorides of amines ῌA2] (data are not shown) and are related to the FAB mass spectra of mixture of two amines whose PA di#erences between A1 and A2. PAs are known are measured. 3.3 Proton a$nity of methamphetamine The FAB mass spectrum of the mixture of methyl- In the FAB mass spectra of the mixture of metham- amine (A1)and ethylamine (A2)isshown in Fig. 1 as the phetamine (A1)and some reference bases (A2)with high typical example. The signiﬁcant ions observed are [A1 PA, the intensities of proton bound heterodimer [A1ῌH ῌ ῌ ῌ ῌ ῌH] at m/z 32, [A2ῌH] at m/z 46, [2A1ῌH] at m/z ῌA2] are too small to obtain the CAD spectra. There- ῌ ῌ 63, [A1ῌHῌA2] at m/z 77, [2A2ῌH] at m/z 91, [A1ῌ fore, the dissociation of the cluster ion, [A1ῌ ῌ ῌ ῌ HClῌA1ῌH] at m/z 99, [A1ῌHClῌA2ῌH] at m/z HClῌA2ῌH] ,isused to decide the PA of metham- ῌ 113, and [A2ῌHClῌA2ῌH] at m/z 127. In general, phetamine. ῌ the intensity of [A1ῌHῌA2] tends to decrease Table 1 lists the PAs of reference bases obtained ῌ ῌ as A1 and/or A2 have higher PA values. from ref. 1 and ln([A1H] /[A2H] )results obtained 3.2 Fragmentation of the cluster ion [A1ῌHClῌ from the CAD spectra. Figure 3 shows a plot of ῌ ῌ ῌ A2ῌH] ln([A1H] /[A2H] ) vs.PA(A2). Least-squares analysis Figure 2 shows the MI (A) and the CAD (B) spectra of gives the following relationship and correlation coe$- ῌ the cluster ion, [A1ῌHClῌA2ῌH] ,from the mixture cient, 1) ῌ ῌ of two amines whose PA are known in the literature. ln([A1H] /[A2H] )῎῍0.063 PA(A1)ῌ61.04 , In Fig. 2-B-a, protonated molecules of methylamine (PA r῎0.96 .

Fig. 4. (continued)

ῌ199ῌ S. Matsumura, H. Takezawa, and K. Isa

Table 2. PA Order of Methamphetamine and Its Analogs alkyl chain, 3,4-methylenedioxy group and methoxy group in aromatic ring also increase PA values. 4. Conclusions

We studied the fragmentation of the cluster ion, [A1 ῌ ῌHClῌA2ῌH] ,and the relative abundances of [A1ῌ ῌ ῌ H] and [A2ῌH] from the fragmentation of [A1ῌHCl ῌ ῌA2ῌH] are found to be related to PA di#erences between compound A1 and compound A2. We apply this method in order to obtain the PA values of some drugs of abuse and the result is amphetamine῍methamphetamine (965 kJ/mol)῍ephedrine ῍ MDMA ῍ MDEA ῍ dimethylamphetamine ῍ methoxyphenamine. The proton a$nity of methampheta-

mine from dissociation of the cluster ion, [A1ῌHClῌA2 ῌH]ῌ,is965 kJ/mol. Acknowledgments This research is in part supported by Toyota Physi- cal and Chemical Research Institute. We are also grateful to Professor Emeritus Hisashi Matsuda of Osaka University and JEOL Ltd. for ﬁna- ncial support by MATSUDA Fund. References

1) S. G. Lias, J. F. Liebman, and R. D. Levin, J. Phys. Chem. Ref. Data, 13,695 (1984). The proton a$nity of methamphetamine is obtained 2) S. G. Lias, J. E. Bartmess, J. F. Liebman, J. L. Holmes, R. D. Levin, and W. G. Mallard, J. Phys. Chem. Ref. Data, 17 from the dissociation of the cluster ion, [A1ῌHClῌA2ῌ H]ῌ,as965 kJ/mol. (Suppl. No. 1) (1988). 3.4 Proton a$nities of drugs of abuse 3) Ana M. Cardoso, Silvia M. G. Alexandre, Cristina M. F. Barros, A. J. Ferrer-Correia, and N. M. M. Nibbering, The order of PAs of seven abused drugs, which are Adv. Mass Spectrom., 14,A021940/1 (1998). methamphetamine analogs, is suggested on the basis of 4) R. G. Cooks and T. L. Kruger, J. Am. Chem. Soc., 99,1279 ῌ ῌ ῌ the fragmentation of the cluster ion, [A1 HCl A2 (1977). ῌ H] , from the mixture of two hydrochlorides (sulfate 5) S. A. McLuckey, D. Cameron, and R. G. Cooks, J. Am. for amphetamine) of compounds. Chem. Soc., 103,1313 (1981). The results are shown in Fig. 4 and Table 2. Though 6) K. Isa, T. Omote, and M. Amaya, Org. Mass Spectrom., 25, 2-phenylethylamine is not an abused drug, it is listed as 620 (1990). areference. Methamphetamine and amphetamine are 7) X. Li and A. G. Harrison, Org. Mass Spectrom., 28,366 stimulants. Ephedrine and dimethyamphetamine are (1993). controlled as the synthetic precursors of stimulants. 8) H.-F. Grutzmacher and A. Caltapanides, J. Am. Soc. Mass MDMA and MDEA are narcotics. Methoxyphenamine Spectrom., 5,826 (1994). is one of the doping substances in sport. 9) R. G. Cooks, J. S. Patrick, T. Kotiaho, and S. A. McLuc- The PAs increase in the order 2-phenylethylamine key, Mass Spectrom. Rev., 13,287 (1994). 10) J. Cao and J. L. Holmes, Int. J. Mass Spectrom., 195/196, (925 kJ/mol)῍amphetamine῍methamphetamine (965 525 (2000). kJ/mol)῍ephedrine῍MDMA῍MDEA῍dimethylam- 11) S. Matsumura, R. Tsukamoto, and K. Isa, J. Mass Spec- ῍ phetamine methoxyphenamine. From Table 2, the trom. Soc. Jpn., 48,333 (2000). substitution of one hydrogen atom of the amino group by a methyl group increases PA as described else- Keywords:Proton a$nity, Kinetic method, CAD (CID), Hy- where.3) The presence of an OH group at carbon of the drochlorides, Methamphetamine

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