Table I. Normal Ranges of Various Methods of Determining T? and Ta T3,
Td,pg/lOO ml blood serum
ng/100 ml blood serum
138 f 23 (N = 8 2 ) O 137 f 23 (N = 82)
a
145 f 25 146 i 20 (N = 23)
7.65 f 1.07 (N
134 f 21 (N= 76)
7.58 f 1.28 (N = 76)
=
23)
Method
Authors
Radioimmunoassay Gas-liquid chromatography Radioimmunoassay Liquid chromatography Liquid chromatography
T. Mitsuma et al. (12) T. Mitsuma et al. (12) J. Lieblich et al. (13) K. Horn et al. (6)
G. Knapp et al.
(mean 2~ standard deviation).
and the measuring parameters (measuring period and temperature of reaction) of the digital apparatus for catalytic measurement of the thyroid hormones (8). The most suitable parameters for the catalytic determination of T3 proved to be 20 "C and 160 sec; for the determination of T4 they were 20 "C and 40 sec. The measuring range for the T3 determination extends from 0.02 to 3.00 pg of T3/100 ml blood serum. The measuring range of the T4 determination can be varied greatly by measuring any portion of the eluted T4. If 0.2 ml of the eluted T4 is measured, then the measuring range extends between 0.2 and 30 pg T4/100 ml of blood serum. The precision of the method was tested by means of a pool serum, whose results were within the normal range. Measurement of the T3 yielded 0.12 f 0.012 pg/100 ml and of the T4, 6.6 f 0.4 pg/100 ml blood serum (mean f std dev, N = 20). Furthermore, T3 and T4 determinations were also performed for 76 healthy subjects to establish the normal
range of the method. Table I shows a comparison of these test values with results obtained by other authors using immunological or chromatographic methods. The method described has proven to be of great value especially in routine clinical analysis, as it can be quickly and easily performed. The time needed for the complete separation cycle, including concentration by evaporation of the eluted T3, is approximately 3 hours.
ACKNOWLEDGMENT The authors want to thank K . W. Budna for his valuable cooperation. Received for review July 23, 1973. Accepted November 15, 1973. (12) T. Mitsuma, N. Nihei, M . C. Gershengorn, and C . S. Hollander, J. Clin. Invest.. 50,2679 (1971). (13) J. Lieblich and D. Utiger, J. Clin. Invest., 51, 157 (1972).
lsobutane Chemical ionization Mass Spectra of Lanthanide Perfluorinated /?-Diketonates T.
H. Risby, P. C. Jurs, and F. W. Lampe
Department of Chemistry, The Pennsylvania State University, University Park. Pa. 76802
A. L. Yergey Scientific Research Instruments Corporation. 6707 Whitestone Road, Baltimore. Md. 21 207.
lates have been previously studied by gas chromatography The isobutane chemical ionization mass spectra of the ( 2 )and electron impact mass spectrometry (3, 4 ) . lanthanide 2,2,6,6-tetramethylheptane-3,5-dionates A representative fragmentation pattern before the mass [Ln(thd)3] have previously been described (1).This work spectrum becomes too complicated is shown below ( 4 ) : has shown the intrinsic potential of chemical ionization mass spectrometry (CIMS) over electron impact mass (Mol wt = 0) [Ln (fod )3 1 spectrometry (EIMS) for the analysis of metals. The CI [Ln(fod)3-(CH,)]+ (Mol wt = 15) mass spectra contained no fragmentation in the region of [Ln(fod)3-(F)l+ (Mol wt = 19) the parent ion as compared to the E1 mass spectra which [Ln(fod)3-(Fz)l+ (Mol wt = 38) contained extensive fragmentation. In order that metals [Ln(fod)3-(C3H8)IA (Mol wt = 44) may be studied by EIMS and CIMS volatile complexes [Ln(fod)3-(C4H,)]+ (Mol wt = 57) must be prepared, and this earlier study used the non-flu[Ln(fod)3-(C3F,)]+ (Mol w t = 169) 2,2,7,7-tetramethylheptane-3,5-dione orinated ligand (Mol wt = 295) [Ln(fod121 [H(thd)]. This ligand was used as it was felt that it would The extensive fragmentation produced by EIMS, although probably be less susceptible to fragmentation than fluodesirable for the elucidation of molecular structure, is a rinated /3-diketones for no stable fragments such as hydrodistinct limitation for the ultra-trace analysis of mixtures. gen fluoride could be lost. In the present study, a fluorinated ligand has been used (1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedione C S . Springer, Jr , D. W. Meek, and R . E. Sievers, Inorg. Chem., 6. [H(fod)]) to complex the lanthanide elements. These che1105 (1967). +
+
(1) T H Risby. P C Jurs, F C h e m , 46, 161 (1974)
726
W
Lampe and A
L Yergey Ana/
A N A L Y T I C A L C H E M I S T R Y , V O L . 46, NO. 6, M A Y 1974
E. R . Kowalski. T. L. isenhour, and R. E. Sievers, Anal. Chem., 41, 998 (1969) T H Risby and T L Isenhour, unpublished data, 1973
Table I. Calculated Relative P e a k Intensities for M(fod)$ m/e
1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065
La
0.63 69.96 23.75 4.91 0.75
...
... ... ... ... ...
...
... ... ... ... ... ... ...
...
... ... ...
...
... ... ... ... ... ... ... ... ... ...
... ... .
I
Nd
Pr
.
... ...
... ... ...
...
... ...
...
... 70.37 23.92 4.94 0.76
...
...
... ...
...
... ...
... ... ... ... ...
...
...
... ...
... ...
... ... ...
... ... .
I
.
... ... ... ...
... ... ... ... ...
... ...
Sm
.
...
.
19.08 15.05 21.04 12.35 15.38 4.71 4.95 1.50 4.24 1.39 0.28 0.04
...
... ... ...
...
... ... ... ... ...
...
... ...
...
...
... ... ... ... ...
... ...
...
... ... ...
Eu
Gd
... ...
...
... ... ...
...
...
2.17 0.74 0.15 10.56 11.49 13.16 9.21 2.55 19.28 6.45 17.30 5.64 1.12 0.17
...
...
...
... ...
... ... ...
...
... ...
... ... ... ...
... ... ... ... ...
... ...
...
...
... ... ... ...
...
... ... ... ...
33.65 11.44 39.09 12.85 2.58 0.40
... .
.
I
... ...
... ...
... ... ...
... ... ...
... ...
...
... ... ... ...
... ...
...
...
...
... ... ...
...
0.14 0.05 1.52 10.88 18.04 16.68 22.38 6.88 16.76 5.43 1.OB 0.17
... ...
...
...
...
...
...
...
...
...
... ... ... ...
...
... ...
... ...
...
... ... ... ... ...
... ... ...
70.37 23.92 4.94 0.76
...
...
...
...
... ...
...
...
... ...
...
... ...
...
...
...
...
... ... ...
However, CIMS produces a mass spectrum which has only one major ion which is the protonated molecule. As a result, this parent ion can be readily used to identify an unknown compound. CIMS could have inherently a much greater sensitivity than EIMS as the majority of the molecules of the compound are in one major peak and not dispersed among a fragmentation pattern. EXPERIMENTAL Chelate Preparation. The lanthanide tris-1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octane dionates were prepared by the procedure which has already previously been described (2). The chelate formed was a monoaquo Ln(fod)s which was found to dehydrate when sublimed in a mass spectrometer and therefore it could be used directly. Electron Impact Mass Spectrometer. The E1 mass spectra were run on an Associated Electronics Industries MS-902 double focusing mass spectrometer operating at low resolution. The ionization source was run at 140 "C, the accelerating potential was 8 kV, and the ionizing voltage was 70 eV. The samples were introduced into the ionization source on a direct insertion probe. Chemical Ionization Mass Spectrometer. The CI mass spectra were obtained using a Scientific Research Instruments Corporation DRUGSPECT System using isobutane as the reagent gas, which has previously been described ( I ) . An aliquot of solution ( 2 ~ 1 approximately ) 1 parts per thousand (by weight, in terms of the lanthanide in benzene) was evaporated onto the direct insertion probe. The temperature of the ionization source was 125 "C and all the other conditions were identical to those previously reported ( I ) . The amu of the peaks were determined by the use of a mass marker which had been calibrated with other standards.
Ho
DY
... ... ... ...
...
Tb
...
... ... ... ... ...
... ... ... .
I
.
... ...
...
...
...
... ... ... ... ... ... ...
... ... ... ... ...
Er
...
...
... ... ...
... ...
...
...
...
...
... ...
... ...
... ... ... ... ... ...
...
...
...
... ...
...
... ... ...
...
...
...
...
...
... ...
...
...
0.04 0.01 0.07 0.02 1.62 13.84 22.60 24.63 27.21 8.17 1.58 0.21
... ...
... ... ...
... ... ... ... ... ...
...
...
...
...
... ... ... ... ...
... ...
...
...
70 :37 23.92 4.94 0.76
... ...
...
... ... ...
...
...
...
... ... ... ... ...
...
... 0.10 0.03 1.10 0.37 23.59 24.15 26.19 7.86 11.98 3.77 0.74 0.11
...
...
... ...
...
...
...
...
...
...
...
1.u
... ...
...
...
... ...
Yb
Tm
... ... ... ... ...
...
...
... ... I
.
.
...
...
...
... ...
...
...
...
... ...
...
...
...
...
...
.
...
I
.
...
... 70.37 23.92 4.94 0.76
.., .., ... ..,
...
... ...
0.09 0.03 2.14 10.79 18.93 17.30 27.46 8.58 10.65 3.29 0.63 0.10
...
... ... ... ... ... ... ...
... ...
...
... ... ... I
.
.
... ... ... ... ... ... ...
...
... ...
... ...
... ... ...
... ... ...
... ...
...
68.55 25.12 5.44 0.87 0.02
RESULTS AND DISCUSSION In order that the CI mass spectra may be interpreted, a similar computation of relative intensities as has been previously described ( 1 ) was performed and it is shown in Table I. The nominal m / e position of the parent peak shows that the chelates contain three ligands (885 amu), the metal atom, and one extra hydrogen. Thus, 139La(fod)3produces an ion of mass 139 885 1 = 1025 for the case where there are no 13C, *H, and l8O atoms in the ligands. The results shown in Table I are a calculation based on all the isotopic contributions to the intensities a t a particular mass position. The CI mass spectra obtained for the lanthanide chelates were found to be in agreement with the intensities shown in Table I. However, in contrast to the earlier results of the Ln(thd)3 chelates, the CI mass spectra of Ln(fod)3 were found to show minor fragment peaks at 18 and 38 or 37 amu below the protonated parent peaks. The peak resulting from the loss of 18 amu cannot be readily explained as water is not easily removed from the chelate for it would result in the breaking of one of the chelate's six-membered rings. A preliminary investigation of the CI mass spectra of the same lanthanide chelates using ammonia as the reagent gas yielded a large peak due to [Ln(fod)sNHa]' and a smaller peak due to [Ln(fod)sH]+. Thus, the peaks in-
+
+
A N A L Y T I C A L C H E M I S T R Y , VOL. 4 6 , N O . 6 , M A Y 1 9 7 4
* 727
Table 11. Observed Ions in Ln(fod)aC.I. Mass Spectra Major ion, m/e
Metal
1025 1027 1030 1038 1039 1044 1045 1050 1051 1054 1055 1060 1061
La
Pr Nd
Sm Eu Gd
Tb DY Ho ElTm Yb L"
No.of p a k s i n letminor gmup peak,m/e
3 3
10 13 5 9 3 7 3 8
3 8
3
1007 1009 1012 1020 1021 1024 1027 1032 1033 1036 1037 1042 1043
Fragment
Zndminor peak,m/e
Fragment
987 989 992 1001 1001 1006 1007 1012 1013 1017 1017 1022 1023
moo Figure 1.
lsobutme chemical ionization mass spectrum of
Sm(fod)s
910
lsobutarle chemical ioriization mass spectrum of Tb(fod)3and Ho(fod) 3 in a mixture Figure 3.
~.
.
the primary process oi simple proton transfer, fluorinated isobutenes are thought to be formed. A summary of the mass spectra observed between 900 and 1100 amu for all the lanthanides is shown in Table 11. Figure 1 shows the CI mass spectrum of Sm(fod)a. Samarium has seven naturally occurring isotopes 144Sm 3.09%, 147Sm 14.97%, 14%m 11.24%, lagSrn' 13.83%, 1T.m 7.44%, 152311 26.72%, and 154Sm 22.71%, and Table I shows that one expects to find the peaks in the following order: three large, one medium, one small, one large, one medium, one large, and finally one medium peak, and Figure 1depicts this relationship. The CI mass spectrum shown in Figure 1 agrees with the calculated intensity pattern shown in Table I. Also shown in this figure are the two minor peaks due to fragmentation. Figure '2 shows the E1 mass spectrum of Sm(fod)a and again the isotopic abundances of the peaks are shown, but the spectrum shows much greater fragmentation. The major peak is not due to the parent ion but is due to the parent ion minus 57 amu which corresponds to the loss of a CaHg group. The greater resolution shown in the E1 mass spectrum of Figure 2 than in the CI mass spectrum of Figure 1 is the result of the greater resolving power of the AEI MS902 compared with the SlUC quadrupole. However, the advantage of a linear or nearly linear mle scale with quadrupole mass spectrometers cannot be stressed enough, especially with CIMS where there are few fragment peaks to use to count the mass units. Figure 3 shows CIMS of a mixture of Tb(fod)a and Ho(fod)a in an approximately 1:l ratio. It is readily apparent that these two compounds may be distinguished. A major peak at 1045 is indicative of [Tb(fod)~H]+and similarly a peak a t 1051 of [Ho(fod)3H]+. More complex mixtures may be analyzed by the use of computer time averaging. ,
Figure 2.
Electron impact mass spectrum of S m ( f o d ) l
volving the losses of 18, 37, or 38 amu in the isobutane spectra of the lanthanide chelates are probably not due to the presence of traces of incompletely fluorinated ligands. The most satisfactory explanation of the fragment peaks at 18, 37, and 38 amu helow the parent peak is that the collision complex formed upon impact of the chelate and the C4Hg+ has sufficient lifetime to allow molecular rearrangements to occur. In place of the isobutene formed by
728
-
ANALYTiCAL CHEMISTRY, VOL. 46, NO. 6. MAY 1974
ACKNOWLEDGMENT
neceiveu
IUT
r e v ~ e wf i u g u u ~ 8 ,
IS,U. ~
__
.
c
c
c
~
~
~
