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Mass spectrometric characterization of desorbed species from weathered activated charcoals
98
Letters to the Editor
[Co(olefin)(PR,),] is in progress. X-Ray results obtained so far indicate formation of fairly high stages NaC,. Ackno&dgements-The assistance of H. Mijhwald and R. Sauter is gratefully acknowledged. This work was supported by the Fonds der Chemischen Industrie and the Deutsche Forschungsgemeinschaft. Anorganisch-chembches Insiitut, Technische Unitlersitiit Miinchen. Lichtenbergstr. 4, D-8046 Garching, F.R.G.
2. 3.
J. 0. BESENHARD 4. H. W~rrv 5. 6.
Anorganisehe Chemie I. Eduard-Zintl-Ins&&, TH Darmstadi. Holchschulstr. 4. D-6100 Darmstadi, F.R.G.
H.-F. KLEIN 7. 8. 9.
REFERENCES H.-F. Klein, J. Gross and J. 0. Besenhard, Angew. Chem. Int. Ed. 19, 491 (1980). J. 0. Besenhard, H.-F. Klein, J. Gross, H. Mijhwald and J. J. Nickl, Synth. Met. 4, 51 (1981). J. 0. Besenhard, I. ,Kain, H.-F. Klein, H. Mijhwald and H. Witty, In: Intercalculated Graphite (Edited by M. S. Dresselhaus, G. Dresselhaus, J. E. Fischer and M. J. Moran), p. 221. North-Holland, New York (1983). G. Eichinger and J. 0. Besenhard, 1. Electroanal. Chem. 72, 1 (1976). H.-F. Klein, H. Witty, J. Riede and U. Schubert, J. Chem. Sot. Chem. Comm., 231 (1983). H.-F. Klein, J. Gross, J.-M. Basset and U. Schubert, Z. Naturforsch. 35b, 614 (1980). J. 0. Besenhard, J. Electroanal. Chem. 94, 77 (1978). D. Guerard and A. Herold, Carbon 13, 337 (1975). D. Billaud, E. McRae, J. F. Ma&he and A. Herold, Synch. Met. 3, 21 (1981).
CarbonVol.22.No. 1, pp. 98-99,1984 Printed in Great Britain.
ORW6223/84 $3.00 + .OO Pergamoo Press Ltd.
Mass spectrometric characterization of desorbed species from weathered activated charcoals (Received 17 January 1983)
The experimental results for thermal desorption of charcoal adsorbates must be interpreted with extreme caution because of carbon-induced reactions which can yield novel products. This precaution is particularly relevant with respect to desorption techniques used for the characterization of materials with environmental/biological significance[l-51 and for chemical analysis&81. Our studies have shown that an example of this problem is the application of desorption/mass spectrometry to weathered charcoals impregnated with triethylenediamine (TEDA). This material is widely used for trapping some nuclear fission products[9]. The samples analyzed were 5% TEDA-impregnated coalbase charcoals that had been weathered in a flow of outdoor air for periods of up to 20 months. Using direct probe/mass spectrometry (DP/MS), a charcoal sample (l-2 mg) was placed into a glass capillary on a
probe tip and inserted into the mass spectrometer ion source. The sample was heated at 30”C/min from 50-3OO”C, and the desorbed species were ionized and mass analyzed. The results, presented in Table 1, show that the most abundant ions were: SOr+ (m/z 64), methylbenzene (m/z 91-benzyl or tropylium ion), dimethylbenzene (m/z 106), TEDA (m/z 112) and an unknown m/z 80 ion. The sulfurcontaining compounds were adsorbed from the air, as indicated by the ion abundances of m/z 48 and 64, which increased with longer weathering times. The possible sources of these compounds include effluent gases of wastetreatment plants, coal-burning power plants, and jet aircraft, all of which were in the environment of the weathering site. Figure 1 is a plot of the percentage of the total ion current of these sulfur-containing ions vs weathering time of the charcoals. The linear correlation observed demonstrates
Table 1. Desorbed species from TEDA-impregnated $ Intensity
Weathering Sample Charcoal No.
Time (Months)
n=48
n=64
1
0
*
l
2
1
0.5
1.6
3
6
4.0
13.0
4
9
6.1
17.8
5
15
8.5
19.5
6
20
11.1
21.1
charcoals
Ratio
n=80 6.0
(1,,/ITx100)
n=91
n=106
n=112
*
l
4.9
3.1
2.1
2.7
4.2
9.9
4.4
0.9
4.5
5.7
5.0
*
5.3
4.4
6.0
*
2.6
4.0
1.5
*
.9
In:
absolute ion current of the m/z n ion
IT:
total ion current of all ions, m/z 30-300
l :
ion current indistinguishable
from background level
99
Letters to the Editor
Table 2. Results of mass-analyzed ion kinetic energy spectrometry (MIKES) study % Intensity Sample Pyridazine Pyrimidine
TIME, months
Fig. 1. Accumulation of m/z 48 and 64 in weathered TEDA-impregnated coal/base charcoals.
that DP/MS is an effective method to determine relative weathering times of charcoals. In fact, the ranking of charcoals according to the duration of weathering (Table 1) was determined prior to knowledge of the actual weathering times. The observation that the ion abundances (m/z 91 and 106) do not correlate with weathering may indicate that they are related to degradation products on the charcoal surface. As expected, the fresh, unweathered TEDA-impregnated charcoal was found to have the largest abundance of TEDA and the least of the contaminant ions. It should be noted that the m/z 80 ion could not be identified with DP/MS. Thus, to study the desorbed compounds in more detail and to identify the m/z 80 ion, thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS) was used. The charcoal samples (lO-50mg) were heated under helium flow, and the desorbed compounds were trapped on a cooled GC column. Following desorption, the desorbate was separated and analyzed with the GC/MS. Using this technique, sharp and narrow GC peaks were measured in contrast to the broad desorption profiles obtained with DP/MS. The electron impact mass spectrum of the GC peak corresponding to the compound yielding the m/z 80 ion allowed the identification of this compound. It was tentatively identified as one of three isomers: pyridaxine, pyrimidine, or pyrazine (ortho, meta, or paradiaxine). TD/GC/MS studies revealed that the combination of TEDA, the carbon surface, and some thermal energy (threshold cu. 1OOC) were required for the m/z 80 decomposition product to form. The m/z 80 ion was not observed when TEDA was desorbed from glass wool or glass surfaces. Mass-analyzed ion kinetic energy spectrometry (MIKES) with collision-induced dissociation[lO] was used to determine which of the three isomeric diaxines corresponded to the m/z 80 ion desorbed from the TEDA-impregnated charcoals. This method involves the selection of one m/z-value ion with the first momentum-analyzing sector (magnetic), followed by collision-induced dissociation of the mass-selected ions between the two sectors to form characteristic fragment ions and, finally, the analysis of the fragment ions with the second energy-analyzing sector (ekectric). Table 2 presents the results of the MIKES study.
n=m/z no
53.4
Ratio 52 m/z
Un/IgjxlOO) n=m/z
51
53 observed 27.8
Pyrazine
44.6
23.2
Charcoal
42.6
22.3
The TEDA-impregnated charcoal was heated on a probe in the ion source. The m/z 80 ion was mass selected, and the collision-induced fragment ions were measured. of these products, m/z 53,52, and 51 were among the most abundant ions. The pure diaxines were analyzed in the same manner. Comparison of the relative, ion intensities, m/z 52/53 and 51/53, from the pure and desorbed m/z 80 ions enabled us to assign the pyraxine (paradiazine) structure to the m/z 80 which is formed from the TEDA-impregnated charcoal. Considering the structure of TEDA, the para isomer is the most plausible product. In further studies in which TEDA vapor was passed over a heated charcoal, the reaction products were swept into the ion source. These experiments verified that under these conditions TEDA does react with the charcoal to produce the para isomer. Although the exact reaction mechanism is not known, the possibility of such decompositions must be kept in mind in analyses not only for TEDA but also for all compounds desorbed from charcoals. We have shown that mass spectrometry is useful for the
characterization of charcoal adsorbates. These methods have applications to the study of adsorbate and absorbate interactions with carbon surfaces as well as to chemical analysis[6-81. However, the interpretation of these data must be viewed with extreme caution because of the possibility of chemical reactions occuring on the carbon. Chemistry Division Naval Research Laboratory Washington, DC 20315, U.S.A.
MARK M. Ross JOSEPHE. CAMPANA Vtcron R. Det~z
REFERENCES 1.K. Alben, Anal. Chem. 52, 1821 (1980). 2. J. A. Yergey, T. H. Risby and S. S. Lestx, Anal. Chem. 54, 354 (1982). 3. A. DiLorenzo,
Adv. in Mass Spectrometry gB, 1377 (1978). 4. D. Schuetzle, T. L. Riley, T. J. Prater, T. M. Harvey and D. F. Hunt. Anal. Chem. 54. 265 (1982). 5. W. Bertsch,‘R. C. Chang and'A. Zl&kis,‘J. Chrom. Sci. 12, 175 (1979). 6. W. V. Ligon, Jr. and R. L. Johnson, Jr., Anal. Chem. 48, 481 (1976). 7. M. M. Ross and R. J. Colton, Anal. Chem. 55, 150 (1983). 8. V. R. Deitz, Effects of Weathering on Impreg. Charcoal Performance. NRL Memo. Rpt., 4516, September
(1981). 9. V. R. Deitz (Ed.), Removal of Trace Contam. from the Air. ACS Symp. Ser., 17, ACS, Washington, DC (1975). 10. F. W. McLafferty, in High Performance Mass Spectrometry: Chemical Applications (Edited by M. L.
Gross); R. G. Cooks, J. H. Beynon, R. M. Caprioli and G. R. Lester, Metastable Ions. Elsevier, Amsterdam (1973).
Letters to the Editor
[Co(olefin)(PR,),] is in progress. X-Ray results obtained so far indicate formation of fairly high stages NaC,. Ackno&dgements-The assistance of H. Mijhwald and R. Sauter is gratefully acknowledged. This work was supported by the Fonds der Chemischen Industrie and the Deutsche Forschungsgemeinschaft. Anorganisch-chembches Insiitut, Technische Unitlersitiit Miinchen. Lichtenbergstr. 4, D-8046 Garching, F.R.G.
2. 3.
J. 0. BESENHARD 4. H. W~rrv 5. 6.
Anorganisehe Chemie I. Eduard-Zintl-Ins&&, TH Darmstadi. Holchschulstr. 4. D-6100 Darmstadi, F.R.G.
H.-F. KLEIN 7. 8. 9.
REFERENCES H.-F. Klein, J. Gross and J. 0. Besenhard, Angew. Chem. Int. Ed. 19, 491 (1980). J. 0. Besenhard, H.-F. Klein, J. Gross, H. Mijhwald and J. J. Nickl, Synth. Met. 4, 51 (1981). J. 0. Besenhard, I. ,Kain, H.-F. Klein, H. Mijhwald and H. Witty, In: Intercalculated Graphite (Edited by M. S. Dresselhaus, G. Dresselhaus, J. E. Fischer and M. J. Moran), p. 221. North-Holland, New York (1983). G. Eichinger and J. 0. Besenhard, 1. Electroanal. Chem. 72, 1 (1976). H.-F. Klein, H. Witty, J. Riede and U. Schubert, J. Chem. Sot. Chem. Comm., 231 (1983). H.-F. Klein, J. Gross, J.-M. Basset and U. Schubert, Z. Naturforsch. 35b, 614 (1980). J. 0. Besenhard, J. Electroanal. Chem. 94, 77 (1978). D. Guerard and A. Herold, Carbon 13, 337 (1975). D. Billaud, E. McRae, J. F. Ma&he and A. Herold, Synch. Met. 3, 21 (1981).
CarbonVol.22.No. 1, pp. 98-99,1984 Printed in Great Britain.
ORW6223/84 $3.00 + .OO Pergamoo Press Ltd.
Mass spectrometric characterization of desorbed species from weathered activated charcoals (Received 17 January 1983)
The experimental results for thermal desorption of charcoal adsorbates must be interpreted with extreme caution because of carbon-induced reactions which can yield novel products. This precaution is particularly relevant with respect to desorption techniques used for the characterization of materials with environmental/biological significance[l-51 and for chemical analysis&81. Our studies have shown that an example of this problem is the application of desorption/mass spectrometry to weathered charcoals impregnated with triethylenediamine (TEDA). This material is widely used for trapping some nuclear fission products[9]. The samples analyzed were 5% TEDA-impregnated coalbase charcoals that had been weathered in a flow of outdoor air for periods of up to 20 months. Using direct probe/mass spectrometry (DP/MS), a charcoal sample (l-2 mg) was placed into a glass capillary on a
probe tip and inserted into the mass spectrometer ion source. The sample was heated at 30”C/min from 50-3OO”C, and the desorbed species were ionized and mass analyzed. The results, presented in Table 1, show that the most abundant ions were: SOr+ (m/z 64), methylbenzene (m/z 91-benzyl or tropylium ion), dimethylbenzene (m/z 106), TEDA (m/z 112) and an unknown m/z 80 ion. The sulfurcontaining compounds were adsorbed from the air, as indicated by the ion abundances of m/z 48 and 64, which increased with longer weathering times. The possible sources of these compounds include effluent gases of wastetreatment plants, coal-burning power plants, and jet aircraft, all of which were in the environment of the weathering site. Figure 1 is a plot of the percentage of the total ion current of these sulfur-containing ions vs weathering time of the charcoals. The linear correlation observed demonstrates
Table 1. Desorbed species from TEDA-impregnated $ Intensity
Weathering Sample Charcoal No.
Time (Months)
n=48
n=64
1
0
*
l
2
1
0.5
1.6
3
6
4.0
13.0
4
9
6.1
17.8
5
15
8.5
19.5
6
20
11.1
21.1
charcoals
Ratio
n=80 6.0
(1,,/ITx100)
n=91
n=106
n=112
*
l
4.9
3.1
2.1
2.7
4.2
9.9
4.4
0.9
4.5
5.7
5.0
*
5.3
4.4
6.0
*
2.6
4.0
1.5
*
.9
In:
absolute ion current of the m/z n ion
IT:
total ion current of all ions, m/z 30-300
l :
ion current indistinguishable
from background level
99
Letters to the Editor
Table 2. Results of mass-analyzed ion kinetic energy spectrometry (MIKES) study % Intensity Sample Pyridazine Pyrimidine
TIME, months
Fig. 1. Accumulation of m/z 48 and 64 in weathered TEDA-impregnated coal/base charcoals.
that DP/MS is an effective method to determine relative weathering times of charcoals. In fact, the ranking of charcoals according to the duration of weathering (Table 1) was determined prior to knowledge of the actual weathering times. The observation that the ion abundances (m/z 91 and 106) do not correlate with weathering may indicate that they are related to degradation products on the charcoal surface. As expected, the fresh, unweathered TEDA-impregnated charcoal was found to have the largest abundance of TEDA and the least of the contaminant ions. It should be noted that the m/z 80 ion could not be identified with DP/MS. Thus, to study the desorbed compounds in more detail and to identify the m/z 80 ion, thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS) was used. The charcoal samples (lO-50mg) were heated under helium flow, and the desorbed compounds were trapped on a cooled GC column. Following desorption, the desorbate was separated and analyzed with the GC/MS. Using this technique, sharp and narrow GC peaks were measured in contrast to the broad desorption profiles obtained with DP/MS. The electron impact mass spectrum of the GC peak corresponding to the compound yielding the m/z 80 ion allowed the identification of this compound. It was tentatively identified as one of three isomers: pyridaxine, pyrimidine, or pyrazine (ortho, meta, or paradiaxine). TD/GC/MS studies revealed that the combination of TEDA, the carbon surface, and some thermal energy (threshold cu. 1OOC) were required for the m/z 80 decomposition product to form. The m/z 80 ion was not observed when TEDA was desorbed from glass wool or glass surfaces. Mass-analyzed ion kinetic energy spectrometry (MIKES) with collision-induced dissociation[lO] was used to determine which of the three isomeric diaxines corresponded to the m/z 80 ion desorbed from the TEDA-impregnated charcoals. This method involves the selection of one m/z-value ion with the first momentum-analyzing sector (magnetic), followed by collision-induced dissociation of the mass-selected ions between the two sectors to form characteristic fragment ions and, finally, the analysis of the fragment ions with the second energy-analyzing sector (ekectric). Table 2 presents the results of the MIKES study.
n=m/z no
53.4
Ratio 52 m/z
Un/IgjxlOO) n=m/z
51
53 observed 27.8
Pyrazine
44.6
23.2
Charcoal
42.6
22.3
The TEDA-impregnated charcoal was heated on a probe in the ion source. The m/z 80 ion was mass selected, and the collision-induced fragment ions were measured. of these products, m/z 53,52, and 51 were among the most abundant ions. The pure diaxines were analyzed in the same manner. Comparison of the relative, ion intensities, m/z 52/53 and 51/53, from the pure and desorbed m/z 80 ions enabled us to assign the pyraxine (paradiazine) structure to the m/z 80 which is formed from the TEDA-impregnated charcoal. Considering the structure of TEDA, the para isomer is the most plausible product. In further studies in which TEDA vapor was passed over a heated charcoal, the reaction products were swept into the ion source. These experiments verified that under these conditions TEDA does react with the charcoal to produce the para isomer. Although the exact reaction mechanism is not known, the possibility of such decompositions must be kept in mind in analyses not only for TEDA but also for all compounds desorbed from charcoals. We have shown that mass spectrometry is useful for the
characterization of charcoal adsorbates. These methods have applications to the study of adsorbate and absorbate interactions with carbon surfaces as well as to chemical analysis[6-81. However, the interpretation of these data must be viewed with extreme caution because of the possibility of chemical reactions occuring on the carbon. Chemistry Division Naval Research Laboratory Washington, DC 20315, U.S.A.
MARK M. Ross JOSEPHE. CAMPANA Vtcron R. Det~z
REFERENCES 1.K. Alben, Anal. Chem. 52, 1821 (1980). 2. J. A. Yergey, T. H. Risby and S. S. Lestx, Anal. Chem. 54, 354 (1982). 3. A. DiLorenzo,
Adv. in Mass Spectrometry gB, 1377 (1978). 4. D. Schuetzle, T. L. Riley, T. J. Prater, T. M. Harvey and D. F. Hunt. Anal. Chem. 54. 265 (1982). 5. W. Bertsch,‘R. C. Chang and'A. Zl&kis,‘J. Chrom. Sci. 12, 175 (1979). 6. W. V. Ligon, Jr. and R. L. Johnson, Jr., Anal. Chem. 48, 481 (1976). 7. M. M. Ross and R. J. Colton, Anal. Chem. 55, 150 (1983). 8. V. R. Deitz, Effects of Weathering on Impreg. Charcoal Performance. NRL Memo. Rpt., 4516, September
(1981). 9. V. R. Deitz (Ed.), Removal of Trace Contam. from the Air. ACS Symp. Ser., 17, ACS, Washington, DC (1975). 10. F. W. McLafferty, in High Performance Mass Spectrometry: Chemical Applications (Edited by M. L.
Gross); R. G. Cooks, J. H. Beynon, R. M. Caprioli and G. R. Lester, Metastable Ions. Elsevier, Amsterdam (1973).