Journal of Analytical and Applied Pyrolysis, 17 (1990) 371-379
Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands

EFFECT OF ADDING MET
AL POWDER AND INORGANIC SALTMETALSALTYSISPYROLYSISPYROLYSISTO A PYROLYSIS FOIL ON SELECTIVE PYROLOF PHENYL ALKYLAMINES BY CURIE-POINTPYROLYSIS-GAS
CHROMATOGRAPHYPYROLYSIS-GAS CHROMATOGRAPHY
MINEMASA HIDA and TOSHIYUKI MITSUI *Criminal Science Laboratory, Aichi Prefecture, 2-1 -1, Sannomaru, Naka-ku,
Nagoya 460 (Japan)

YOSHIKAZU FUJIMURA
Department of Industrial Chemistry, Faculty of Engineering, University of Chubu,
1200, Matsumoto-cho, Kasugai 487 (Japan)(Received January 10, 1990; accepted March 8, 1990)
ABSTRACTThe purpose of this study was to determine the effects on pyrolysis of metal powder andinorganic salt additives. Aniline, benzylamine, 2-phenyl-l-ethylamine and 3-phenyl-l-propylamine were used as samples for pyrolysis, because they have a benzene ring and an aminogroup as common structural units, and alkyl side chains of varying length. It can beconcluded that the choice of metal and inorganic salt additives is one of the most importantfactors in the design of procedures allowing a high degree of control over the products ofpyrolysis. It is suggested that the choice of metal should be made on the basis of bonddissociation energy, and the choice of salt on the basis of cation complexation ability withamine.
Gas chromatography; phenyl alkylamines; pyrolysis, Curie-point.

INTRODUCTION
Pyrolysis-gas chromatography (Py-GC) is one of the most powerful
techniques available for the study of various polymers and essentiallynon-volatile compounds [1]. However, ordinary pyrolysis operations aredifficult to apply to quantitative analysis, since sufficient reproducibility andprecision cannot be obtained. In a series of articles [2-5] we have reported
the results of analysis of medicines, agrochemicals and other chemicals by
Curie-point Py-GC. The analytical technique we have developed involves

pyrolysis of a sample in the presence of a mixture of a metal powder and an
inorganic salt on a pyrolysis foil (pyrofoil). Thus procaine hydrochloride has
been determined by Py-GC at 590°C with nickel powder:potassium
iodide: ammonium sulfate (10:3:2 wt.%) [2], with a relative standard
deviation of about 2%. A number of local anesthetics have been determinedin a similar manner. The herbicide Paraquat has been determined by Py-GC
at 445°C in the presence of a mixture of nickel powder and potassium
iodide (2:1 wt%) [3]. The sensitivity of the method was about 70 times
greater than in the absence of the mixture. Glyphosate has been determinedby Py-GC at 590°C with chromium powder and sodium carbonate (2:1wt%) [4], with reproducibility almost equal to that achieved by gas chromatography/mass spectrometry. Although we have also shown that themolecular weight of the sample can be used as an indication as to which
metal additive to choose, obtaining satisfactory results has proved difficult[5].
The objective of the present work was to determine the effects of various
metal powder and inorganic salt additives. Aniline, benzylamine, 2-phenyl1-ethylamine and 3-phenyl-l-propylamine were used as pyrolysis samples,
because they have a benzene ring and an amino group as common structuralunits, and alkyl side chains of varying length.
EXPERI MENTAL

Apparatus and reagents
A Curie-point pyrolyzer (Japan Analytical Industry Co. Ltd., ModelJHP-2) was directly coupled to a gas chromatograph (Hitachi Model 163)
equipped with a flame ionization detector (FID). The temperatures of thepyrolyzer unit and the tube connecting the pyrolyzer and gas chromatographwere maintained at 150 and 200°C, respectively. The analytical column wasa stainless steel tube (2 mX3 mm I.D.) packed with 10% PEG 20M
supported on 80-100 mesh Chromosorb. The GC oven program used was asfollows: an initial oven temperature of 40°C, an isothermal period foraniline, a 5°C/min ramp to 80°C for benzylamine, a 7.5°C/min ramp to120°C for 2-phenyl-l-ethylamine, and a 10°C/min ramp to 130°C for
3-phenyl-l-propylamine (Table 1). FID signals were processed using a
Hewlett-Packard Model 3390A integrator.
Metal powders, metal chlorides and aniline purchased from Wako Pure
Chemical Ind. (Osaka, Japan) were used without further purification. Benzylamine, 2-phenyl-l-ethylamine and 3-phenyl-l-propylamine were obtained
from Tokyo Kasei Ind. (Tokyo, Japan). Benzylamine and 3-phenyl-l-pro-TABLE 1
Operating conditions of the instrument
Pyrolyzer
Japan Analytical Ind. JHP-2
Oven temperature
150°C
Pipe temperature
200°C
Pyrolysis time5s
Gas chromatograph
Hitachi 163
Column
10% PEG 20M chromosorb(AW-DMCS) 3 mm I.D.X2 mColumn temperature *(a)40°C(b)40-80°C, 5°C/min(c) 40-120°C, 7.5 °C/min(d) 40-130° C, 10° C/min
Carrier gas
N2Detector
FID Range 102, 103* (a) Aniline hydrosulfate, (b) benzylamine hydrochloride, (c) 2-phenyl-l-ethylamine hydrochloride, (d) 3-phenyl-l-propylamine hydrochloride.

hydrosulfate and hydrochloride salts, respectively. The amines were used asaqueous solutions. The metal chlorides were used as their hexahydrates,
except for manganese chloride, which was used as a tetrahydrate.

Procedure
The following procedure was used. Adequate amounts of metal powder
and metal chloride were mixed thoroughly in an agate mortar. The mixture
was placed onto a piece of pyrofoil (about 9 mm X 22 mm, 0.05 mm thick)using a micro-spatula. The sample solution was added using a micro-syringe,
the needle head of which had been flattened so that the whole sample
solution could be injected onto the pyrofoil. The solvent on the pyrofoil was
evaporated to dryness on a hot plate at about 100°C. The pyrofoil was
loaded into the pyrolyzer after careful folding. The Py-GC conditions areshown in Table 1. About 40 ì/g of sample were used for each experimental
determination. The experiments were then developed as follows.
(1) Metal powder. 20 mg samples of metal powder were added to thepyrofoil. The metals used were aluminum, chromium, manganese, iron,nickel, copper and zinc. The optimum metal was chosen so as to maximize
the yield of aromatic hydrocarbons (e.g. benzene, toluene) as measured by
the peak area of largest detector response, and so as to obtain a simple
pyrogram.
(2) Inorganic salt. Mixtures of 4 mg of metal chloride and 20 mg of theoptimum metal powder were added to the pyrofoil. The salts used weremagnesium chloride, aluminum chloride, manganese chloride, ferric chloride, cobaltous chloride and nickel chloride. The optimum salt was chosen in
the same manner as was the optimum metal.

(3) Amount of salt added. Mixtures of 1-20 mg of the optimum salt and10 mg of the optimum metal were added to the pyrofoil. The optimum
amount of salt was chosen in the same manner as was the optimum metal.
(4) Pyrolysis temperature. The optimum mixture of salt and metal wasadded to seven kinds of pyrofoil (333, 386, 445, 500, 590, 670 and 764ºC),
in order to observe the effect of pyrolysis temperature. The optimum
temperature was chosen in the same manner as was the optimum metal.
RESULTS AND DISCUSSION
Effects on pyrolysis of metal additives
The effects of the metal additives on the pyrolysis of benzylaminehydrochloride are shown in Fig. 1. From Fig. 1 and Table 2, it can be seenthat when a metal of high Curie point was used, the sample amines
decomposed into small fragments. If the metal had a Curie point, thepyrolysis temperature was close to that Curie point temperature for theapparatus used. When the Curie point of the metal was higher than thetemperature of the pyrofoil, the pyrolysis temperature was achieved at theCurie point. The relationships between the metal added and the production
yields of benzene, toluene, ethylbenzene and propylbenzene are summarizedin Table 2. As can be seen from Table 2, the maximum total production for
all the amines was observed when chromium powder was added to thepyrofoil. The pyrolysis temperature was close to the temperature of thepyrofoil when chromium was used as the metal additive, because chromium
does not have a Curie point. Chromium powder was chosen as the optimum

TABLE 2Effects of metal powders on peak areas of pyrolysis products ( X 103)

To the pyrofoil (500ºC) was added 20 mg metal powder for 41.1 µg aniline sulfate and 40.2µg 3-phenyl-l-propylamine hydrochloride. To the pyrofoil (590ºC) was added 20 mg metalpowder for 41.2 µg benzylamine hydrochloride and 41.5 µg 2-phenyl-l-ethylamine hydrochloride.

metal powder, to be used in the subsequent experiments. Further, dissociation of the amino groups was predominantly observed when chromium wasused. On the other hand, manganese promoted dissociation of the sample
amine into the benzene ring and methylene group. This can be explained by
the fact that manganese has a Curie point of 1131ºC and the sample waspyrolyzed at about 1131ºC, which was higher than the temperature of thepyrofoil. It seems that the results obtained were related to the Curie pointsof the metal powder additives [6].

Effects on pyrolysis of metal chloride additives
The effects of the salt additives on the pyrolysis of benzylamine hydrochloride are shown in Fig. 2. The relationships between the metal chloride
added and the production yields of benzene, toluene, ethylbenzene andpropylbenzene are presented in Table 3. In general, yields of pyrolysis
products were higher when ferric chloride, nickel chloride and aluminum
chloride were used than when other salts were used. Dissociation of theamines into the benzene ring and methylene group was predominantly
observed with nickel chloride and aluminum chloride. Further, ferric chloride and nickel chloride were superior to the other salts in terms of theireffect on the dissociation of the amino groups. The exact weight of aluminum
chloride used was difficult to determine because of its high deliquescence.
As a result, ferric chloride was used for the pyrolysis of aniline andbenzylamine, and nickel chloride was used for 2-phenyl-l-ethylamine and3-phenyl-l-propylamine. In the presence of only chromium powder, themost abundant products obtained from pyrolysis of 2-phenyl-l-ethylamineFig, 2. Effects of inorganic salts on the pyrolysis of benzylamine hydrochloride To thepyrofoil (590ºC) was added a mixture of 4 mg salt and 20 mg chromium powder with 41.2µg beruylamine hydrochloride. Dashed areas, benzene; plain areas, toluene.

and 3-phenyl-l-propylamine were toluene and ethylbenzene, respectively. By
contrast, in the presence of a mixture of chromium and nickel chloride, themost abundant products were ethylbenzene and benzene, respectively(Tables 2 and 3).

Effects on pyrolysis of the amount of metal chloride added
Figures 3a and 3b illustrate the effects of the amount of nickel chloride
hexahydrate on, respectively, peak area and formation ratio of pyrolysis

products obtained from 3-phenyl-l-propylamine hydrochloride. Figure 3ashows that the peak area of the products increased up to 5 mg and remained
almost constant about 5 mg. Figure 3b shows that the formation ratios ofbenzene and toluene decreased and that of propylbenzene increased up to 5and 10 mg, respectively, and that the ratios thereafter remained almostconstant. Ethylbenzene increased up to 5 mg, and then gradually decreased.
Figures 3a and 3b combined indicate that the same reactions would occur inthe range 10-20 mg of nickel chloride hexahydrate.

Effects on pyrolysis of the pyrolysis temperature
The effects of varying the temperature for the pyrolysis of 3-phenyl-lpropylamine hydrochloride (40.2 µg) with a mixture of 10 mg of chromiumand 15 mg of nickel chloride hexahydrate are shown in Figs. 4a and 4b.
Figure 4a shows that yields of benzene, ethylbenzene and propylbenzene
were highest at 445º C, while the yield of toluene increased with increasing
temperature. The peak areas of benzene, ethylbenzene and propylbenzene
decreased above 445º C, because of the decomposition of the 3-phenyl-lpropylamine into small fragments. The formation ratio of benzene wasroughly constant above 445º C, and those of ethylbenzene and propylbenzene decreased slightly above 500º C, as can be seen from Fig. 4b. Figures
4a and 4b suggest that the formation reaction of toluene differs from theformation reactions of the other products. The recommended pyrolysis
conditions for the amines considered are summarized in Table 4.
Figure 5 shows typical pyrograms of 3-phenyl-l-propylamine hydrochloride. The observed benzene peak area at about 4.5 min from the optimum
condition (Fig. 5d) was about 30 times as large as that observed without any
additives (Fig. 5a).
CONCLUSIONS
It can be concluded from this study that the choice of metal and inorganic
salt additives is one of the most important factors in the design of procedures allowing a high degree of control over the products of pyrolysis. Ourfindings suggest that the metal powder and inorganic salt chosen affect thepyrolysis temperature and the ratio of pyrolysis products, respectively. The
peak areas of the pyrolysis products and the formation ratios are importantfactors in the determination of the amines considered. Future publicationswill address the results of further studies in this area.
REFERENCES
1 S. Tsuge and H. Ohtani, Pyrolysis-Gas Chromatography of Polymers:
Fundamentals andData Compilation, Tekunoshisutem, Japan, 1989.
2 Y. Minami, T. Mitsui and Y. Fujimura, Bunseki Kagaku, 37 (1988) 259.
3 T. Mitsui, Y. Minami and Y. Fujimura, Bunseki Kagaku, 36 (1987) 821.
4 M. Hida, T. Mitsui and Y. Fujimura, Bunseki Kagaku, 38 (1989) 87.
5 M. Hida, T. Mitsui and Y. Fujimura, J. Anal. Appl. Pyrolysis, 17 (1990) 181.
6 Metal Data Book, 1974, Japan Metals Society, Maruzen, p. 10.