Chromato-mass-spectrometric identification using partition coefficients in the system of hexane-2,2,2-Trifluoroethanol

Article abstract of DOI:10.1134/S1070363212080105

An additional characteristic of organic compounds, the partition coefficients in the heterophase solvent system n-hexane-2,2,2-trifluoroethanol, is shown to be useful for refining the results of chromatographic and gas chromatography-mass spectrometric identification. This opportunity is the most important for compounds that were not yet characterized by either mass spectra or chromatographic retention indices. Pleiades Publishing, Ltd., 2012.

Full text of DOI:10.1134/S1070363212080105

ISSN 1070-3632, Russian Journal of General Chemistry, 2012, Vol. 82, No. 8, pp. 1391–1399. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © I.G. Zenkevich, 2012, published in Zhurnal Obshchei Khimii, 2012, Vol. 82, No. 8, pp. 1311–1320.
Chromato-Mass-Spectrometric Identification
Using Partition Coefficients in the System
of Hexane–2,2,2-Trifluoroethanol
I. G. Zenkevich
St. Petersburg State University, Chemistry Department, Universitetskii pr. 26, St. Petersburg, 198504 Russia
e-mail: izenkevich@mail15.com
Received December 1, 2011
Abstract—An additional characteristic of organic compounds, the partition coefficients in the heterophase
solvent system n-hexane–2,2,2-trifluoroethanol, is shown to be useful for refining the results of chromato-
graphic and gas chromatography–mass spectrometric identification. This opportunity is the most important for
compounds that were not yet characterized by either mass spectra or chromatographic retention indices.
DOI: 10.1134/S1070363212080105
The most effective nowadays method for identifica-
tion of trace organic compounds in complex mixtures
is the gas chromatography–mass spectrometry. The
objective reasons of this consist in the high infor-
mativity of mass spectra (multidimensional analytic
parameters), complete “computerization” of data
processing, the availability of efficient algorithms for
interpreting mass spectrometric data and, more
important, the availability of a sufficiently detailed
database of mass spectra. For example, the latest
version of the database NIST11/2011/EPA/NIH (2011)
includes 243 893 standard (electron ionization) mass
spectra of 212 961 compound [1]. However, the per-
formance of mass spectrometry in no way precludes
the use of known methods of chromatographic iden-
tification, primarily those based on the use of retention
indices (RI). Although being objectively less infor-
mative (one-dimensional parameters), they allow to
distinguish many types of compounds with almost
identical mass spectra, including structural isomers. At
the same time, the use of only the RI values, without
any additional information, is not sufficient for une-
quivocal identification, so they are usually combined
with other characteristics of the test compounds. Thus,
one of the recommendations is the parallel determina-
tion of RI by varying the polarity of stationary phases
called gas chromato-partition method [4, 5]. It involves
the characterization of the analytes partition coef-
ficients (Kpart.) in a two-component heterophase sys-
tems formed by organic solvents partially soluble in
each other. The Kpart. values are usually expressed as a
ratio of equilibrium mass-volume concentrations in a
nonpolar (c ) and polar (c ) layers. Hence, the analysis
of each layer of the heterophase system is required to
determine Kpart., which roughly doubles the total time
of the measurement:
1
2
K
part. = c
1
/c
2
≈ S
1
/S
2
,
(1)
where S and S are the peak areas of the respective
1
2
component measured at equal volumes of the respec-
tive layers.
An important advantage of this technique is that it,
unlike the determination of RI on the phases of
different polarity, completely eliminates the ambiguity
at comparing the signals of a compound in various
chromatograms.
In determining the Kpart. using Eq. (1) the results
accuracy depends on the constancy of the ratio c /c
1
2
and reproducibility of measurements of the peak
absolute area. To provide the condition c /c ≈ const,
1
2
the total concentration of analytes in heterophase
systems should not exceed about 3% [5]. To assess the
influence of the second factor, the known relation (2)
is used, in which the relative standard deviation (coef-
[2,3], but in the case of multicomponent mixtures this
can lead to a significant uncertainty of the results.
Among all the chromatographic techniques, perhaps
the only one remains important up to now: the so-
ficients of variation, δX = s /X) is marked by δ:
X
1
391

1
392
ZENKEVICH
(2)
viously. The applicability of this relation was shown
2
1
2 1/2
δKpart. = [δS
2
+ δS ] .
by the example of heterophase systems hexane–
acetonitrile [5], hexane–nitromethane [7] and hexane–
In order to reduce the influence of the dosing
accuracy on the accuracy of Kpart., an internal reference
is added sometimes to the heterophase system with
known Kpart. value, so the absolute peak area can be
replaced by the more reproducible relative area:
2
,2,2-trifluoroethanol [8]. A feature of the latter system
is that its polar component contains active hydrogen
atoms. Among such systems, only the heptane–2,2,2-
trifluoroethanol combination has previously been
described [9], for which the values of Kpart. of various
compounds were measured and a possibility of
calculating them using multilinear regression equations
were demonstrated. However, the features of
heterophase systems containing polar components with
active hydrogen atoms for identification of analytes so
far have not been characterized in detail.
K
p
1
art. ≈ Kpart.ref. (S /Sref.1)/(S
2
/Sref.2),
(3)
where Sref.1 and Sref.2 are the reference peaks area in
layer 1 and 2, respectively.
2
2 1/2
δK'part. = [δKpart.ref2 + δ(S
1
/Sref.1) + δ(S
2
/Sref.2) ] . (4)
2
2
i
2
i
2
However, actually: δ(S /S ) < δS < δS + δS ,
ref.i
i
ref.i
but δKpart.ref ≈ δKpart., so, in general, δK'part. > δK and,
consequently, the use of internal standards do not reduce
the random errors in the determination of partition
coefficients.
The present work considers the capabilities and
features of refining interpretation of the results of chromato-
graphic and gas chromatography–mass spectrometry
data for identification of organic compounds using the
partition coefficients in the hexane–2,2,2-trifluoro-
ethanol system.
General requirements for sample preparation in gas
chromato-partition method are similar to the well-
known guidelines for the preparation of derivatives
(
derivatization) of the test compounds for the chro-
matographic analysis [6]. To obtain the derivatives, the
sample is treated with an excess of reagent (the exact
amount is not determined commonly) and, sometimes
left to stand for some time to complete the reaction
There are no chemical constraints of the use of
polar solvents containing active hydrogen atoms in the
hydroxy groups in the chromato-partition method. The
value of pK of 2,2,2-trifluoroethanol is 12.4 [10],
a
(
heat is permissible). In the second case (at the
which is higher than, for example, the value of pKa
measuring Kpart.) a part of the sample is dosed into a
heterophase system, stirred vigorously and, after
splitting the system, each layer is analyzed separately.
It is desirable to avoid keeping the samples at a
controlled temperature since the contributions to the
Kpart. variations due to variations of ambient tem-
perature should not exceed the random errors at the
dosage, estimated by the expressions (2) and (4).
used in gas chromato-partition method for nitro-
methane [7] (a CH acid, pK = 10.4). However, a
a
common problem in application of any polar solvent is
the presence of uncontrolled water impurities [11],
which may significantly affect the value of Kpart.
.
The effect of water impurities in a polar solvent
on the values of partition coefficients. Comparing the
published results of studies, it may be noted that
unfortunately in measuring the partition coefficients
the testing of water content in polar solvent, as well as
removal of water when its content is too high, are often
neglected. This can introduce significant additional
errors in the measurement of Kpart. because the
impurity of such polar compound as water (ε ~78–80,
μ ~1.8 D) in the polar solvent affects the mutual
solubility of the components of heterophase systems
and, consequently, the value of Kpart.. The NIST
database illustrated a considerable scatter in the data
on the mutual solubility of nonpolar and polar organic
solvents caused probably by the presence of water in
the polar component [12]. For example, the solubility
of acetonitrile in hexane according to various estimates
falls to the range from 2.87 to 6.02 wt % at the same
temperature 298.2 K.
One of the most interesting algorithms of using
Kpart. in conjunction with retention indices is the ability
to classify analytes according to homologous series
(
group identification) and the use of differential
analysis parameter j [5]:
j = k RI – log Kpart.
,
(5)
–2
where the coefficient k = 10 log K (CH ) is propor-
part.
2
tional to the difference in free solvation energies of
homologous difference CH in the two phases of the
2
system [5]; it characterizes selectivity of the system
with respect to different homologous series.
The values of k and j are calculated by the method
of least-squares from the data for the known analytes,
and then they can be used for group identification of
the homologs of the same series not characterized pre-
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CHROMATO-MASS-SPECTROMETRIC IDENTIFICATION
1393
Table 1. Effect of trace amounts of water in the polar solvent (before and after drying with the molecular sieves) on the
partition coefficients of organic compounds in the hexane–2,2,2–trifluoroethanol heterophase system
Compound
Kрart.±s
K
(water content 1.1 wt %)
Kрart.±s
K
(water content < 0.01 wt %)
Low polar compounds (Kpart. > 1)
1
-Bromodecane
37.1±1.6
37.1±0.6
13.2±0.2
5.5±0.1
p-Pentylbenzene
-Bromo-4-methylbenzene
13.6±1.5
1
5.5±0.1
Compounds of moderate polarity (Kpart. < 1)
n-Butyl acetate
n-Hexyl acetate
0.23±0.05
0.35±0.04
0.16±0.04
0.20±0.03
0.13±0.01
0.22±0.02
0.08±0.01
0.10±0.02
2
2
-Hexanone
-Heptanone
Another example of the adverse effects of water
contained in polar solvents is given in [13]. To obtain
trimethylsilyl derivatives of the analyzed compounds
in the 0.5 ml of n-hexane and 0.5 ml of nitromethane
value of Kpart. < 1 of the compounds of medium
polarity is reduced 1.6–2.0-fold.
1
Consequently, it is necessary to check the water
content in polar organic solvents forming heterophase
systems and, if necessary, to carry out their
dehydration. The example (3) below shows that some
compensation of the water effect on the value of Kpart.
can be obtained at the stage of data processing, but, in
general, this leads to additional errors in the results.
(
Aldrich) containing 1 mg of the studied compound
Kotowska et al. [13] had to add to the mixture 20 μl of
pyridine and 50 (!) μl of N,O-bis(trimethylsilyl)
trifluoroacetamide (BSTFA). The necessity to use
large amounts of silylating reagent is due to the fact
that it mainly reacted with the water admixture in the
nitromethane (hydrolyzed) and not with the analyte. As
a result, the concentration of additional components in
the polar layer reaches ~(20 + 50)/(500 + 20 + 50) ≈
The partition coefficients in the hexane–2,2,2-
trifluoroethanol system of 67 compounds belonging to
12 homologous series were measured in [8].
Combining these data with the RI reference values for
standard nonpolar polydimethylsiloxane stationary
phases allows us the estimation of the value of the
differential parameter j [Eq. (5)] for 13 homologous
series. The values obtained are listed in Table 2 in
comparison with the j values for the same series in the
system of hexane–acetonitrile.
1
2%, well above the recommended permissible value
of ~3% [5] and, hence, leads to the inevitable
distortions of all Kpart. values identified in [13].
The need of drying polar organic solvents used for
the determination of Kpart. has been mentioned
specifically in several articles. In the case of aprotic
compounds (acetonitrile [5], nitromethane [7]) it is
possible to use anhydrous magnesium sulfate for this
purpose. In the case of hydroxy-containing solvents
Features of the hexane–2,2,2-trifluoroethanol
heterophase system. The most significant distinction
(
including 2,2,2-trifluoroethanol) it is preferable to use
of
the
heterophase
system
hexane–2,2,2-
molecular sieves [8]. Table 1 illustrates the effect of
impurity of water in the polar component of the
hexane–2,2,2-trifluoroethanol system on the values of
Kpart. of some compounds (a more complete version of
Table 1 is given in [8]). While the values of Kpart. > 1
for weakly polar compounds (alkyl bromides,
alkylarenes) with variations in the water content from
trifluoroethanol from the previously characterized
systems of hexane–acetonitrile [5] and hexane–
nitromethane [7] consists in the closeness of the
parameters j in the series of compounds containing the
same heteroatoms but differing in the values of the
1
In keeping with the used terms the compounds with Kpart. ≈ 0
1
.1 to < 0.01wt% (below the limit of detection using
should be classed as strongly polar where the influence of trace
quantities of water is negligible.
katharometer) remain practically the constant, the
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394
ZENKEVICH
Table 2. The values of the j parameter [Eq. (5)] in the system hexane–2,2,2-trifluoroethanol (I) for some homologous series
[
(
8] (in ascending order) in comparison with the values of the j parameter of the same series in the hexane–acetonitrile system
II) [5]
a
Homologous series
Alkanes
General formula
j ± 2s
j
(I)
j
j ± s (II)
C
n
C
n
C
n
C
n
C
n
C
n
C
n
C
n
C
n
C
n
C
n
C
n
C
n
H
H
H
H
H
H
H
H
H
H
H
H
H
2n+2 (0)
–0.17±0.06
0.20±0.18
0.64±0.04
0.69±0.08
0.84±0.04
0.96±0.04
1.52±0.08
1.58±0.04
2.26±0.08
2.37±0.06
2.41±0.04
2.65±0.16
2.79±0.10
–0.40±0.07
–0.19±0.09
0.62±0.18
0.60±0.04
0.70±0.05
Alkenes
2n (1)
Alkyl iodides
Alkyl bromides
Alkylarenes
2n+1I (0)
2n+1Br (0)
2n–6 (4)
b
Aryl bromides
Alkyl trihloracetates
Alkyl benzoates
Alkyl acetates
Alkanols
2n–7Br (4)
1.00±0.09
1.18±0.07
1.68±0.25
1.02±0.12
1.61±0.12
1.23±0.11
–
2n–3
2n–8
O
2
2
Cl
3
(1)
O
(5)
2n
2
O (1)
2n+2O (0)
2nO (1)
Alkanones
Arylalkanols
Alkyl aryl ketones
2n–6O (4)
2n–8O (5)
1.69±0.08
a
b
The values of formal incertainty are given in parentheses. Rating by additive scheme using the values of j for alkylarenes, alkyl
bromides, and alkanes.
formal unsaturation (FU) by unity. They include such
pairs of series as alkanols (2.37±0.03) and alkanones
between the maximum and minimum j values listed in
Table 2 is 2.79–0.17 = 2.62 for the system hexane–
2,2,2-trifluoroethanol {value of the coefficient k in Eq.
(
2.41±0.02), arylalkanols (2.65±0.08) and alkyl aryl
–
3
ketones (2.79±0.05). In all these cases, the difference
in the parameter j does not exceed the sum of the
corresponding standard deviations, |j –j | < (s + s ),
(5) is (1.67±0.12)×10 ] and 1.69 – (–0.40) = 2.09 for
–
3
the system hexane–acetonitrile [k = (1.0±0.2)×10
[5]}, which illustrates the great selectivity of the first
of them in relation to different homologous series.
1
2
1
2
which was not observed for the previously investigated
heterophase systems. Thus, when the hexane–2,2,2-
trifluoroethanol system is used for the homologous
series of compounds differing by structural fragments
C–X and C=X (at least for X = C, O), the j values are
close. Apparently, the reason for this is the
fundamentally different nature of intermolecular
interactions of analytes with polar solvents lacking or
containing functional groups with active hydrogen
atoms (in the latter case the main interaction is
apparently the hydrogen bonding). No less interesting
properties of this system is the similarity of j values of
alkanols (2.37±0.03) and alkyl acetates (2.26±0.04), as
well as the fact that the j value of alkyl benzoates
The use of a heterophase system hexane–2,2,2-
trifluoroethanol in the chromatographic and
chromatography–mass spectrometric identification.
The simplest version of the identification of individual
components of analyzed samples includes an in-
dependent comparison of the retention indices (RI) and
the partition coefficients (Kpart.) with reference data.
The same is used for the group identification
(
assignment to the respective homologous series): it is
based on the combinations of RI and Kpart. in the form
of differential parameter j. After the assignment to a
series, further refinement of the structure of the
homolog is performed, based on the detailed inter-
pretation of the RI values.
(
(
1.58±0.02) is much smaller than that of alkyl acetates
2.26±0.04). These features of the combined hexane–
2
,2,2-trifluoroethanol solvent, on the one hand, reduce
Example (1). An illustration of the “standard” use
of hexane–2,2,2-trifluoroethanol system is the
identification of major components of essential oils of
cow parsnip (Heracleum) [14], which include a limited
the informativity of the Kpart. values, but, on the other
hand, can be effectively used for the identification of
unknown substances [see example (3)]. The difference
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CHROMATO-MASS-SPECTROMETRIC IDENTIFICATION
1395
Table 3. Retention indices, partition coefficients, and j parameters used for the identification of the products of reaction of
cyclohexanone with PCl [see example (2)]
5
RI
K
part.
j
Δj
Result of the identification
1,1-Dichlorocyclohexane
9
81±2
5.3
0.91
1.62
2.32
1
188±2
2.3
1.1
0.71
0.70
1,1,2-Trichlorocyclohexane
1
414±2
1r-cis-2-trans-3-cis-4-Tetrachlorocyclohexane
number of series of the compounds, mainly mono-
terpenes C H and alkyl alkanoates RCO R'. But
cyclohexane and 1,1-dichlorocyclohexane (0.71) cor-
responds to the increment of the chlorine atom. Note
that the j value of the compound with IR = 1414 differs
from the j value of 1,1,2-trichlorocyclohexane by
almost the same magnitude (Δj = 0.70). Such additivity
evidences that this product should be attributed
unambiguously to tetrachlorcyclohexanes. Further re-
finement of its structure requires a comparison of the
RI value of this component with the estimates of RI
values for all the isomeric tetrachlorocyclohexanes
1
0
16
2
more interesting is the possibility to use the chromato-
partition method for the identification of compounds
that have never been characterized previously by mass
spectra, gas chromatographic retention indices or the
partition coefficients.
Example (2). Application of chromato-partition
method is effective in the identification of the products
of regio nonselective organic reactions even in the
absence of pre-defined Kpart. values of the components
of the reaction mixtures and/or j parameters of the
corresponding series. As an example consider the
identification of the minor product of the reaction
between cyclohexanone and phosphorus pentachloride,
the main ones being 1,1-dichlorocyclohexane and
(
including diastereomers) by the additive scheme
considered in [16], which indicates the highest
probability of the 1r-cis-2-trans-3-cis-4-tetrachloro-
cyclohexane. Note that in this example the iden-
tification is carried out without the involvement of the
mass spectrometric information, but only on the basis
of gas chromatographic data.
1
,1,2-trichlorocyclohexane [15]. Among the minor com-
ponents, a compound with RI = 1414±2 predominated.
The determination of RI and Kpart. of these products in
a heterophase system hexane–2,2,2-trifluoroethanol
Hence the regularities in the changes of the
parameters like K ., ΔKpart., j, and Δj in the taxonomic
part
groups of isomers, homologs (the variable structural
fragment is the homologous difference), and of
congeners (the variable structural fragment is the
number of heteroatoms or functional groups) in
dependence on the type of the structural variations in
the organic molecules can be represented as follows:
(
they regularly decrease from 5.3 to 1.1, which is
consistent with the increasing number of chlorine
atoms in the molecule) allows the evaluation of the
corresponding j values (listed in Table 3). The dif-
ference between the j values of 1,1,2-trichloro-
Taxonomic group of organic
K
рart.
ΔKрart.
j
Δj
compounds
Isomers
≈ const
≠ const
≠ const
–
≈ const
≈ const
≠ const
–
–
Homologs
Congeners
≈ const
≠ const, sign(ΔKрart.) = const
≈ const
These capabilities of the chromato-partition method
confirm its effectiveness in solving such problems as
the identification of products of alkylation of arenes
identification of the sample components belonging to
different taxonomic groups is valid for any hetero-
phase system. Such systems may not necessarily be the
two-component, that is, the removal of the water traces
(third component) from the polar solvents is not
necessary, and the total concentration of analytes in
such systems can significantly exceed the allowable
~3% for the determination of Kpart. [5]. Similar prin-
ciples form the basis of the rapid chromatographic
[17], which include not only a large number of
isomers, but, in some cases, homologs (a consequence
of the fragmentation of the intermediately formed
carbenium ions). It is appropriate to note that such a
comparison of trends in the values of Kpart., ΔKpart., j,
and Δj, rather than their absolute values, for the
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ZENKEVICH
monitoring of the “heterogeneity” of multicomponent
samples [18].
The mass spectrometric data allow us to identify
some of the detected components, but some of these
results require further clarification using the RI values.
The detected compounds are α-phenylethyl alcohol (I)
(RIexp.= 1060±1, RIref. = 1048±11), acetophenone (II)
(RIexp.= 1065±1, RIref. = 1041±9), pentenylbenzene [the
main component of III, the responses include (1-
isopropylethenyl)benzene], pentenylbenzene with
undetermined structure IV, and butyrophenone VI.
The RIexp. = 1188±2 of the last component does not
match RIref. = 1225±12 of butyrophenone, so it must be
identified as isobutyrophenone (RIref. = 1174±12). It is
reasonable to assume that the main component of the
mixture is the expected (1,2-dimethyl-1-propenyl)
benzene, but it is not directly supported by the
uncertain results of mass spectrometric identification.
The set of revealed minor components clearly points to
the scheme of synthesis of this compound on the basis
of acetophenone, since from the practice of monitoring
the purity of chemicals it is known that they usually
contain traces of substances used in the final stages of
their synthesis:
The last example concerns one of the complicated
cases of identification of previously unknown com-
pounds using the partition coefficients in the hetero-
phase system hexane–2,2,2-trifluoroethanol taking into
account specific features of the system.
Example (3). In a sample of (1,2-dimethyl-1-
propenyl)benzene stored for a long time eight
components were revealed in an amount exceeding
1
%. Table 4 shows their absolute retention times,
estimated relative content in the mixture obtained by
internal normalization, retention indices obtained by
two modes of analysis, partition coefficients in the
system of hexane–2,2,2-trifluoroethanol, the corres-
ponding values of the j parameter, and the standard
mass spectra. A feature of this example is the use of
2
,2,2-trifluoroethanol that has not been preliminary
dried, which requires an additional correction of the
Kpart. values.
O
OH
(
(
1) (CH ) CHMgBr
3 2
2) H O
H+
2
+
_
H O
2
III
IV
The retention index of the main component
1094±2) corresponds to the reference value RIref. of
The influence of traces of water in polar solvents on
the values of Kpart. of the compounds with moderate
polarity (Kpart. <1, in this example the compounds II,
V, VI, and VIII) can be partially compensated by
introducing corrections accounting for the j values. To
do this, one must either add to the analyzed sample the
compounds with known j value, or use the data for the
components already present in the mixture. In this
case, two of them (acetophenone II, j = 2.44, and
isobutyrophenone VI, j = 2.35) belong to the series of
alkyl aryl ketones that have been characterized (j =
(
(
1,2-dimethyl-1-propenyl)benzene
(1094±3)
that
allows its unambiguous identification, despite the
uncertainty of the interpretation of mass spectra. As for
the second isomer C H (RIexp. = 1112±2, RIref. is
1
1
14
unknown), it naturally must be identified as (1-
isopropylethenyl)benzene, consistently with the
estimates of boiling points of isomers obtained by
using the ACD software: 191.7±7.0°C (isomer III) and
1
99.9±7.0°C (isomer IV) [19].
2
.79±0.05, Table 2), hence, Δj = 0.35 and 0.44,
Two components of the sample, V and VII, are
characterized by the same molecular weight (M = 162)
respectively (mean value is 0.40). Table 4 lists the jcorr.
values adjusted for this correction. Their comparison
shows that all values are in the range 2.57–2.84, that is,
correspond to the j values of arylalkanols (2.65±0.08)
and aryl alkyl ketones (2.79±0.05), as well as the
respective isomeric compounds with the same
molecular formulas C H O and C H O.
and similar mass spectra [main signals belong to
1
00
fragmentation ions with even mass numbers, (m/z)
04] and hence they are isomers. Due to unique nature
of their mass spectra the results of their identification
using the NIST database[1] are negative. In such cases,
=
1

1
1
14
11 12
to solve the problem, all of the available analytical
parameters should be used, including partition coef-
ficients in heterophase solvent systems.
Taking into account the above chemical
information (method of synthesis and prolonged
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 82 No. 8 2012

CHROMATO-MASS-SPECTROMETRIC IDENTIFICATION
1397
Table 4. The chromatographic and mass spectrometric characterization of the components in the sample of (1,2-dimethyl-1-
propenyl)benzene [see example (3)]
d
a
Relative content
in the mixture, %
b
c
j
Comp. no.
Retention index
1068±3,
K
рart.
Mass spectrum [m/z ≥ 40, Irel. ≥ 2%]
(jcorr.
)
I (9.46)
~1
–
–
123(4), 122(39) [M], 121(4), 108(8), 107(100), 104(3), 91(2), 80(7),
1060±1
79(97), 78(20), 77(36), 74(2), 65(2), 63(3), 53(9), 52(5), 51(18), 50
(
6), 45(4), 43(28)
II (9.59)
~1
55
1077±3,
0.23
9.6
2.44 121(4), 120(41) [M], 106(8), 105(100), 78(8), 77(82), 76(3), 75(2), 74
(2.84) (3), 65(2), 63(2), 52(3), 51(30), 50(11), 43(13)
1065±1
III (10.65)
1094±2,
102±1
0.84 147(6), 146(43) [M], 145(5), 132(12), 131(100), 130(3), 129(11), 128
1
(6), 127(2), 117(5), 116(10), 115(10), 105(3), 104(5), 103(27), 102(5),
9
6
2(4), 91(41), 89(2), 79(2), 78(4), 77(19), 76(3), 75(2), 68(4), 67(4),
5(6), 64(4), 63(3), 53(5), 52(2), 51(11), 50(3), 41(4)
IV (11.09)
18
5
1112±2,
117±1
9.2
0.89 147(8), 146(75) [M], 145(12), 132(11), 131(100), 130(5), 129(17),
1
128(10), 127(4), 118(2), 117(10), 116(14), 115(16), 105(10), 104(2),
103(9), 102(3), 92(4), 91(49), 89(3), 78(5), 77(13), 76(2), 71(2), 68
(2), 67(5), 65(7), 64(5), 63(4), 58(2), 53(7), 52(2), 51(10), 50(3), 41(6)
V (12.14)
VI (13.46)
1147±2,
154±1
0.56
2.17 163(2), 162(17) [M], 161(62), 147(5), 143(2), 129(2), 121(2), 120(3),
(2.57) 119(9), 105(18), 104(100), 103(41), 102(4), 91(8), 79(5), 78(58), 77
1
(
27), 76(3), 65(2), 63(3), 59(6), 52(4), 51(13), 50(4), 43(18), 41(6)
11
2
1188±2,
201±1
0.43
–
2.35 148(12) [M], 106(8), 105(100), 78(3), 77(40), 76(2), 51(12), 50(3), 43
(2.75) (2), 41(3)
1
VII (13.94)
VIII (14.21)
1211±3,
218±1
–
162(5) [M], 147(8), 129(3), 128(3), 119(7), 115(2), 105(10), 104(100),
1
103(13), 102(4), 91(11), 79(2), 78(12), 77(13), 76(2), 74(3), 65(2), 63
(
2), 60(2), 59(52), 52(2), 51(7), 50(2), 43(13), 41(6)
7
1225±3,
228±1
–
2.23 163(3), 162(34) [M], 161(100), 147(11), 143(5), 134(2), 133(14), 132
(2.63) (2), 131(15), 130(2), 129(9), 128(5), 121(2), 120(5), 119(13), 118(5),
1
1
17(50), 116(8), 115(33), 105(13), 104(2), 103(4), 102(2), 92(7), 91
(
(
83), 90(2), 89(4), 79(2), 78(7), 77(17), 76(2), 71(3), 65(12), 64(3), 63
5), 57(2), 55(6), 53(3), 52(2), 51(14), 50(4), 43(17), 41(8)
a
b
c
The retention time for the option 3 is given in parentheses. The values of RI for options 1 and 3, respectively. The partition coefficients
are determined with the option 2 and calculated using the RI for option 1. For the minor components (< 1–2%), the determination of Kpart.
d
with an acceptable accuracy is impossible. The values of j are calculated using RI determined with option 1, Kpart. with option 2. jcorr. is
the j value for compounds of moderate polarity (Kpart. < 1) corrected according to the data for acetone and isobutyrophenone.
+
100
keeping of the test sample), the compounds with the
ions [M – CH CHO] with (m/z)
= 90 [1].
3
molecular formula C H O (M = 162) can be assigned
Consequently, the presence in the molecular structure
of compounds V and VII (M = 162) of the fragment
>C(CH ) should give rise to the peaks of the homolog
1
1
12
to the series of arylalkanols, arylalkenols and aryl-
substituted cyclic ethers (in all cases different types of
coupling of different structural fragments of molecules
are possible). However, the unique characteristics of
3
2
+
ions [M – (CH ) CO] , with m/z = 104.
3
2
Thus, the compounds V and VII are isomeric
oxiranes corresponding to the isomeric alkenyl-
benzenes III and IV:
1
00
the mass spectra of isomers V and VII [(m/z)
=
1
04], allows the exclusion of all options save aryl-
substituted oxiranes. Actually only the known mass
spectra of the compounds of this class beginning with
the simplest representatives contain the peaks of
fragment ions with even mass numbers. For example,
the mass spectra of (E)- and (Z)-2-methyl-3-
phenyloxiranes (M = 134) which contain a structural
O
O
V
VII
fragment >CH–CH show characteristic peaks of the
3
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 82 No. 8 2012

1
398
ZENKEVICH
This assumption is confirmed by the ratio of such
phenyloxirane]. Getting the absolute estimates of RI
for such strained structures is difficult, but, as a first
approximation, we can apply the algorithm involving
the calculation of RI by analogy with the schemes of
“assembling” the target structures from less complex
precursors [20, 21]:
isomers (~5:2, similar to 55:18) and a similarity in the
sequence of their gas chromatographic elution. The
latter follows from the estimates of boiling points
using the ACD software: 212.9±9.0°C (trimethyl-
phenyloxirane) and 227.9±9.0°C [2-(1-methylethyl)-2-
O
O
O
O
_
+
V
_
_
_
_
_
+
(
1037
1072
+
15)
+
(686
+
16)
(542
+
6)
=
=
(1181 23)
O
O
O
O
_
+
V
_
_
_
_
+
_
+
(
+
9)
+
(686
+
16)
(649
17)
(1109 25)
The two obtained RI estimates differ considerably,
but their average value (1145±34) agrees with the
experimental value of the RI of compound V (1147±2).
conductivity detector, the circuit current 170 mA,
column 2 m×4 mm, sorbent SEPARON BD, column
temperature 190°C, evaporator temperature 200°C. Dosing
was performed with a MSH-10 syringe, sample volume
The mass spectrum of the last component detected
in the sample with M = 162 and RI = 1225±3 (VIII)
also cannot be identified using the database [1]. Given
the value of jcorr. of this compound (2.63), we can
assume that it belongs to the series of arylalkenols, but
unequivocal establishment of its structure is not
possible. Additive estimates similar to the above do
not coincide with the experimental RI values for any of
the proposed structures.
2
μl. Under identical conditions initial samples and
those with the addition of a known amount of water
100 μl water per 5 μl of 2,2,2-trifluoroethanol, dilution
(
of samples is not taken into account) were analyzed.
To eliminate the influence of the water traces on the
partition coefficients of polar compounds, trifluoro-
ethanol was dried over zeolites NaX pre-calcined at a
temperature of 300°C for 4 h. The initial water content
in trifluoroethanol varied within 1.0–1.5 wt %, after
drying, it was below the detection limit (0.01 wt %).
Thus, using the mass spectra, chromatographic
retention parameters, and partition coefficients in
heterophase systems we showed in this example that in
the alkenylbenzene sample during its storage the
respective oxiranes accumulated. It is possible that
they are not the primary products of oxidation, but
originate from the intermediately formed hydro-
peroxides. As for the partition coefficients proper, we
can conclude that they do not belong to the most
informative analytical parameters, but in combination
with other characteristics of the analytes are certainly
useful in solving the problems of identification.
Determination of partition coefficients in hetero-
phase system hexane–2,2,2-trifluoroethanol. In
order to determine Kpart., in a stoppered 10 ml vial con-
taining 0.5–2 ml of hexane and 0.5–2 ml of 2,2,2-
trifluoroethanol was dosed 10–50 μl of analyzed
sample so that the total concentration of all com-
ponents based on the total volume of the solvent
should not exceed 2%. The resulting two-phase system
was intensively shaken for 5–10 s and then, after
separation of layers, each layer was analyzed.
Determination of Kpart. was performed by analysis
of equal volumes of each phase of the solvent system
in accordance with the guidelines given in [5]. Dosing
of samples was carried out with a MSH-10 syringe, the
sample volume 3.2 μl. The Kpart. value was taken equal
to the ratio of the peak areas of each component in two
layers, Kpart. ≈ S /S .
EXPERIMENTAL
Determination of water in 2,2,2-trifluoroethanol.
Gas chromatographic determination of water content in
,2,2-trifluoroethanol was performed by the method of
adding a reference substance [11]. Conditions of
analysis: chromatograph GCHF 18.3 with a thermal
2
1
2
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 82 No. 8 2012

CHROMATO-MASS-SPECTROMETRIC IDENTIFICATION
1399
Gas chromatographic analysis was performed on
a Biokhrom-1 chromatograph with a flame ionization
detector and a WCOT quartz column 25 m × 0.20 mm
filled with OV-101 (film thickness 0.20 mm), ramp
3. Zenkevich, I.G., Zh. Analit. Khim., 2003, vol. 58, no. 2,
p. 119.
4. Berezkin, V.G., Lowilova, V.D., Pankov, A.G., and
Yagodovskii, V.D., Khromato-raspredelitel’nyi metod
(Chromatographic Distribution Method), Moscow: Nauka,
1976.
–
1
from 60 to 220°C at the rate 6°C min , carrier gas
–
1
nitrogen, linear rate 20 cm s , split ratio 1:30, the
evaporator temperature 200°C, detector temperature
5
. Zenkevich, I.G. and Vasil’ev, A.V., Zh. Analit. Khim,
993, vol. 48, no. 3, p. 473.
1
2
50°C (mode 1), and on a Tsvet-100 chromatograph
6
. Zenkevich, I.G., Encyclopedia of Chromatography,
with a flame ionization detector and glass column 3 m ×
New York: Taylor & Francis, 2010, vol. 1, p. 562.
3
0
mm packed with 5% SE-30 on Chromaton N (0.20–
.25 mm), ramp from 60 to 200°C at the rate 6.4°C min
–1
7. Zenkevich, I.G. and Cibul’skaya, I.A., Zh. Fiz. Khim.,
997, vol. 71, no. 2, p. 341.
1
(
3
mode 2). Carrier gas nitrogen, the flow volume rate
0 ml min , evaporator temperature 200°C. To
–
1
8. Kushakova, A.S. and Zenkevich, I.G., Abstract of
Papers, Vseros. Simp. “Khromatografiya i khromato-
mass-spektrometriya” (All-Russian symp. “Chromato-
graphy and Chromatography–Mass Spectrometry”),
Moscow, 2008, p. 74.
measure the peak areas a TR-2213 integrator and
UniChrom software (version 4.x-5) was used. In order
to determine the semi-logarithmic retention indices, to
the analyzed samples was added a mixture of reference
n-alkanes C –C ; for the RI calculation the program
9
. Qian, J. and Poole, C.F., J. Chromatogr. (A), 2007,
8
14
vol. 1143, p. 276.
QBasic contained in the manual [22] was used and the
Microsoft Excel software. The source of RI reference
values is the NIST database [1].
1
1
0. http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml-
acidity2.htm.
1. Zenkevich, I.G., Kushakova,A.S., and Mamedova, F.T.,
/
Analitika i Kontrol’, 2009, vol. 13, no. 2, p. 106.
2. http://srdata.nist.gov/solubility/.
3. Kotowska, U. and Isidorov ,V.A., Cent. Eur. J. Chem.,
Chromatography–mass spectrometry analysis of
the sample of (1,2-dimethyl-1-propenyl)benzene (no. 3)
was performed on a gas chromatograph–mass spec-
trometer QP-2010 Plus (Shimadzu, Japan) using a
WCOT quartz column 25 m×0.20 mm with a
stationary phase DB-5 MS (0.33 mm film thickness )
at ramp from 50°C (1 min) to 200°C (10 min) at the
rate 10°C min (option 3). The temperature of
evaporator 250°C, interface 280°C, ion source 200°C.
Sample volume 0.1 ml, split ratio 1:150. The
ionization energy 70 eV, mass range 35–450 Da.
1
1
2
011. Vol. 9, no. 5. P. 813.
1
1
4. Kushakova, A.S., Tkachenko, K.G., and Zenkevich, I.G.,
Khim. Rastit. Syr’ya, 2010, no. 4, p. 111.
5. Brown, A.B., Chronister, C.W., Watkins, D.M., Maz-
zaccaro, R.J., Rajski, S.R., Fontain, M.G., Mckay, S.E.,
and Gibson, T.L., Synth. Commun., 1995, vol. 25,
p. 485.
–
1
1
6. Zenkevich, I.G., Eliseenkov, E.V., and Kasatochkin, A.N.,
Khromatographiya, 2009, vol. 70, p. 839.
The reaction conditions of cyclohexanone with
17. Zenkevich, I.G., Ukolov, A.I., Kushakova, A.S., and
Gustyleva, L.K., Zh. Analit. Khim, 2011, vol. 66, no. 12,
p. 1282.
18. Zenkevich, I.G., Lab. Zh., 2003, no. 1(3), p. 44.
19. Zenkevich, I.G., Zh. Fiz. Khim, 2003, vol. 77, no. 1,
phosphorus pentachloride in CCl are in line with the
4
recommendations of [15]. The sample of (2,3-
dimethyl-1-propenyl)benzene [bp 67.5°C (9 mm Hg),
2
0
20
nD 1.5985, d4 0.9004] is selected from the collection
of prof. B.V. Ioffe (St. Petersburg State University).
p. 92.
2
0. Zenkevich, I.G., Eliseenkov, E.V., Kasatochkin, A.N.,
Zhakovskaya, Z.A., and Khoroshko, L.O., J. Chroma-
togr. (A), 2011, vol. 1218, p. 3291.
REFERENCES
1
2
. NIST11/2011/EPA/NIH Mass Spectral Library.
Software/Data Version (NIST11); NIST Standard
Reference Database, 69, 2011, National Institute of
Standards and Techno-logy, Gaithersburg, MD 20899;
http://webbook.nist.gov.
. Vigdergauz, M.S., Semenchenko, L.V., Ezrec, V.A.,
and Bogoslovskii, Yu.N., Kachestvennyi gazo-khro-
matograficheskii analiz (Qualitative Chromatographic-
Gas Analysis), Moscow: Nauka, 1978.
2
2
1. Zenkevich, I.G. and Ukolov, A.I., Zh. Obshch. Khim.,
2
011, vol. 81, no. 9, p. 1479.
2. Stolyarov, B.V., Savinov, I.M., Vitenberg, A.G.,
Karkova, L.A., Zenkevich, I.G., Kalmanovskii, V.I., and
Kalambet, Yu.A., Prakticheskaya gazovaya
i
zhidkostnaya khromatografiia (Practical Gas and Liquid
Chromatography), St. Petersburg: Sankt-Peterburg. Gos.
Univ., 2002.
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