528
Russian Chemical Bulletin, International Edition, Vol. 59, No. 3, pp. 528—532, March, 2010
Isothiocyanates as derivatization reagents in the determination
of 1,1ꢀdimethylhydrazine by gas chromatography
coupled with mass spectrometry
S. A. Paramonov, A. V. Ul´yanov, and A. K. Buryak
A. N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences,
Building 4, 31 Leninsky prosp., 119991 Moscow, Russian Federation.
Eꢀmail: chromꢀms@mail.ru
Alkyl isothiocyanates were proposed for the determination of 1,1ꢀdimethylhydrazine (DMH)
in the form of 4ꢀalkylꢀ1,1ꢀdimethylthiosemicarbazides by gas chromatography coupled with
mass spectrometry (GCꢀMS). 4ꢀAlkylꢀ1,1ꢀdimethylthiosemicarbazides are selectively formed
under mild conditions in the absence of catalysts. During the chromatography, these thiosemiꢀ
carbazides are efficiently resolved from excess of alkyl isothiocyanates. A possibility of identifiꢀ
cation of DMH derivatives on the basis of the chromatographic retention parameters and
fragmentation data under electron ionization conditions was demonstrated.
Key words: gas chromatography, mass spectrometry, 1,1ꢀdimethylhydrazine, isothiocyanꢀ
ates, thiosemicarbazides.
1
,1ꢀDimethylhydrazine (DMH) is a highly reactive
tion of ammonia and aliphatic amines by HPLC with UV
1
1
compound widely used as a component of rocket propelꢀ
lant and in fine organic synthesis and semiconductor proꢀ
duction. The reliable determination of DMH in the proꢀ
duction and use, the evaluation of purity, and the determiꢀ
nation of the impurity content are important tasks.
The existing chromatographic1—3 and GCꢀMS methꢀ
ods4—8 of analysis are based on the transformation of DMH
into a more convenient analytical form using derivatizaꢀ
tion reagents and have several drawbacks: derivatization is
carried out at elevated temperature; considerable excess of
the reagent is used; acidꢀbase catalysts capable of accelerꢀ
ating DMH decomposition are used; inefficient chromatoꢀ
graphic resolution of a reagent—product pair; low inforꢀ
mative content of mass spectra that do not allow DMH to
be reliably identified.
detection. Allyl isothiocyanate was used for the determiꢀ
nation by pyrolytic GCꢀMS of the content of aromatic
amines in the form of the corresponding aryl isothiocyanꢀ
ates obtained by the pyrolysis of NꢀallylꢀN´ꢀarylthioureas
1
2
in the injector of the chromatograph. Nevertheless, no
isothiocyanates were proposed for DMH determination
by gas chromatography or GCꢀMS.
The purposes of the present work are the study of the
reactivity of DMH in reactions with alkyl isothiocyanates,
selectivity of derivatization, formation of byꢀproducts.
chromatographic behavior of derivatization products, regꢀ
ularities of their fragmentation in the electron ionization
(EI) mode, and evaluation of a possibility of DMH identiꢀ
fication from chromatographic and GCꢀMS data.
Compounds with isocyanate and isothiocyanate groups
are widely used in chromatographic analysis of amino
compounds. It is known that phenyl isocyanate (PIC)
Experimental
9
1
,1ꢀDimethylhydrazine (GOST V 17803ꢀ72) was additionꢀ
vigorously reacts with DMH to form a series of products,
whose composition depends on the reactant ratio. For
instance, to obtain the equimolar addition product capaꢀ
ble of acting as an analytical form, it is necessary to use
a threefold excess of DMH. Because of this fact and
formation of oligoureas, PIC cannot be used in the deterꢀ
mination of DMH. Another substantial disadvantage of
PIC is its nonꢀselectivity to Nꢀ and Oꢀnucleophiles, such
as secondary amines, alcohols, thiols, carboxylic acids,
hydroxylamines, and water, which impedes the determiꢀ
nation. Phenyl isothiocyanate was used in the determinaꢀ
ally distilled from sodium hydroxide. Ethyl isothiocyanate and
allyl isothiocyanate (Aldrich), dichloromethane (special purity
grade, Kriokhrom, Russia), graphitized thermal carbon black
2
–1
(
GTC, Sterling MT) with a specific surface of 7.6 m g , and
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0
sodium hydroxide (analytical purity grade, KhIMMED, Russia)
were used.
Analysis was carried out on a JEOL JMSꢀD300 GCꢀMS
instrument coupled with an НРꢀ5890 chromatograph. A quartz
capillary column 30 m × 0.53 mm with the DBꢀ5 (J&W) stationꢀ
ary phase was used for chromatographic resolution; the chroꢀ
matographic resolution conditions were as follows: injector temꢀ
perature 300 °C, gas carrier (helium) rate 5 mL min– , flow ratio
1
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 517—520, March, 2010.
066ꢀ5285/10/5903ꢀ0528 © 2010 Springer Science+Business Media, Inc.
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