304
Anal. Chem. 1981, 53, 304-308
increasing uptake for manganese in base. The complexing characteristics of the remaining nonradioactive elements (Li, Be, Rb, Cs, Zr, Nb, Hf, and Ta) are now being determined. The properties of the poly(dithi0carbamate) resin for the metals of this investigation remain to be tested at trace concentration levels and in column rather than batch modes. However, previous experience with other elements (13, 17) suggests that once the optimum pH for chelation is determined in batch studies, collection of trace concentration levels by column techniques provides quantitative recovery. The results of this study and those reported previously for water, milk, and urine samples (13, 17) indicate that the poly(dithi0carbamate) resin possesses unique potential for many applications in environmental, pollution, geochemical, and biological problems for which the determination of trace amounts of metals by ICP-AES and other spectrochemical methods is presently limited by the high concentrations of iron or alkali and alkaline earth elements. The development of some typical applications is presently under way.
ACKNOWLEDGMENT The assistance of G. Dabkowski in preparing the resin samples and contributing the synthesis test data and the discussions with M. B. Colella concerning the resin digestion are greatly appreciated.
LITERATURE CITED Berman, S. S.; McLaren, J. W.; Willie, S. N. Anal. Cbem. 1980, 52, 488-492. Haas, W. J.; Fassel, V. A. "Elemental Analysis of Biological Materials, Technical Report Series, No. 197"; Internatlonal Atomic Energy Agency: Vienna, Austria, 1979; Chapter 9, pp 167-199. Fassel, V. A. Anal. Cbem. 1979, 57,1290A. Baudin, G. Prog. Anal. At. Spectrosc. 1980, 3 , 1-63. Fassel, V. A.; Knlseley, R. N.; Butler, C. C. "Analysis and Application of the Rare Earth Materials"; Mlchelsen, 0. B., Ed., Universitetsfor-
logqet: Osio, Norway, 1973; pp 71-86.
(6) Nikdei, S.; Massoumi, A.; Winefordner, J. D. Mlcrochem. J . 1979, 24,
1-7. (7) Broekaert, J. A. C.; Leis, F.; Laqua. K. Spectrocblm. Acta, Part 6 1979, 348, 73-84. (8) Larson, G. F.; Fassei V. A.; Winge, R. K; Kniseley, R. N. Appl. SpectrOSC. 1978, 30, 384-391. (9) Fassel, V. A.; Katzenberger, J. M.; Winge, R. K. Appl. Spectrosc. 1979, 33, 1-5. (10) Larson, G. F.; Fassel, V. A. Appl. Spectrosc. 1979, 33, 592-599. (11) Subramanian, K. S.; Chakrabart, C. L. Prog. Anal. At. Spectrosc. 1979, 2, 287-306. (12) Slavin, W. At. Spectrosc. 1980, 7 , 66-71. (13) Barnes, R. M.; Genna, J. S. Anal. Chem. 1979, 57, 1065-1070. (14) Hlralde, M.; Ito, M; Baba, M.; Kawaguchi, H.; Mizuike. A. Anal. Chem. 1980, 52,804-807. (15) Sturgeon, R. E.; Berman, S. S.; Desaulniers, J. A. H.; Mykytiuk, A. P.; McLaren, J. W.; Russell, D. S. Anal. Chem. 1980, 52, 1585. (16) Bulletin 2020, Bio-Rad Laboratories Product Information, 1978. (17) Hackett, D. S.; Siggia, S. I n "Environmental Analysis"; Ewlng, G. W., Ed., Academic Press: New York, 1977; p 253. (18) Colella, M. B.; Siggia, S.; Barnes, R. M. Anal. Chem. 1980, 52, 967-972. (19) Colella, M. 8.; Sggia, S.; Barnes, R. M. Anal. Chem. 1980, 52, 2347. (20) Bray, J. T.; Reiily, F. T., Jr.; Bates, J. M.; van Rij, A. M.; Porles, W. J. Presented In part at the 14th Annual Conference on Trace Substances In Environmental Health, Columbia, MO, June 1980. (21) Winge, R. K.; Peterson, V. J.; Fassei, V. A. Appl. Spectrosc. 1979, 33, 206-219. (22) Miyazakl, A.; Barnes, R. M. Anal. Chem., companion paper In this issue.
RECEIVED for review August 6,1980. Accepted November 21, 1980. This work was supported by Department of Energy (Office of Health and Environmental Research) Contract DE-AC02-77EV-04320. Results were presented in part at the Sixth Annual Meeting of the Federation of Analytical Chemistry and Spectroscopy Societies, the 29th Annual Meeting of the Japan Society for Analytical Chemistry, and the 27th Canadian Spectroscopy Symposium. A.M. acknowledges the Science and Technology Agency of Japan for his travel support.
Electron Ionization-Flash Desorption in Mass Spectrometry of Tetraalkylammonium Halide Salts Terry D. Lee, William R. Anderson, Jr., and G. Doyle Daves, Jr." Depattment of Chemistry and Biochemical Sciences, Oregon Graduate Center, Beavetton, Oregon 97006
Electron lonlzatlon (EI)m a s spectra of tetraalkylammonium halide salts have been recorded by use of the technlque of electron ionization-flash desorption. These spectra exhlblt R4N+Ions and fragment Ions which characterize the structure of the quaternary ammonium cation. Ion productlon requires both rapid sample heatlng (flash desorption) and electron bombardment and occurs in the gas phase from volatile precursors. The volatile precursors to R4N+ Ions may be Intact R4NX molecules or (R4NX), clusters. Alternatlvely, It Is possible that thermal reductlon of the solld (or molten) saH occurs to yleld neutral R4Nwhich Is volatlle and undergoes electron Impact induced ionlzatlon to R4N+.
In connection with our ongoing research on mass spectrometry of nonvolatile and thermally unstable molecules (I-i'), we report the first electron ionization (EI) mass spectra of tetraalkylammonium salts which exhibit ions characteristic 0003-2700/8 1/0353-0304$01 .OO/O
of the quaternary amine moiety (1, 8). Recent studies of quaternary ammonium salts by field desorption (9-15), electrohydrodynamic (16),secondary ion (ion bombardment) (In,in beam chemical ionization (18, 19),laser desorption (20, 21), and 252Cfplasma (fission fragment induced) desorption (21) mass spectrometries, which (presumably) are surface ionization techniques ( l ) have , been justified largely on the basis of the assumed inaccessability of R4N+ions by E1 mass spectrometry. Prior to the present investigation, E1 mass spectrometry of tetraalkylammonium salts has invariably involved initial thermal dealkylation to achieve volatilization of one or more tertiary amines followed by electron ionization of the pyrolysis products (22). The spectra we have obtained by electron impact-flash desorption mass spectrometry exhibit even electron R4N+ ions and characteristic E1 fragment ions. Electron ionization-flash desorption mass spectrometry involves heating a sample absorbed on a metal surface, positioned within the ion source of a conventional E1 mass 0 1981 American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 53, NO. 2, FEBRUARY 1981 (a)
305
I14 n P r 2 N * = C H 2
58 M L ~ N * = C H ~
M e 4 N I'
M W: 2 0 I
nPr4N*I-
43
90-
MW: 313
142 M I I *
I a
I -c u
60-
5 9 MQN'
501
50-
4i1
40-
: -
170 nPr1'
30 -CHz:N'=CHz
0
I
42
;20 20-
127 I'
20
60 M ~ ~ N H '
10-
IO10 ,L
0 1 30
40
, ', 50
60
7 4 MI,"
,' 70
,
80
, , , ,
I ,
I,'
,
I
0-
86 oPrN*=CH* 'I5
127 I*
cn3
3$
,
,
ro
84
, :
,
, I ,
143 nPr3N'
112
;
, ,
142 144 nPr3N.H
,
,
186 nPf4N'
,
1
90 100 110 120 130 140 150 160
mlz
100
-
+
m/r + n8u2N':CH2
I
(b) EtqN*
I- M W . 2 5 7
8 6 E12N'=CH2
90
-
80
-
70
-
60
-
nBu4N+
30 20 -
I- M W = 3 6 9
50
40
127 1'
2 44
IO
IO
30 4 0
50
60
70
80
90 100 110 120 130 140 I 5 0 160
m/z
1\11 30
40
",I;"
50
1 nBupN*=CHCsH7 (I)n0uI+ 185 n 8 u ~ N '
\
100 n B u N * = C H 2 8 4 8 6 981
70
60
80
70
127 I'
1 8 4 186 n B u 3 N H '
9 0 100 110 120 130 140 I 5 0 160 1 7 0 180 190 2 0 0 210 220 230 2 4 0 2 5 0
m/z
4
--+
Figure 1. Electron ionization-flash desorption mass spectra of (a) tetramethylammoniumiodide, (b) tetraethylammonium iodide, (c) tetra-npropylammonium iodide, and (d) tetra-n-butylammonium iodide. In the spectrum of tetra-n-butyiammonium iodide (d), two Ions appear at nominal m l z 184 in approximately 1:l relative abundance; structures are assigned to them as indicated in the figure.
Table I. Principal Ions in Electron Ionization-Flash Desorption Mass Spectra of Tetraalkylammonium Halide Salts m/z
ion R;N+H
R,N+* R,N+=CHR R, N +-CH, R,N+=CH, R-N+( CH,)=CH, RN+H=CHR R'CH=N+=CHR' RN+H=CH, R=N+=CH~
R+ X+ RX+*
Me4"
Et4N+
F-; Cl-; Br-; I-
CY-; 1-
a
a
74 60 59 58 59 58 58 44 42 44 42 b b ; 35; 79; 121 b ; 37; 81; 121 34; 50; 94; 142 34; 52; 96; 142
130 102 101 100 87 86 72 72 70 58 56 b 35; 127 37; 127 64; 156 66; 156
a Not observed. Beyond recording range of photoplate. m/z 184; 1 (R,N=CHR)+:l RX+.
spectrometer to >lo00 "C in times of 5-500 ms with photoplate ion recording. Unexpectedly, mass spectra of quaternary ammonium salts are easier to obtain by the technique than any other class of nonvolatile compounds we have studied.
EXPERIMENTAL SECTION Tetraalkylammonium halide salts were obtained commercially. Mass spectra were recorded on photoplates with a DuPont (CEC) 21-llOB high-resolution mass spectrometer using electron ionization-flash desorption procedures previously described (1-3,5, 23). Techniques for controlled sample heating and for recording single ion abundance profiles have also been described (23). For spectrum recording, 200 ng-2 pg of quaternary ammonium salt
n-Pr4N* CI-; I-
n-Bu,N+
a 186 144 143 142 115 114 86 100 98 72 70 43 35; 127 37: 127 a; i70
a; 611 242 186 185 184c 143 142 100 128
a-; I-
a
86 84 57 35; 127 31; 127 a; i84c
In the spectrum of n-Bu4N+I-a doublet was observed at dissolved in water was adsorbed onto a molybdenum or tungsten mesh (7).
RESULTS AND DISCUSSION We have studied the series of symmetrical tetraalkylammonium halide salts (R4N+X-:R = methyl, ethyl, n-propyl, n-butyl; X- = iodide, bromide, chloride, fluoride) by the electron ionization-flash desorption technique. Spectra of the tetraalkylammonium iodides, which are typical of the series, are shown in Figure 1; assignments of structure for the principal ions appearing in electron ionization-flash desorption mass spectra of the series are contained in Table I. Electron ionization-flash desorption mass spectra of 1-methylpyridinium iodide and 1-ethylpyridinium bromide (Figure 2)
306
ANALYTICAL CHEMISTRY, VOL. 53, NO. 2, FEBRUARY 1981 142 CH31t
I-
MW=221
I CH3
0
79
I
Ne.
127 I t
2 Q I+ ti
-
I
4 0 1
P
Mv
7(
l0 o
40
50
60
2 5 4 1:
70
90
I00 110 120 130 140 150 160 170 I 8 0 2 5 0 2 6 0 2 7 0 280 2 9 0 300 310 3 2 0
m/z
In C Q,
c
50
315 P y , I t
+
-
C
-
40-
51
0,
(1)
'E 3 0 -
LT 0
20-
50
10
- 4345
O
"
80
,
(
0
9 I
r x
Nt CH2Cfl3
~ ( 2C H ) 3CHiSBr+'
108
H
'
0
il
5
iio
1
I
1000
CH~CH:'B~+ I
I
I
I
1
1
1
1
1*VI
I
I
1
Py2 B rt 2 9 5 297 I II I
relative intensity structural assignment m/z PDMSQ LDMG SIMSQ FDCA~ FDMS~ EI-FDC [(n-Bu,+),I-]+ 6 11 20
